Earth and Planetary Sciences › Oceanography

Marine and coastal ecosystems

Works Count: 91509

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Description

This cluster of papers focuses on the complex interactions between marine biogeochemistry, ecosystem dynamics, and environmental factors such as eutrophication, harmful algal blooms, and climate change. It explores the role of dissolved organic matter, nutrient limitation, and phytoplankton in the oceanic carbon cycle and highlights the impact of global warming on biological productivity and oxygen levels in the oceans.

Keywords

Dissolved Organic Matter; Eutrophication; Harmful Algal Blooms; Oceanic Carbon Cycle; Phytoplankton; Global Warming; Nutrient Limitation; Biological Productivity; Oceanic Oxygen Levels; Climate Change

Characterizing dissolved organic matter fluorescence with parallel factor analysis: a tutorial

2008-11-01

Colin A. Stedmon , Rasmus Bro

A sub‐fraction of dissolved organic matter fluoresces when excited with ultraviolet light. This property is used to quantify and characterize changes in dissolved organic matter (DOM) in aquatic environments. Detailed … A sub‐fraction of dissolved organic matter fluoresces when excited with ultraviolet light. This property is used to quantify and characterize changes in dissolved organic matter (DOM) in aquatic environments. Detailed mapping of the fluorescence properties of DOM produces excitation emission matrices (EEM), which are well suited to multi‐way data analysis techniques (chemometrics). Techniques such as parallel factor analysis (PARAFAC) are increasingly being applied to characterize DOM fluorescence properties. Here, an introduction to the technique and description of the advantages and pitfalls of its application to DOM fluorescence is presented. Additionally a MATLAB based tutorial and toolbox specific to PARAFAC analysis of DOM fluorescence is presented.

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A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization

2000-10-01

Philip W. Boyd , Andrew Watson , Cliff S. Law +7 more

Mathematical formulation of the relationship between photosynthesis and light for phytoplankton

1976-07-01

Alan D. Jassby , Trevor Platt

Eight different mathematical formulations of the photosynthesis—light curve for phytoplankton (up to and including light saturation) were recast in terms of the same two parameters: the initial slope α , … Eight different mathematical formulations of the photosynthesis—light curve for phytoplankton (up to and including light saturation) were recast in terms of the same two parameters: the initial slope α , and the assimilation number P m B . Each equation was tested for its ability to describe empirical data from natural populations of marine phytoplankton: the results of 188 light‐saturation experiments at three coastal locations in Nova Scotia over a 2‐year period. The most consistently useful mathematical representation of the data was found to be the hyperbolic tangent function.

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Analysis of variations in ocean color1

1977-07-01

Anclré Morel , Louis Prieur

Spectral measurements of downwelling and upwelling daylight were made in waters different with respect to turbidity and pigment content and from these data the spectral values of the reflectance ratio … Spectral measurements of downwelling and upwelling daylight were made in waters different with respect to turbidity and pigment content and from these data the spectral values of the reflectance ratio just below the sea surface, R (λ), were calculated. The experimental results are interpreted by comparison with the theoretical R (λ) values computed from the absorption and back‐scattering coefficients. The importance of molecular scattering in the light back‐scattering process is emphasized. The R (λ) values observed for blue waters are in full agreement with computed values in which new and realistic values of the absorption coefficient for pure water are used and presented. For the various green waters, the chlorophyll concentrations and the scattering coefficients, as measured, are used in computations which account for the observed R (λ) values. The inverse process, i.e. to infer the content of the water from R (λ) measurements at selected wavelengths, is discussed in view of remote sensing applications.

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Evaluation of Specific Ultraviolet Absorbance as an Indicator of the Chemical Composition and Reactivity of Dissolved Organic Carbon

2003-09-17

James L. Weishaar , George R. Aiken , Brian A. Bergamaschi +3 more

Specific UV absorbance (SUVA) is defined as the UV absorbance of a water sample at a given wavelength normalized for dissolved organic carbon (DOC) concentration. Our data indicate that SUVA, … Specific UV absorbance (SUVA) is defined as the UV absorbance of a water sample at a given wavelength normalized for dissolved organic carbon (DOC) concentration. Our data indicate that SUVA, determined at 254 nm, is strongly correlated with percent aromaticity as determined by 13C NMR for 13 organic matter isolates obtained from a variety of aquatic environments. SUVA, therefore, is shown to be a useful parameter for estimating the dissolved aromatic carbon content in aquatic systems. Experiments involving the reactivity of DOC with chlorine and tetra- methylammonium hydroxide (TMAH), however, show a wide range of reactivity for samples with similar SUVA values. These results indicate that, while SUVA measurements are good predictors of general chemical characteristics of DOC, they do not provide information about reactivity of DOC derived from different types of source materials. Sample pH, nitrate, and iron were found to influence SUVA measurements.

Thresholds of hypoxia for marine biodiversity

2008-09-30

Raquel Vaquer‐Sunyer , Carlos M. Duarte

Hypoxia is a mounting problem affecting the world's coastal waters, with severe consequences for marine life, including death and catastrophic changes. Hypoxia is forecast to increase owing to the combined … Hypoxia is a mounting problem affecting the world's coastal waters, with severe consequences for marine life, including death and catastrophic changes. Hypoxia is forecast to increase owing to the combined effects of the continued spread of coastal eutrophication and global warming. A broad comparative analysis across a range of contrasting marine benthic organisms showed that hypoxia thresholds vary greatly across marine benthic organisms and that the conventional definition of 2 mg O(2)/liter to designate waters as hypoxic is below the empirical sublethal and lethal O(2) thresholds for half of the species tested. These results imply that the number and area of coastal ecosystems affected by hypoxia and the future extent of hypoxia impacts on marine life have been generally underestimated.

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Nitrogen limitation on land and in the sea: How can it occur?

1991-01-01

PeterM. Vitousek , Robert W. Howarth

DETERMINATION OF CHLOROPHYLL AND PHEO‐PIGMENTS: SPECTROPHOTOMETRIC EQUATIONS1

1967-04-01

Carl J. Lorenzen

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The Evolution and Future of Earth’s Nitrogen Cycle

2010-10-07

Donald E. Canfield , Alexander N. Glazer , Paul G. Falkowski

Atmospheric reactions and slow geological processes controlled Earth's earliest nitrogen cycle, and by ~2.7 billion years ago, a linked suite of microbial processes evolved to form the modern nitrogen cycle … Atmospheric reactions and slow geological processes controlled Earth's earliest nitrogen cycle, and by ~2.7 billion years ago, a linked suite of microbial processes evolved to form the modern nitrogen cycle with robust natural feedbacks and controls. Over the past century, however, the development of new agricultural practices to satisfy a growing global demand for food has drastically disrupted the nitrogen cycle. This has led to extensive eutrophication of fresh waters and coastal zones as well as increased inventories of the potent greenhouse gas nitrous oxide (N(2)O). Microbial processes will ultimately restore balance to the nitrogen cycle, but the damage done by humans to the nitrogen economy of the planet will persist for decades, possibly centuries, if active intervention and careful management strategies are not initiated.

The Hydrophobic Effect: Formation of Micelles and Biological Membranes

1981-02-09

C.H. Walker

UPTAKE OF NEW AND REGENERATED FORMS OF NITROGEN IN PRIMARY PRODUCTIVITY1

1967-04-01

Richard C. Dugdale , John J. Goering

The use of 15 N‐labeled compounds to obtain specific uptake rates for the various nitrogen sources available to the phytoplankton makes it possible to separate the fractions of primary productivity … The use of 15 N‐labeled compounds to obtain specific uptake rates for the various nitrogen sources available to the phytoplankton makes it possible to separate the fractions of primary productivity corresponding to new and regenerated nitrogen in the euphotic zone of the ocean. Measurements of nitrate uptake as a fraction of ammonia plus nitrate uptake have been obtained from the northwest Atlantic and the northeast Pacific oceans. Mean values range from 8.3 to 39.5%, the former being characteristic of subtropical regions and the latter of northern temperate regions or coastal and inland waters. Nitrogen fixation is also a source of new nitrogen. Rates of nitrogen fixation are found to be as high or higher than nitrate uptake, in some cases suggesting an important role for nitrogen‐fixing phytoplankton. The role of zooplankton in regenerating nitrogen as ammonia in the Sargasso Sea is examined theoretically. Probably only about 10% of the daily ammonia uptake by phytoplankton is contributed by the zooplankton living in the upper 100 m.

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Nitrogen, Phosphorus, and Eutrophication in the Coastal Marine Environment

1971-03-12

John H. Ryther , William M. Dunstan

The distribution of inorganic nitrogen and phosphorus and bioassay experiments both show that nitrogen is the critical limiting factor to algal growth and eutrophication in coastal marine waters. About twice … The distribution of inorganic nitrogen and phosphorus and bioassay experiments both show that nitrogen is the critical limiting factor to algal growth and eutrophication in coastal marine waters. About twice the amount of phosphate as can be used by the algae is normally present. This surplus results from the low nitrogen to phosphorus ratio in terrigenous contributions, including human waste, and from the fact that phosphorus regenerates more quickly than ammonia from decomposing organic matter. Removal of phosphate from detergents is therefore not likely to slow the eutrophication of coastal marine waters, and its replacement with nitrogen-containing nitrilotriacetic acid may worsen the situation.

Ocean color chlorophyll algorithms for SeaWiFS

1998-10-15

John E. O’Reilly , Stéphane Maritorena , B. Greg Mitchell +5 more

A large data set containing coincident in situ chlorophyll and remote sensing reflectance measurements was used to evaluate the accuracy, precision, and suitability of a wide variety of ocean color … A large data set containing coincident in situ chlorophyll and remote sensing reflectance measurements was used to evaluate the accuracy, precision, and suitability of a wide variety of ocean color chlorophyll algorithms for use by SeaWiFS (Sea‐viewing Wide Field‐of‐view Sensor). The radiance‐chlorophyll data were assembled from various sources during the SeaWiFS Bio‐optical Algorithm Mini‐Workshop (SeaBAM) and is composed of 919 stations encompassing chlorophyll concentrations between 0.019 and 32.79 μg L −1 . Most of the observations are from Case I nonpolar waters, and ∼20 observations are from more turbid coastal waters. A variety of statistical and graphical criteria were used to evaluate the performances of 2 semianalytic and 15 empirical chlorophyll/pigment algorithms subjected to the SeaBAM data. The empirical algorithms generally performed better than the semianalytic. Cubic polynomial formulations were generally superior to other kinds of equations. Empirical algorithms with increasing complexity (number of coefficients and wavebands), were calibrated to the SeaBAM data, and evaluated to illustrate the relative merits of different formulations. The ocean chlorophyll 2 algorithm (OC2), a modified cubic polynomial (MCP) function which uses Rrs490/Rrs555, well simulates the sigmoidal pattern evident between log‐transformed radiance ratios and chlorophyll, and has been chosen as the at‐launch SeaWiFS operational chlorophyll a algorithm. Improved performance was obtained using the ocean chlorophyll 4 algorithm (OC4), a four‐band (443, 490, 510, 555 nm), maximum band ratio formulation. This maximum band ratio (MBR) is a new approach in empirical ocean color algorithms and has the potential advantage of maintaining the highest possible satellite sensor signal: noise ratio over a 3‐orders‐of‐magnitude range in chlorophyll concentration.

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VERTEX: carbon cycling in the northeast Pacific

1987-02-01

John H. Martin , George A. Knauer , David M. Karl +1 more

Carbon, nitrogen, and phosphorus transport by world rivers

1982-04-01

Michel Meybeck

THE GLOBAL DIAGENETIC FLUX OF PHOSPHORUS FROM MARINE SEDIMENTS TO THE OCEANS: REDOX SENSITIVITY AND THE CONTROL OF ATMOSPHERIC OXYGEN LEVELS THE GLOBAL DIAGENETIC FLUX OF PHOSPHORUS FROM MARINE SEDIMENTS TO THE OCEANS: REDOX SENSITIVITY AND THE CONTROL OF ATMOSPHERIC OXYGEN LEVELS

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Properties of fluorescent dissolved organic matter in the Gironde Estuary

2009-03-20

Arnaud Huguet , Lionel G. Vacher , S. Relexans +3 more

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Global carbon dioxide emissions from inland waters

2013-11-19

Peter A. Raymond , Jens Hartmann , Ronny Lauerwald +7 more

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Iron deficiency limits phytoplankton growth in the north-east Pacific subarctic

1988-01-01

John H. Martin , Steve E. Fitzwater

Our evolving conceptual model of the coastal eutrophication problem

2001-01-01

James E. Cloern

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 210:223-253 (2001) - doi:10.3354/meps210223 … MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 210:223-253 (2001) - doi:10.3354/meps210223 Our evolving conceptual model of the coastal eutrophication problem James E. Cloern* US Geological Survey, MS496, 345 Middlefield Rd., Menlo Park, California 94025, USA *E-mail: [email protected] ABSTRACT: A primary focus of coastal science during the past 3 decades has been the question: How does anthropogenic nutrient enrichment cause change in the structure or function of nearshore coastal ecosystems? This theme of environmental science is recent, so our conceptual model of the coastal eutrophication problem continues to change rapidly. In this review, I suggest that the early (Phase I) conceptual model was strongly influenced by limnologists, who began intense study of lake eutrophication by the 1960s. The Phase I model emphasized changing nutrient input as a signal, and responses to that signal as increased phytoplankton biomass and primary production, decomposition of phytoplankton-derived organic matter, and enhanced depletion of oxygen from bottom waters. Coastal research in recent decades has identified key differences in the responses of lakes and coastal-estuarine ecosystems to nutrient enrichment. The contemporary (Phase II) conceptual model reflects those differences and includes explicit recognition of (1) system-specific attributes that act as a filter to modulate the responses to enrichment (leading to large differences among estuarine-coastal systems in their sensitivity to nutrient enrichment); and (2) a complex suite of direct and indirect responses including linked changes in: water transparency, distribution of vascular plants and biomass of macroalgae, sediment biogeochemistry and nutrient cycling, nutrient ratios and their regulation of phytoplankton community composition, frequency of toxic/harmful algal blooms, habitat quality for metazoans, reproduction/growth/survival of pelagic and benthic invertebrates, and subtle changes such as shifts in the seasonality of ecosystem functions. Each aspect of the Phase II model is illustrated here with examples from coastal ecosystems around the world. In the last section of this review I present one vision of the next (Phase III) stage in the evolution of our conceptual model, organized around 5 questions that will guide coastal science in the early 21st century: (1) How do system-specific attributes constrain or amplify the responses of coastal ecosystems to nutrient enrichment? (2) How does nutrient enrichment interact with other stressors (toxic contaminants, fishing harvest, aquaculture, nonindigenous species, habitat loss, climate change, hydrologic manipulations) to change coastal ecosystems? (3) How are responses to multiple stressors linked? (4) How does human-induced change in the coastal zone impact the Earth system as habitat for humanity and other species? (5) How can a deeper scientific understanding of the coastal eutrophication problem be applied to develop tools for building strategies at ecosystem restoration or rehabilitation? KEY WORDS: Coastal eutrophication · Nutrient enrichment · Estuaries · Nitrogen · Phosphorus · Coastal ecosystems Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 210. Online publication date: January 26, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.

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Processes and patterns of oceanic nutrient limitation

2013-03-29

C. Mark Moore , Matthew M. Mills , Kevin R. Arrigo +7 more

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Sedimentary organic matter preservation: an assessment and speculative synthesis

1995-04-01

John I. Hedges , Richard G. Keil

Coastal marine eutrophication: A definition, social causes, and future concerns

1995-02-01

Scott W. Nixon

Abstract There is a need in the marine research and management communities for a clear operational definition of the term, eutrophication. I propose the following: This definition is consistent with … Abstract There is a need in the marine research and management communities for a clear operational definition of the term, eutrophication. I propose the following: This definition is consistent with historical usage and emphasizes that eutrophication is a process, not a trophic state. A simple trophic classification for marine systems is also proposed: Various factors may increase the supply of organic matter to coastal systems, but the most common is clearly nutrient enrichment. The major causes of nutrient enrichment in coastal areas are associated directly or indirecdy with meeting the requirements and desires of human nutrition and diet. The deposition of reactive nitrogen emitted to the atmosphere as a consequence of fossil fuel combustion is also an important anthropogenic factor. The intensity of nitrogen emission from fertilizer, livestock waste, and fossil fuel combustion varies widely among the countries of the world. It is strongest in Europe, the northeastern United States, India/Pakistan, Japan/Korea, and the Caribbean. This geographical distribution corresponds with many areas where coastal marine eutrophication has become a recent concern. Demographic and social trends suggest that past practices leading to coastal nutrient enrichment are likely to be repeated in the coming decades in the developing countries of Asia, Africa, and Latin America.

Characterization of marine and terrestrial DOM in seawater using excitation-emission matrix spectroscopy

1996-01-01

Paula G. Coble

Fluorescence Excitation−Emission Matrix Regional Integration to Quantify Spectra for Dissolved Organic Matter

2003-11-15

Wen Chen , Paul Westerhoff , Jerry A. Leenheer +1 more

Excitation−emission matrix (EEM) fluorescence spectroscopy has been widely used to characterize dissolved organic matter (DOM) in water and soil. However, interpreting the >10,000 wavelength-dependent fluorescence intensity data points represented in … Excitation−emission matrix (EEM) fluorescence spectroscopy has been widely used to characterize dissolved organic matter (DOM) in water and soil. However, interpreting the >10,000 wavelength-dependent fluorescence intensity data points represented in EEMs has posed a significant challenge. Fluorescence regional integration, a quantitative technique that integrates the volume beneath an EEM, was developed to analyze EEMs. EEMs were delineated into five excitation−emission regions based on fluorescence of model compounds, DOM fractions, and marine waters or freshwaters. Volumetric integration under the EEM within each region, normalized to the projected excitation−emission area within that region and dissolved organic carbon concentration, resulted in a normalized region-specific EEM volume (Φi,n). Solid-state carbon nuclear magnetic resonance (13C NMR), Fourier transform infrared (FTIR) analysis, ultraviolet−visible absorption spectra, and EEMs were obtained for standard Suwannee River fulvic acid and 15 hydrophobic or hydrophilic acid, neutral, and base DOM fractions plus nonfractionated DOM from wastewater effluents and rivers in the southwestern United States. DOM fractions fluoresced in one or more EEM regions. The highest cumulative EEM volume (ΦT,n = ΣΦi,n) was observed for hydrophobic neutral DOM fractions, followed by lower ΦT,n values for hydrophobic acid, base, and hydrophilic acid DOM fractions, respectively. An extracted wastewater biomass DOM sample contained aromatic protein- and humic-like material and was characteristic of bacterial-soluble microbial products. Aromatic carbon and the presence of specific aromatic compounds (as indicated by solid-state 13C NMR and FTIR data) resulted in EEMs that aided in differentiating wastewater effluent DOM from drinking water DOM.

The Oceans, Their Physics, Chemistry, and General Biology

1943-12-31

L. A. Walford , H. U. Iverdrup , Martin W. Johnson +1 more

Four years ago when we started the preparation of this book, we hoped to give a survey of well-established oceanographic knowledge, but it soon became apparent that the book could … Four years ago when we started the preparation of this book, we hoped to give a survey of well-established oceanographic knowledge, but it soon became apparent that the book could not be brought up to date without summarizing and synthesizing the wealth of information that has been acquired within the past dozen years, as well as the many new ideas that have been advanced. Consequently, the book has grown far beyond its originally planned scope, and the presentation has become colored by the personal concepts of the authors. Discussion of many topics, such as the absorption of radiation in the sea, the relations of organisms to the chemical composition of sea water, or the productivity of the sea, has led to tentative conclusions that are perhaps presented here as better substantiated than is actually the case. At the risk of premature generalizations we have, however, preferred definite statements to mere enumeration o uncorrelated observations and conflicting interpretations, believing that the treatment selected would be more stimulating.The book is intended to provide a good deal of factual information, but above all it should be an aid to the beginner and specialist alike in the coordination of the various fields of oceanography. The lists of literature at the ends of chapters are not intended to be exhaustive, but will serve as guides to recent publications. When possible, reference is made to books containing comprehensive bibliographies rather than to original papers.

The inverted microscope method of estimating algal numbers and the statistical basis of estimations by counting

1958-04-01

John Lund , Charlotte Kipling , E. D. Le Cren

Photosynthetic rates derived from satellite‐based chlorophyll concentration

1997-01-01

Michael J. Behrenfeld , Paul G. Falkowski

We assembled a dataset of 14 C‐based productivity measurements to understand the critical variables required for accurate assessment of daily depth‐integrated phytoplankton carbon fixation ( PP ( PP eu ) … We assembled a dataset of 14 C‐based productivity measurements to understand the critical variables required for accurate assessment of daily depth‐integrated phytoplankton carbon fixation ( PP ( PP eu ) u ) from measurements of sea surface pigment concentrations ( C sat )( C sat ). From this dataset, we developed a light‐dependent, depth‐resolved model for carbon fixation (VGPM) that partitions environmental factors affecting primary production into those that influence the relative vertical distribution of primary production ( P z ) z ) and those that control the optimal assimilation efficiency of the productivity profile ( P ( P B opt ). The VGPM accounted for 79% of the observed variability in P z and 86% of the variability in PP eu by using measured values of P B opt . Our results indicate that the accuracy of productivity algorithms in estimating PP eu is dependent primarily upon the ability to accurately represent variability in P b opt . We developed a temperature‐dependent P b opt model that was used in conjunction with monthly climatological images of C sat sea surface temperature, and cloud‐corrected estimates of surface irradiance to calculate a global annual phytoplankton carbon fixation ( PP annu ) rate of 43.5 Pg C yr ‒1 . The geographical distribution of PP annu was distinctly different than results from previous models. Our results illustrate the importance of focusing P b opt model development on temporal and spatial, rather than the vertical, variability.

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Climate-driven trends in contemporary ocean productivity

2006-12-01

Michael J. Behrenfeld , Robert T. O’Malley , David A. Siegel +7 more

Dissolved organic carbon trends resulting from changes in atmospheric deposition chemistry

2007-11-01

Donald T. Monteith , John L. Stoddard , Chris Evans +7 more

Impact of climate change on marine pelagic phenology and trophic mismatch

2004-08-01

Martin Edwards , Anthony J. Richardson

The rise of harmful cyanobacteria blooms: The potential roles of eutrophication and climate change

2011-10-31

Judy O’Neil , T. W. Davis , Michele A. Burford +1 more

Particulate organic matter flux and planktonic new production in the deep ocean

1979-12-01

Richard W. Eppley , Bruce J. Peterson

Ecological and toxicological effects of inorganic nitrogen pollution in aquatic ecosystems: A global assessment

2006-06-19

Julio A. Camargo , Álvaro Alonso

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Harmful algal blooms and eutrophication: Nutrient sources, composition, and consequences

2002-08-01

Donald M. Anderson , Patricia M. Glibert , JoAnn M. Burkholder

Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget

2007-02-01

J. J. Cole , Yves T. Prairie , N. F. Caraco +7 more

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Eutrophication: impacts of excess nutrient inputs on freshwater, marine, and terrestrial ecosystems

1999-01-01

Val H. Smith , David Tilman , Jeffrey C. Nekola

Biogeochemical Controls and Feedbacks on Ocean Primary Production

1998-07-10

Paul G. Falkowski , Richard T. Barber , Victor Smetacek

Changes in oceanic primary production, linked to changes in the network of global biogeochemical cycles, have profoundly influenced the geochemistry of Earth for over 3 billion years. In the contemporary … Changes in oceanic primary production, linked to changes in the network of global biogeochemical cycles, have profoundly influenced the geochemistry of Earth for over 3 billion years. In the contemporary ocean, photosynthetic carbon fixation by marine phytoplankton leads to formation of ∼45 gigatons of organic carbon per annum, of which 16 gigatons are exported to the ocean interior. Changes in the magnitude of total and export production can strongly influence atmospheric CO 2 levels (and hence climate) on geological time scales, as well as set upper bounds for sustainable fisheries harvest. The two fluxes are critically dependent on geophysical processes that determine mixed-layer depth, nutrient fluxes to and within the ocean, and food-web structure. Because the average turnover time of phytoplankton carbon in the ocean is on the order of a week or less, total and export production are extremely sensitive to external forcing and consequently are seldom in steady state. Elucidating the biogeochemical controls and feedbacks on primary production is essential to understanding how oceanic biota responded to and affected natural climatic variability in the geological past, and will respond to anthropogenically influenced changes in coming decades. One of the most crucial feedbacks results from changes in radiative forcing on the hydrological cycle, which influences the aeolian iron flux and, in turn, affects nitrogen fixation and primary production in the oceans.

Eutrophication and harmful algal blooms: A scientific consensus

2008-08-30

J. Heisler , Patricia M. Glibert , JoAnn M. Burkholder +7 more

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Spectrofluorometric characterization of dissolved organic matter for indication of precursor organic material and aromaticity

2001-01-01

Diane M. McKnight , Elizabeth W. Boyer , Paul Westerhoff +3 more

We studied the fluorescence properties of fulvic acids isolated from streams and rivers receiving predominantly terrestrial sources of organic material and from lakes with microbial sources of organic material. Microbially … We studied the fluorescence properties of fulvic acids isolated from streams and rivers receiving predominantly terrestrial sources of organic material and from lakes with microbial sources of organic material. Microbially derived fulvic acids have fluorophores with a more sharply defined emission peak occurring at lower wavelengths than fluorophores in terrestrially derived fulvic acids. We show that the ratio of the emission intensity at a wavelength of 450 nm to that at 500 nm, obtained with an excitation of 370 nm, can serve as a simple index to distinguish sources of isolated aquatic fulvic acids. In our study, this index has a value of ~1.9 for microbially derived fulvic acids and a value of ~1.4 for terrestrially derived fulvic acids. Fulvic acids isolated from four large rivers in the United States have fluorescence index values of 1.4–1.5, consistent with predominantly terrestrial sources. For fulvic acid samples isolated from a river, lakes, and groundwaters in a forested watershed, the fluorescence index varied in a manner suggesting different sources for the seepage and streamfed lakes. Furthermore, we identified these distinctive fluorophores in filtered whole water samples from lakes in a desert oasis in Antarctica and in filtered whole water samples collected during snowmelt from a Rocky Mountain stream. The fluorescence index measurement in filtered whole water samples in field studies may augment the interpretation of dissolved organic carbon sources for understanding carbon cycling in aquatic ecosystems.

A trophic state index for lakes1

1977-03-01

Robert E. Carlson

A numerical trophic state index for lakes has been developed that incorporates most lakes in a scale of 0 to 100. Each major division (10, 20, 30, etc.) represents a … A numerical trophic state index for lakes has been developed that incorporates most lakes in a scale of 0 to 100. Each major division (10, 20, 30, etc.) represents a doubling in algal biomass. The index number can be calculated from any of several parameters, including Secchi disk transparency, chlorophyll, and total phosphorus.

HUMAN ALTERATION OF THE GLOBAL NITROGEN CYCLE: SOURCES AND CONSEQUENCES

1997-08-01

Peter M. Vitousek , John D. Aber , Robert W. Howarth +5 more

Nitrogen is a key element controlling the species composition, diversity, dynamics, and functioning of many terrestrial, freshwater, and marine ecosystems. Many of the original plant species living in these ecosystems … Nitrogen is a key element controlling the species composition, diversity, dynamics, and functioning of many terrestrial, freshwater, and marine ecosystems. Many of the original plant species living in these ecosystems are adapted to, and function optimally in, soils and solutions with low levels of available nitrogen. The growth and dynamics of herbivore populations, and ultimately those of their predators, also are affected by N. Agriculture, combustion of fossil fuels, and other human activities have altered the global cycle of N substantially, generally increasing both the availability and the mobility of N over large regions of Earth. The mobility of N means that while most deliberate applications of N occur locally, their influence spreads regionally and even globally. Moreover, many of the mobile forms of N themselves have environmental consequences. Although most nitrogen inputs serve human needs such as agricultural production, their environmental consequences are serious and long term. Based on our review of available scientific evidence, we are certain that human alterations of the nitrogen cycle have: approximately doubled the rate of nitrogen input into the terrestrial nitrogen cycle, with these rates still increasing; increased concentrations of the potent greenhouse gas N2O globally, and increased concentrations of other oxides of nitrogen that drive the formation of photochemical smog over large regions of Earth; caused losses of soil nutrients, such as calcium and potassium, that are essential for the long-term maintenance of soil fertility; contributed substantially to the acidification of soils, streams, and lakes in several regions; and greatly increased the transfer of nitrogen through rivers to estuaries and coastal oceans. In addition, based on our review of available scientific evidence we are confident that human alterations of the nitrogen cycle have: increased the quantity of organic carbon stored within terrestrial ecosystems; accelerated losses of biological diversity, especially losses of plants adapted to efficient use of nitrogen, and losses of the animals and microorganisms that depend on them; and caused changes in the composition and functioning of estuarine and nearshore ecosystems, and contributed to long-term declines in coastal marine fisheries.

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A simple and efficient method for the solid‐phase extraction of dissolved organic matter (SPE‐DOM) from seawater

2008-06-01

Thorsten Dittmar , Boris Koch , Norbert Hertkorn +1 more

A simple protocol is presented for the solid‐phase extraction of dissolved organic matter (SPE‐DOM) from seawater using commercially prepacked cartridges. The method does not require major instrumentation and can be … A simple protocol is presented for the solid‐phase extraction of dissolved organic matter (SPE‐DOM) from seawater using commercially prepacked cartridges. The method does not require major instrumentation and can be performed in the field. Modified styrene divinyl benzene polymer type sorbents (Varian PPL and ENV) and sorbents of a silica structure bonded with different hydrocarbon chains (Varian C8, C18, C18OH, and C18EWP) were considered. Except for C18OH, which heavily contaminated the samples, none of the sorbents leached significant amounts of dissolved organic carbon (DOC) or nitrogen (DON). Samples from the North Brazil shelf with strong mixing gradients of terrigenous and marine DOM were used to compare the various sorbents. PPL was the most efficient—on average, 62% of DOC was recovered as salt‐free extracts. C18 was found to be most efficient among the silica‐based sorbents, but it showed only two‐thirds of the extraction efficiency of PPL. As indicated by [ 1 H]NMR, C/N, and δ 13 C analyses, PPL extracted a more representative proportion of DOM than C18. Therefore, PPL was used for comparative studies in the Gulf of Mexico and Antarctica. From brackish marsh and river waters, 65% and 62% of total DOC, respectively, could be extracted. For purely marine DOM in Antarctica and the deep sea, the extraction efficiency was lower (43% on average). The efficiency of the new method to isolate marine DOM is better than or similar to highly laborious methods. A further advantage is the complete desalination of the sample. The isolation of a major DOM fraction, which is salt‐free, offers many possibilities to further characterize DOM by advanced analytical techniques.

Spreading Dead Zones and Consequences for Marine Ecosystems

2008-08-14

Robert J. Díaz , Rutger Rosenberg

Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. The formation of dead zones has been exacerbated by the increase … Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. The formation of dead zones has been exacerbated by the increase in primary production and consequent worldwide coastal eutrophication fueled by riverine runoff of fertilizers and the burning of fossil fuels. Enhanced primary production results in an accumulation of particulate organic matter, which encourages microbial activity and the consumption of dissolved oxygen in bottom waters. Dead zones have now been reported from more than 400 systems, affecting a total area of more than 245,000 square kilometers, and are probably a key stressor on marine ecosystems.

Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and pheopigments

1994-12-01

Nicholas A. Welschmeyer

A fluorometric method is described which provides sensitive measurements of extracted chlorophyll a free from the errors associated with conventional acidification techniques. Fluorometric optical configurations were optimized to produce maximum … A fluorometric method is described which provides sensitive measurements of extracted chlorophyll a free from the errors associated with conventional acidification techniques. Fluorometric optical configurations were optimized to produce maximum sensitivity to Chl a while maintaining desensitized responses from both Chl b and pheopigments. Under the most extreme Chl b :Chl a ratio likely to occur in nature (1 : 1 molar), the new method results in only a 10% overestimate of the true Chl a value, while estimates from older acidification methods are 2.5‐fold low. Under conditions of high pheopigment concentrations (pheo a: Chl a = 1 : 1 molar), the new method provides Chl a estimates that are equivalent to those determined from the acidification technique. The new simple method requires a single fluorescence determination and provides adequate sensitivity for small sample sizes (<200 ml) even in the most oligotrophic marine and freshwater environments.

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Retrieval of water-leaving radiance and aerosol optical thickness over the oceans with SeaWiFS: a preliminary algorithm

1994-01-20

Howard R. Gordon , Menghua Wang

The second generation of ocean-color-analyzing instruments requires more accurate atmospheric correction than does the Coastal Zone Color Scanner (CZCS), if one is to utilize fully their increased radiometric sensitivity. Unlike … The second generation of ocean-color-analyzing instruments requires more accurate atmospheric correction than does the Coastal Zone Color Scanner (CZCS), if one is to utilize fully their increased radiometric sensitivity. Unlike the CZCS, the new instruments possess bands in the near infrared (NIR) that are solely for aiding atmospheric correction. We show, using aerosol models, that certain assumptions regarding the spectral behavior of the aerosol reflectance employed in the standard CZCS correction algorithm are not valid over the spectral range encompassing both the visible and the NIR. Furthermore, we show that multiple-scattering effects on the algorithm depend significantly on the aerosol model. Following these observations, we propose an algorithm that utilizes the NIR bands for atmospheric correction to the required accuracy. Examples of the dependence of the error on the aerosol model, the turbidity of the atmosphere, and surface roughness (waves) are provided. The error in the retrieved phytoplankton-pigment concentration (the principal product of ocean-color sensors) induced by errors in the atmospheric correction are shown to be <20% in approximately 90% of the cases examined. Finally, the aerosol thickness (τ(α)) is estimated through a simple extension of the correction algorithm. Simulations suggest that the error in the recovered value of τ(α) should be ≲ 10%.

Carbon to volume relationships for dinoflagellates, diatoms, and other protist plankton

2000-04-26

Susanne Menden‐Deuer , Evelyn J. Lessard

Cellular carbon and nitrogen content and cell volume of nutritionally and morphologically diverse dinoflagellate species were measured to determine carbon to volume (C:vol) and nitrogen to volume (N:vol) relationships. Cellular … Cellular carbon and nitrogen content and cell volume of nutritionally and morphologically diverse dinoflagellate species were measured to determine carbon to volume (C:vol) and nitrogen to volume (N:vol) relationships. Cellular C and N content ranged from 48 to 3.0 × 10 4 pgC cell −1 and 11 to 2,656 pgN cell −1 for cells ranging in volume from 180 to 2.8 × 10 5 µm 3 . C and N density in dinoflagellates decreased significantly with increasing cell volume. C:N ratios ranged from 3.44 to 6.45. C:vol and N:vol in dinoflagellates are significantly related as expressed by the equations pgC cell −1 = 0.760 × volume 0.819 and pgN cell −1 = 0.118 × volume 0.849 . Previously published data were combined to compare C:vol relationships in different phylogenetic protist groups, including chlorophytes, chrysophytes, prasinophytes, and prymnesiophytes. Our analysis indicated differences between the C:vol relationships available for ciliates. A new C:vol relationship for diatoms was established (pgC cell −1 = 0.288 × volume 0.811 ). Dinoflagellates are significantly more C dense than diatoms. Except for diatoms, we found few significant differences between C:vol relationships of different phylogenetic groups. Consequently, one C:vol relationship for taxonomically diverse protist plankton excluding diatoms was determined (pgC cell −1 = 0.216 × volume 0.939 ). In the combined data set, carbon density was not constant but decreased significantly with increasing cell volume. Using constant C:vol conversion factors for plankton over large size ranges will cause systematic errors in biomass estimates.

Absorption spectral slopes and slope ratios as indicators of molecular weight, source, and photobleaching of chromophoric dissolved organic matter

2008-05-01

John R. Helms , Aron Stubbins , Jason D. Ritchie +3 more

A new approach for parameterizing dissolved organic matter (DOM) ultraviolet‐visible absorption spectra is presented. Two distinct spectral slope regions (275‐295 nm and 350‐400 nm) within log‐transformed absorption spectra were used … A new approach for parameterizing dissolved organic matter (DOM) ultraviolet‐visible absorption spectra is presented. Two distinct spectral slope regions (275‐295 nm and 350‐400 nm) within log‐transformed absorption spectra were used to compare DOM from contrasting water types, ranging from wetlands (Great Dismal Swamp and Suwannee River) to photobleached oceanic water (Atlantic Ocean). On the basis of DOM size‐fractionation studies (ultrafiltration and gel filtration chromatography), the slope of the 275‐295‐nm region and the ratio of these slopes ( S R ; 275‐295‐nm slope : 350‐400‐nm slope) were related to DOM molecular weight (MW) and to photochemically induced shifts in MW. Dark aerobic microbial alteration of chromophoric DOM (CDOM) resulted in spectral slope changes opposite of those caused by photochemistry. Along an axial transect in the Delaware Estuary, large variations in S R were measured, probably due to mixing, photodegradation, and microbial alteration of CDOM as terrestrially derived DOM transited through the estuary. Further, S R varied by over a factor of 13 between DOM‐rich wetland waters and Sargasso Sea surface waters. Currently, there is no consensus on a wavelength range for log‐transformed absorption spectra. We propose that the 275‐295‐nm slope be routinely reported in future DOM studies, as it can be measured with high precision, it facilitates comparison among dissimilar water types including CDOM‐rich wetland and CDOM‐poor marine waters, and it appears to be a good proxy for DOM MW.

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Primary Production of the Biosphere: Integrating Terrestrial and Oceanic Components

1998-07-10

Christopher B. Field , Michael J. Behrenfeld , James T. Randerson +1 more

Integrating conceptually similar models of the growth of marine and terrestrial primary producers yielded an estimated global net primary production (NPP) of 104.9 petagrams of carbon per year, with roughly … Integrating conceptually similar models of the growth of marine and terrestrial primary producers yielded an estimated global net primary production (NPP) of 104.9 petagrams of carbon per year, with roughly equal contributions from land and oceans. Approaches based on satellite indices of absorbed solar radiation indicate marked heterogeneity in NPP for both land and oceans, reflecting the influence of physical and ecological processes. The spatial and temporal distributions of ocean NPP are consistent with primary limitation by light, nutrients, and temperature. On land, water limitation imposes additional constraints. On land and ocean, progressive changes in NPP can result in altered carbon storage, although contrasts in mechanisms of carbon storage and rates of organic matter turnover result in a range of relations between carbon storage and changes in NPP.

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Global Iron Connections Between Desert Dust, Ocean Biogeochemistry, and Climate

2005-03-31

T. D. Jickells , Zhisheng An , K. K. Andersen +7 more

The environmental conditions of Earth, including the climate, are determined by physical, chemical, biological, and human interactions that transform and transport materials and energy. This is the “Earth system”: a … The environmental conditions of Earth, including the climate, are determined by physical, chemical, biological, and human interactions that transform and transport materials and energy. This is the “Earth system”: a highly complex entity characterized by multiple nonlinear responses and thresholds, with linkages between disparate components. One important part of this system is the iron cycle, in which iron-containing soil dust is transported from land through the atmosphere to the oceans, affecting ocean biogeochemistry and hence having feedback effects on climate and dust production. Here we review the key components of this cycle, identifying critical uncertainties and priorities for future research.

Eutrophication science: where do we go from here?

2009-02-25

Val H. Smith , David W. Schindler

Daily Analyzed Fields of Ocean Surface Chlorophyll for the Global Ocean: Integrating OCM-3 Chlorophyll Data with Coupled Physical-Biogeochemical Model Using Particle Filter Approach

2025-06-26

Smitha Ratheesh , M. Jishad , Neeraj Agarwal +5 more | Journal of the Indian Society of Remote Sensing

A correction model for quenching effects on chlorophyll a fluorescence measurements in lakes

2025-06-25

Samantha L. Sharp , Alexander L. Forrest , Derek C. Roberts +2 more | Limnology and Oceanography Methods

Abstract Characterizing the vertical structure of phytoplankton biomass is key to understanding the light, nutrient, and mixing dynamics driving lake ecosystems. In situ fluorometry is widely used in limnology to … Abstract Characterizing the vertical structure of phytoplankton biomass is key to understanding the light, nutrient, and mixing dynamics driving lake ecosystems. In situ fluorometry is widely used in limnology to obtain chlorophyll a (Chl a ) measurements as proxies for phytoplankton biomass. Unfortunately, daytime fluorometry signals are biased by non‐photochemical quenching, limiting the value of these measurements. Phytoplankton utilize this quenching process to dissipate excess light energy as heat, which contaminates daytime fluorometry measurements with reductions in measured Chl a . Despite the ubiquitous impacts of non‐photochemical quenching on fluorometer measurements, there is no universal correction method for inland waters. We propose a novel model for correcting non‐photochemical quenching impacts in lake systems as a simple exponential function of available light in the water column. This model was developed from data collected from two lakes representing the endmembers in terms of lake productivity and clarity, thus producing a model with possible application to other systems. The study sites are ultraoligotrophic Lake Tahoe, CA‐NV, and hypereutrophic Clear Lake, CA. Our proposed non‐photochemical quenching correction model demonstrates good performance ( R 2 = 0.74) when tested on an independent dataset from Lake George, NY. We applied the model to vertical data profiles from Lake Tahoe and Clear Lake to more accurately evaluate the vertical distribution of Chl a in these lakes. The results of this research have wide‐reaching benefits by enabling more accurate interpretation and application of Chl a fluorescence measurements in lakes with a range of conditions.

Evaluating Potential Changes from Nitrogen to Phosphorus Nutrient Limitation of Phytoplankton Growth in North Inlet Estuary, SC

2025-06-25

Catherine Schlenker , James L. Pinckney | Estuaries and Coasts

The satellite chlorophyll signature of Lagrangian eddy trapping varies regionally and seasonally within a subtropical gyre

2025-06-25

Alexandra E. Jones-Kellett , Michael J. Follows | Ocean science

Abstract. Vertical motions of mesoscale ocean eddies modulate the resource environment, productivity, and phytoplankton biomass in the ocean's subtropical gyres. The horizontal circulations can trap or disperse the eddy-driven chlorophyll … Abstract. Vertical motions of mesoscale ocean eddies modulate the resource environment, productivity, and phytoplankton biomass in the ocean's subtropical gyres. The horizontal circulations can trap or disperse the eddy-driven chlorophyll anomalies, which can be observed from space. From 2 decades of satellite remote sensing observations in the North Pacific Subtropical Gyre (NPSG), we compared the chlorophyll anomalies within “leaky” eddy boundaries identified using an Eulerian sea level anomaly (SLA) method and within strictly coherent “trapping” bounds derived from Lagrangian particle simulations. On average, NPSG Lagrangian coherent vortices maintain stronger chlorophyll anomalies than Eulerian SLA eddies due to the limitation of lateral dilution. This is observed in both cyclones and anticyclones. However, there is variability in the biological signature of trapping by sub-region and season. Eddy trapping of positive chlorophyll anomalies is most significant in the southern regions of the NPSG, counter to expectations from a commonly used Eulerian metric of eddy trapping. We found weak relationships between eddy age and the magnitude of surface chlorophyll anomalies in most long-lived Lagrangian coherent vortices; the strongest exception was in wintertime anticyclones in the lee of the Hawaiian Islands, where chlorophyll increases throughout eddy lifetimes. Overall, our results challenge the assumption that Eulerian-identified mesoscale eddy boundaries are coherent and suggest that Lagrangian trapping, combined with regional and seasonal factors, shapes the chlorophyll concentrations of subtropical mesoscale eddies.

Climate-driven projections of cyanobacterial harmful algal bloom expansion in coastal waters

2025-06-25

Malik Al-Wardy , Erfan Zarei , Mohammad Reza Nikoo +1 more | The Science of The Total Environment

Long-term Responses of Benthic Diatom Assemblages to Phosphorus Fertilization in an Arctic Stream

2025-06-24

Lars A. Carlson , Mark B. Edlund , William B. Bowden | Freshwater Science

Addressing the aggregation phenomenon in a model AIE coupled ESIPT active probe: correlating aggregation states to their photodynamics

2025-06-24

Arghyadeep Bhattacharyya , Manoj Das | ChemPlusChem

In the current work, we report a comprehensive study on the spectrodynamic behaviour of 4-dimethylamino-2'-hydroxychalcone (DMHC) in crystalline state and in aggregated state in water (pH 7.0) by the aid … In the current work, we report a comprehensive study on the spectrodynamic behaviour of 4-dimethylamino-2'-hydroxychalcone (DMHC) in crystalline state and in aggregated state in water (pH 7.0) by the aid of steady-state and time-resolved spectroscopy. Our studies revealed that the ESIPT process is slow in the crystalline state (τESIPT=3.0 ns) with the emission dominated by ESIPT from 600 nm onwards, with little contribution (550-570 nm) from the local emission with lower lifetime of emission (τlocal-emission=140 ps). Spectrodynamic studies in the aqueous solution of DMHC shows the emission lifetime values are both lowered in the aqueous solution with emission from aggregates and the solvated DMHC molecules in aqueous solution (τlocal-emission =90 ps and τESIPT=35 ps and 1.4 ns). We concluded that DMHC shows ESIPT emission from the J-aggregated forms, whereas in aqueous solutions, the ESIPT emission in water occurs from the H-aggregates. The current report holds importance owing to the detailed spectrodynamic dissection of the aggregation phenomenon of a model AIE coupled ESIPT active molecule and delineates how the spectrodynamic behaviour of each aggregated form differs in terms of the nature of the aggregates formed (J- and H-aggregates), which shall aid in the understanding and construction of tailor-made AIE active molecules.

Spaceborne active-passive optical fusion bathymetry in coastal waters: the implications of ICESat-2 photons

2025-06-23

Jinchen He , Shuhang Zhang , Tinghui Zhang +1 more | International Journal of Digital Earth

Chlorophyll-a in the Chesapeake Bay Estimated by Extra-Trees Machine Learning Modeling

2025-06-23

Nikolay P. Nezlin , SeungHyun Son , Salem Ibrahim Salem +1 more | Remote Sensing

Monitoring chlorophyll-a concentration (Chl-a) is essential for assessing aquatic ecosystem health, yet its retrieval using remote sensing remains challenging in turbid coastal waters because of the intricate optical characteristics of … Monitoring chlorophyll-a concentration (Chl-a) is essential for assessing aquatic ecosystem health, yet its retrieval using remote sensing remains challenging in turbid coastal waters because of the intricate optical characteristics of these environments. Elevated levels of colored (chromophoric) dissolved organic matter (CDOM) and suspended sediments (aka total suspended solids, TSS) interfere with satellite-based Chl-a estimates, necessitating alternative approaches. One potential solution is machine learning, indirectly including non-Chl-a signals into the models. In this research, we develop machine learning models to predict Chl-a concentrations in the Chesapeake Bay, one of the largest estuaries on North America’s East Coast. Our approach leverages the Extra-Trees (ET) algorithm, a tree-based ensemble method that offers predictive accuracy comparable to that of other ensemble models, while significantly improving computational efficiency. Using the entire ocean color datasets acquired by the satellite sensors MODIS-Aqua (>20 years) and VIIRS-SNPP (>10 years), we generated long-term Chl-a estimates covering the entire Chesapeake Bay area. The models achieve a multiplicative absolute error of approximately 1.40, demonstrating reliable performance. The predicted spatiotemporal Chl-a patterns align with known ecological processes in the Chesapeake Bay, particularly those influenced by riverine inputs and seasonal variability. This research emphasizes the potential of machine learning to enhance satellite-based water quality monitoring in optically complex coastal waters, providing valuable insights for ecosystem management and conservation.

Role of ox-bow lakes towards carbon sink and resilience of warming effect

2025-06-23

Ripan Ghosh , Manashi Haldar , Sandipta Debanshi +1 more | Spatial Information Research

Three-dimensional distribution of nutrients and phytoplankton biomass in a semi-enclosed region of the Gulf of California during different ENSO phases

2025-06-23

Carlos Mauricio Torres-Martínez , María Adela Monreal‐Gómez , Erik Coria‐Monter +3 more | Botanica Marina

Abstract This study examined the three-dimensional distribution of nutrients and phytoplankton biomass, as measured by chlorophyll- a (Chl- a ) concentration, in the Bay of La Paz, Gulf of California, … Abstract This study examined the three-dimensional distribution of nutrients and phytoplankton biomass, as measured by chlorophyll- a (Chl- a ) concentration, in the Bay of La Paz, Gulf of California, during different phases of the El Niño Southern Oscillation (ENSO). Two multidisciplinary research cruises were conducted in November 2014 and November 2016, corresponding to El Niño and La Niña conditions, respectively. A CTD Rosette System was used to gather high-resolution hydrographic data and collect seawater samples at different depths for chemical analyses (nutrients and Chl- a ). Meteorological data were obtained from a local weather station. The results indicated significant differences between the two study periods. The composition of water masses varied during both events. Notable contrasts were observed in nutrient concentrations, especially at 30 m depth; the maximum concentration of Soluble Reactive Si was 152.46 µM in 2014, compared to only 8.48 µM in 2016. Chl- a levels also showed variations with depth and between the two cruises, being significantly higher in 2014 (7.60 mg m −3 ) than in 2016 (1.70 mg m −3 ). This study enhances the understanding of the dynamics of ENSO events, given that the collections were conducted during both an El Niño and a La Niña phase. However, it is worth noting that the La Niña was influenced by an extreme El Niño event occurring in the same year, which likely masked the effects of the subsequent La Niña.

Nuisance alga reduces lake partial pressure of carbon dioxide and carbon flux to the atmosphere in boreal lakes

2025-06-23

Karla Münzner , Eva S. Lindström , Thomas Rohrlack | Limnology and Oceanography

Abstract Boreal lakes are generally seen as sources of carbon dioxide (CO 2 ) to the atmosphere, even though a part of them are periodically undersaturated with CO 2 and … Abstract Boreal lakes are generally seen as sources of carbon dioxide (CO 2 ) to the atmosphere, even though a part of them are periodically undersaturated with CO 2 and have the potential to be net‐autotrophic. This undersaturation is the result of photosynthetic activity by phytoplankton, especially flagellated species like Gonyostomum semen , which form high‐biomass blooms in brown water lakes. We hypothesized that CO 2 reduction by G. semen is common across boreal lakes, and that those reductions vary with dissolved organic carbon (DOC) concentrations across lakes. In our field study, we explored how G. semen abundance affected the partial pressure of CO 2 ( p CO 2 ) in the water column and the estimated carbon flux to the atmosphere in four lakes in Sweden and Norway in summer 2021. We found that lake p CO 2 and carbon flux to the atmosphere decreased with increasing G. semen abundances, though all lakes still emitted CO 2 to the atmosphere. High DOC concentrations acted as a limiting factor for G. semen growth, indicating that G. semen 's potential to reduce p CO 2 and carbon flux to the atmosphere weakens with increasing DOC concentrations. Still, G. semen 's impact on p CO 2 and carbon flux to the atmosphere is relevant in a wider spatial context, because G. semen and other motile flagellated species are expected to increase in range and bloom frequency in boreal lakes. Thus, we propose that CO 2 fixation via photosynthesis is an underestimated factor in controlling CO 2 dynamics in boreal lakes, and that it should be included in large‐scale CO 2 budget calculations.

Distribution pattern and climate response of marine biological carbon pump

2025-06-23

Minhan Dai | Science China Earth Sciences

An Overview of the Design and Realized Performance of Ocean Colour Monitor (OCM-3) Payload On-Board the Oceansat-3 (EOS-06) Mission

2025-06-22

Vishnukumar D. Patel , Manoj Kumar , Pradeep Soni +7 more | Journal of the Indian Society of Remote Sensing

Real‐time quality assessment for Biogeochemical Argo radiometric profiles

2025-06-21

Giovanni La Forgia , Emanuele Organelli | Limnology and Oceanography Methods

Abstract An ever‐increasing number of Biogeochemical (BGC) Argo floats equipped with radiometric sensors have been deployed across the World Ocean. To date, more than 50,000 vertical profiles from 0 to … Abstract An ever‐increasing number of Biogeochemical (BGC) Argo floats equipped with radiometric sensors have been deployed across the World Ocean. To date, more than 50,000 vertical profiles from 0 to at least 250 dbar of photosynthetically available radiation and downwelling irradiance at 3, narrow wavelengths have been acquired. For scientific use of radiometric data, corrections for temperature effects and sensor drift are necessary. However, these adjustments are only partially provided in delayed mode, almost a year after acquisition and distribution. This makes automatic, real‐time quality control (RT‐QC) data processing of BGC‐Argo radiometry critically important. Nevertheless, only a range test has been applied to real‐time radiometric profiles, so far. By leveraging the full dataset of multispectral radiometric measurements from various BGC‐Argo platform types, we have developed a robust RT‐QC protocol for processing radiometric data and profiles, aimed at identifying potential sensor malfunctions, particularly those related to temperature effects. Data quality flags are attributed to each data point by considering the expected shape of the radiometric profile associated with the solar elevation during data acquisition. For both daytime and nighttime profiles, the new protocols automatically unveil data potentially dominated by temperature effects. The proposed methodology remains resilient to sensor drift and unstable sea conditions, and it also holds promise for adaptation to data from cutting‐edge hyper‐spectral sensors mounted on BGC‐Argo floats.

Complexing fluorescent dissolved organic matter (FDOM) along the Parnaíba River Delta, Northeast Brazil

2025-06-20

Thays Thayanne Luz Santos , Stéphane Mounier , Rozane Valente Marins | Chemosphere

High bioavailability of soil-derived dissolved organic carbon in the high Arctic fjord (Kongsfjorden, Svalbard Archipelago)

2025-06-20

Katarzyna Koziorowska‐Makuch , Przemysław Makuch , Fernando Aguado Gonzalo +1 more | Frontiers in Earth Science

To assess the bioavailability in the soil-derived dissolved organic carbon (DOC), and to estimate potential remineralization kinetics for different bioavailable fractions of DOC, the long-lasting (180 days) incubation experiments of … To assess the bioavailability in the soil-derived dissolved organic carbon (DOC), and to estimate potential remineralization kinetics for different bioavailable fractions of DOC, the long-lasting (180 days) incubation experiments of soil leachates were performed. The soil material was collected from the catchments of two contrasting rivers - Bayelva and Londonelva in Kongsfjorden (Arctic fjord in West Spitsbergen, Svalbard Archipelago). Both sampling sites were located close to the shore, where coastal erosion and tides directly affect the surface soil layer. The results indicate that the soil leachates contain a lot of DOC, which is highly bioavailable, even 68%–87% can be susceptible to biodegradation. The obtained decay curves allowed us to distinguish three DOC fractions: labile, semi-labile, and refractory. The contribution of the most labile DOC fraction is small and ranges from 13% in the Bayelva region to 25% in the Londonelva catchment but it remineralizes quickly once transported to the fjord, while the semi-labile DOC, whose half-life is measured in months, is much more abundant (74% and 43% of total DOC, respectively). These differences in the contribution of particular DOC fractions between stations can result from the different composition and provenance of organic matter. Nevertheless, this high lability of terrestrial DOC indicates that its supply to the fjords water column has the potential to play an essential role in sustaining the bacterial loop in the fjord and, through CO 2 release, in amplifying ocean acidification in the coastal zone.

Analytical Workflow for Tracking Aquatic Biomass Responses to Sea Surface Temperature Changes

2025-06-20

Teodoro Semeraro , Jessica Titocci , Lorenzo Liberatore +5 more | Environments

Ocean ecosystem services provisioning is driven by phytoplankton, which form the base of the ocean food chain in aquatic ecosystems and play a critical role as the Earth‘s carbon sink. … Ocean ecosystem services provisioning is driven by phytoplankton, which form the base of the ocean food chain in aquatic ecosystems and play a critical role as the Earth‘s carbon sink. Phytoplankton is highly sensitive to temperature, making it vulnerable to the effects of temperature variations. The aim of this research was to develop and test a workflow analysis to monitor the impact of sea surface temperature (SST) on phytoplankton biomass and primary production by combining field and remote sensing data of Chl-a and net primary production (NPP) (as proxies of phytoplankton biomass). The tropical zone was used as a case study to test the procedure. Firstly, machine learning algorithms were applied to the field data of SST, Chl-a and NPP, showing that the Random Forest was the most effective in capturing the dataset’s patterns. Secondly, the Random Forest algorithm was applied to MODIS SST images to build Chl-a and NPP time series. The time series analysis showed a significant increase in SST which corresponded to a significant negative trend in Chl-a concentrations and NPP variation. The recurrence plot of the time series revealed significant disruptions in Chl-a and NPP evolutions, potentially linked to El Niño–Southern Oscillation (ENSO) events. Therefore, the analysis can help to highlight the effects of temperature variation on Chl-a and NPP, such as the long-term evolution of the trend and short perturbation events. The methodology, starting from local studies, can support broader spatial–temporal-scale studies and provide insights into future scenarios.

Effects of Nutrients on the Phytoplankton Community Structure in Zhanjiang Bay

2025-06-20

Zhen Zeng , Fajin Chen , Qibin Lao +1 more | Journal of Marine Science and Engineering

With rapid economic and social development, eutrophication in coastal areas is currently one of the most severe environmental problems worldwide. However, our understanding of the response of the phytoplankton community … With rapid economic and social development, eutrophication in coastal areas is currently one of the most severe environmental problems worldwide. However, our understanding of the response of the phytoplankton community structure to the intensification of coastal eutrophication is still relatively limited. Here, seasonal phytoplankton, environmental factors, and nutrients were investigated in 2009 and 2019 in Zhanjiang Bay, where eutrophication has intensified in recent years, to analyze the variation in nutrient structure and its impact on the phytoplankton community. The results revealed that the DIP and DSI concentrations in 2019 were higher than those in 2009. However, dissolved inorganic nitrogen (DIN) has decreased substantially over the past several decades, which is due mainly to the decrease in anthropogenic nitrogen emissions, the substantial increase in the intrusion of high-salinity seawater, and the high-phosphorus wastewater discharged from urban industries. This resulted in a decrease in phytoplankton cell abundance, phytoplankton composition, and species diversity (H′) in 2019 compared with 2009. In addition, the superior N transport, storage, and response strategy to a low N supply of diatoms, especially Skeletonema and Chaetoceros, might benefit the growth of diatoms under low DIN conditions. The lower DIN/DIP ratio in 2019 favored the growth of diatoms, especially Skeletonema and Chaetoceros, leading diatoms to dominate the phytoplankton assemblage. This study demonstrates how changes in nutrient structure alter the community structure of phytoplankton, providing new insights into deepening our understanding of eco-environmental evolution.

Chromophoric dissolved organic matter in the Athabasca Oil Sands Region, Canada, and its association to lake acid sensitivity

2025-06-20

Dane Blanchard , Mark Gordon , Huy Dang +5 more | The Science of The Total Environment

Chromophoric dissolved organic matter (CDOM) represents a broad class of organic compounds that absorb visible and ultraviolet light and can influence numerous aquatic system functions. The Athabasca Oil Sands Region … Chromophoric dissolved organic matter (CDOM) represents a broad class of organic compounds that absorb visible and ultraviolet light and can influence numerous aquatic system functions. The Athabasca Oil Sands Region (AOSR) in Alberta, Canada, contains an abundance of boreal lakes suspected to possess high quantities of CDOM. However, CDOM within these lakes has never been investigated; moreover, the potential impact of shifting acid-base chemistry (possibly linked to industrial acid deposition) is largely unknown. This study characterized CDOM within fifty acid sensitive lakes in the AOSR using fluorescence spectroscopy and parallel factor analysis (PARAFAC) to ultimately identify the sources and processes acting on organic matter, and to explore the potential link between CDOM and lake water acid-base chemistry. Four fluorescent components including two humic-like (C1, C2) and two amino acid-like (C3, C4) compounds were identified through PARAFAC. Multivariate analysis indicated that C1 and C2 likely originated from surrounding peatlands and were associated with lake water colour and dissolved organic carbon, respectively (Spearman correlation coefficient [RS] > 0.7). Strong associations with metals and variables reflective of irradiation (RS > 0.65) suggested that the comparatively aromatic C1 formed CDOM-metal complexes that were vulnerable to photodegradation. Both C3 and C4 remained largely unresolved due to limited associations with the available data; however, C3 spectra were similar to anthropogenic fluorescent species reported in the literature. Weak associations were observed between CDOM variables and pH and alkalinity, providing limited evidence to suggest that CDOM and acid-base chemistry shared a direct relationship within AOSR lakes.

Greener green and bluer blue: Ocean poleward greening over the past two decades

2025-06-19

Haipeng Zhao , Manfredi Manizza , M. Susan Lozier +1 more | Science

Although the global greening associated with climate change is well documented on land, similar trends in the ocean have not been thoroughly identified. Using satellite observations of ocean chlorophyll a … Although the global greening associated with climate change is well documented on land, similar trends in the ocean have not been thoroughly identified. Using satellite observations of ocean chlorophyll a (Chl) concentration, we show that the surface ocean experienced a poleward greening from 2003 to 2022. Contemporaneously, the subtropical regions of the Northern Hemisphere experienced a decrease in Chl. As such, the latitudinal disparity in Chl, as documented by an inequality index, has been increasing over the past two decades, particularly in the Northern Hemisphere. Rising water temperatures may primarily influence the Chl trends. The increasing Chl inequality-marked by "greener green and bluer blue" waters-has the potential to cascade to higher trophic levels, with implications for the fisheries and economies of coastal nations.

A novel ratio algorithm for estimation of pCO2 fields in the Northern Indian ocean region using satellite oceanographic data

2025-06-19

Ibrahim Shaik , Kande Vamsi Krishna , P. V. Nagamani | Measurement

PhA-MOE: Enhancing Hyperspectral Retrievals for Phytoplankton Absorption Using Mixture-of-Experts

2025-06-19

Weiwei Wang , Bingqing Liu , Song Gao +4 more | Remote Sensing

As a key component of inherent optical properties (IOPs) in ocean color remote sensing, phytoplankton absorption coefficient (aphy), especially in hyperspectral, greatly enhances our understanding of phytoplankton community composition (PCC). … As a key component of inherent optical properties (IOPs) in ocean color remote sensing, phytoplankton absorption coefficient (aphy), especially in hyperspectral, greatly enhances our understanding of phytoplankton community composition (PCC). The recent launches of NASA’s hyperspectral missions, such as EMIT and PACE, have generated an urgent need for hyperspectral algorithms for studying phytoplankton. Retrieving aphy from ocean color remote sensing in coastal waters has been extremely challenging due to complex optical properties. Traditional methods often fail under these circumstances, while improved machine-learning approaches are hindered by data scarcity, heterogeneity, and noise from data collection. In response, this study introduces a novel machine learning framework for hyperspectral retrievals of aphy based on the mixture-of-experts (MOEs), named PhA-MOE. Various preprocessing methods for hyperspectral training data are explored, with the combination of robust and logarithmic scalers identified as optimal. The proposed PhA-MOE for aphy prediction is tailored to both past and current hyperspectral missions, including EMIT and PACE. Extensive experiments reveal the importance of data preprocessing and improved performance of PhA-MOE in estimating aphy as well as in handling data heterogeneity. Notably, this study marks the first application of a machine learning–based MOE model to real PACE-OCI hyperspectral imagery, validated using match-up field data. This application enables the exploration of spatiotemporal variations in aphy within an optically complex estuarine environment.

High‐resolution dataset of stable carbon isotope of dissolved inorganic carbon (<scp>δ13C</scp>‐<scp>DIC</scp>) from the North Atlantic Ocean

2025-06-19

Zhentao Sun , Hui Gao , Bo Dong +3 more | Limnology and Oceanography Letters

Abstract The stable isotope ratio of dissolved inorganic carbon ( δ 13 C‐DIC) is a valuable tracer for investigating carbon cycling in aquatic environments. However, its potential remains underutilized due … Abstract The stable isotope ratio of dissolved inorganic carbon ( δ 13 C‐DIC) is a valuable tracer for investigating carbon cycling in aquatic environments. However, its potential remains underutilized due to limited data availability. Fewer than 15% of cruise samples are analyzed for δ 13 C‐DIC, as isotope analysis using isotope ratio mass spectrometry is labor‐intensive and restricted to onshore laboratories. We present over 3500 δ 13 C‐DIC measurements from the 2023 Global Ocean Ship‐based Hydrographic Investigations Program A16N cruise in the North Atlantic. Notably, three‐quarters of these measurements were conducted onboard using a CO 2 extraction device coupled with cavity ring‐down spectroscopy, a more efficient and cost‐effective method. This extensive dataset provides δ 13 C‐DIC values with spatial resolution comparable to other ocean carbonate chemistry and biogeochemical parameters. This dataset supports improved quantification of anthropogenic CO 2 uptake and storage, and may facilitate the development of algorithms to estimate δ 13 C‐DIC in under sampled regions.

Prediction of red tide outbreaks in inter‐connected coastal environments using time‐series hyperspectral data and transformer‐based graph convolution network

2025-06-19

Ming Xie , Ying Li , Zhichen Liu +1 more | Limnology and Oceanography Methods

Abstract The accurate predictions on the red tide outbreaks in coastal regions can reduce their negative impacts on the marine environment and human life. Currently, the red tide prediction is … Abstract The accurate predictions on the red tide outbreaks in coastal regions can reduce their negative impacts on the marine environment and human life. Currently, the red tide prediction is generally accomplished by monitoring some related key factors, which are difficult to obtain on large spatial scales. Combining a transformer encoder with a graph convolution network (GCN), this study proposed an integrated model for red tide prediction that makes comprehensive use of the time‐series hyperspectral data obtained through remote sensing methods. The topological graphs are constructed based on the multi‐band spectral indices in the interconnected observation points, which are further analyzed using a GCN to obtain the topological features. After that, the temporal features of such topological graphs are extracted based on a transformer encoder, which are used for red tide prediction. The results show that the proposed model achieves reasonable predictions using the input period of 3 d before the date of red tide outbreaks, and the accuracy can reach about 92% with the input period of 5 d. The ablation experiments indicate that both the topological features obtained by the GCN and the temporal features obtained by the transformer encoder play significant roles in the prediction task of red tide outbreaks. The proposed model achieves the red tide prediction in interconnected coastal environments through the fusion of spectral‐, topological‐, and temporal features, and is expected to provide early alarms on red tide outbreaks for maritime and oceanic agencies.

Poleward greening of the global oceans

2025-06-19

Raphael M. Kudela | PubMed

Shifts in phytoplankton populations could affect marine ecology and fisheries around the world. Shifts in phytoplankton populations could affect marine ecology and fisheries around the world.

Ảnh hưởng của nhiệt độ và vi tảo làm thức ăn đến sinh trưởng, sinh sản của loài Copepoda pseudodiaptomus annandalei

2025-06-18

Đoàn Xuân Nam , Trang Trần Thị Lê , Trần Văn Dũng +3 more | Tạp chí Khoa học - Công nghệ Thủy Sản Trường Đại học Nha Trang

Nghiên cứu này nhằm đánh giá tác động của ba loài vi tảo khác nhau (Chaetoceros muelleri, Isochrysis galbana, Tetraselmis chuii) ở hai mức nhiệt độ (30°C và 34°C) đến … Nghiên cứu này nhằm đánh giá tác động của ba loài vi tảo khác nhau (Chaetoceros muelleri, Isochrysis galbana, Tetraselmis chuii) ở hai mức nhiệt độ (30°C và 34°C) đến tăng trưởng, tỷ lệ sống, khả năng sinh sản, tỷ lệ trứng nở và tổng số ấu trùng của loài Pseudodiaptomus annandalei. Trong thí nghiệm đầu tiên, ấu trùng mới nở được nuôi trong bình thủy tinh 5 lít nước với mật độ ban đầu 500 con/L, sử dụng ba loài vi tảo khác nhau làm thức ăn ở hai mức nhiệt độ. Mỗi nghiệm thức được lặp lại ba lần. Hằng ngày, mỗi nghiệm thực được thu 300 ml nước mẫu để xác định giai đoạn phát triển và đo tốc độ tăng trưởng chiều dài của loài P. annandalei ở các giai đoạn khác nhau. Thí nghiệm thứ hai được thực hiện với 500 ấu trùng mới nở trong bình thủy tinh 1 lít nước, duy trì các điều kiện nhiệt độ và nguồn thức ăn giống thí nghiệm trước. Các thông số được theo dõi gồm tỷ lệ sống, khả năng sinh sản, tỷ lệ trứng nở và số lượng ấu trùng trên mỗi con cái. Mười con đực trưởng thành và mười con cái trưởng thành được bố trí trong bình thủy tinh 1 lít nước, sử dụng ba loài vi tảo khác nhau làm thức ăn, mỗi nghiệm thức được lặp lại năm lần. Hằng ngày, số lượng ấu trùng được ghi nhận trong 10 ngày để tính tổng số ấu trùng trên mỗi con cái. Kết quả cho thấy, quần thể P. annandalei phát triển nhanh hơn và có các chỉ tiêu sinh sản cao hơn khi nuôi ở 30°C so với 34°C. Trong ba loài vi tảo khác nhau thử nghiệm, việc sử dụng I. galbana hoặc C. muelleri làm thức ăn giúp P. annandalei có tốc độ tăng trưởng chiều dài tốt hơn so với khi ăn T. chuii. Do đó, sự kết hợp giữa nhiệt độ 30°C và hai loài vi tảo I. galbana hoặc C. muelleri được xem là điều kiện tối ưu để nuôi sinh khối loài Copepoda này. Từ khóa: Vi tảo, Pseudodiaptomus annandalei, phát triển, sinh sản, tỷ lệ sống, tỷ lệ nở. ABSTRACT This study aimed to evaluate the effects of three different microalgae species (Chaetoceros muelleri, Isochrysis galbana, Tetraselmis chuii) under two temperature conditions (30°C and 34°C) on the growth, survival rate, reproductive capacity, hatching rate, and total number of larvae of Pseudodiaptomus annandalei. In the first experiment, newly hatched larvae were cultured in 5-liter glass containers at an initial density of 500 individuals/L, using three different microalgae species as feed at two temperature levels. Each treatment was replicated three times. Daily, 300 ml of water was sampled to determine developmental stages and measure the growth rate of adults based on body length. The second experiment was conducted with 500 newly hatched larvae in 1-liter glass containers, maintaining the same temperature conditions and different microalgae species as in the previous experiment. The monitored parameters included survival rate, reproductive capacity, hatching rate, and the number of larvae per female. Ten adult males and ten adult females were placed in 1-liter glass containers and fed one of the three different microalgae species. Each treatment was replicated five times. The number of larvae was recorded daily over ten days to determine the total number of larvae per female. The results showed that the P. annandalei population grew faster and exhibited higher reproductive indicators at 30°C than at 34°C. Among the three tested different microalgae species, feeding P. annandalei with I. galbana or C. muelleri resulted in better growth in body length than feeding with T. chuii. Therefore, the combination of 30°C and the microalgae species I. galbana or C. muelleri is considered the optimal condition for the mass culture of this copepod species. Keywords: Microalgae, Pseudodiaptomus annandalei, growth, reproduction, survival, hatching.

Long-term changes in dissolved organic matter quality are unrelated to ecosystem recovery from acidification in the Adirondack region (New York, USA)

2025-06-18

Colin M. Beier , Suvarna Badri , Nicholas A. LoRusso +4 more | Biogeochemistry

Amazonian floodplain lakes’ carbon-based structure and interactions of plankton communities are constrained by hydrology

2025-06-18

Luana Morais da Rosa , Luciana de Souza Cardoso , Luciane Oliveira Crossetti +7 more | Aquatic Sciences

AlgAlert: A two-level approach for algae bloom prediction using deep learning

2025-06-18

Areej Alsini , Amina Saeed , Dawood Amin | Ecological Informatics

Environmental Controls on Chlorophyll-a and Dissolved Oxygen Variability in Contrasting Basins of the Northern Indian Ocean

2025-06-18

Kunal Chakraborty , Linta Rose , B. Rohith +2 more | Marine Environmental Research

The distribution of nutrients and chlorophyll-a in the temperate coast of China: implications for marine ecological risks in the context of global warming

2025-06-18

Dapeng Bai , Hongxian Chu , Yongcai Feng +2 more | Frontiers in Marine Science

Introduction Nutrients directly regulate the level of primary productivity, which is crucial for the stability of marine ecosystems. However, under the context of human activities leading to global warming, factors … Introduction Nutrients directly regulate the level of primary productivity, which is crucial for the stability of marine ecosystems. However, under the context of human activities leading to global warming, factors influencing alterations in coastal nutrient dynamics remain a mystery. Methods A study was conducted to investigate the spatial distribution characteristics of nutrients and chlorophyll-a at 55 stations in the Bohai Bay region during the autumn of 2021. Results The dominant factor influencing coastal zone ecology in the surveyed area was identified as temperature. Multiple factors (e.g., riverine input, sediment release, atmospheric deposition, and hydrodynamics) collectively impacted nutrient dynamics. The temperature along the north-south transect was consistent, with a distinct demarcation at 118.68°E (19°C), where the temperature gradient exhibited a pronounced east-high, west-low pattern. The temperature difference between the surface and bottom waters was minimal. In the high-temperature eastern region, the redox potential was high (above 100 mV), and very few locations had low dissolved oxygen levels, indicating active aerobic microbial activity. This led to the decomposition of substantial organic matter, resulting in elevated ammonia-nitrogen concentrations, and low pH levels. The presence of ammonia-nitrogen promoted the growth and reproduction of planktonic organisms. Discussion Therefore, we are concerned that global climate warming may trigger changes, and even worsen, marine ecological environments in temperate coastal regions, necessitating heightened attention from researchers.

AlgicideDB: a comprehensive database enhanced by large language models for algicide management and discovery

2025-06-18

Zhangqi Zuo , Peng Ji , Chaowei Zhang +4 more | Frontiers in Microbiology

Harmful algal blooms (HABs) are increasing in frequency and intensity worldwide, posing significant threats to aquatic ecosystems, fisheries, and human health. While chemical algicides are widely used for HABs control … Harmful algal blooms (HABs) are increasing in frequency and intensity worldwide, posing significant threats to aquatic ecosystems, fisheries, and human health. While chemical algicides are widely used for HABs control due to their rapid efficacy, the lack of systematic data integration and concerns over environmental toxicity limit their broader application. To address these challenges, we developed AlgicideDB, a manually curated database containing 1,672 algicidal records on 542 algicides targeting 110 algal species. Using this database, we analyzed the physicochemical properties of algicides and proposed an algicide-likeness scoring function to facilitate the exploration of compounds with antialgal properties. Additionally, we evaluated the acute toxicity of algicidal compounds to non-target aquatic organisms of different trophic levels to assess their ecological risks. The platform also incorporates a large language model (LLM) enhanced by retrieval-augmented generation (RAG) to address HAB-related queries, supporting decision-making and facilitating knowledge dissemination. AlgicideDB, available at http://algicidedb.ocean-meta.com/#/ , serves as an innovative and comprehensive platform to explore algicidal compounds and facilitate the development of safe and effective HAB control strategies.

Distribution patterns of nitrous oxide during the summer season in the Prydz Bay, eastern Southern Ocean

2025-06-18

Jiexia Zhang , Damian L. Arévalo‐Martínez , Liyang Zhan +6 more | Acta Oceanologica Sinica

A continual-learning-based multilayer perceptron for improved reconstruction of three-dimensional nitrate concentrations

2025-06-18

Xiang Yu , Huadong Guo , Jiahua Zhang +6 more | Earth system science data

Abstract. Nitrate plays a crucial role in marine ecosystems, as it influences primary productivity. Despite its ecological significance, accurately mapping its three-dimensional (3D) concentration on a large scale remains a … Abstract. Nitrate plays a crucial role in marine ecosystems, as it influences primary productivity. Despite its ecological significance, accurately mapping its three-dimensional (3D) concentration on a large scale remains a considerable challenge due to the inherent limitations of existing methodologies. To address this issue, this study proposes a continual-learning-based multilayer perceptron (MLP) model to reconstruct the 3D ocean nitrate concentrations above 2000 m depth over the pan-European coast. The continual-learning strategy enhances the model generalization by integrating knowledge from Copernicus Marine Environmental Monitoring Service (CMEMS) nitrate data, effectively overcoming the spatial limitations of Biogeochemical Argo (BGC-Argo) observations in comprehensive nitrate characterization. The proposed approach integrates the advantages of extensive spatial remote sensing observations, the precision of BGC-Argo measurements, and the broad knowledge from simulated nitrate datasets, exploiting the capacity of neural networks to model their nonlinear relationships between multisource sea surface environmental variables and subsurface nitrates. The model achieves excellent performance in profile cross-validation (R2=0.98, RMSE = 0.592 µmol kg−1) and maintains robustness across diverse 3D validation scenarios, suggesting its effectiveness in filling observational gaps and reconstructing the 3D nitrate field. Then, the spatiotemporal distribution of the reconstructed 3D nitrate field from 2010 to 2023 reveals a spatial distribution pattern, an interannual upward trend, and the degree of consistency in vertical variation. The contributions of all 22 input features to the model's estimation were quantified using Shapley additive explanation values. This study reveals the potential of the proposed approach to overcome observational limitations and provide further insights into the 3D ocean condition. The reconstructed 3D nitrate dataset is freely available at https://doi.org/10.5281/zenodo.14010813 (Yu et al., 2024).

Synergistic Use of Scatterometer and Ocean Colour Monitor Onboard EOS-06 Satellite for Various Oceanographic Applications

2025-06-17

Neeraj Agarwal , M. Jishad , Jai Kumar +7 more | Journal of the Indian Society of Remote Sensing

A High‐Precision Analytical Technique for Dissolved N2 Isotopes in Aquatic Systems: Biogeochemical Applications and Determination of Solubility Equilibrium Isotope Effects

2025-06-17

Katelyn McPaul , Scott D. Wankel , Alan Seltzer | Rapid Communications in Mass Spectrometry

ABSTRACT Rationale The isotopic composition of dissolved dinitrogen gas (δ 15 N‐N 2 ) in water can offer a powerful constraint on the sources and pathways of nitrogen cycling in … ABSTRACT Rationale The isotopic composition of dissolved dinitrogen gas (δ 15 N‐N 2 ) in water can offer a powerful constraint on the sources and pathways of nitrogen cycling in aquatic systems. However, because of the large presence of atmosphere‐derived dissolved N 2 in these systems, high‐precision (on the order of 0.001‰) measurements of N 2 isotopes paired with inert gas measurements are required to disentangle atmospheric and biogeochemical signals. Additionally, the solubility equilibrium isotope fractionation of N 2 and its temperature and salinity dependence are underconstrained at this level of precision. Methods We introduce a new technique for sample collection, processing, and dynamic dual‐inlet mass spectrometry allowing for high‐precision measurement of δ 15 N‐N 2 and δ(N 2 /Ar) with simultaneous measurement of δ( 40 Ar/ 36 Ar) and δ(Kr/N 2 ) in water. We evaluate the reproducibility of this technique and employ it to redetermine the solubility equilibrium isotope effects for dissolved N 2 across a range of temperatures and salinities. Results Our technique achieves measurement reproducibility (1σ) for δ 15 N‐N 2 (0.006‰) and δ(N 2 /Ar) (0.41‰) suitable for tracing biogeochemical nitrogen cycling in aquatic environments. Through a series of air–water equilibration experiments, we find a N 2 solubility equilibrium isotope effect (ε = α/1000 − 1, where α = ( 29 N 2 / 28 N 2 ) dissolved /( 29 N 2 / 28 N 2 ) gas ) in water of ε(‰) = 0.753 − 0.004• T where T is the temperature (°C), with uncertainties on the order of 0.001‰ over the temperature range of ~2°C–23°C and salinity range of ~0–30 psu. We find no apparent dependence of ε on salinity. Conclusions Our new method allows for high‐precision measurements of the isotopic composition of dissolved N 2 and Ar, and dissolved N 2 /Ar and Kr/N 2 ratios, within the same sample. Pairing measurements of N 2 with inert gases facilitates the quantification of excess N 2 from biogeochemical sources and its isotopic composition. This method allows for a wide range of applications in marine, coastal, and freshwater environments to characterize and quantitatively constrain potential nitrogen‐cycling sources and pathways and to differentiate between physical and biological isotope signals in these systems.

Relative Contributions of Environmental Variables and Zooplankton to Microphytoplankton Abundance, Diversity, and Community Assembly in a Shallow Coastal Area

2025-06-17

Yuan Ma , L. C. Tan , Yu Ma +6 more | Thalassas An International Journal of Marine Sciences

Cascading river damming amplifies photosynthetic organic matter production and DOC transport

2025-06-16

Deliang He , Wanfa Wang , Yuanbi Yi +6 more | Water Research

River inflow and seawater intrusion shape distinct phytoplankton communities in Jinghai Bay, a coastal bay of the Yellow Sea

2025-06-16

J. Sui , Dong-Sheng Ding , Yan Zhang +4 more | Marine Environmental Research

Silicon's role in enhancing cadmium substitution for zinc in Thalassiosira weissflogii: implications for heavy metal detoxification in marine environments

2025-06-16

Kai Jiao , Zhuyin Tong , Wupeng Xiao +3 more | Marine Pollution Bulletin

Land-use management and climate change can enhance the autotrophic capacity and reduce the CO2 emissions of karst aquatic ecosystems

2025-06-15

Liangxing Shi , Yuhao Zhao , Sibo Zeng +7 more | Water Research

Spectral characteristics of organic matter from algae and its complexation with copper: a case study of Ulva prolifera

2025-06-15

Tianzi Zhang , Limin Zhou , Yuyuan Wang +3 more | Marine Environmental Research

Iron (oxyhydr)oxide-driven chemodiversity in algal-derived dissolved organic matter: Mechanistic coupling of electron transfer and radical-induced bond cleavage under light and dark conditions

2025-06-15

Zelong Yan , Minhan Pi , Tingting You +3 more | Water Research X

Annual Cycle, Abundance and Species Composition of Appendicularia in the Bay of Boka Kotorska (Southern Adriatic, NE Mediterranean)

2025-06-14

Vera Vukanić , Miodrag Malović , Darko Jevremović | Acta Zoologica Bulgarica

Appendicularians often constitute a significant portion of mesozooplankton tunicates in marine ecosystems. This study examines the spatial variations in the annual cycles of functional groups of planktonic Appendicularia in response … Appendicularians often constitute a significant portion of mesozooplankton tunicates in marine ecosystems. This study examines the spatial variations in the annual cycles of functional groups of planktonic Appendicularia in response to environmental changes within the Bay of Boka Kotorska. Monthly sampling over the course of a year during 2008/09 was conducted at seven stations, each characterised by distinct hydrographic conditions. Appendicularians exhibited spatial variations in their annual cycles across the seven stations. Based on these findings, it is proposed that the observed spatial variations in the annual cycles of functional groups of planktonic Appendicularia may reflect changes in hydrographic conditions. We present hydrographic data alongside information on the presence, abundance and distribution of eight species of two genera: Oikopleura dioica Fol, O. longicauda Vogt, O.fusiformis Fol, Fritillaria aequatorialis Lohmann, F. megachille Fol, F. pellucida (Busch), F. haplostoma Fol and F. borealis Lohmann. We also provide an overview of the occurrence of the dinoflagellate N. scintillans and its relationship with Appendicularia in the Bay of Boka Kotorska.