Effects of increased concentrations of inorganic nitrogen and dissolved organic matter on phytoplankton in boreal lakes with differing nutrient limitation patterns

Abstract. Transformations of dissolved organic matter (DOM) in boreal lakes lead to large greenhouse gas emissions as well as substantial carbon storage in sediments. Using novel molecular characterization approaches and photochemical degradation experiments we studied how seasonal patterns in water column stratification affected the DOM in a Swedish lake under early spring and summer conditions. Dissolved organic carbon (DOC) concentrations were consistently higher above the sediment when compared to surface waters throughout the sampling periods. Photobleaching alone could not explain this difference in DOC because the lake was covered by 40 cm-thick ice during late winter sampling and still showed the same DOC trend. The differences in the molecular diversity between surface DOM in winter and summer were consistent with ongoing photobleaching/decarboxylation and a possible bacterial consumption of photo-products. Additional photo-degradation experiments using simulated sunlight showed a production of highly oxidized organic molecules and low molecular weight compounds in all late winter samples and also in the deep water sample in summer. In the surface summer DOM sample, few such molecules were produced during the photo-degradation experiments, confirming that DOM was already photobleached prior to the experiments. This study suggests that photobleaching, and therefore also the ice cover during winter, plays a central role in surface DOM transformation, with important differences in the molecular composition of DOM between surface and deep boreal lake waters. The release of DOC from boreal lake sediments also contribute to this pattern. Photochemical degradation of DOM may be more extensive following ice-out and water column turnover when non-light exposed and thereby photosensitive DOM is photo-mineralized. Hence, the yearly DOM photo-mineralization may be greater than inferred from studies of recently light-exposed DOM.

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Sedimentation in Boreal Lakes—The Role of Flocculation of Allochthonous Dissolved Organic Matter in the Water Column

Ecosystems ◽

10.1007/s10021-008-9162-z ◽

2008 ◽

Vol 11 (5) ◽

pp. 803-814 ◽

Cited By ~ 119

Author(s):

Eddie von Wachenfeldt ◽

Lars J. Tranvik

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Water Column ◽

Boreal Lakes

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Methane and Dissolved Organic Matter in the Ground Ice Samples from Central Yamal: Implications to Biogeochemical Cycling and Greenhouse Gas Emission

Geosciences ◽

10.3390/geosciences10110450 ◽

2020 ◽

Vol 10 (11) ◽

pp. 450

Author(s):

Petr B. Semenov ◽

Anfisa A. Pismeniuk ◽

Sergei A. Malyshev ◽

Marina O. Leibman ◽

Irina D. Streletskaya ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Greenhouse Gases ◽

Greenhouse Gas Emission ◽

Inorganic Nitrogen ◽

Biogeochemical Cycling ◽

Ground Ice ◽

Carbon And Nitrogen ◽

Ice Wedge ◽

Permafrost Thawing

Permafrost thawing leads to mobilization of the vast carbon pool into modern biogeochemical cycling through the enhanced release of dissolved organic matter (DOM) and production of greenhouse gases (CO2 and CH4). In this work, we focus on the study of methane and DOM distribution and genesis in the ground ice samples of thermodenudational exposure in the Central Yamal (Russian Arctic). We propose that the liberation of the ice-trapped CH4 and generation of CO2 by DOM mineralization are the earliest factors of atmospheric greenhouse gases emission as a result of permafrost thawing. The observed enormously “light ” isotope signatures of methane (δ13C < −80‰, δD < −390‰) found in the tabular ground ice units significantly divergent in morphology and localization within the exposuremay be related to subzero (cryogenic) carbonate reduction a as significant factor of the local methane enrichment. DOM is mainly formed (>88%) by biochemically refractory humic acids. Distribution of the labile protein-like DOM reflects the specific features of carbon and nitrogen cycles in the tabular ground ice and ice wedge samples. Tabular ground ice units are shown to be a significant source of methane and high quality organic matter as well as dissolved inorganic nitrogen (DIN). Ice wedges express a high variation in DOM composition and lability.

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Processing of Naturally Sourced Macroalgal- and Coral-Dissolved Organic Matter (DOM) by High and Low Microbial Abundance Encrusting Sponges

Frontiers in Marine Science ◽

10.3389/fmars.2021.640583 ◽

2021 ◽

Vol 8 ◽

Author(s):

Sara Campana ◽

Meggie Hudspith ◽

David Lankes ◽

Anna de Kluijver ◽

Celine Demey ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Inorganic Nitrogen ◽

Carbon Assimilation ◽

The Other ◽

Microbial Abundance ◽

Differential Processing ◽

Coral Reef Ecosystems ◽

Encrusting Sponges ◽

Bulk Tissue

Sponges play a key role in (re)cycling of dissolved organic matter (DOM) and inorganic nutrients in coral reef ecosystems. Macroalgae and corals release different quantities of DOM and at different bioavailabilities to sponges and their microbiome. Given the current coral- to algal-dominance shift on coral reefs, we assessed the differential processing of macroalgal- and coral-DOM by three high and three low microbial abundance (HMA and LMA) encrusting sponge species. We followed the assimilation of naturally sourced 13C- and 15N-enriched macroalgal- and coral-DOM into bulk tissue and into host- versus bacteria-specific phospholipid fatty acids (PLFAs). Additionally, we compared sponge-processing of the two natural DOM sources with 13C- and 15N-enriched laboratory-made diatom-DOM. All investigated sponges utilized all DOM sources, with higher assimilation rates in LMA compared to HMA sponges. No difference was found in carbon assimilation of coral- versus macroalgal-DOM into bulk tissue and host- versus bacteria-specific PLFAs, but macroalgal nitrogen was assimilated into bulk tissue up to eight times faster compared to the other sources, indicating its higher bioavailability to the sponges. Additionally, LMA sponges released significantly more inorganic nitrogen after feeding on macroalgal-DOM. Therefore, we hypothesize that, depending on the abundance and composition of the sponge community, sponges could catalyze reef eutrophication through increased turnover of nitrogen under coral-to-algal regime shifts.

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High bacterial carbon demand and low growth efficiency at a tropical hypereutrophic estuary: importance of dissolved organic matter remineralization

Brazilian Journal of Oceanography ◽

10.1590/s1679-87592017137406503 ◽

2017 ◽

Vol 65 (3) ◽

pp. 382-391 ◽

Cited By ~ 2

Author(s):

Mariana Guenther ◽

Eliane Gonzalez-Rodriguez ◽

Manuel Flores-Montes ◽

Moacyr Araújo ◽

Sigrid Neumann-Leitão

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Inorganic Nitrogen ◽

Growth Efficiency ◽

Trophic Levels ◽

Carbon Demand ◽

Bacterioplankton Production ◽

Tropical Estuarine ◽

The Tropics

Abstract Simultaneous measurements of bacterioplankton production (BP) and respiration (BR) are imperative to understand the magnitude of carbon cycle in the lower trophic levels of the aquatic systems, but are still scarce in the tropics. The present study was performed in a highly productive estuary (Recife harbor, 08°03'S; 34°52'W, NE Brazil) where bacterial carbon demand (BCD=BP+BR) and growth efficiency (BGE=BP/BCD) were evaluated in order to estimate the major role of bacterioplankton: source or sink of organic carbon. In spite of the high BP rates (0.03-0.4 µMC h-1), the extremely high BR rates (0.5-4.1 µMC h-1) led to low BGE (0.02-0.29), possibly due to the high temperatures (>25ºC) and strong inorganic nitrogen limitation (N:P ratios) The high BCD and low BGE indicate the major role of bacterioplankton as dissolved organic matter remineralizers, fueling the primary productivity of the system. These findings contradict what could be expected from studies in highly productive temperate estuaries (where BGE is usually > 0.30) and highlight the importance of increasing in situ BP and BR estimates in tropical estuarine systems in order to better understand the role of these systems in global carbon cycling.

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Effects of nitrate and phosphate supply on chromophoric and fluorescent dissolved organic matter in the Eastern Tropical North Atlantic: a mesocosm study

Biogeosciences ◽

10.5194/bg-12-6897-2015 ◽

2015 ◽

Vol 12 (23) ◽

pp. 6897-6914 ◽

Cited By ~ 4

Author(s):

A. N. Loginova ◽

C. Borchard ◽

J. Meyer ◽

H. Hauss ◽

R. Kiko ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

North Atlantic ◽

Inorganic Nitrogen ◽

Bacterial Biomass ◽

Open Ocean ◽

Nutrient Concentrations ◽

Fluorescent Dissolved Organic Matter ◽

Tropical North Atlantic ◽

Mesocosm Experiments

Abstract. In open-ocean regions, as is the Eastern Tropical North Atlantic (ETNA), pelagic production is the main source of dissolved organic matter (DOM) and is affected by dissolved inorganic nitrogen (DIN) and phosphorus (DIP) concentrations. Changes in pelagic production under nutrient amendments were shown to also modify DOM quantity and quality. However, little information is available about the effects of nutrient variability on chromophoric (CDOM) and fluorescent (FDOM) DOM dynamics. Here we present results from two mesocosm experiments ("Varied P" and "Varied N") conducted with a natural plankton community from the ETNA, where the effects of DIP and DIN supply on DOM optical properties were studied. CDOM accumulated proportionally to phytoplankton biomass during the experiments. Spectral slope (S) decreased over time indicating accumulation of high molecular weight DOM. In Varied N, an additional CDOM portion, as a result of bacterial DOM reworking, was determined. It increased the CDOM fraction in DOC proportionally to the supplied DIN. The humic-like FDOM component (Comp.1) was produced by bacteria proportionally to DIN supply. The protein-like FDOM component (Comp.2) was released irrespectively to phytoplankton or bacterial biomass, but depended on DIP and DIN concentrations. Under high DIN supply, Comp.2 was removed by bacterial reworking, leading to an accumulation of humic-like Comp.1. No influence of nutrient availability on amino acid-like FDOM component in peptide form (Comp.3) was observed. Comp.3 potentially acted as an intermediate product during formation or degradation of Comp.2. Our findings suggest that changes in nutrient concentrations may lead to substantial responses in the quantity and quality of optically active DOM and, therefore, might bias results of the applied in situ optical techniques for an estimation of DOC concentrations in open-ocean regions.

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The role of photomineralization for CO 2 emissions in boreal lakes along a gradient of dissolved organic matter

Limnology and Oceanography ◽

10.1002/lno.11594 ◽

2020 ◽

Author(s):

Lina Allesson ◽

Birgit Koehler ◽

Jan‐Erik Thrane ◽

Tom Andersen ◽

Dag O. Hessen

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Boreal Lakes

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