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- Bartoli, M., et al.
(author)
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Denitrification, Nitrogen Uptake, and Organic Matter Quality Undergo Different Seasonality in Sandy and Muddy Sediments of a Turbid Estuary
- 2021
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In: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 11
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Journal article (peer-reviewed)abstract
- The interaction between microbial communities and benthic algae as nitrogen (N) regulators in poorly illuminated sediments is scarcely investigated in the literature. The role of sediments as sources or sinks of N was analyzed in spring and summer in sandy and muddy sediments in a turbid freshwater estuary, the Curonian Lagoon, Lithuania. Seasonality in this ecosystem is strongly marked by phytoplankton community succession with diatoms dominating in spring and cyanobacteria dominating in summer. Fluxes of dissolved gas and inorganic N and rates of denitrification of water column nitrate (D-w) and of nitrate produced by nitrification (D-n) and sedimentary features, including the macromolecular quality of organic matter (OM), were measured. Shallow/sandy sites had benthic diatoms, while at deep/muddy sites, settled pelagic microalgae were found. The OM in surface sediments was always higher at muddy than at sandy sites, and biochemical analyses revealed that at muddy sites the OM nutritional value changed seasonally. In spring, sandy sediments were net autotrophic and retained N, while muddy sediments were net heterotrophic and displayed higher rates of denitrification, mostly sustained by D-w. In summer, benthic oxygen demand increased dramatically, whereas denitrification, mostly sustained by D-n, decreased in muddy and remained unchanged in sandy sediments. The ratio between denitrification and oxygen demand was significantly lower in sandy compared with muddy sediments and in summer compared with spring. Muddy sediments displayed seasonally distinct biochemical composition with a larger fraction of lipids coinciding with cyanobacteria blooms and a seasonal switch from inorganic N sink to source. Sandy sediments had similar composition in both seasons and retained inorganic N also in summer. Nitrogen uptake by microphytobenthos at sandy sites always exceeded the amount loss via denitrification, and benthic diatoms appeared to inhibit denitrification, even in the dark and under conditions of elevated N availability. In spring, denitrification attenuated N delivery from the estuary to the coastal area by nearly 35%. In summer, denitrification was comparable (similar to 100%) with the much lower N export from the watershed, but N loss was probably offset by large rates of N-fixation.
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- Lesutiene, J., et al.
(author)
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Role of mysid seasonal migrations in the organic matter transfer in the Curonian Lagoon, south-eastern Baltic Sea.
- 2008
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In: ESTUARINE COASTAL AND SHELF SCIENCE. - : Elsevier BV. - 0272-7714. ; 80:2, s. 225-234
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Journal article (peer-reviewed)abstract
- We investigated population dynamics, growth and feeding of an omnivorous mysid, Paramysis lacustris, performing seasonal horizontal migrations in the Curonian Lagoon. In autumn, increased predation pressure and deteriorated feeding conditions, due to zooplankton and phytoplankton decline in the open water, forces mysids to migrate to the shoreline, where large amounts of decaying submersed vegetation occur at the end of plant growth season. Using stable isotope analysis and mixing models, we evaluated relative importance of decaying submersed macrophytes, lagoon phytoplankton and mesozooplankton in the diet of mysids during this period. In September- November, mysids actively grew and produced three cohorts. Specific growth rates of adults (10.9 +/- 1.9 mm) and subadults (6 +/- 0.5 mm)were 3 and 9% DW d(-1), respectively, resulting in population somatic production of 36 g DW m(-2). Both delta N-15 and delta C-13 of mysids varied in concert with those in suspended and bottom particulate organic matter (POM) and mesozooplankton. The mixing models estimated that 45% of mysid diets were composed of bottom POM originated from the decaying macrophyte Potamogeton perfoliatus, 45% by suspended POM largely consisting of phytoplankton. while mesozooplankton contributed less than 10% of the diet. This diet composition differs from that in summer, when mysids rely mostly on zooplankton and phytoplankton. Therefore, mysid horizontal migrations and their ability to efficiently utilize littoral detritus improve the efficiency of macrophyte detritus transfer up the food chain and inshore/offshore habitat coupling in the Curonian Lagoon.
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