The effects of variable riverine inputs and seasonal shifts in phytoplankton communities on nitrate cycling in a coastal lagoon

Estuarine systems, being situated at the interface between land and marine environments, are important sites for nitrate (NO3–) retention and processing due to large inputs, long retention time, and high biogeochemical activity. However, it remains uncertain how pelagic and benthic processes control...

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Main Authors: Mindaugas Zilius, Rūta Barisevičiūtė, Stefano Bonaglia, Isabell Klawonn, Elise Lorre, Tobia Politi, Irma Vybernaite-Lubiene, Maren Voss, Donata Overlinge, Paul A. Bukaveckas
Format: Article
Language:English
Published: Frontiers Media S.A. 2024-12-01
Series:Frontiers in Marine Science
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Online Access:https://www.frontiersin.org/articles/10.3389/fmars.2024.1497246/full
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author Mindaugas Zilius
Rūta Barisevičiūtė
Stefano Bonaglia
Stefano Bonaglia
Isabell Klawonn
Elise Lorre
Tobia Politi
Tobia Politi
Irma Vybernaite-Lubiene
Maren Voss
Donata Overlinge
Paul A. Bukaveckas
author_facet Mindaugas Zilius
Rūta Barisevičiūtė
Stefano Bonaglia
Stefano Bonaglia
Isabell Klawonn
Elise Lorre
Tobia Politi
Tobia Politi
Irma Vybernaite-Lubiene
Maren Voss
Donata Overlinge
Paul A. Bukaveckas
author_sort Mindaugas Zilius
collection DOAJ
description Estuarine systems, being situated at the interface between land and marine environments, are important sites for nitrate (NO3–) retention and processing due to large inputs, long retention time, and high biogeochemical activity. However, it remains uncertain how pelagic and benthic processes control NO3– cycling and how the relative importance of these processes is affected by seasonal changes in estuarine conditions. We measured the suite of processes governing NO3– cycling in the Curonian Lagoon (Southeast Baltic Sea) during two time periods representing spring and summer conditions. We show that in spring, benthic dissimilatory and assimilatory NO3– processes prevailed, while in summer, pelagic assimilatory processes dominated. During spring, warming temperatures and riverine nitrogen (N) inputs were associated with the onset of diatom blooms. N assimilation by diatoms resulted in the delivery of particulate organic N and organic matter to the benthos, resulting in greater denitrification in the sediments and a flux of NO3– from the water column to the sediments. In summer, phytoplankton blooms of buoyant cyanobacteria and high rates of assimilatory uptake dominated, resulting in greater particulate organic N export from the lagoon into the sea. Given the low dissolved inorganic N concentrations in summer, high uptake indicates that the pelagic community possessed a nutritional strategy to efficiently utilize multiple N forms at high rates. Overall, our findings show that diatom-dominated communities foster strong benthic-pelagic coupling, whereas cyanobacteria dominance is associated with pelagic-based N cycling. While this study sheds new light on mechanisms of NO3– retention in the Curonian Lagoon, further spatiotemporal resolution is recommended to better represent the variability in rates and to include other Baltic lagoons for a comprehensive understanding of N cycling in shallow estuarine systems.
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series Frontiers in Marine Science
spelling doaj-art-6d70328f14dd4922ba6e2a6c7d30d18b2024-12-23T05:10:16ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452024-12-011110.3389/fmars.2024.14972461497246The effects of variable riverine inputs and seasonal shifts in phytoplankton communities on nitrate cycling in a coastal lagoonMindaugas Zilius0Rūta Barisevičiūtė1Stefano Bonaglia2Stefano Bonaglia3Isabell Klawonn4Elise Lorre5Tobia Politi6Tobia Politi7Irma Vybernaite-Lubiene8Maren Voss9Donata Overlinge10Paul A. Bukaveckas11Marine Research Institute, Klaipeda University, Klaipeda, LithuaniaState Research Institute, Center for Physical Sciences and Technology, Vilnius, LithuaniaMarine Research Institute, Klaipeda University, Klaipeda, LithuaniaDepartment of Marine Sciences, University of Gothenburg, Gothenburg, SwedenDepartment of Biological Oceanography, Leibniz Institute for Baltic Sea Research, Rostock, GermanyMarine Research Institute, Klaipeda University, Klaipeda, LithuaniaMarine Research Institute, Klaipeda University, Klaipeda, LithuaniaDepartment of Marine Sciences, University of Gothenburg, Gothenburg, SwedenMarine Research Institute, Klaipeda University, Klaipeda, LithuaniaDepartment of Biological Oceanography, Leibniz Institute for Baltic Sea Research, Rostock, GermanyMarine Research Institute, Klaipeda University, Klaipeda, LithuaniaCenter for Environmental Studies, Virginia Commonwealth University, Richmond, VA, United StatesEstuarine systems, being situated at the interface between land and marine environments, are important sites for nitrate (NO3–) retention and processing due to large inputs, long retention time, and high biogeochemical activity. However, it remains uncertain how pelagic and benthic processes control NO3– cycling and how the relative importance of these processes is affected by seasonal changes in estuarine conditions. We measured the suite of processes governing NO3– cycling in the Curonian Lagoon (Southeast Baltic Sea) during two time periods representing spring and summer conditions. We show that in spring, benthic dissimilatory and assimilatory NO3– processes prevailed, while in summer, pelagic assimilatory processes dominated. During spring, warming temperatures and riverine nitrogen (N) inputs were associated with the onset of diatom blooms. N assimilation by diatoms resulted in the delivery of particulate organic N and organic matter to the benthos, resulting in greater denitrification in the sediments and a flux of NO3– from the water column to the sediments. In summer, phytoplankton blooms of buoyant cyanobacteria and high rates of assimilatory uptake dominated, resulting in greater particulate organic N export from the lagoon into the sea. Given the low dissolved inorganic N concentrations in summer, high uptake indicates that the pelagic community possessed a nutritional strategy to efficiently utilize multiple N forms at high rates. Overall, our findings show that diatom-dominated communities foster strong benthic-pelagic coupling, whereas cyanobacteria dominance is associated with pelagic-based N cycling. While this study sheds new light on mechanisms of NO3– retention in the Curonian Lagoon, further spatiotemporal resolution is recommended to better represent the variability in rates and to include other Baltic lagoons for a comprehensive understanding of N cycling in shallow estuarine systems.https://www.frontiersin.org/articles/10.3389/fmars.2024.1497246/fullcoastal filterlagoonpelagic assimilationdenitrificationDNRAphytoplankton
spellingShingle Mindaugas Zilius
Rūta Barisevičiūtė
Stefano Bonaglia
Stefano Bonaglia
Isabell Klawonn
Elise Lorre
Tobia Politi
Tobia Politi
Irma Vybernaite-Lubiene
Maren Voss
Donata Overlinge
Paul A. Bukaveckas
The effects of variable riverine inputs and seasonal shifts in phytoplankton communities on nitrate cycling in a coastal lagoon
Frontiers in Marine Science
coastal filter
lagoon
pelagic assimilation
denitrification
DNRA
phytoplankton
title The effects of variable riverine inputs and seasonal shifts in phytoplankton communities on nitrate cycling in a coastal lagoon
title_full The effects of variable riverine inputs and seasonal shifts in phytoplankton communities on nitrate cycling in a coastal lagoon
title_fullStr The effects of variable riverine inputs and seasonal shifts in phytoplankton communities on nitrate cycling in a coastal lagoon
title_full_unstemmed The effects of variable riverine inputs and seasonal shifts in phytoplankton communities on nitrate cycling in a coastal lagoon
title_short The effects of variable riverine inputs and seasonal shifts in phytoplankton communities on nitrate cycling in a coastal lagoon
title_sort effects of variable riverine inputs and seasonal shifts in phytoplankton communities on nitrate cycling in a coastal lagoon
topic coastal filter
lagoon
pelagic assimilation
denitrification
DNRA
phytoplankton
url https://www.frontiersin.org/articles/10.3389/fmars.2024.1497246/full
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