Complex drivers of primary production along an anthropised estuary (Seine estuary—France)
The Seine estuary is a typical model of a system in which phosphorus (P) inputs have been considerably reduced to reduce past eutrophication, with a parallel decrease in phytoplankton biomass. However, reducing P alone while concentrations of nitrate (N) remains high led to a dystrophic nutrient bal...
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2023-06-01
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| Series: | Frontiers in Environmental Science |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fenvs.2023.1216732/full |
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| author | Léon Serre-Fredj Léon Serre-Fredj Léo Chasselin Léo Chasselin Orianne Jolly Pascal Claquin Pascal Claquin |
| author_facet | Léon Serre-Fredj Léon Serre-Fredj Léo Chasselin Léo Chasselin Orianne Jolly Pascal Claquin Pascal Claquin |
| author_sort | Léon Serre-Fredj |
| collection | DOAJ |
| description | The Seine estuary is a typical model of a system in which phosphorus (P) inputs have been considerably reduced to reduce past eutrophication, with a parallel decrease in phytoplankton biomass. However, reducing P alone while concentrations of nitrate (N) remains high led to a dystrophic nutrient balance in the estuary (high N/P and N/Si). To identify the drivers of primary production and phytoplankton communities in the highly anthropised Seine estuary, sampling was performed along a 110-km stretch over a period of 3 years. Photosynthetic parameters were measured with a single turnover active fluorimeter and the phytoplankton community was assessed using a fluoroprobe and flow cytometry. The results revealed an annual primary production of 33 g C.m−2.y−1 which was largely controlled by light availability (turbidity) but also by nutrients in late spring and summer period. Massive blooms, not seen since 2002, were observed in a specific area of the estuary. None of the nutrients measured explained the particular location of the blooms but phytoplankton production and productivity indicators were higher in this specific zone excluding a biomass accumulation phenomenon. The local effect of tide slowdown increasing water residence time in this exact part of the estuary could explain the bloom area. The question thus arises: does phosphate play a role as a limiting nutrient? The diatom bloom led to total depletion of Si, but no clear limitation of P was observed. Nevertheless, the decrease in Si appears to have played a key role by triggering a succession from diatoms (microphytoplankton) to chlorophytes (nanophytoplankton) and hence affecting phytoplankton composition. The N/P balance appeared to be more important than the absolute concentration of P to explain the phytoplankton dynamics and the biomass decrease observed the last decades. |
| first_indexed | 2024-03-13T02:30:57Z |
| format | Article |
| id | doaj.art-34bc493cc4c449e8854a1fe1e3387c7c |
| institution | Directory Open Access Journal |
| issn | 2296-665X |
| language | English |
| last_indexed | 2024-03-13T02:30:57Z |
| publishDate | 2023-06-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Environmental Science |
| spelling | doaj.art-34bc493cc4c449e8854a1fe1e3387c7c2023-06-29T16:45:43ZengFrontiers Media S.A.Frontiers in Environmental Science2296-665X2023-06-011110.3389/fenvs.2023.12167321216732Complex drivers of primary production along an anthropised estuary (Seine estuary—France)Léon Serre-Fredj0Léon Serre-Fredj1Léo Chasselin2Léo Chasselin3Orianne Jolly4Pascal Claquin5Pascal Claquin6Normandie Université, Université de Caen Normandie, Centre de Recherches en Environnement Côtier (CREC)—Station Marine, Luc-sur-Mer, FranceLaboratoire Biologie des ORganismes et Ecosystèmes Aquatiques (BOREA, UMR CNRS 8067), Muséum National d’Histoire Naturelle, Sorbonne Université, Université de Caen Normandie, Université des Antilles, CREC—Station Marine, Luc-sur-Mer, FranceNormandie Université, Université de Caen Normandie, Centre de Recherches en Environnement Côtier (CREC)—Station Marine, Luc-sur-Mer, FranceLaboratoire Biologie des ORganismes et Ecosystèmes Aquatiques (BOREA, UMR CNRS 8067), Muséum National d’Histoire Naturelle, Sorbonne Université, Université de Caen Normandie, Université des Antilles, CREC—Station Marine, Luc-sur-Mer, FranceNormandie Université, Université de Caen Normandie, Centre de Recherches en Environnement Côtier (CREC)—Station Marine, Luc-sur-Mer, FranceNormandie Université, Université de Caen Normandie, Centre de Recherches en Environnement Côtier (CREC)—Station Marine, Luc-sur-Mer, FranceLaboratoire Biologie des ORganismes et Ecosystèmes Aquatiques (BOREA, UMR CNRS 8067), Muséum National d’Histoire Naturelle, Sorbonne Université, Université de Caen Normandie, Université des Antilles, CREC—Station Marine, Luc-sur-Mer, FranceThe Seine estuary is a typical model of a system in which phosphorus (P) inputs have been considerably reduced to reduce past eutrophication, with a parallel decrease in phytoplankton biomass. However, reducing P alone while concentrations of nitrate (N) remains high led to a dystrophic nutrient balance in the estuary (high N/P and N/Si). To identify the drivers of primary production and phytoplankton communities in the highly anthropised Seine estuary, sampling was performed along a 110-km stretch over a period of 3 years. Photosynthetic parameters were measured with a single turnover active fluorimeter and the phytoplankton community was assessed using a fluoroprobe and flow cytometry. The results revealed an annual primary production of 33 g C.m−2.y−1 which was largely controlled by light availability (turbidity) but also by nutrients in late spring and summer period. Massive blooms, not seen since 2002, were observed in a specific area of the estuary. None of the nutrients measured explained the particular location of the blooms but phytoplankton production and productivity indicators were higher in this specific zone excluding a biomass accumulation phenomenon. The local effect of tide slowdown increasing water residence time in this exact part of the estuary could explain the bloom area. The question thus arises: does phosphate play a role as a limiting nutrient? The diatom bloom led to total depletion of Si, but no clear limitation of P was observed. Nevertheless, the decrease in Si appears to have played a key role by triggering a succession from diatoms (microphytoplankton) to chlorophytes (nanophytoplankton) and hence affecting phytoplankton composition. The N/P balance appeared to be more important than the absolute concentration of P to explain the phytoplankton dynamics and the biomass decrease observed the last decades.https://www.frontiersin.org/articles/10.3389/fenvs.2023.1216732/fullflow cytometryvariable fluorimetryphytoplankton communitiesmultispectral fluorimetryeutrophication |
| spellingShingle | Léon Serre-Fredj Léon Serre-Fredj Léo Chasselin Léo Chasselin Orianne Jolly Pascal Claquin Pascal Claquin Complex drivers of primary production along an anthropised estuary (Seine estuary—France) Frontiers in Environmental Science flow cytometry variable fluorimetry phytoplankton communities multispectral fluorimetry eutrophication |
| title | Complex drivers of primary production along an anthropised estuary (Seine estuary—France) |
| title_full | Complex drivers of primary production along an anthropised estuary (Seine estuary—France) |
| title_fullStr | Complex drivers of primary production along an anthropised estuary (Seine estuary—France) |
| title_full_unstemmed | Complex drivers of primary production along an anthropised estuary (Seine estuary—France) |
| title_short | Complex drivers of primary production along an anthropised estuary (Seine estuary—France) |
| title_sort | complex drivers of primary production along an anthropised estuary seine estuary france |
| topic | flow cytometry variable fluorimetry phytoplankton communities multispectral fluorimetry eutrophication |
| url | https://www.frontiersin.org/articles/10.3389/fenvs.2023.1216732/full |
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