Impact of contaminated-sediment resuspension on phytoplankton in the Biguglia lagoon (Corsica, Mediterranean Sea)

In shallow human-impacted systems, sediment resuspension events can result in pulsed exposures of pelagic organisms to multiple contaminants. Here, we examined the impact of the resuspension of contaminated sediment on phytoplankton in the Biguglia lagoon (Corsica, Mediterranean Sea), by conducting an in situ microcosm experiment over a 96-hour period. Natural phytoplankton was exposed to elutriates prepared from a contaminated sediment resuspension simulating process, and its functional and structural responses were compared with those of non-exposed phytoplankton. The elutriates displayed moderate multiple contamination by trace metals and PAHs. Our results show that elutriate exposure induced both functional and structural phytoplankton changes. Elutriates strongly stimulated phytoplankton growth after 24 h of exposure. They also enhanced phytoplankton photosynthetic performance during the first hours of exposure (up to 48 h), before reducing it towards the end of the experiment. Elutriates were also found to slightly stimulate Bacillariophyceae, and conversely to slightly inhibit Dinophyceae in the short term. Additionally, they stimulated phycocyanin-rich picocyanobacteria in the short term (8-48 h) before inhibiting it in the longer term (72-96 h), and to inhibit eukaryotic nanophytoplankton at short term (8-48 h) before stimulating it in the longer term (72-96 h). Sediment resuspension is thus likely to have a significant effect on the global dynamics of phytoplankton in contaminated coastal environments

Temporal changes in zooplankton indicators highlight a bottom-up process in the Bay of Marseille (NW

International audienceSixteen years (2005-2020) of zooplankton monitoring in the Bay of Marseille (N-W Mediterranean Sea) are analyzed in relation to physical, meteorological, climatic and biotic data. Samples were collected every two weeks by a vertical haul (0-55 m) of a 200 µm plankton net. Different indices characterizing the mesozooplankton are compared: biomass dry weight of four size fractions between 200 and 2000 µm; abundances of the whole of the mesozooplankton and of 13 main taxonomic groups defined from plankton imagery; seasonal onset timing of each zooplankton group; and two other types of indices, the first characterized diversity based on abundance data; and the second derived from zooplankton size spectra shape. The multi-indices approach showed different dynamics and the indices were complementary to disentangle changes in zooplankton. While the biomass of the four mesozooplankton siz

Mesozooplankton variability in the Bay of Marseille (NW Mediterranean): towards understanding the trophic context of small pelagics

In the Gulf of Lion, biomass, size and body condition of some small pelagic fish diminished since 2007. Bottom-up control by a modification of mesozooplankton is the main hypothesis which could explain such observation (Saraux et al. 2019, Chen et al. 2019, 2021). Since 2004, mesozooplankton has been monitored bimensually at the SOLEMIO station of RNO SOMLIT program, east of the Gulf of Lion. This work aimed at highlighting mode of changes in the environment which could explain variations in the zooplankton community in the Bay of Marseille on the 2005-2021 period. Time series of climatic indexes, meteorological data, physico-chemical data, microphytoplankton data, pico-nanoplankton and zooplankton data has been compiled. Dynamic Factor Analysis (DFA) allowed to describe 2 interannual trends in the biotic and abiotic environment of zooplankton. Those trends highlighted: a fast diminution (2005-2009) in nutrients concentrations, suspended particulate matters, carbon and nitrogen organic particulate, an offshore signal between 2005- 2008, and an increase since 2011 of abundance and a diminution of size indexes of most of planktonic groups. Mesozooplankton has been characterized by three trends. The first, highlighted the diminution of biomass of all size class. The second linked biomass variations of the bigger size class (1000 - 2000 μm) with modifications of size structure anddiversity community structure. The second environmental trend explained variations of biomass diminution by size class (200-300 and 500-200 μm) after 2011. Seasonal patterns of the mesozooplankton groups have been described and are typical of coastal sites in the NW-Mediterranean Sea, with a spring peak production for biomass, calanoids and oithonoids and a summer peak for chaetognaths, crustaceans, cnidarians, salp and pteropods. The diversity community shift in 2011, seemed to have affected the seasonal pattern of some mesozooplankton variable. Lower peak values were observable in the second half of the series for size-class biomasses, calanoids and oithonoids abundances, while stronger signal was detected for summer peak-like groups. To discuss on the implication of those change for the higher trophic level, the date from which cumulative annually production (biomasses and abundances) overpassed the 0.3-percentile cumulative production of the series (DCAP) were derived for mesozooplankton groups. The year-to-year variations showed a delay of DCAP for size class biomass and for total zooplankton, calanoids and oithonoids abundances after 2011. Finally, the relation between winter environmental context and zooplankton DCAP has been investigated. We highlighted that wintertemperature and winter abundance of nano-eukaryotes were among the variable the most correlated with zooplankton DCAP. The results described a shift, 2011, in the pelagic ecosystem of the Bay of Marseille and allow to discuss on the bottom- up control of plankton on small pelagic fish

Mesozooplankton variability in the Bay of Marseille (NW Mediterranean): towards understanding the trophic context of small pelagics

In the Gulf of Lion, biomass, size and body condition of some small pelagic fish diminished since 2007. Bottom-up control by a modification of mesozooplankton is the main hypothesis which could explain such observation (Saraux et al. 2019, Chen et al. 2019, 2021). Since 2004, mesozooplankton has been monitored bimensually at the SOLEMIO station of RNO SOMLIT program, east of the Gulf of Lion. This work aimed at highlighting mode of changes in the environment which could explain variations in the zooplankton community in the Bay of Marseille on the 2005-2021 period. Time series of climatic indexes, meteorological data, physico-chemical data, microphytoplankton data, pico-nanoplankton and zooplankton data has been compiled. Dynamic Factor Analysis (DFA) allowed to describe 2 interannual trends in the biotic and abiotic environment of zooplankton. Those trends highlighted: a fast diminution (2005-2009) in nutrients concentrations, suspended particulate matters, carbon and nitrogen organic particulate, an offshore signal between 2005- 2008, and an increase since 2011 of abundance and a diminution of size indexes of most of planktonic groups. Mesozooplankton has been characterized by three trends. The first, highlighted the diminution of biomass of all size class. The second linked biomass variations of the bigger size class (1000 - 2000 μm) with modifications of size structure anddiversity community structure. The second environmental trend explained variations of biomass diminution by size class (200-300 and 500-200 μm) after 2011. Seasonal patterns of the mesozooplankton groups have been described and are typical of coastal sites in the NW-Mediterranean Sea, with a spring peak production for biomass, calanoids and oithonoids and a summer peak for chaetognaths, crustaceans, cnidarians, salp and pteropods. The diversity community shift in 2011, seemed to have affected the seasonal pattern of some mesozooplankton variable. Lower peak values were observable in the second half of the series for size-class biomasses, calanoids and oithonoids abundances, while stronger signal was detected for summer peak-like groups. To discuss on the implication of those change for the higher trophic level, the date from which cumulative annually production (biomasses and abundances) overpassed the 0.3-percentile cumulative production of the series (DCAP) were derived for mesozooplankton groups. The year-to-year variations showed a delay of DCAP for size class biomass and for total zooplankton, calanoids and oithonoids abundances after 2011. Finally, the relation between winter environmental context and zooplankton DCAP has been investigated. We highlighted that wintertemperature and winter abundance of nano-eukaryotes were among the variable the most correlated with zooplankton DCAP. The results described a shift, 2011, in the pelagic ecosystem of the Bay of Marseille and allow to discuss on the bottom- up control of plankton on small pelagic fish

Mesozooplankton variability in the Bay of Marseille (NW Mediterranean): towards understanding the trophic context of small pelagics

International audienceIn the Gulf of Lion, biomass, size and body condition of some small pelagic fish diminished since 2007. Bottom-up control by a modification of mesozooplankton is the main hypothesis which could explain such observation (Saraux et al. 2019, Chen et al. 2019, 2021). Since 2004, mesozooplankton has been monitored bimensually at the SOLEMIO station of RNO SOMLIT program, east of the Gulf of Lion. This work aimed at highlighting mode of changes in the environment which could explain variations in the zooplankton community in the Bay of Marseille on the 2005-2021 period. Time series of climatic indexes, meteorological data, physico-chemical data, microphytoplankton data, pico-nanoplankton and zooplankton data has been compiled. Dynamic Factor Analysis (DFA) allowed to describe 2 interannual trends in the biotic and abiotic environment of zooplankton. Those trends highlighted: a fast diminution (2005-2009) in nutrients concentrations, suspended particulate matters, carbon and nitrogen organic particulate, an offshore signal between 2005- 2008, and an increase since 2011 of abundance and a diminution of size indexes of most of planktonic groups. Mesozooplankton has been characterized by three trends. The first, highlighted the diminution of biomass of all size class. The second linked biomass variations of the bigger size class (1000 - 2000 μm) with modifications of size structure anddiversity community structure. The second environmental trend explained variations of biomass diminution by size class (200-300 and 500-200 μm) after 2011. Seasonal patterns of the mesozooplankton groups have been described and are typical of coastal sites in the NW-Mediterranean Sea, with a spring peak production for biomass, calanoids and oithonoids and a summer peak for chaetognaths, crustaceans, cnidarians, salp and pteropods. The diversity community shift in 2011, seemed to have affected the seasonal pattern of some mesozooplankton variable. Lower peak values were observable in the second half of the series for size-class biomasses, calanoids and oithonoids abundances, while stronger signal was detected for summer peak-like groups. To discuss on the implication of those change for the higher trophic level, the date from which cumulative annually production (biomasses and abundances) overpassed the 0.3-percentile cumulative production of the series (DCAP) were derived for mesozooplankton groups. The year-to-year variations showed a delay of DCAP for size class biomass and for total zooplankton, calanoids and oithonoids abundances after 2011. Finally, the relation between winter environmental context and zooplankton DCAP has been investigated. We highlighted that wintertemperature and winter abundance of nano-eukaryotes were among the variable the most correlated with zooplankton DCAP. The results described a shift, 2011, in the pelagic ecosystem of the Bay of Marseille and allow to discuss on the bottom- up control of plankton on small pelagic fish

Supplementary information on environmental and zooplankton monitoring.

Supplementary information on environmental and zooplankton monitoring.</p

Fig 3 -

Year-to-year variations in the A) relative and B) absolute abundance of the 13 best recognized zooplankton taxa. Note that the graph is zoomed on the y values below 0.6 to better see the species with low relative abundance. Abundances in the bottom panel are expressed as number of individuals.m-3. The taxa are sorted by importance over the whole zooplankton time series.</p

Fig 2 -

Results of the FPCA (A & B) and MDS (C & D) analysis to derive community structure indices. Influence of factorial axis (A for first PC and B for second PC) on the shape of the functional object (size spectra curve). Black line is the mean functional curve of the FPCA. Red curve (+ symbol) and blue curve (- symbol) represent respectively the positive and negative influence of the factorial axis on the size spectra shape. Limits of the x-axis of A & B graphs are set to 200 to 1000 μm, as the main variations of the influence of the factorial axis on the functional object are observable before 1000 μm ESD. Representation of the ordination of the MDS (C: first vs second axis, D: first vs third axis). The black dots correspond to the projections on the 2D space of the samples. The red labels correspond to the centroids position of the taxa. Taxa abbreviations correspond to the following groups: app: appendicularians; biva: bivalves; cala: calanoids copepods; chae: chaetognaths; cnid: cnidarians; crust: crustaceans (without copepods); eggs: fish eggs; erga: ergasilida copepods; harp: harpacticoids copepods; naup: copepods nauplii; oith: oithonids copepods; pter: pteropods; salp: salp.</p

Summary of the results of the dynamic factor analysis.

Summary of the results of the dynamic factor analysis.</p

Performance of ParticleTrieur software for the detection of individuals.

Performance of ParticleTrieur software for the detection of individuals.</p