AMORE (Advanced Modeling and Research on Eutrophication) is an interdisciplinary consortium compo... more AMORE (Advanced Modeling and Research on Eutrophication) is an interdisciplinary consortium composed of biologists and physical and ecological modellers focusing their research activities on coastal eutrophication in the eastern Channel and Southern Bight of the North Sea with special interest in harmful Phaeocystis colony blooms. The long-term objective of AMORE is to develop a a tri-dimensional ecological model - MIRO&CO - able to predict the magnitude and geographical extent of Phaeocystis colony blooms in the Eastern Channel and Southern Bight of the North Sea with focus on the Belgian Coastal Zone (BCZ) and in response to varying short-term climate conditions and riverine nutrient (N, P, Si) loads. To achieve this objective, AMORE has developed an integrated research methodology that involves and combines in an interactive way the collection of historical and new field data, process-level studies, statistical analysis, mathematical modelling and data assimilation. In this appro...
This study is a first effort to compile the largest possible body of data available from differen... more This study is a first effort to compile the largest possible body of data available from different plankton databases as well as from individual published or unpublished datasets regarding diatom distribution in the world ocean. The data obtained originate from time series studies as well as spatial studies. This effort is supported by the Marine Ecosystem Data (MAREDAT) project, which aims at building consistent data sets for the main PFTs (Plankton Functional Types) in order to help validate biogeochemical ocean models by using converted C biomass from abundance data. Diatom abundance data were obtained from various research programs with the associated geolocation and date of collection, as well as with a taxonomic information ranging from group down to species. Minimum, maximum and average cell size information were mined from the literature for each taxonomic entry, and all abundance data were subsequently converted to biovolume and C biomass using the same methodology.
Although eutrophication induced by anthropogenic nutrient enrichment is a driver of shifts in com... more Although eutrophication induced by anthropogenic nutrient enrichment is a driver of shifts in community composition and eventually a threat to marine biodiversity, the causes and consequences on ecosystem functioning remain greatly unknown. In this study, by applying a trait-based approach and measuring niche breadth of diatoms and copepods, the drivers and underlying mechanisms of the seasonal species succession of these ecological communities in a coastal system dominated in spring by Phaeocystis blooms were explored. It is suggested that the seasonal succession of diatoms and copepods is the result of several trade-offs among functional traits that are controlled by the seasonal abiotic and biotic pressure encountered by the plankton communities. The results of this study highlight that a trade-off between competition and predator, i.e., weak competitors are better protected against predation, plays an important role in promoting plankton species richness and triggers the Phaeocy...
Eutrophication as a consequence of anthropogenic nutrient enrichment is one of the major threats ... more Eutrophication as a consequence of anthropogenic nutrient enrichment is one of the major threats to biodiversity in nearshore and coastal marine waters, and consequently, for ecosystem functioning. This study explores changes in the biological organization of copepod assemblages along a Chl a gradient through an upscaling analysis of regional datasets from the coastal waters of the Mediterranean Sea. Results show that omnivorous copepods using passive and/or ambush feeding strategy are favored as Chl a increases, and copepod community shifts towards trophic homogenization by favoring generalist feeders against specialists. To our knowledge, this is the first report of functional homogenization of copepods as the result of eutrophication. The present study also demonstrates the potential use of trait-based approaches to explore the effect of human disturbances on marine copepod assemblages in marine ecosystems.
This study explored the potential interactions and relations of the putative Symbiotic/Decomposer... more This study explored the potential interactions and relations of the putative Symbiotic/Decomposer/Parasitic community (SymbDec) with other taxa and predominant environmental parameters in the eastern English Channel (EEC) over a 2.5 years period (32 sampling dates). The EEC is a meso-eutrophic coastal system portrayed by intense reoccurring patterns in plankton succession with blooms of the Haptophyte Phaeocystis globosa and abundant populations of colonial diatoms and dinoflagellate grazers before and after the bloom. The study of the V2-V3 hypervariable region of the 18S rRNA gene allowed an overview of the planktonic community, which consisted of 32 high-level taxonomic groups. Forty-two percent of the identified OTUs belonged to symbionts, decomposers or other putative parasitic taxa belonging mainly to Syndiniales (MALV-MArine ALveolates), Fungi, Cercozoa, Perkinsea, and others, most of which were plankton parasites. We examined the Local Similarity Analysis (LSA) network of lag delayed correlations on the 142 most abundant OTUs (>0.1% of the total number of reads). LSA showed that 99 OTUs had highly significant connections, involving 26 OTUs characterized as potential parasites, and 2 decomposers. The parasitic network had "small world" characteristics, rendering the assemblage more robust to abiotic variations, but more exposed to the removal of highly associated taxa. The majority of the highly connected OTUs belonged to MALV, which were mainly connected with dinoflagellates, suggesting that it might play an important role on dinoflagellate top-down control. The bloom forming P. globosa was not observed in connection with parasitic OTUs in the network. Four environmental parameters (O 2 , N, T, and N/P) were strongly connected with only 11 OTUs, while correlations between microbes dominated the network.
The diversity of planktonic eukaryotic microbes was studied at a coastal station of the eastern E... more The diversity of planktonic eukaryotic microbes was studied at a coastal station of the eastern English Channel (EEC) from March 2011 to July 2015 (77 samples) using high throughput sequencing (454-pyrosequencing and Illumina) of the V2-V3 hypervariable region of the 18S SSU rDNA gene. Similar estimations of OTU relative abundance and taxonomic distribution for the dominant higher taxonomic groups (contributing >1% of the total number of OTUs) were observed with the two methods (Kolmogorov-Smirnov p-value = 0.22). Eight super-groups were identified throughout all samples: Alveolata, Stramenopiles, Opisthokonta, Hacrobia, Archeaplastida, Apusozoa, Rhizaria, and Amoebozoa (ordered by decreasing OTU richness). To gain further insight into microbial activity in the EEC, ribosomal RNA was extracted for samples from 2013-2015 (30 samples). Analysis of 18S rDNA and rRNA sequences led to the detection of 696 and 700 OTUs, respectively. Cluster analysis based on OTUs' abundance indicated three major seasonal groups that were associated to spring, winter/autumn, and summer conditions. The clusters inferred from rRNA data showed a clearer seasonal representation of the community succession than the one based on rDNA. The rRNA/rDNA ratio was used as a proxy for relative cell activity. When all OTUs were considered, the average rRNA: rDNA ratio showed a linear trend around the 1:1 line, suggesting a linear relation between OTU abundance (rDNA) and activity (rRNA). However, this ratio was highly variable over time when considering individual OTUs. Interestingly, the OTU affiliated with P. globosa displayed rRNA: rDNA ratio that allowed to delimit high vs low abundance and high vs low activity periods. It unveiled quite well the Phaeocystis bloom dynamic regarding cell proliferation and activity, and could even be used as early indicator of an upcoming bloom.
This study explored the relevance of the use of a trait-based approach to explain seasonal phytop... more This study explored the relevance of the use of a trait-based approach to explain seasonal phytoplankton succession and the underlying mechanisms that structure phytoplankton assemblages and promote nitrogen use efficiency (NUE) in the temperate coastal waters of the eastern English Channel (EEC). A 3 yr time series of phytoplankton abundance assessed by flow cytometry was combined with a selection of traits related to resource utilization (light and inorganic nutrients), grazing resistance, and maximum growth, mainly sourced from the literature. Our results showed that the identified functional groups (FGs) ranged deterministically along a temporal gradient of light and nutrient availability, according to several fundamental trade-offs. These trade-offs, which reflected different ecological strategies, were distributed along 1 axis of niche differentiation. This favoured different FGs through time, and consequently allowed them to partition those available resources. The observed functional divergence of the phytoplankton community deviated from that of the expected, random one. It showed that as light increased, the phytoplankton community assembly was mainly driven by competition and grazing pressure, which eventually favoured those FGs that were fastest growing and less vulnerable to predation. Structural equation modeling evidenced that a phytoplankton community, functionally dominated by FGs that were relatively large, fast-growing, and well-adapted to higher light, promoted NUE. Together, these results confirmed the potential use of laboratory-measured functional traits to explore environment−trait linkages in phytoplankton. They also showed the possibility of further extending this approach to identify the mechanisms driving phytoplankton community assembly, structure, and related ecosystem processes.
Please note that this is an author-produced PDF of an article accepted for publication following ... more Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.
The planktonic haptophyte Phaeocystis has been suggested to play a fundamental role in the global... more The planktonic haptophyte Phaeocystis has been suggested to play a fundamental role in the global biogeochemical cycling of carbon and sulphur, but little is known about its global biomass distribution. We have collected global microscopy data of the genus Phaeocystis and converted abundance data to carbon biomass using speciesspecific carbon conversion factors. Microscopic counts of single-celled and colonial Phaeocystis were obtained both through the mining of online databases and by accepting direct submissions (both published and unpublished) from Phaeocystis specialists. We recorded abundance data from a total of 1595 depth-resolved stations sampled between 1955-2009. The quality-controlled dataset includes 5057 counts ESSDD 5, 405-443, 2012
The inter-annual variability of the fish and macrocrustacean spring community on an intertidal sa... more The inter-annual variability of the fish and macrocrustacean spring community on an intertidal sandy beach near the Canche estuary (North of France) was studied from 2000 to 2013 based on weekly spring sampling over an 11-year period. Twenty-eight species representing 21 families were collected during the course of the study. The community was dominated by a few abundant species accounting for > 99% of the total species densities. Most individuals caught were young-of-the-year indicating the importance of this ecosystem for juvenile fishes and macrocrustaceans. Although standard qualitative community ecology metrics (species composition, richness, diversity, evenness and similarity) indicated notable stability over the study period, community structure showed a clear change since 2009. Densities of P. platessa, P. microps and A. tobianus decreased significantly since 2009, whereas over the period 2010-2013, the contribution of S. sprattus to total species density increased 4-fold. Co-inertia and generalised linear model analyses identified winter NAO index, water temperature, salinity and suspended particular matter as the major environmental factors explaining these changes. Although the recurrent and dense spring blooms of the Prymnesiophyte Phaeocystis globosa is one of the main potential threats in shallow waters of the eastern English Channel, no negative impact of its temporal change was detected on the fish and macrocrustacean spring community structure.
A Phaeocystis sp. (Prymnesiophyceae) bloom regularly occurs in April–May in the Eastern English C... more A Phaeocystis sp. (Prymnesiophyceae) bloom regularly occurs in April–May in the Eastern English Channel. In the literature, views are divided about the in situ appetence of copepods for this alga. In a study carried out in the coastal waters off the bay of Somme, at the end of the bloom, from 29 of April to 1 of May 1996, HPLC
... eutrophication phenomenon. Foaming is considered as a minor nuisance compared to other forms ... more ... eutrophication phenomenon. Foaming is considered as a minor nuisance compared to other forms of environmental disturbance such as oil pollution, garbage or dead jelly fishes on the beaches, bad weather conditions. The socio-economic impact of ...
Background: Massive phytoplankton blooms, like the recurrent Phaeocystis proliferation observed e... more Background: Massive phytoplankton blooms, like the recurrent Phaeocystis proliferation observed every year in the Eastern English Channel (EEC), have a significant influence on the overall planktonic community structure and their food web dynamics. As well as being an important area for local fisheries, the EEC is an ideal ecosystem for work on microbial diversity. This is because, although its environmental context is relatively complex, it is reasonably well understood due to several years of monitoring and morphological observations of its planktonic organisms. The objective of our study was to better understand the under-explored microbial eukaryotic diversity relative to the Phaeocystis bloom. Methodology and Principal Findings: The community structure of microplankton (diatoms, haptophytes, ciliates and dinoflagellates) was studied through morphological observations and tag pyrosequencing. During the annual Phaeocystis spring bloom, the phytoplankton biomass increased by 34-fold, while the microzooplankton biomass showed a 4-fold increase, representing on average about 4.6% of the biomass of their phytoplankton prey. Tag pyrosequencing unveiled an extensive diversity of Gymnodiniaceae, with G. spirale and G. fusiformis representing the most abundant reads. An extended diversity of Phaeocystales, with partial 18S rDNA genes sequence identity as low as 85% was found, with taxa corresponding to P. globosa, but also to unknown Phaeocystaceae. Conclusions: Morphological analyses and pyrosequencing were generally in accordance with capturing frequency shifts of abundant taxa. Tag pyrosequencing allowed highlighting the maintenance of microplankton diversity during the Phaeocystis bloom and the increase of the taxa presenting low number of reads (minor taxa) along with the dominant ones in response to biotic and/or abiotic changing conditions. Although molecular approaches have enhanced our perception on diversity, it has come to light that the challenge of modelling and predicting ecological change requires the use of different complementary approaches, to link taxonomic data with the functional roles of microbes in biogeochemical cycles.
AMORE (Advanced Modeling and Research on Eutrophication) is an interdisciplinary consortium compo... more AMORE (Advanced Modeling and Research on Eutrophication) is an interdisciplinary consortium composed of biologists and physical and ecological modellers focusing their research activities on coastal eutrophication in the eastern Channel and Southern Bight of the North Sea with special interest in harmful Phaeocystis colony blooms. The long-term objective of AMORE is to develop a a tri-dimensional ecological model - MIRO&CO - able to predict the magnitude and geographical extent of Phaeocystis colony blooms in the Eastern Channel and Southern Bight of the North Sea with focus on the Belgian Coastal Zone (BCZ) and in response to varying short-term climate conditions and riverine nutrient (N, P, Si) loads. To achieve this objective, AMORE has developed an integrated research methodology that involves and combines in an interactive way the collection of historical and new field data, process-level studies, statistical analysis, mathematical modelling and data assimilation. In this appro...
This study is a first effort to compile the largest possible body of data available from differen... more This study is a first effort to compile the largest possible body of data available from different plankton databases as well as from individual published or unpublished datasets regarding diatom distribution in the world ocean. The data obtained originate from time series studies as well as spatial studies. This effort is supported by the Marine Ecosystem Data (MAREDAT) project, which aims at building consistent data sets for the main PFTs (Plankton Functional Types) in order to help validate biogeochemical ocean models by using converted C biomass from abundance data. Diatom abundance data were obtained from various research programs with the associated geolocation and date of collection, as well as with a taxonomic information ranging from group down to species. Minimum, maximum and average cell size information were mined from the literature for each taxonomic entry, and all abundance data were subsequently converted to biovolume and C biomass using the same methodology.
Although eutrophication induced by anthropogenic nutrient enrichment is a driver of shifts in com... more Although eutrophication induced by anthropogenic nutrient enrichment is a driver of shifts in community composition and eventually a threat to marine biodiversity, the causes and consequences on ecosystem functioning remain greatly unknown. In this study, by applying a trait-based approach and measuring niche breadth of diatoms and copepods, the drivers and underlying mechanisms of the seasonal species succession of these ecological communities in a coastal system dominated in spring by Phaeocystis blooms were explored. It is suggested that the seasonal succession of diatoms and copepods is the result of several trade-offs among functional traits that are controlled by the seasonal abiotic and biotic pressure encountered by the plankton communities. The results of this study highlight that a trade-off between competition and predator, i.e., weak competitors are better protected against predation, plays an important role in promoting plankton species richness and triggers the Phaeocy...
Eutrophication as a consequence of anthropogenic nutrient enrichment is one of the major threats ... more Eutrophication as a consequence of anthropogenic nutrient enrichment is one of the major threats to biodiversity in nearshore and coastal marine waters, and consequently, for ecosystem functioning. This study explores changes in the biological organization of copepod assemblages along a Chl a gradient through an upscaling analysis of regional datasets from the coastal waters of the Mediterranean Sea. Results show that omnivorous copepods using passive and/or ambush feeding strategy are favored as Chl a increases, and copepod community shifts towards trophic homogenization by favoring generalist feeders against specialists. To our knowledge, this is the first report of functional homogenization of copepods as the result of eutrophication. The present study also demonstrates the potential use of trait-based approaches to explore the effect of human disturbances on marine copepod assemblages in marine ecosystems.
This study explored the potential interactions and relations of the putative Symbiotic/Decomposer... more This study explored the potential interactions and relations of the putative Symbiotic/Decomposer/Parasitic community (SymbDec) with other taxa and predominant environmental parameters in the eastern English Channel (EEC) over a 2.5 years period (32 sampling dates). The EEC is a meso-eutrophic coastal system portrayed by intense reoccurring patterns in plankton succession with blooms of the Haptophyte Phaeocystis globosa and abundant populations of colonial diatoms and dinoflagellate grazers before and after the bloom. The study of the V2-V3 hypervariable region of the 18S rRNA gene allowed an overview of the planktonic community, which consisted of 32 high-level taxonomic groups. Forty-two percent of the identified OTUs belonged to symbionts, decomposers or other putative parasitic taxa belonging mainly to Syndiniales (MALV-MArine ALveolates), Fungi, Cercozoa, Perkinsea, and others, most of which were plankton parasites. We examined the Local Similarity Analysis (LSA) network of lag delayed correlations on the 142 most abundant OTUs (>0.1% of the total number of reads). LSA showed that 99 OTUs had highly significant connections, involving 26 OTUs characterized as potential parasites, and 2 decomposers. The parasitic network had "small world" characteristics, rendering the assemblage more robust to abiotic variations, but more exposed to the removal of highly associated taxa. The majority of the highly connected OTUs belonged to MALV, which were mainly connected with dinoflagellates, suggesting that it might play an important role on dinoflagellate top-down control. The bloom forming P. globosa was not observed in connection with parasitic OTUs in the network. Four environmental parameters (O 2 , N, T, and N/P) were strongly connected with only 11 OTUs, while correlations between microbes dominated the network.
The diversity of planktonic eukaryotic microbes was studied at a coastal station of the eastern E... more The diversity of planktonic eukaryotic microbes was studied at a coastal station of the eastern English Channel (EEC) from March 2011 to July 2015 (77 samples) using high throughput sequencing (454-pyrosequencing and Illumina) of the V2-V3 hypervariable region of the 18S SSU rDNA gene. Similar estimations of OTU relative abundance and taxonomic distribution for the dominant higher taxonomic groups (contributing >1% of the total number of OTUs) were observed with the two methods (Kolmogorov-Smirnov p-value = 0.22). Eight super-groups were identified throughout all samples: Alveolata, Stramenopiles, Opisthokonta, Hacrobia, Archeaplastida, Apusozoa, Rhizaria, and Amoebozoa (ordered by decreasing OTU richness). To gain further insight into microbial activity in the EEC, ribosomal RNA was extracted for samples from 2013-2015 (30 samples). Analysis of 18S rDNA and rRNA sequences led to the detection of 696 and 700 OTUs, respectively. Cluster analysis based on OTUs' abundance indicated three major seasonal groups that were associated to spring, winter/autumn, and summer conditions. The clusters inferred from rRNA data showed a clearer seasonal representation of the community succession than the one based on rDNA. The rRNA/rDNA ratio was used as a proxy for relative cell activity. When all OTUs were considered, the average rRNA: rDNA ratio showed a linear trend around the 1:1 line, suggesting a linear relation between OTU abundance (rDNA) and activity (rRNA). However, this ratio was highly variable over time when considering individual OTUs. Interestingly, the OTU affiliated with P. globosa displayed rRNA: rDNA ratio that allowed to delimit high vs low abundance and high vs low activity periods. It unveiled quite well the Phaeocystis bloom dynamic regarding cell proliferation and activity, and could even be used as early indicator of an upcoming bloom.
This study explored the relevance of the use of a trait-based approach to explain seasonal phytop... more This study explored the relevance of the use of a trait-based approach to explain seasonal phytoplankton succession and the underlying mechanisms that structure phytoplankton assemblages and promote nitrogen use efficiency (NUE) in the temperate coastal waters of the eastern English Channel (EEC). A 3 yr time series of phytoplankton abundance assessed by flow cytometry was combined with a selection of traits related to resource utilization (light and inorganic nutrients), grazing resistance, and maximum growth, mainly sourced from the literature. Our results showed that the identified functional groups (FGs) ranged deterministically along a temporal gradient of light and nutrient availability, according to several fundamental trade-offs. These trade-offs, which reflected different ecological strategies, were distributed along 1 axis of niche differentiation. This favoured different FGs through time, and consequently allowed them to partition those available resources. The observed functional divergence of the phytoplankton community deviated from that of the expected, random one. It showed that as light increased, the phytoplankton community assembly was mainly driven by competition and grazing pressure, which eventually favoured those FGs that were fastest growing and less vulnerable to predation. Structural equation modeling evidenced that a phytoplankton community, functionally dominated by FGs that were relatively large, fast-growing, and well-adapted to higher light, promoted NUE. Together, these results confirmed the potential use of laboratory-measured functional traits to explore environment−trait linkages in phytoplankton. They also showed the possibility of further extending this approach to identify the mechanisms driving phytoplankton community assembly, structure, and related ecosystem processes.
Please note that this is an author-produced PDF of an article accepted for publication following ... more Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.
The planktonic haptophyte Phaeocystis has been suggested to play a fundamental role in the global... more The planktonic haptophyte Phaeocystis has been suggested to play a fundamental role in the global biogeochemical cycling of carbon and sulphur, but little is known about its global biomass distribution. We have collected global microscopy data of the genus Phaeocystis and converted abundance data to carbon biomass using speciesspecific carbon conversion factors. Microscopic counts of single-celled and colonial Phaeocystis were obtained both through the mining of online databases and by accepting direct submissions (both published and unpublished) from Phaeocystis specialists. We recorded abundance data from a total of 1595 depth-resolved stations sampled between 1955-2009. The quality-controlled dataset includes 5057 counts ESSDD 5, 405-443, 2012
The inter-annual variability of the fish and macrocrustacean spring community on an intertidal sa... more The inter-annual variability of the fish and macrocrustacean spring community on an intertidal sandy beach near the Canche estuary (North of France) was studied from 2000 to 2013 based on weekly spring sampling over an 11-year period. Twenty-eight species representing 21 families were collected during the course of the study. The community was dominated by a few abundant species accounting for > 99% of the total species densities. Most individuals caught were young-of-the-year indicating the importance of this ecosystem for juvenile fishes and macrocrustaceans. Although standard qualitative community ecology metrics (species composition, richness, diversity, evenness and similarity) indicated notable stability over the study period, community structure showed a clear change since 2009. Densities of P. platessa, P. microps and A. tobianus decreased significantly since 2009, whereas over the period 2010-2013, the contribution of S. sprattus to total species density increased 4-fold. Co-inertia and generalised linear model analyses identified winter NAO index, water temperature, salinity and suspended particular matter as the major environmental factors explaining these changes. Although the recurrent and dense spring blooms of the Prymnesiophyte Phaeocystis globosa is one of the main potential threats in shallow waters of the eastern English Channel, no negative impact of its temporal change was detected on the fish and macrocrustacean spring community structure.
A Phaeocystis sp. (Prymnesiophyceae) bloom regularly occurs in April–May in the Eastern English C... more A Phaeocystis sp. (Prymnesiophyceae) bloom regularly occurs in April–May in the Eastern English Channel. In the literature, views are divided about the in situ appetence of copepods for this alga. In a study carried out in the coastal waters off the bay of Somme, at the end of the bloom, from 29 of April to 1 of May 1996, HPLC
... eutrophication phenomenon. Foaming is considered as a minor nuisance compared to other forms ... more ... eutrophication phenomenon. Foaming is considered as a minor nuisance compared to other forms of environmental disturbance such as oil pollution, garbage or dead jelly fishes on the beaches, bad weather conditions. The socio-economic impact of ...
Background: Massive phytoplankton blooms, like the recurrent Phaeocystis proliferation observed e... more Background: Massive phytoplankton blooms, like the recurrent Phaeocystis proliferation observed every year in the Eastern English Channel (EEC), have a significant influence on the overall planktonic community structure and their food web dynamics. As well as being an important area for local fisheries, the EEC is an ideal ecosystem for work on microbial diversity. This is because, although its environmental context is relatively complex, it is reasonably well understood due to several years of monitoring and morphological observations of its planktonic organisms. The objective of our study was to better understand the under-explored microbial eukaryotic diversity relative to the Phaeocystis bloom. Methodology and Principal Findings: The community structure of microplankton (diatoms, haptophytes, ciliates and dinoflagellates) was studied through morphological observations and tag pyrosequencing. During the annual Phaeocystis spring bloom, the phytoplankton biomass increased by 34-fold, while the microzooplankton biomass showed a 4-fold increase, representing on average about 4.6% of the biomass of their phytoplankton prey. Tag pyrosequencing unveiled an extensive diversity of Gymnodiniaceae, with G. spirale and G. fusiformis representing the most abundant reads. An extended diversity of Phaeocystales, with partial 18S rDNA genes sequence identity as low as 85% was found, with taxa corresponding to P. globosa, but also to unknown Phaeocystaceae. Conclusions: Morphological analyses and pyrosequencing were generally in accordance with capturing frequency shifts of abundant taxa. Tag pyrosequencing allowed highlighting the maintenance of microplankton diversity during the Phaeocystis bloom and the increase of the taxa presenting low number of reads (minor taxa) along with the dominant ones in response to biotic and/or abiotic changing conditions. Although molecular approaches have enhanced our perception on diversity, it has come to light that the challenge of modelling and predicting ecological change requires the use of different complementary approaches, to link taxonomic data with the functional roles of microbes in biogeochemical cycles.
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