Seasonal metabolic dynamics of microeukaryotic plankton : a year-long metatranscriptomic study in a temperate sea

Seasonal fluctuations profoundly affect marine microeukaryotic plankton composition and metabolism, but accurately tracking these changes has been a long-standing challenge. In this study, we present a year-long metatranscriptomic data set from the Southern Bight of the North Sea, shedding light on the seasonal dynamics in temperate plankton ecosystems. We observe distinct shifts in active plankton species and their metabolic processes in response to seasonal changes. We characterized the metabolic signatures of different seasonal phases in detail, thereby revealing the metabolic versatility of dinoflagellates, the heterotrophic dietary strategy of Phaeocystis during its late-stage blooms, and stark variations in summer and fall diatom abundance and metabolic activity across nearby sampling stations. Our data illuminate the varied contributions of microeukaryotic taxa to biomass production and nutrient cycling at different times of the year and allow delineation of their ecological niches.IMPORTANCEEcosystem composition and metabolic functions of temperate marine microeukaryote plankton are strongly influenced by seasonal dynamics. Although monitoring of species composition of microeukaryotes has expanded recently, few methods also contain seasonally resolved information on ecosystem functioning. We generated a year-long spatially resolved metatranscriptomic data set to assess seasonal dynamics of microeukaryote species and their associated metabolic functions in the Southern Bight of the North Sea. Our study underscores the potential of metatranscriptomics as a powerful tool for advancing our understanding of marine ecosystem functionality and resilience in response to environmental changes, emphasizing its potential in continuous marine ecosystem monitoring to enhance our ecological understanding of the ocean's eukaryotic microbiome. Ecosystem composition and metabolic functions of temperate marine microeukaryote plankton are strongly influenced by seasonal dynamics. Although monitoring of species composition of microeukaryotes has expanded recently, few methods also contain seasonally resolved information on ecosystem functioning. We generated a year-long spatially resolved metatranscriptomic data set to assess seasonal dynamics of microeukaryote species and their associated metabolic functions in the Southern Bight of the North Sea. Our study underscores the potential of metatranscriptomics as a powerful tool for advancing our understanding of marine ecosystem functionality and resilience in response to environmental changes, emphasizing its potential in continuous marine ecosystem monitoring to enhance our ecological understanding of the ocean's eukaryotic microbiome

Towards 3D SPM monitoring in the North Sea using multibeam sonar

Monitoring suspended particulate matter (SPM) in coastal areas is essential for research, management and protection of coastal ecosystems. In the Belgian part of the North Sea, the dynamic nature of SPM variability and the increasing human activities (offshore windmill parks, dredging and dumping) call for 3D monitoring of these natural and human-induced SPM changes.Multibeam echosounders (MBES) provide, in addition to bathymetry and seafloor backscatter data, a 3D dataset of acoustic measurements in the water column, which can be used to monitor SPM in coastal waters. Although MBES water column data are commonly used by fisheries and gas seepage research, only a handful of studies focus on the quantification of SPM in the water column.During the Timbers project, we developed a novel methodology to convert MBES water column data into 3D SPM maps. In contrast to most studies that deploy the MBES from stations, we quantified SPM using MBES from a sailing vessel. Simultaneous optical and acoustic measurements were collected during ship transects to yield an empirical relation using linear regression modeling. This relationship was then used to convert the acoustic measurements into a 3D grid that displays the mass concentration of SPM. The large spatial coverage of these SPM maps allows us to observe phenomena in the water column that otherwise would be missed by traditional monitoring approaches. Furthermore, several valuable lessons were learned. In particular, the interpretation of the acoustic signal is not straightforward, which makes it difficult to distinguish between different types of scatterers (sediment, plankton, flocs, bubbles, fish, etc.) captured by the MBES. Hence, additional research efforts focusing on discriminating scatterers in the water column are needed to unlock the full monitoring potential of MBES water column data.In the ongoing Turbeams project, we are exploring multi-frequency approaches to differentiate between various scatterers and their wide spectrum of sizes. Additionally, we are applying imaging tools on collected water samples and we are using underwater cameras that capture particles in their natural environment. These improvements will help to move towards operational use of MBES as a common tool for SPM monitoring in the future.</jats:p

Temperature-induced copepod depletion and the associated wax of Bellerochea in Belgian coastal waters : implications and shifts in plankton dynamics

Since 2018, severe and recurrent copepod depletions have been observed in Belgian coastal waters. These depletions have been described as temperature-induced mass mortality events. This paper confirms the relation of copepod abundance anomalies with periods of high temperature based on new data. Although severe, the effects, consequences and implications of this depletion remain unknown. Our study suggests that the absence of zooplanktonic predators in autumn, together with the availability of nutrients discharged via the Scheldt estuary, allowed a bloom of the diatom Bellerochea, in a season otherwise characterised by low phytoplanktonic activity. Although the bloom reaches high abundances, its effects on the marine environment are not yet visible. The enormous abundances are likely to induce small-scale oxygen depletions which might further translate to the environment. Communities of Calanoida, Canuelloida and Cyclopoida tend to recover from the annual autumn depletion, although the typical autumn peak is entirely missing in the years subject to severe heat waves and associated high water temperatures. As a result, copepod dynamics have drastically changed since the first observed depletion and associated bloom of Bellerochea in 2018

Multiscale harmonised automated observations of phytoplankton biomass, diversity and productivity dynamics in the English Channel and North Sea as part of the coastal Pilot Super Site approach (JERICO S3)

International audienceMultiscale harmonised automated observation of phytoplankton is essential for accurately monitoring changes in marine coastal ecosystems state and functioning. Novel approaches are currently applied within the English Channel and North Sea coastal Pilot Super Site of the Joint European Research Infrastructure for Coastal Observatories (JERICO-S3) for provision of sustained multidisciplinary observations. This site is characterized by significant connectivity to adjacent seas, strong hydrodynamics and high riverine inputs, influencing biogeochemical and biological processes like high productivity and recurring phytoplankton blooms, some them of potential impact on marine food webs, as well as human health and economy. The intrinsic knowledge on phytoplankton biomass, diversity and productivity dynamics are completed, at different spatial and temporal scales, through the harmonisation of observations (including near-real time in vivo automated approaches implemented for almost a decade). Integrated phytoplankton observations are carried out combining reference methods with innovative automated in vivo imaging inflow/in situ/benchtop devices, automated flow cytometers, as well as multispectral/variable fluorometers, implemented in fixed autonomous stations, moorings, dedicated cruises and ships of opportunity (FerryBox). Functional and taxonomical diversity are addressed in the frame of different monitoring networks carried out in four contrasted ecosystems from the Celtic Seas and English Channel to the German Bight in the North Sea. Moreover, the models used to compute high resolution-resolved photosynthetic parameters and primary production using variable fluorescence measurements give insights into different seasonal patterns, which are respectively synchronous or in delay with that of chlorophyll biomass and community changes. These measurements provide a more precise information on the distribution and dynamics of phytoplankton functional groups (flow cytometry) and main taxa (imaging) at high spatial and temporal resolution assigning community changes to different bloom situations and pelagic habitats state, complementing physical, biogeochemical and biological variables. Finally, harmonisation in data pipelines conform to the FAIR principle and synthesis based on conventional statistics as well as on IA/ML approaches makes it possible to address scientific, societal and economic challenges through a new perspective, facing global and local changes

Multiscale harmonised automated observations of phytoplankton biomass, diversity and productivity dynamics in the English Channel and North Sea as part of the coastal Pilot Super Site approach (JERICO S3)

International audienceMultiscale harmonised automated observation of phytoplankton is essential for accurately monitoring changes in marine coastal ecosystems state and functioning. Novel approaches are currently applied within the English Channel and North Sea coastal Pilot Super Site of the Joint European Research Infrastructure for Coastal Observatories (JERICO-S3) for provision of sustained multidisciplinary observations. This site is characterized by significant connectivity to adjacent seas, strong hydrodynamics and high riverine inputs, influencing biogeochemical and biological processes like high productivity and recurring phytoplankton blooms, some them of potential impact on marine food webs, as well as human health and economy. The intrinsic knowledge on phytoplankton biomass, diversity and productivity dynamics are completed, at different spatial and temporal scales, through the harmonisation of observations (including near-real time in vivo automated approaches implemented for almost a decade). Integrated phytoplankton observations are carried out combining reference methods with innovative automated in vivo imaging inflow/in situ/benchtop devices, automated flow cytometers, as well as multispectral/variable fluorometers, implemented in fixed autonomous stations, moorings, dedicated cruises and ships of opportunity (FerryBox). Functional and taxonomical diversity are addressed in the frame of different monitoring networks carried out in four contrasted ecosystems from the Celtic Seas and English Channel to the German Bight in the North Sea. Moreover, the models used to compute high resolution-resolved photosynthetic parameters and primary production using variable fluorescence measurements give insights into different seasonal patterns, which are respectively synchronous or in delay with that of chlorophyll biomass and community changes. These measurements provide a more precise information on the distribution and dynamics of phytoplankton functional groups (flow cytometry) and main taxa (imaging) at high spatial and temporal resolution assigning community changes to different bloom situations and pelagic habitats state, complementing physical, biogeochemical and biological variables. Finally, harmonisation in data pipelines conform to the FAIR principle and synthesis based on conventional statistics as well as on IA/ML approaches makes it possible to address scientific, societal and economic challenges through a new perspective, facing global and local changes

Automated optical approaches for in vivo multiscale monitoring of phytoplankton communities and HABs in the English Channel and North Sea

International audienceAutomated optical observations of phytoplankton communities are currently implemented in eastern English Channel and southern North Sea on different platforms (fixed autonomous stations, moorings, dedicated cruises and measurements/ships of opportunity) as a complement of long term monitoring networks in the. These marginal seas are characterized by significant connectivity to adjacent ocean and seas, strong hydrodynamics and low to high riverine inputs, influencing biogeochemical and biological processes like high productivity and recurring phytoplankton blooms, including some Harmful Algal Blooms-HABs of potential impact on marine food webs, as well as on human health and economy. Integrated phytoplankton observations are carried out combining reference methods with innovative automated in vivo imaging inflow/in situ/benchtop devices, pulse shape-recording flow cytometers, as well as in vivo multispectral fluorometers. These measurements provide information on the distribution and dynamics of phytoplankton functional groups (flow cytometry) and main taxa (imaging) at high spatial and temporal resolution assigning community changes to different bloom situations and pelagic habitats state, complementing physical, biogeochemical and biological variables. The in vivo approaches allow tracking HABs at different spatial and temporal scales, through the harmonisation of observations (including near-real time in vivo automated approaches implemented for almost a decade), at almost real time, and become a helpful tool for managers of these events. Finally, harmonisation in data pipelines conform to the FAIR principle and synthesis based on conventional statistics as well as on IA/ML approaches makes it possible to address scientific, societal and economic challenges through a new perspective, facing global and local changes

Automated optical approaches for in vivo multiscale monitoring of phytoplankton communities and HABs in the English Channel and North Sea

International audienceAutomated optical observations of phytoplankton communities are currently implemented in eastern English Channel and southern North Sea on different platforms (fixed autonomous stations, moorings, dedicated cruises and measurements/ships of opportunity) as a complement of long term monitoring networks in the. These marginal seas are characterized by significant connectivity to adjacent ocean and seas, strong hydrodynamics and low to high riverine inputs, influencing biogeochemical and biological processes like high productivity and recurring phytoplankton blooms, including some Harmful Algal Blooms-HABs of potential impact on marine food webs, as well as on human health and economy. Integrated phytoplankton observations are carried out combining reference methods with innovative automated in vivo imaging inflow/in situ/benchtop devices, pulse shape-recording flow cytometers, as well as in vivo multispectral fluorometers. These measurements provide information on the distribution and dynamics of phytoplankton functional groups (flow cytometry) and main taxa (imaging) at high spatial and temporal resolution assigning community changes to different bloom situations and pelagic habitats state, complementing physical, biogeochemical and biological variables. The in vivo approaches allow tracking HABs at different spatial and temporal scales, through the harmonisation of observations (including near-real time in vivo automated approaches implemented for almost a decade), at almost real time, and become a helpful tool for managers of these events. Finally, harmonisation in data pipelines conform to the FAIR principle and synthesis based on conventional statistics as well as on IA/ML approaches makes it possible to address scientific, societal and economic challenges through a new perspective, facing global and local changes