Towards a comprehensive C-budgeting approach of a coccolithophorid bloom in the Northern Bay of Biscay (June 2006)

A biogeochemical multidisciplinary survey was carried out in the northern Bay of Biscay, in early June 2006, during which 14C-based primary production and calcification were determined as well as O2-based community respiration. Contemporary remote sensing images showed several patches of high reflectance (HR) in the investigated area. Based on remote sensing and in situ measured biogeochemical parameters, the area exhibited varying coccolithophorid bloom stages from its early development to the post-bloom stages. The major HR patch, characterizing a post-stationary stage of the bloom, was located between 48°N and 49°N over the shelf along the continental margin. It was associated with moderate chlorophyll-a levels, never exceeding 1.0 µg L-1, dissolved phosphorus and silica depletion, and undersaturation of CO2 with respect to atmospheric equilibrium. Considered as the main drivers of the C cycle in this area, the CO2 fluxes associated with primary production, calcification and respiration were integrated in order to provide a comprehensive C budget in the area

Biogeochemistry of a late marginal coccolithophorid bloom in the Bay of Biscay

Coccolithophores, among which Emiliania huxleyi (Ehux) is the most abundant and widespread species, are the dominant calcifying phytoplankton in the temperate zone of the world’s oceans. Within the framework of the “Climate and Atmosphere” Belgian Federal Science Policy Office programme, the continental margin of the Northern Bay of Biscay (North Atlantic Ocean) was visited in June 2006 during a multidisciplinary investigation of a late-spring bloom dominated by Ehux. Field sampling was assisted by daily transmission to the RV Belgica of remote sensing images, indicating the bloom development in the area. Various stations on the shelf and the shelf-break were sampled for the vertical distributions of nutrients, Transparent Exopolymer Particles (TEP), chlorophyll-a and particulate carbon concentrations. These data will be presented, here, in relation with 14C based integrated primary production, dissolved esterase activity and the bacterial community structure to emphasize the importance of coccolithophorid blooms in the biogeochemistry of the Northern Atlantic’s continental shelf

Biogeochemistry and carbon budget during a coccolithophorid bloom in the northern Bay of Biscay (June 2006)

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Biogeochemistry of a late coccolithophorid bloom at the continental margin of the Bay of Biscay

Recent findings have led to growing concern regarding the impact of ocean acidification on marine calcifyers, but little is known about their biogeochemistry in natural (field) conditions (a major but overlooked pre-requisite for realistic modelling of the future evolution of marine C cycling in a high CO2 world). The changes that will undergo these species in the near future and the biological feedback to decreasing oceanic pH are still open to debate. Coccolithophores, among which Emiliania huxleyi (Ehux) is the most abundant and widespread species, are the dominant calcifying phytoplankton in the subpolar and temperate zones of the worlds oceans. Within the framework of the Climate and Atmosphere Belgian Federal Science Policy Office programme, the continental margin of the Northern Bay of Biscay (North Atlantic Ocean) was visited in June 2006 during a transdisciplinary investigation of a late-spring bloom dominated by Ehux. Remote sensing images, transmitted onboard on a daily basis, were of valuable significance to pinpoint the coccolithophorid bloom along the margin, and to sample stations with contrasted biogeochemical properties.We determined 14C-based primary production and calcification rates, as well as pelagic respiration rates (O2 incubations). The magnitude of the biological and carbonate carbon fluxes will be synthesized and discussed in the light of biogeochemical parameters, such as Transparent Exopolymer Particles (TEP), chlorophyll-a, particulate carbon concentrations, particle dynamics and particulate organic carbon export (deduced from 234Th fluxes). Additional information on the bloom biogeochemistry will be presented (activity of dissolved esterase enzymes and bacterial community structure) to emphasize the importance of coccolithophorid blooms in the contemporary carbon cycle