Phytoplankton dynamics in contrasting early stage North Atlantic spring blooms: composition, succession, and potential drivers

• Published in: Biogeosciences 2015-04, Vol.12 (8), p.2395-2409
• Main Authors: Daniels, C. J, Poulton, A. J, Esposito, M, Paulsen, M. L, Bellerby, R, St John, M, Martin, A. P
• Format: Article
• Language: English
• Subjects: Bacillariophyceae; Basins; Biogeochemistry; Biomass; Blooms; Carbon; Carbon cycle; Cells; Chlorophyll; Chlorophyll a; Community composition; Community structure; Composition; Diatoms; Dynamic structural analysis; Dynamics; Exports; Grazing; Hypotheses; Marine ecosystems; Marine microorganisms; Mixed layer; Organic carbon; Organic matter; Phenology; Phytoplankton; Picoplankton; Plankton; Predation; Primary production; Spring; Trophic relationships; Winter; Zooplankton
• ISSN: 1726-4189; 1726-4170; 1726-4189
• DOI: 10.5194/bg-12-2395-2015

The spring bloom is a key annual event in the phenology of pelagic ecosystems, making a major contribution to the oceanic biological carbon pump through the production and export of organic carbon. However, there is little consensus as to the main drivers of spring bloom formation, exacerbated by a lack of in situ observations of the phytoplankton community composition and its evolution during this critical period. We investigated the dynamics of the phytoplankton community structure at two contrasting sites in the Iceland and Norwegian basins during the early stage (25 March–25 April) of the 2012 North Atlantic spring bloom. The plankton composition and characteristics of the initial stages of the bloom were markedly different between the two basins. The Iceland Basin (ICB) appeared well mixed down to >400 m, yet surface chlorophyll a (0.27–2.2 mg m−3) and primary production (0.06–0.66 mmol C m−3 d−1) were elevated in the upper 100 m. Although the Norwegian Basin (NWB) had a persistently shallower mixed layer (