Biogeosciences, 12, 2395–2409, 2015 www.biogeosciences.net/12/2395/2015/ doi:10.5194/bg-12-2395-2015 © Author(s) 2015. CC Attribution 3.0 License. Phytoplankton dynamics in contrasting early stage North Atlantic spring blooms: composition, succession, and potential drivers C. J. Daniels1, A. J. Poulton2, M. Esposito2, M. L. Paulsen3, R. Bellerby4,5,6, M. St John7, and A. P. Martin2 1Ocean and Earth Sciences, National Oceanography Centre Southampton, University of Southampton, Southampton, UK 2Ocean Biogeochemistry and Ecosystems, National Oceanography Centre, University of Southampton Waterfront Campus, Southampton, UK 3Department of Biology, Marine Microbiology Department, University of Bergen, Bergen, Norway 4Norwegian Institute for Water Research (NIVA), Bergen, Norway 5Uni Bjerknes Centre, Bergen, Norway 6State Key Laboratory for Estuarine and Coastal Research, East China Normal University, Shanghai, China 7National Institute of Aquatic Resources, Technical University of Denmark, Charlottenlund, Denmark Correspondence to: C. J. Daniels (
[email protected]) Received: 1 December 2014 – Published in Biogeosciences Discuss.: 6 January 2015 Revised: 23 March 2015 – Accepted: 4 April 2015 – Published: 24 April 2015 Abstract. The spring bloom is a key annual event in the phe- was potentially limited by physicochemical and/or biological nology of pelagic ecosystems, making a major contribution factors such as grazing. to the oceanic biological carbon pump through the produc- Diatoms dominated the ICB, with the genus Chaetoceros tion and export of organic carbon. However, there is little (1–166 cells mL−1) being succeeded by Pseudo-nitzschia consensus as to the main drivers of spring bloom formation, (0.2–210 cells mL−1). However, large diatoms (> 10 µm) exacerbated by a lack of in situ observations of the phyto- were virtually absent (< 0.5 cells mL−1) from the NWB, plankton community composition and its evolution during with only small nano-sized (< 5 µm) diatoms (i.e.