Biogeochemical responses to late-winter storms in the Sargasso Sea. IV. Rapid succession of major phytoplankton groups

• Published in: Deep-sea research. Part I, Oceanographic research papers Oceanographic research papers, 2009-06, Vol.56 (6), p.892-908
• Main Authors: Lomas, M.W., Roberts, N., Lipschultz, F., Krause, J.W., Nelson, D.M., Bates, N.R.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Aquatic life; Bacillariophyceae; Biogeochemistry; Biological and medical sciences; Cyanobacteria; Diatoms; Earth, ocean, space; Eukaryotes; Exact sciences and technology; Export production; External geophysics; Fundamental and applied biological sciences. Psychology; Marine; Marine biology; New production; Nitrate uptake; Oceanography; Physical and chemical properties of sea water; Physics of the oceans; Phytoplankton community composition; Picoeukaryotes; Plankton; Sea water ecosystems; Synecology
• ISSN: 0967-0637; 1879-0119
• DOI: 10.1016/j.dsr.2009.03.004

In this paper, we present multi-parameter data on phytoplankton community composition, and its response to storm events in the Sargasso Sea in late February and early March of 2 years (2004 and 2005). Observed physical conditions spanned a continuum from pulsed destratification/stratification to continuous mixing, with a corresponding range of phytoplankton growth responses. The pulsed destratification/stratification condition resulted in a rapid (1–2 d) doubling of euphotic zone chlorophyll (Chl-a) along with a rapid succession, days timescale, from diatoms to haptophytes and then to cyanobacteria. Deep (>300 m) continuous mixing led to a slow (8–9 d) doubling of autotrophic biomass with no observed succession in the phytoplankton community. These different temporal responses appear to be due to differences between nutrient-limited and light-limited phytoplankton growth, although differences in grazing rates or selective grazing cannot be ruled out. Unexpectedly, we found that flow cytometrically enumerated picoeukaryotes were not accounted for in HPLC-pigment derived phytoplankton classifications and did not covary with any of the pigments quantified. Yet, the picoeukaryotes were positively related to increases in total Chl-a and increased carbon export, suggesting an important but as yet unknown role in the Sargasso Sea carbon cycle.