Patterns of plankton communities in subtropical waters off the Canary Islands during the late winter bloom

The microbial planktonic community of the subtropical waters around Gran Canaria Island, Canary Islands, was studied before, during and after the typical late winter bloom. The study consisted of a weekly sampling from October 2005 to June 2006 at five stations. Abundances and biomass of heterotrophic prokaryotes, small autotrophic plankton (picoplankton 0.2–2 μm in ESD), heterotrophic and autotrophic nanoflagellates (nanoplankton mainly in the range of 3–4 μm in ESD), microzooplankton (mainly ciliates and dinoflagellates 15–200 μm in ESD) and mesozooplankton (> 200 μm in ESD) were estimated in order to know the effect of the winter mixing. During all the period of study, microplankton abundance was dominated by small athecate dinoflagellates (15–20 μm in ESD) whereas its biomass was dominated by aloricate ciliates (20–30 μm and > 40 μm in ESD). The bloom began with the increase of autotrophic picoplanktonic cells and small diatoms. Consecutively, nano-, micro-, and mesozooplankton biomass also increased. During the development of the winter bloom, picoplankton, heterotrophic nanoflagellates, microzooplankton, mainly aloricate ciliates, and mesozooplankton showed inverse trends suggesting that the bloom is a succession of complex top-down controls.