Planktonic biomass variability during a late winter bloom in the subtropical waters off the Canary Islands

Abstract

Planktonic biomass from heterotrophic prokaryotes to mesozooplankton was assessed in the Canary Island waters in order to study the characteristic late winter bloom of subtropical waters. Weekly sampling was performed between January and August 2005 at 6 stations around the island of Gran Canaria. The bloom observed in this study showed the common increase in chlorophyll in February–March. However, the study of the biomass of different components of the planktonic community unveils a succession of peaks of monthly periodicity. The bloom started with an increase in large primary producers and was followed by several alternating peaks of heterotrophic nanoflagellates, microplankton and mesozooplankton. During the period studied, mesozooplankton, autotrophic picoplankton and heterotrophic prokaryotes showed similar trends, whereas nano- and microplankton depicted an inverse pattern. Our results show that the late winter bloom in subtropical waters is much more complex than that inferred from the simple increase in chlorophyll associated with the drop of temperature during winter.