Micro- and mesozooplankton responses during two contrasting summers in coastal Antarctic environment

GARCIA, M.; HOFFMEYER, M.; LÓPEZ ABBATE, M.C.; BARRÍA DE CAO, M; PETTIGROSSO, R.; ALMANDOZ G. O.; HERNANDO, M.; SCHLOSS, I. R.

POLAR BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2016 vol. 39 p. 123 - 137

0722-4060

Rapid climate-driven melting of coastal glaciers may control plankton dynamics in the Western Antarctic Peninsula. In Potter Cove, 25 de Mayo/King George Island, phytoplankton is tightly coupled to meltwater input, but no information on zooplankton is available on this regard. The aim of this study was to examine the structure and dynamics of microzooplankton and mesozooplankton in two zones (the inner and outer Potter Cove) differently impacted by glacier melting during two contrasting austral summers (2010 and 2011). Microzooplankton composition differed between zones and years, and its total biomass was highest far from the glacier influence and during 2010. Mesozooplankton composition and biomass were similar in both zones and years. Colder than usual conditions in summer 2010 prevented glacier melting, favoring the development of an exceptional micro-sized diatom bloom (~190 µg C l-1 and >15 µg l-1 chlorophyll-a), which was tightly followed by a maximum in large copepods abundance. After the bloom and in coincidence with intense glacier melting large diatoms were replaced by nanophytoplankton, and large copepods by microzooplankton (aloricate ciliates and dinoflagellates). In 2011, normal (warmer than in 2010) temperatures and low salinity waters resulted in low phytoplankton abundances, probably controlled by a high biomass of tintinnids. Large copepods might have exerted a high grazing pressure on aloricate ciliates and heterotrophic dinoflagellates. Our results suggest that the joint effect of water temperature, salinity and phytoplankton availability appears to be the primary factors structuring the micro- and mesozooplankton community, and that zooplankton was an important factor controlling phytoplankton biomass in Potter Cove during these two different summers.