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

GARCIA M.D.; HOFFMEYER M.S.; LÓPEZ ABBATE M.C.; BARRÍA DE CAO M.S.; PETTIGROSSO R.E.; ALMANDOZ G.O.; HERNANDO M.P.; SCHLOSS I.R.

POLAR BIOLOGY

SPRINGER

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

0722-4060

Rapid climate-driven melting of coastal glaciers in the Western Antarctic Peninsula is an important factor controlling plankton dynamics. In Potter Cove, 25 de Mayo/King George Island phytoplankton is tightly coupled to environmental conditions, which in turn are modulated by meltwater input. The aim of this study was to examine the structure and dynamics of microzooplankton and mesozooplankton in two zones (the inner and outer cove) differently impacted by glacier melting during two contrasting austral summers (2010 and 2011). Microzooplankton composition differed between zones and years. Total biomass was lower close to the glacier and during 2011. Mesozooplankton composition and biomass were similar in both zones and years. Colder than usual conditions in January 2010 favored the development of an herbivorous food web, with an exceptional micro-sized diatom bloom (>10 µg l-1 chlorophyll-a), which was tightly coupled to a peak of large copepods. Large diatoms were later replaced by nanophyplankton and large copepods by microzooplankton (aloricate ciliates and dinoflagellates). In 2011 a high biomass of large copepods could have exerted grazing pressure on aloricate ciliates and heterotrophic dinoflagellates, while the high water temperature could favor the development of tintinnids that would control the phytoplankton biomass, in a microbial food web type. Ours results suggest that zooplankton is an important factor controlling phytoplankton biomass and food web dynamics. The joint effect of water temperature and salinity and phytoplankton composition appears to be the primary factors structuring zooplankton community in Potter Cove.