Interannual fluctuations in copepod abundance and contribution of small forms in the Drake Passage during austral summer

THOMPSON GUSTAVO; DINOFRIO ESTELA; ALDER VIVIANA

HELGOLAND MARINE RESEARCH

SPRINGER

Año: 2012 vol. 66 p. 127 - 138

1438-387X

The relative importance of small forms of copepods has been historically underestimated by the traditional use of 200-300 µm mesh nets. This work quantified the distribution and abundance of copepods, considering two size fractions (<300 µm and >300 µm), in superficial waters (9 m deep) of the Drake Passage and contributed to the knowledge of their interannual fluctuations among three summers. Four types of nauplii and eleven species of copepods at copepodite and adult stages were identified, with abundance values of up to 13 ind/L and 28,300 µg C/m3. The <300-µm fraction, composed of Oithona similis, small cyclopoids and nauplii, dominated the copepod communities in the three years; it accounted for more than 77% of the total number and for between 40-63% of the total biomass. Changes in density and biomass values among the three cruises differed according to copepod size fraction and water mass; the >300-µm fraction showed no changes among the three years, both in Antarctic (density and biomass) and Subantarctic waters (density), whereas the <300-µm fraction showed higher (density and biomass) values in 2001 both in Subantarctic and Antarctic waters. Sea surface temperature and its anomaly accounted for the largest proportion of variability in copepod density and biomass, particularly for the <300-µm fraction.