Specific growth rates of protozooplankton in the marginal ice zone of the central Barents Sea during spring

Abstract

Protozooplankton growth was measured by incubation in a walk-in cooling room at 5°C of filtered seawater from six stations on a south–north transect from open water through drift ice and into fast ice in the central Barents Sea (72°30′N–76°32′N). Eight species of naked ciliates, two species of tintinnids, seven species of athecate dinoflagellates and nine species of thecate dinoflagellates grew in the 24 and 48 h bottle incubations. Maximum potential mean specific growth rates of 0.84, 0.59, 0.39 and 0.39 d−1, respectively, indicated a hierarchy in growth rates determined by taxonomic differences where growth of naked ciliates > tintinnids > athecate dinoflagellates > thecate dinoflagellates. The mean±SD in situ temperature (4 to −1.8°C) corrected growth rates (Q10=2.8) for the six stations (0.74±0.31, 0.74±0.16, 0.25±0.16, 0.23±0.27 d−1) also suggested a higher growth for ciliates in comparison to dinoflagellates. Additionally, it revealed that the naked ciliates responded to the increased food availability, whereas this was not the case for all other groups of protozooplankton.