Abundance and age of viable resting eggs of the calanoid copepod Boeckella poppei Mrázek in sediments: evidence of egg banks in two Antarctic maritime lakes

Abstract

The existence of egg banks not only ensures the survival of zooplankton through harsh periods, but could also affect microevolutionary dynamics. Whether zooplankton at high latitudes can build up an egg bank in sediments, as occurs at lower latitudes, is still unknown. The distribution and age of viable resting eggs of the calanoid copepod Boeckella poppei Mrazek in sediments of two small freshwater lakes on King George Island were determined by slicing sediment cores at 1-cm intervals. Most viable resting eggs were found near the sediment surface, with abundance sharply declining to very low values at the depth of 5 cm, although eggs were present as deep as 9 cm in the sediments of Yanouhu Lake. The egg abundances in Xihu Lake and Yanouhu Lake were estimated to be 9.2 × 104 and 7.2 × 104 eggs m−2, respectively. 210Pb dating indicated a relatively constant sedimentation rate (0.023 cm year−1) in Xihu Lake, which was used to estimate the mean age (46.8 year), the maximum age (195.7 year), and the mortality rate (1.64 % year−1) of resting eggs of B. poppei in Xihu Lake. The accumulation of resting eggs with long-term viability in sediments provided the first evidence for the existence of egg banks in two Antarctic maritime lakes. An egg bank may serve as an overwintering strategy for B. poppei in Antarctica, enhance their ability to cope with random extreme changes, and contribute to their broad distribution.