Feeding Ecology Of Marine Copepods And Their Grazing Impacts On Phytoplankton

Copepod feeding activities and their grazing impacts on the phytoplankton biomass and primary production were studies by the Gut fluorescence method in the coastal waters of China ( the Bohai Sea, Yellow Sea, East China Sea, Laizhou Bay and Weihe Estuary) and the Southern Ocean ( the Prydz Bay and its adjacent area). The results mainly include:Coastal Waters:The mean level of gut pigments increased with increasing size. But the gut evacuation rates did not vary with the experimental temperature and body size. Copepods usually performed feeding rhythms with maximum level at midnight and their feeding activities changed with the tide rhythms at the estuary area. In the Laizhou Bay, the daily grazing rate of the copepod population on phytoplankton was 20.81—98.35% of the primary production and 2.53—6.36% of the phytoplankton standing stock in summer. In the Weihe estuary, the daily grazing rate of the dominant species population on phytoplankton inside the river was less than 3% of the primary production and 1% of the phytoplankton standing stock. But outside the river, it showed a grazing impress on the phytoplankton community (32.28% of primary production and 14.12% of the stock). In the Bohai Sea, the grazing impact on phytoplankton by copepod was equivalent to 11.9% of the chlorophyll-a standingstock and 53.3% of the primary production during the spring cruise. And it was equivalent to 6.3%of the chlorophyll-a standing stock and >100% of the primary production during the autumn cruise. In the Yellow Sea and East China Sea, the grazing impact on phytoplankton by copepod was relatively lower, which equivalent to 11.2% of the chlorophyll-a standing stock during the spring cruise and 6.1% (range: 1.4-15.4%) during the autumn cruise.The consumption of phytoplankton was mainly caused by grazing of the small size group of copepods (200-500(m), which accounted for >50% of the copepod population consumption in the coastal waters of China.The Southern Ocean:At the marginal ice zone of Antarctica in summer, the microzooplankton was the dominated phytoplankton consumer. Salps also played an important role on control of phytoplankton where swarming occurs. The grazing of copepods had a relatively smaller effect on phytoplankton biomass development.