Mesozooplankton grazing in the coastal Gulf of Alaska: Neocalanus spp. vs. other mesozooplankton

Liu, H., Dagg, J. M., Napp, J. M., and Sato, R. 2008. Mesozooplankton grazing in the coastal Gulf of Alaska: Neocalanus spp. vs. other mesozooplankton. – ICES Journal of Marine Science, 65: 351–360.Three species of large calanoid copepod, Neocalanus flemingeri, Neocalanus plumchrus, and Neocalanus cristatus, dominate the spring biomass of mesozooplankton in the Subarctic Pacific. We compared the grazing impact of Neocalanus species on phytoplankton with grazing by the remainder of the mesozooplankton community in the coastal and shelf waters of the Gulf of Alaska during spring and summer 2003. Neocalanus spp. and other mesozooplankton fed mainly on particles >20 µm, and phytoplankton in the smaller size-fractions (20 µm in the outer-shelf region, where chlorophyll a concentrations were 20 µm daily phytoplankton production in the inner- and mid-shelf regions where chlorophyll a concentrations were typically >5 mg m−3 with blooms of large diatoms. In summer, without Neocalanus spp. in the surface layer, mesozooplankton grazing accounted for a very small proportion of phytoplankton production across the whole shelf.