Zooplankton grazing can potentially affect the biomass and composition of phytoplankton communities directly and indirectly. Low chlorophyll a concentration for a given TP concentration and simplified fishless food webs lead to the expectation that zooplankton community grazing rates are high in Subarctic regions; however, zooplankton community grazing rates have not been determined for Subarctic lakes/ponds. We estimated zooplankton community grazing rates on phytoplankton in 12 lakes and ponds in Wapusk National Park, Canada using a microcosm grazing experiment. Lakes and ponds differed in zooplankton taxonomic composition, Chl-a concentration, and zooplankton biomass. We found that the grazing rates on the total chlorophyll a (GR Total) ranged 0-13. 7% grazed per day and the grazing rates on the edible (<30 μm, GR <30) chlorophyll a was 0 to 16. 7% per day. GR Total increased with lake Daphnia and cladoceran biomass, as did GR <30, which also had a negative relationship with the total in-lake Chl-a. The calculated zooplankton grazing rates were within the range found for larger, temperate lakes.
All Science Journal Classification (ASJC) codes
- Aquatic Science