Spring Phytoplankton Abundance and Productivity in Grand Traverse Bay, Lake Michigan, 1970

Abstract

In May 1970, phytoplankton abundance in Grand Traverse Bay ranged from 1455 cells/ml to 3355 cells/mi. Highest standing crop estimates were obtained from stations in the lower portion of the west arm. Lowest standing crop estimates were obtained from stations in the upper east arm. The same populations dominated the assemblages at all stations and estimated diversity of assemblages was relatively high and uniform, ranging from 2.3 to 2.6, Estimates of primary productivity from the same stations ranged from 3.8 mg C m3 hr to 9.1 mg C m3 hr1 and followed the same general pattern of areal distribution as the standing crop estimates. In June, standing crop estimates increased significantly, with values ranging from 2500 cells/ml to 6469 cells/ml. Highest standing crops again were found at stations in the lower west arm, in the vicinity of Traverse City. Similar dominant populations were present again at all stations, but estimated diversity of the assemblages at all stations decreased, with values ranging from 1.8 to 2.2. Estimates of primary productivity were more variable during the June sampling period, with values ranging from 2.7 mg C m hr- 1 to 13.4 mg C m~3 hr- 1 , with greatest differences again being between most productive stations in the lower west arm and least productive stations in the upper east arm. (Key words: Phytoplankton;, standing crop; productivity; Grand Traverse Bay).