Effect of herbicide (Diuron and Imazapyr) on phytoplankton of San Francisco bay

Two herbicides (diuron and imazapyr) were shown to have a negative effect on primary productivity of a mixed natural phytoplankton community from the San Francisco Estuary. Productivity was affected immediately after diuron exposure and after 48 hour (chronic) exposure, while imazapyr only showed effects with chronic exposure. In addition to effects on productivity, nutrient uptake decreased with increasing herbicide concentration. Phytoplankton biomass and abundance decreased with increasing herbicide concentration, and the phytoplankton community composition shifted with added diuron and imazapyr. Centric diatoms as a percent of the phytoplankton community\ud decreased while flagellates increased