Heat wave brings an unprecedented red tide to San Francisco Bay

An exceptional red tide in San Francisco Bay was observed on 8 September 2004. The red tide had chlorophyll concentrations approaching 200 mg/m3 (Figure 1) in red/purple surface streaks containing high abundances of the dinoflagellate Akashiwo sanguinea. Red tides and harmful algal blooms (HABs) are common features of coastal ecosystems, and their growing frequency is a suspected outcome of coastal eutrophication.

However, the authors have never observed a dinoflagellate bloom of this scale during 28 years of sampling in the nutrient-rich San Francisco Bay. Phytoplankton biomass along this transect is typically <5mg Chla/m3, and has never exceeded 21 mg Chla/m3 during summer-autumn.