Plankton Species Diversity in the San Francisco Bay and Beyond
Authors:Gregory Boris, Gretchen Coffman, Isabella Maegli, Whitney Tashiro, Stacy Weatherford
Mentor:Gretchen Coffman, Assistant Professor of Environmental Science, University of San Francisco
Phytoplankton, zooplankton, and krill are the base of the marine ecosystem food web around the world. The abundance of plankton and krill is positively correlated to the abundance of organisms that feed on them in the San Francisco Bay. We hypothesized that more extreme abiotic conditions in the open ocean would create lower plankton species diversity than in the San Francisco Bay. To investigate species diversity and abundance of phytoplankton, we sampled abiotic factors of temperature, salinity, water clarity, nutrient levels, dissolved oxygen, air temperature, and wind speed along a 30 mile transect from the San Francisco Bay through the Gulf of the Farallons National Marine Sanctuary in October 2012 and 2013. We also investigated the variation in organism diversity at various depths. We collected water samples using a grab sampler and measured salinity, temperature, and dissolved oxygen using a Hach HQ40d meter. We sampled air temperature and wind speed using a Kestrel meter. Plankton was collected dragging a plankton net for 10 minutes at each location. Results of our first year of data showed that marine ecosystems exhibiting the most extreme abiotic conditions (around the Farallon Islands) resulted in the lowest species diversity, whereas the highly variable abiotic conditions of the San Francisco Bay contained the highest species diversity. Furthermore, plankton species diversity was highest around the Farallon Islands 27 miles offshore, significantly lower in the San Francisco Bay, and absent off the Continental shelf. Copepods were the most abundant species at all sites. However, water clarity was clearest in the Pacific Ocean (17-28.5 ft) and lowest in the San Francisco Bay (4 ft), indicating higher plankton productivity. Data collection by students in the USF Environmental Science Department over the next 20 years will elucidate relationships between biotic and abiotic factors in aquatic ecosystems of San Francisco Bay.