Factors Affecting Phytoplankton Biodiversity and Toxin Production

This dissertation reports a survey of water quality, algal biodiversity, and toxin production in Southern California lakes, ponds, bays, and lagoons along the California coastline, in five counties from Santa Barbara to San Diego. Samples were analyzed for pH, electrical conductivity, total dissolved solids, dissolved oxygen, alkalinity, chlorophyll–a, total phosphorous, phosphate, total dissolved phosphorous, dissolved organic and inorganic phosphorous, particulate phosphorous, total nitrogen, total dissolved nitrogen, dissolved organic and inorganic nitrogen, nitrate, nitrite, and ammonium. Algal assays were conducted for phytoplankton identification and numbers, and indices of biodiversity (richness and evenness) were calculated to ascertain relationships between nutrients and algal growth, especially beneficial Chlorophyta and toxic Cyanophyta. After identifying several sites which contained algal toxins in excess of drinking water limits and high numbers of the cyanobacterium, Microcystis, research was continued to ascertain the impact of Microcystis on algal biodiversity. A series of beakers was inoculated with Microcystis, in addition to the genera of algae that were most commonly seen throughout our study sites, and a control set of beakers was prepared without Microcystis. Weekly algal assays were conducted for five weeks, and richness and evenness were calculated. Having demonstrated that Microcystis negatively impacts algal biodiversity, we tested the effectiveness of a Blue ProTM water treatment facility in removing this colonial organism from a small, freshwater lake, in addition to removal of dissolved nutrients required for its growth. While using this technology at Mason Lake (Irvine, CA, USA), PO4 levels and algal compositions were evaluated in one sample of lake water before and after treatment. A PO4 restriction assay on the algae in Mason Lake at that time revealed the PO4 threshold needed for algal growth was 0.02 mg - L-1. Our study demonstrated that water chemistry factors are correlated with the presence of the cyanobacterium, Microcystis, and that removal of that species may allow green algae to increase in numbers, improving biodiversity in ponds and small lakes. The application of this knowledge will benefit zooplankton, fishes, endangered birds, and other organisms in those habitats