UC Irvine

The Southern California Bight is representative of a highly productive coastal ecosystem that is heavily influenced by intense urbanization. Along this unique coastal ecosystem resides a dense human population. Consequently, these waters are subject to large anthropogenic pulses of nutrient species and pollutants. Such inputs may have both positive and negative consequences at nearly all trophic levels. For primary producers, nutrient enrichment means there is more biologically active resources that help facilitate growth and reproduction. This often results in shifts to community composition between the multiple classes of phytoplankton and cyanobacteria found in the region.This body of work aims to evaluate the interaction between anthropogenic nutrient enrichment and phytoplankton community dynamics at both point and non-point source locations. Specifically, the intent was to identify and monitor seasonal variations of common SCB species and identify others capable of causing human harm and/or ecological destruction. Environmental conditions including temperature, salinity, dissolved oxygen, and nutrient concentrations were collected to elucidate possible initiators of harmful algal bloom (HAB) events. Additionally, we performed an incubation using water samples collected from a super saline site that had been frequently seeded with SCB phytoplankton species until as recent as the 1980’s. However, there was no evidence of current HAB species at the site. In Chapter 2, we find that there was no significant difference in environmental conditions or community composition between waters collected near a wastewater outfall and waters collected at a reference site up current. In Chapter 3, we determine that the current assemblage of marine diatoms and dinoflagellates at the Salton Sea have adapted and continue to adapt to changing conditions expected for the region. Rapid additions of trace elements and salinity fluctuations resulted in a toxicity effect for many species. Smaller sized picoeukaryotes were able to adapt to changing conditions more rapidly and may suggest a shift in community composition if rapid change occurs. In Chapter 4, we show that environmental conditions are more seasonally variable in estuarine systems when compared to coastal open waters. Some HAB species have demonstrated a wider range of tolerance to these factors and might possibly utilize estuaries as refuge until conditions allow for growth in open water.