Response of Primary Production to Changing Conditions in Salton Sea Water Chemistry

The Salton Sea is a body of water that formed in Southern California as the result of an engineering accident when waters were diverted from the Colorado River to support year-round crop production in the Imperial Valley. The waters that continue to feed it today are heavily contaminated with elevated nutrients and chemicals used as pesticides. With these contaminants also flow salts that have concentrated in the Sea through the evaporation of surface water and subsequently raised salinity levels far beyond what may be found in the ocean. Recently, policy driven reduction of inflow has intensified the rise in salinity and exposed previously submerged sediments as the Sea has experienced a reduction in volume. Freshly exposed sediments are of special concern as they contain high concentrations of chemicals that have precipitated and fallen out of the water column. The combination of these factors has stressed the local ecosystem to the point of near collapse. One of the only biological assemblages that remains in high abundance are the primary producers. This study looks to evaluate these phytoplankton populations and develop an outlook for the future health of the region. To date, two in situ incubations (summer and spring) have been conducted which consider continued changes in salinity and possible localized atmospheric dust deposition scenarios. Preliminary chlorophyll analysis indicated that any abrupt changes to salinity, be it freshening or concentrating, had adverse effects on the phytoplankton population when compared against a control. This trend was more pronounced during the summer months where the community experienced an overall decline throughout the sixty-hour incubation when subjected to changing salinity. These results were confirmed within the smaller picophytoplankton communities using flow cytometry instrumentation and rendered similar trends. Similarly, dust additions used to simulate atmospheric deposition caused chlorophyll concentrations to decline when compared to the control. These results imply that the current populations are well adjusted to present conditions and will respond negatively to increased rates of change in deposition and salinity that may occur should policy makers force further reduction of inflow.