Relating fish kills to upwellings and wind patterns in the Salton Sea

In recent years, the extreme eutrophication of the Salton Sea has been associated with massive fish kills and associated bird kills. Analysis of the magnitude and direction of high wind events indicates that major fish kills are preceded by strong and persistent wind events, with a 24-h accumulated wind magnitude above a critical threshold of approximately 90 m/s. Twelve of the 14 cases of reported fish kills analyzed were found to be preceded by such wind conditions. The winds could potentially produce upwellings of hypolimnetic water at the upwind end of the Sea, resulting in the entire water column being low in dissolved oxygen and high in concentrations of hydrogen sulfide and ammonium. Remotely sensed thermal infrared data from the MODIS instrument on the Terra satellite was available for 5 of the 14 fish kills analyzed. Evaluation of satellite-derived surface temperature maps for these 5 fish kills shows that upwellings did take place after the wind events, affecting a large fraction of the Sea's area. The location of the upwelling and the fish kills coincided in all cases, confirming the relationship among wind patterns, upwellings, and fish kills in the Salton Sea. The importance of physically mediated processes, such as upwellings, need to be considered in evaluating future remediation strategies for the Salton Sea.