Determining the effects of El Nino - Southern Oscillation events on coastal water quality

The importance of the El Nino-Southern Oscillation (ENSO) on regional-scale climate variability is wen recognized, although the associated effects on local weather patterns are poorly understood. Little work has addressed the ancillary impacts of climate variability at the community level, which req uire analysis at a local scale. In coastal communities water quality and pu blic health effects are of particular interest. Here we describe the histor ical influence of ENSO events on coastal water quality in Tampa Bay, Florid a (USA) as a test case. Using approximate randomized statistics, we show si gnificant ENSO influences on water quality, particularly during winter mont hs, with significantly greater fecal pollution levels during strong El Nino winters and significantly lower levels during strong La Nina winters as co mpared to neutral conditions. Similar significant patterns were also noted for El Nino and La Nina fall periods. The success of the analyses demonstra tes the feasibility of assessing local effects associated with large-scale climate variability. It also highlights the possibility of using ENSO forec asts to predict periods of poor coastal water quality in urban regions whic h local agencies may use to make appropriate preparations.