Dolphin Sightings in the Vicinity of Land/Ocean Biogeochemical Observatories: Relationships with Weather and Water Quality

The objective of this study was to test the potential influence of short-term changes in water quality on the frequency of sightings of common dolphins (Tursiops truncatus) in the Indian River Lagoon, Florida The study was based on two data sources: (1) Land/Ocean Biogeochemical Observatories (LOBOs) that provided real-time monitoring of multiple water quality and weather parameters, and (2) standardized methods for identifying and counting individual dolphins using photo-identification techniques. Water quality parameters included salinity, water color (chromophoric dissolved organic matter), conductivity, dissolved oxygen concentration, oxygen saturation, chlorophyll, nitrate and phosphate concentrations, temperature, and turbidity. Weather was assessed using data for air temperature, barometric pressure, humidity, light, and wind speed and direction. Variables were measured continuously over a one-year period and analyzed as the mean for each parameter the hour before, during, and after each dolphin sighting period. Short-term variations in sightings within 0.5 km of the LOBO were measured using previously established photo-identification techniques on a weekly basis. In multivariable regression analyses, statistically significant inverse associations were found between air temperature and the frequency of dolphin sightings for all three time periods. The results demonstrate the feasibility of integrating variation in weather and water chemistry data with dolphin movements as potential indicators of ecosystem quality and climate change.