Decade-Scale Trend in Sea Water Salinity Revealed Through δ18O Analysis of Montastraea annularis Annual Growth Bands

Hourly temperature data was collected from the Hen and Chickens Reef in the Florida Keys between 1975 and 1988 and compared to the δ¹⁸O of Montastraea annularis skeleton that grew during the same interval. Despite high-resolution sampling the authors were unable to obtain the full temperature-induced δ¹⁸O range in the skeleton. The data suggest that, during the summer, evaporation causes isotopic enrichment in the water, partially masking the temperature-induced signal. The data also show that oxygen isotopic composition of seawater at the reef has increased since 1981. This increase indicates that salinity has increased slightly during the past decade, perhaps as a result of increased evaporation in waters of Florida Bay and the Keys. -from Authors