Spatiotemporal variation of phosphorus and the effect of local currents on its distribution in Petacalco Bay, Guerrero, Mexico

Abstract

The contribution of continental water to the coastal zone has a significant impact on ecosystems worldwide. Continental waters provide nutrients in different concentrations and their distribution is conditioned by local marine circulation dynamics and seasonality of river inputs. The Balsas River, one of the most important in Mexico, discharges its water into Petacalco Bay, with a considerable nutrient content. This work studied the spatiotemporal variability of the orthophosphate and total phosphorus contents and their relation with salinity, turbidity and coastal circulation. Maximum orthophosphate concentrations in the bay were 19.56 ∞M in April/May, 10.50 ∞M in February and 9.31 ∞M in August. The high total phosphorus contents were 40.98 ∞M in April/May and 20.54 ∞M in August, indicating an eutrophied coastal environment, result of the wastewaters discharged by the industries established along the river's estuary and dispersed throughout the bay by the local currents. An accumulation of water originating from the Balsas River was recorded in the central-eastern portion of the bay. There were small cyclonic and anticyclonic superficial gyres off the Petacalco Estuary during most of the months studied (February, June, August, October and December) that had the same direction at 10 m depth or were inverted in April and December, with a displacement toward the E–NE, allowing us to verify the diffusion of the phosphorus.