Photosynthetic responses of phytoplankton in a thermically polluted coastal zone of the Gulf of Mexico

Photosynthetic behavior of phytoplankton was analyzed emphasizing the short -term responses to light and temperature. Samples were obtained in a tropic al coastal zone with permanent hot water discharges from a thermoelectric p lant. They were collected in five periods between March 1993 and October 19 94 in four sites where temperatures ranged from 23 to 36 degrees C. Field d ata analysis did not show significative differences between the species com position and relative abundance of communities from different sampling site s. Response to photosynthesis experiments was segregated according to the o rigin of microalgae assemblages and composition of samples. photosynthesis behavior presented alterations in algae assemblages sampled in the site whe re hot water is discharged, suchas rates reduction, higher light requiremen ts, and lower temperature to achieve photosynthetic production than the oth er algae communities. Therefore, both structure and function analysis must he integrated in order to understand better the disturbed ecosystems.