Phytoplankton dynamics of the Guajataca reservoir, Puerto Rico

Tropical reservoirs frequently suffer from high rates of sediment and nutrient loads (SALAS & MARTINO 200 l, WETZEL 200 l). Alloctonous nutrient inputs through runoff largely control the entrance o f nutrients and other dissolved and particulate materials; however, interna! cycling during mixis is a mechanism for the vertical transfer and exchange of nutrient through the water column. Seasonal changes in precipitation and thermal regimes are important driving factors for water column stratification and mixing pattems in the tropics (HORNE & ÜOLDMAN 1994). The excessive input of nutrients influences the structure and dynamics ofthe phytoplankton community by increasing primary production and altering species composition (CHALAR 2006). Hence, assessing the phytoplankton assemblage of a reservoir can be used as an indicator of its trophic state and overall ecological integrity (REYNOLDS 1986). There is limited information of phytoplankton diversity and temporal dynamics in tropical zones (LEWIS 1978, TuNDISI 1986, KALF & WATSON 1986, ÜONZÁLEZ & ÜRTAZ 1998), and in reservoirs ofPuerto Rico (CANDELAS-REYES 1956, JOBIN et al. 1979, ÜUINONES-MÁRQUEZ 1980, ÜARCÍA & TILLY 1982). The purpose of this research was to characterize the spatial, temporal, and vertical dynamics of the phytoplanktonic community and its relation with the water column physico-chemical characteristics.