Factors Effecting Phytoplankton Assemblages in the Lafayette River Estuary

Chemical and physical parameters were measured with phytoplankton species composition and abundance in the Lafayette River from August to October 1981. Stations located in four distinct areas of the river were statistically analyzed to determine data relationships. Environmental factors considered as potentially influencing the presence and numbers of phytoplankton were salinity, temperature, Secchi depth, tidal phase, orthophosphate, combined nitrates and nitrites, ammonia, and reactive silicates. The River mouth had higher salinity and nutrient values, with lower temperatures than the other river sections. Diatoms were the dominant cells in this section of the River. At mid-river, salinity and nutrient concentrations decreased, with higher temperatures noted. Common to this area were diatoms and a larger number of phytoflagellates. In the two River branches, flagellated cells were dominant, with increasing numbers of chlorophytes and cyanophytes. Environmental conditions associated with these areas were low salinity, high temperatures and increased nutrient levels. Discriminant Function and Pearson Correlation analyses were conducted separately on environmental and biological data sets. Adjacent stations were not significantly different environmentally. However, in areas located other than next to one another, clusters were statistically different at the α \u3c.005 level of significance. Visual comparisons between the two sets of analyses showed that stations grouped in the same cluster 75% of the time. Of the remaining fraction, half of the cases were associated with severe storm conditions