Effects of environmental factors on the distribution and morphology of Victorella pavida (Ectoprocta) in Lake Pontchartrain, Louisiana, and vicinity

Abstract

Victorella pavida was studied during 1971, 1973, 1974 and 1975. Its distribution along a decreasing salinity gradient was investigated and its mean low-salinity limit was found to nearly correspond to the boundary between the oligohaline and limnetic estuarine salinity zones. Because it was abundant and uniformly distributed in low salinities, and was absent in the limnetic range, it could be used as an indicator species to determine the maximum extent of brackish-water intrusion in estuarie. In most collections there was a relationship between zooid branching and salinity; however, this relationship did not appear to be related to salinityper se but to the effect of salinity on growth rate and interspecific competition, which in turn affected colony morphology. It occurred in waters which had a wide range of physiocochemical conditions and was the predominant epifaunal species in an outfall canal which received sewage and storm-water discharge from New Orleans. Because of its dominance of the epifauna in areas with poor water quality it appears to be an important species to consider when species association and abundance are used to assess environmental quality.