Nanoplankton biodiversity in the Pettaquamscutt River Estuary, Rhode Island, U.S.A.
Biodiversity of the nanoplankton was investigated within the Pettaquamscutt River Estuary (PRE) in southern Rhode Island, U.S.A. through light and electron microscopy. Five stations were sampled along the salinity gradient of the estuary to determine spatial and temporal variation in the nanoplanktonic community. Salinity and nutrient data indicated that there were two distinct regions within the estuary, classified as the “lower river region” and the “upper river region”. Nanoplankton always dominated the phytoplankton biomass (as chlorophyll a) in the upper river region, but not in the lower river. Live samples indicated that there is an abundant and diverse assemblage of protists within the PRE nanoplankton, including representatives of most known classes. Loricate choanoflagellates, chrysophytes (sensu lato), and the heterotrophic genus Thaumatomastix Lauterborn were investigated in greater detail with transmission electron microscopy. Species richness within these target taxa varied spatially and temporally, although only temporal variability was significant. On average, species richness was greatest at the middle sampling station, indicating maximal diversity at the middle river station and minimal diversity at the least and most saline stations, although these differences were not statistically significant. Relative species richness of the target taxa varied between the lower, middle, and upper river stations, and the diversity maxima in each region were slightly offset in time. A new choanoflagellate species and a new variety are described, in addition to nine undescribed species within the Chrysophyceae and Thaumatomastix. The PRE supports an uncommonly diverse loricate choanoflagellate assemblage and many Thaumatomastix species. Based upon the taxa examined in detail for this survey, the PRE is one of the most diverse estuarine environments examined for flagellate diversity to date. ^ A mesocosm experiment to test the outcome of nutrient enrichment upon nanoplankton species diversity found little effect. Species diversity increased significantly over time in the control and phosphorus-only treatments by the Margalef Diversity Index, but none of the other diversity indices. Analysis of similarity showed that heterotroph/autotroph ratios varied significantly over time, but not by treatment. The results highlight the need for a better understanding of the role of mixotrophic species in nanoplankton communities. ^
Biology, Ecology|Biology, Oceanography
"Nanoplankton biodiversity in the Pettaquamscutt River Estuary, Rhode Island, U.S.A."
Dissertations and Master's Theses (Campus Access).