Phytoplankton Composition Within the Tidal Freshwater-Oligohaline Regions of the Rappahannock and Pamunkey Rivers in Virginia

The Rappahannock River is a major river system across north central Virginia prior to entering the Chesapeake Bay. In contrast, the Pamunkey River is smaller in size and joins the Mattoponi River to form the York River, which flows parallel to the Rappahannock before it also flows into Chesapeake Bay. A unique mixing area for both flora and environmental conditions exists in the tidal freshwater-oligohaline region of both rivers. This is a dynamic mixing section where freshwater and estuarine species are subject to the interaction of river flow and daily tidal rhythms. The phytoplankton composition in this region of the two rivers was identified over a 13.5-year period (July 1986–December 1999). The results indicated freshwater and estuarine populations forming a diverse assemblage of 268 taxa, with diatoms, chlorophytes, and cyanoprokaryotes the dominant flora. Phytoplankton in this region were predominantly freshwater taxa (e.g., \u3e70%), with a diverse diatom assemblage representing \u3e90% of the estuarine flora at these sites

Phytoplankton Development Within Tidal Freshwater Regions of Two Virginia Rivers

Phytoplankton composition and the range of seasonal patterns of abundance are presented for the tidal freshwater regions in two Virginia rivers based on data accumulated monthly from 1986 through 1999. Diatoms dominated the flora during spring, summer, and fall, whereas, other taxonomic categories were more representative when the river flow rates decreased, allowing for a more stable water system and increased residency time within this tidal region during summer and early fall. This summer/fall period was associated with increased water temperatures, higher productivity rates and chlorophyll levels, increased total phytoplankton abundance and species diversity. The major components of the summer flora were autotrophic picoplankton, chlorophytes, and cyanobacteria. Mean, maximum, and minimum monthly abundance figures are given for the different phytoplankton categories, and total phytoplankton biomass and abundance, over this 13-year period. Although one station showed considerable influx of oligohaline water into its tidal freshwater region during sampling, no significant relationships were associated with phytoplankton biomass or productivity to these changing salinities. For article, see: http://digitalcommons.odu.edu/biology_fac_pubs/92

Phytoplankton Development Within Tidal Freshwater Regions of Two Virginia Rivers, USA

Phytoplankton composition and the range of seasonal patterns of abundance are presented for the tidal freshwater regions in two Virginia rivers based on data accumulated monthly from 1986 through 1999. Diatoms dominated the flora during spring, summer, and fall, whereas, other taxonomic categories were more representative when the river flow rates decreased, allowing for a more stable water system and increased residency time within this tidal region during summer and early fall. This summer/fall period was associated with increased water temperatures, higher productivity rates and chlorophyll levels, increased total phytoplankton abundance and species diversity. The major components of the summer flora were autotrophic picoplankton, chlorophytes, and cyanobacteria. Mean, maximum, and minimum monthly abundance figures are given for the different phytoplankton categories, and total phytoplankton biomass and abundance, over this 13-year period. Although one station showed considerable influx of oligohaline water into its tidal freshwater region during sampling, no significant relationships were associated with phytoplankton biomass or productivity to these changing salinities

On the Ecological Status of the Concept Boundary Conditions - A Few Methodological Remarks

Plant and animal populations are frequently found in habitats where the environmental conditions are considered extreme or challenging for life form to exist. These conditions may be classified as either: (1) Supreme: a situation characteristic of degradation conditions where only a few species live under stress, and (2) Extra-ordinary: habitats that provide high biodiversity that are under stress conditions. Due to the differences in what we consider extreme conditions, it is necessary to distinguish between these two categories, because they are not comparable. Our presentation will include examples of these two extreme environmental categories

A Review of Phytoplankton Composition Within Chesapeake Bay and Its Tidal Estuaries

Based on a continuous 20-year data base ofmonthly sampling in Chesapeake Bay and tidal regions of its major tributaries, 1454 phytoplankton taxa have been identified in these waters. They represent a diverse assemblage of species with a dominant diatom flora throughout the year, in addition to large seasonal representation by chlorophytes, cyanobacteria, cryptophytes and dinoflagellates. Included among this flora were 34 potential harmful or toxin producing species. The phytoplankton compositions associated with the seasonal successional patterns are discussed, in addition to characterizing the dominant floral relationships, with comparison to early composition records within the Bay. Several of the present day most common taxa were similar to those reported in sediment cores from the Bay dating to periods prior to European settlement. Comparison with collections made ~8 decades ago (1916–1922) within Chesapeake Bay indicated several of the same dominant flora remain dominant today; however, their cell concentrations are now significantly greater along with an increased diversity of species compared with these earlier studies

Comparison of Phytoplankton and Autotrophic Picoplankton Populations Over a 24-Hour Period From a Pond\u27s Surface and Subsurface Waters

Phytoplankton abundance and composition relationships within the surface layer changed over short time periods (4-6 hours) in comparison with more constant associations at 2 cm below the surface. Both strata had a diverse algal flora (\u3e50 taxa), but no distinct neuston assemblage characterized the surface layer algal composition over the 24-hour study. The similarity between the two strata indicated the floral composition of the surface layer came from the water column algae below the surface. Chlorophytes, diatoms, cyanobacteria, and cryptophytes represented the most abundant algal categories for both strata with a total mean phytoplankton abundance of 3,566 cells ml-1 at the surface and 40,532 cells ml-1 at 2 cm over the 24 hours. The autotrophic picoplankton had generally similar levels of abundance over time. Their mean abundance for the 24 hours was 469 and 599 X 103 cells ml-1 at the surface and 2 cm respectively

Algal composition and abundance in the neuston surface micro layer from a lake and pond in Virginia (U.S.A.)

A comparative study was conducted that characterized the algae within the neuston, ca 2 mm below the surface, and the algae in the water column from two freshwater habitats. There were significant differences in total algal abundance and the abundance of diatoms, cyanoprokaryotes, and chlorophytes between the neuston and water column algae of these two regions during each season and at both sites. The pond neuston was dominated by chlorophytes, with total algal abundance ranging seasonally from 0.6 to 59.6 × 10-3 cells ml-1 compared to water column algal concentrations of 4.1 to 40.4 × 10-3 cells ml-1. The lake was dystrophic, with diatoms the most common and abundant species, with the neuston algal abundance ranging from 0.09 to 1.31 × 10-3 cells ml-1, and the water column algae from 0.19 to 2.70 × 10-3 cells ml-1. Proximity to the variable nature of the surface layer was not a deterrent for neuston algal development, which frequently reached bloom status and contained a diverse assemblage of taxa