| Virginia
Journal of Science.
2005. Vol 56 (2) : 67-82 |
| Phytoplankton
Development Within Tidal Freshwater Regions of Two Virginia Rivers, U.S.A. Harold G. Marshall1 and Lubomira Burchardt2, 1Department of Biological Sciences, Old Dominion University, Norfolk, VA, 23529-0266, U.S.A., 2Department of Hydrobiology, Collegium Biologicum, Adam Mickiewicz University, 61-614 Poznan, Poland ABSTRACT
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.Key words: Phytoplankton, Virginia, Rappahannock, Pamunkey, tidal freshwater |