NEW: Annual Report - George Mason University

D. Zooplankton
Figure 44. Rotifer density by Dominant Taxa (#/L). Cove.
35
Rotifers are the most smallest
and most abundant metazoan
zooplankton in most
freshwater systems including
the freshwater tidal Potomac
River. Rotifers generally grow
to maximum numbers in the
summer and are scarce in the
winter.
Dominant taxa in the cove and
river in 2003 include:
Brachionus
Conochilidae
Filinia
Keratella
Polyarthra
Trichocerca
All of these taxa are common
in freshwater systems.
Rotifers increased rapidly in early May and then again in late July in the cove reaching a
maximum of nearly 4000/L (Figure 44). Keratella was the dominant in spring with
Brachionus becoming most important in the summer. Filinia and Trichocerca were also
abundant in the summer bloom and Keratella resurged in late September. In the river the
period of elevated rotifer abundance was more restricted. Brachionus and Keratella
bloomed simultaneously in early June with Conochilidae becoming important in late July
and early August. By late September all rotifers had declined substantially.
Figure 45. Rotifer Density by Dominant Taxa (#/L). River.
Brachionus (c. 50 um)
Conochilidae