Ohio River zooplankton growth rates and community assemblages and their relationship to abiotic and biotic factors in navigational dam pools
Sluss, Tamara; Jack, Jeffrey D.
The relationship between zooplankton population growth rates and community assemblages to both abiotic and biotic parameters in the Ohio River was investigated in this study with semi-Lagrangian sampling over a two year period. Using multiple regression, we determined that population growth rates of different taxa of zooplankton respond differently to environmental variables yet growth rates were indeed positive for several taxa indicating autochthonous secondary production in the river's navigation pools. Population growth rates of Bosmina were the most consistent of all taxa followed by cyclopoids. Bosmina population growth rates were negatively correlated with turbidity (R2 = 0.392), and Daphnia with discharge, but only slightly (R2 = 0.397). Cyclopoids correlated negatively with Keratella population growth rates (R2 = 0.371), a sign of biotic interactions taking place. Furthermore, Ohio River zooplankton community assemblages appear altered by navigation dams within the same navigational pool (upstream and downstream sites) as indicated by ordination analysis on all study dates (Wilks lambda <0.0001). Difference in potamoplankton assemblages differed on two of four surveys between the Ohio River sites and two of its tributaries, the Kentucky and Wabash Rivers. The results from this study provide evidence that zooplankton community structure and perhaps food webs differ among habitats within navigation pools. The negative impact of discharge on larger-bodied Cladocera and selection for rotifers witnessed in this study agrees with results from other large river studies and appears to be a widespread phenomenon in temperate managed rivers.