Print PageD. lumholzi is native to southwestern Asia, Australia and Africa. It was first detected in Texas in 1990, and has since been found in 152 water bodies ranging from Florida to California, Louisiana to the Great Lakes, with the highest concentration of sites in the central/southeastern U.S. Because this species has long spines protruding from its head and tail, it is less susceptible to fish predation than most local species. Earlier studies suggest that populations of D. lumholtzi peak in late summer, when lakes and reservoirs are warm. This late summer peak seems to limit competition with local Daphnia species, which usually peak earlier in the year. Here we report on a preliminary study to determine the extent of the D. lumholtzi invasion in SC and timing of peak D. lumholtzi in the state.
In a preliminary study we surveyed 10 lakes located across the state. We used a combination of vertical open water and horizontal shoreline sampling at each of the ten lakes. All samples were collected form mid-May to mid-June, 2009. For this year’s field work we conducted more extensive and frequent surveys to determine the exact timing of D. lumholtzi populations compared to other zooplankton species. Three lakes that were shown to have D. lumholtzi populations in the preliminary study were surveyed every two weeks to determine the population demography of D. lumholtzi and other cladocerans. In addition, numerous other lakes were sampled to determine how far D. lumholtzi has spread throughout the state.
Results/Conclusions
We found D. lumholzi in four of the ten lakes, including in one previously unreported location in the northeastern part of the state (Lake Wallace). Additionally, we found significant densities (average of 1.3/liter) earlier in the season than reported elsewhere. This suggests that competition with local Daphnia species may be higher than has been previously reported.
