2004 Proceedings, Southern Weed Science Society
Volume 57 Section XIII

"Distribution of Hydrilla (Hydrilla verticillata) and Native Submersed Macrophytes in Lake Gaston, North Carolina and Virginia"

J.D. Madsen, R.M. Stewart, A. Way, and C.S. Owens

ABSTRACT

Lake Gaston has a history of invasive aquatic plant nuisance problems, the most recent from the invasion of hydrilla. We surveyed Lake Gaston in September 1999 using a point-intercept method, and studied selected sites using hydroacoustic surveys and box core sampling for shoot and tuber biomass. A total of twenty different plant species were identified for Lake Gaston. By conservative estimate, hydrilla can colonize to a depth of 3.1m in Lake Gaston. Therefore, hydrilla could potentially colonize 2,023 ha or 25% of the lake’s surface area. While a large proportion of the littoral zone (<3.1 m) was vegetated (76%), providing adequate cover for littoral zone fish; the vast majority of the vegetation is nonnative Hydrilla verticillata (65%). Total plant biomass averaged 67.2 g m-2, and was 93% hydrilla. Hydrilla is by far the dominant aquatic plant in the lake. Biomass levels themselves were not high for hydrilla, probably due to poor transparency. Tuber density was low for monoecious hydrilla, and comparable to sites with dioecious hydrilla. The low tuber numbers may be due to intensive hydrilla management. The main restriction for more vegetation, and the enhancement of native vegetation, is poor water clarity in the lake.