Volume

39 2001

Issue

1

Page

75

Title

Dispersal of Native and Nonnative Aquatic Plant Species in the San Marcos River, Texas

Author(s)

C.S. OWENS, J.D. MADSEN, R.M. SMART and R.M. STEWART

Keywords

Hydrilla verticillata, hydrilla, East Indian hygrophila, Hygrophila polysperma propagule, fragments

Abstract

The San Marcos River is a spring-fed system which originates from the Edwards Aquifer, south of Austin, Texas. Due to excellent water clarity, and consistent temperatures and flows, a diverse community of native and nonnative aquatic plants have developed, including Hydrilla verticillata. Samples were collected quarterly of floating plant fragments to determine biomass loadings, fragment counts and establishment of propagules. The biomass loadings and establishment will be discussed in this paper. Hydrilla fragment biomass loadings were significantly greater in March for site 1 (downstream of Spring Lake) due to the presence of a harvester on Spring Lake, which are the headwaters of the San Marcos River. Additionally, there was a significant increase in plant fragment biomass at site 3 which is located directly below several high recreational use areas on the San Marcos River for the September and June sampling periods. Hydrilla fragments collected from the river, transported to the LAERF and planted, were able to establish between 70 and 83% of all plants.