Document Type

Technical Report

Publication Date

6-1-1996

Keywords

Zebra mussel, Lake Dardanelle, Water quality

Abstract

Zebra mussels recently invaded southern waterways including the Arkansas River. Large-scale filtration of suspended particulate matter by dense populations could alter reservoir ecosystem function. Furthermore, they attach to hard surfaces, thereby threatening normal operations of artificial structures. We designed this study to provide baseline data prior to establishment of high population levels of zebra mussels in Lake Dardanelle. The characterization of spatial and temporal variability in water quality, zooplankton, phytoplankton, and macrophytes will allow testing of several hypotheses. We sampled zebra mussel veliger and settling juvenile densities and zooplankton densities at four fixed sites and the key water quality variables at three of the sites biweekly from July 1995 through June 1996. Data from previous years regarding the above parameters is contained in other reports. Production of zebra mussel veligers was approximately the same between the 1994-1995 and 1995-1996 sample seasons, but the number of adults increased dramatically. Veliger density frequently exceeded 20/L and the mean density of adults was > 4,000 m2 during the 1995-1996 sample season. We observed substantial increases in ion concentrations, phosphate, conductivity, and Secchi disk visibility this sample season compared to the 1994-1995 sample season. Mean concentrations for calcium, magnesium, sulfate, chloride, and phosphate increased 43%, 42%, 42%, 48%, and 50%, respectively. Mean conductivity increased 44%, and four of the five highest Secchi disk readings taken the past three years were recorded in 1996. We observed substantial decreases in turbidity (31%), total dissolved solids (23%), and total phosphorous (13%). Densities of major zooplankton taxa were not substantially different this season compared with the 1994-1995 sample season. We observed slight increases in mean concentrations of chlorophylls a, b, and c, and a slight decrease in the mean percent coverage of rooted marcrophytes, but the values were not substantially different than those that we observed during the 1994-1995 sample season.

Report Number

PUB 179

Page

80

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