Award Date

5-1-2012

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Water Resource Management

First Committee Member

Michael Nicholl

Second Committee Member

Kumud Acharya

Third Committee Member

Craig Palmer

Fourth Committee Member

Carl Reiber

Fifth Committee Member

Ronald Smith

Number of Pages

79

Abstract

Quagga (Dreissena bugensis) mussel veliger growth was compared under two dietary conditions: 1) only seston present in Lake Mead water; and 2) Lake Mead seston plus algae (Isochrysis galbana). Shell length, width, and area were compared as a function of time for the two treatments. It was expected that mussels would exhibit faster growth when supplemented with I. galbana than with Lake Mead water alone. However, no significant difference was observed between the control and I. galbana treatments. This result was unexpected and may have been caused by water quality, the nutritional content of Lake Mead seston, and/or over feeding.

The first experimental investigation of desiccation tolerance for Dreissena bugensis (quagga) veligers is presented. Desiccation tolerances of veligers four weeks post capture was examined under low, medium, and high humidity conditions. Veligers were exposed to dry conditions for fixed periods of time to determine the minimum dry time required to achieve 100% mortality. Data collected shows a positive correlation between desiccation tolerance time and humidity level. There is currently no data regarding desiccation tolerances of quagga veligers. Experiment results will be applicable to management strategies regarding control of quagga mussel colonization as well as watercraft and equipment decontamination. Additional research is required to examine the desiccation tolerance of younger veligers.

Spawning of Dreissena bugensis under laboratory conditions has been reported to be a challenge. Due to the time and labor-intensive nature of the process, little research has been conducted. A comprehensive understanding of spawning is necessary to better predict the implications that introduction of quagga mussels will have on an ecosystem. We evaluated three methods to induce spawning in quagga mussels: external application of serotonin, temperature shock, and gonad slurry. Mussels were individually exposed to the spawning treatments, and success or failure to produce gametes was observed. We also examined the relationship between shell length, time to spawn, and gamete production. We found that temperature shock produced a maximum of 22% spawning success. The addition of gonad slurry showed a slight increase over temperature shock producing a response of 32%. Serotonin was found to produce the highest percent spawning with a 77% success rate. Our results show that a clear dose response relationship exists between serotonin concentration and spawning response, and that consistent spawning of both males and females is observed following exposure to serotonin at concentrations at or above 5x10-4 M. We found no correlation between mussel size and clutch size or time to spawn; however, the time delay between serotonin exposure and spawning onset was found to be greater in females than males.

Keywords

Desiccation; Drying; Dreissena bugensis; Introduced aquatic organisms; Invasive species; Quagga; Quagga mussel; Spawning; United States – Lake Mead; Veliger

Disciplines

Environmental Sciences

Language

English


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