Award Date

12-1-2012

Degree Type

Thesis

Degree Name

Master of Public Health (MPH)

Department

Environmental and Occupational Health

First Committee Member

Shawn Gerstenberger

Second Committee Member

David Wong

Third Committee Member

Mark Buttner

Fourth Committee Member

Vernon Hodge

Number of Pages

71

Abstract

The Lake Mead National Recreational Area was created by the construction of the Hoover Dam during the years 1931-1936. In January 2007, the quagga mussel (Dreissena rostriformis bugensis), was found in Lake Mead. This became the first known Dreissenid species in the southwest and the only time a large water system was first infested by the quagga mussel and not the zebra mussel (Dreissena polymorpha). This invasive species has quickly spread to Lake Mohave and further down the lower Colorado River drainage. The microscopic size (70 µm or larger) of the veliger life stage makes it impossible to see with the unaided eye and difficult to remove from water delivery pipes and fish stocking trucks. This invasive mussel has affected the stocking abilities of the United States Bureau of Reclamation Lower Colorado River Multi-Species Conservation Program Fish Augmentation Plan. One purpose of this study is to determine if quagga veligers can be completely removed from lake water by a combination of sand, zeolite, and paper filtration. Results for the filtration experiment show that the relative risk of transferring quagga mussels to Willow Beach National Fish Hatchery during a night of larval collections is low. Filtered lake water provides a significant reduction of veligers present in the water compared to the unfiltered lake water (p=.009). The other purpose of this study is to determine if exposure to different doses of ultraviolet radiation can damage or kill veligers. The UV exposure doses were 1, 3, 6, and 12 times through the SafeGUARD UV system. After exposure, 50 veligers were observed at time 0, 24, 48, 72, and 96 hours. Results from the UV study show that at an exposure of 12 times through UV at an observation time of 96 hours there was 100% mortality of veligers observed. It also shows that there is a significant difference in mortality of veligers between cycle 1 and multiple cycles (p< 0.05) while there is no statistical difference between cycles 3, 6, and 12 (p> 0.05). 3:6 (p=.5322), 3:12 (p=.5071), or 6:12 (p=.9688).

Keywords

Biocide; Dreissena rostriformis bugensis; Filters and filtration; Introduced aquatic organisms; Quagga mussel; Sand filter; Ultraviolet radiation; United States – Lake Mead National Recreation Area; Veliger

Disciplines

Environmental Health | Environmental Sciences

Language

English


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