A Comparison of the Effects of Petroleum Substances on the Settlement of the Eastern Oyster, Crassostrea virginica

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Alsept, Karen Sue
Oyster; petroleum; crabs; estuaries
thesis / dissertation description
In Galveston Bay, Texas, the eastern oyster, Crassostrea virginica, is found throughout the bay both intertidal along mudflats and subtidal where their self-built reefs extend vertically deeper. The eastern oyster is an important ecological and economical resource and as such has led to studies regarding their community structure to permit effective creation of artificially built reefs and restoration of existing ones. The presence of the oil and gas industry coupled with increased oyster mortality led to investigations to determine the effects of petroleum substances on the setting, growth, and mortality of the eastern oyster. Many of those studies indicated increased settlement and increased growth of oysters on substrate coated with oil. A field conducted experiment was used to assess the settlement of oyster larvae on cleaned oyster shells coated with two different types of petroleum substances (mineral oil and motor oil), comparing viscosities, in a shallow bayou in Galveston, Texas, where the eastern oyster dominates the intertidal zone. Oyster shells were used as cultch material and divided into three groups; a non-treated control group, mineral oil treated group, and a motor oil treated group. Nekton assemblages, distributions of the ivory barnacle, Balanus eberneus, and Dermo disease infection were assessed. Settlement of oyster larvae occurred in all three groups with no significant difference of preference; algae and sediment present on the shells coupled with the presence of predators most likely caused reduced numbers of spat settlement. Species richness was equal among the groups but varied in evenness of individual species.