Effect of Pollution on Genetic Diversity in Marine Populations in the Southern California Bight

Ma, Xiao Li

Department of Natural Sciences Loma Linda University,USA

Two intertidal invertebrate species, the bay mussel M. galloprovincialis and the acorn barnacle Balanus glandula, were collected from seven different bay sites along the Southern California coast to test if environmental contamination is associated with the decrease of genetic diversity at the population level. Collections were made at three relatively pristine "clean" sites and four "impacted" sites which were exposed to heavy industrial or boating activity and which had previously been identified as having measurable levels of pollution.

The "Comet" assay (Single Cell Gel electrophoresis) was performed to measure single-strand DNA breaks in mussels at several of the sites in order to confirm differing impacts of pollution on the animals at the different sites. In this assay, cells in impacted populations with increased DNA damage displayed increased migration from the nuclear region towards the anode during electrophoresis. Genetic diversity at the different sites was assessed by comparing fragment polymorphisms generated from genomic DNA by RAPD-PCR (Randomly Amplified Polymorphic DNA - Polymerase Chain Reaction). All populations exhibited a large amount of genetic diversity and were genetically similar to each other. However, several different measures of diversity indicated that for most primers, the populations of both species from impacted sites had lower genetic diversity compared to populations from clean sites. Individuals at impacted sites were more likely to share the same haplotypes than were those from clean sites. Few bands seen in the clean sites were absent from the impacted sites or vice versa, but a number of bands which were common in the clean site populations were significantly less common in the impacted populations.

Together, these results suggest that pollution at the impacted sites may act as a selection force decreasing genetic diversity among the resident invertebrate populations.