Impact of Environmental Contaminants on the Threeridge Mussel (Amblema plicata) in the Guadalupe River Basin, Texas




Britton, Stacey Lea

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Aquatic pollution has contributed to the significant decline of unionid mussel populations throughout North America. In this study, adult Threeridge (Amblema plicata) were collected from 8 sites within the Guadalupe River basin and the concentration of 8 essential (Co, Cu, Fe, Mn, Mo, Ni, Se, Zn) and 8 nonessential (Ag, As, Cd, Cr, Hg, Pb, Sn, V) trace elements were determined in gill and foot tissue using microwave acid digestion and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis. Water samples were also collected at each site and analyzed for nutrient concentrations including total nitrogen, total phosphorus, and ammonium, as well as the presence of fecal coliform bacteria (Escherichia coli) to better understand local water quality. The physiological response of A. plicata to contaminants was quantified through biomarker analysis (lipid peroxidation, antioxidant capacity against peroxyl radicals, and protein concentration) of gill tissue. Overall, the concentration of both essential and nonessential elements was higher in the gills than in the foot at all sites; however, Hg was higher in foot tissue at upstream sites and not significantly different from gills at downstream sites. The two uppermost study sites on the San Marcos and Guadalupe Rivers were characterized by higher Hg and As, respectively and the lower four sites (UC, LC, UV, and LV) were characterized by higher Cd concentrations. No relationship was evident between the spatial variation in trace element concentrations in gill tissue and the investigated biomarkers. Higher nutrient concentrations at sites upstream of Upper Cuero correlated with a) higher lipid peroxidation and lower antioxidant capacity against free radicals, indicating greater oxidative stress, and b) lower protein concentration indicating reduced overall health. This is the first in-depth study on the impact of environmental contaminants on unionid mussels in Texas rivers and the findings suggest that mussels are exposed to a mixture of urban, industrial, and agriculturally-derived contaminants; however, future cage transplant studies are needed to further understand the impact of environmental contaminants on unionid mussels in the Guadalupe River Basin.



Freshwater mussels, Trace elements


Britton, S. L. (2018). <i>Impact of environmental contaminants on the threeridge mussel (Amblema plicata) in the Guadalupe River Basin, Texas</i> (Unpublished thesis). Texas State University, San Marcos, Texas.


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