Lake browning, or an increase in terrestrially derived dissolved organic matter (DOM) entering a lake, can result in decreases in that lake’s water transparency. Decreases in water transparency may cause a reduction in underwater exposure to damaging ultraviolet radiation (UV). Centrarchid fish are known to host a variety of external parasites that are sensitive to UV and may benefit from decreasing water transparency. In northeastern North America and Europe, key economically and culturally important recreational and sport fisheries are composed of many Centrarchid fish. Additionally, lake browning has led to as much as a doubling of DOM in many of these lakes—which is likely to reduce the underwater exposure to UV, and possibly, the ability for these surface-dwelling fish to use UV exposure to rid themselves of external parasites. We hypothesize that Centrarchid fish parasite prevalence can be mediated by the presence of UV. We caught 20 fish from three lakes of differing water transparencies and counted the parasites embedded in two zones of each fish (“UV-exposed” and “UV-refuged). We predicted that the number of parasites would increase with decreasing water transparency, and the number of parasites on the UV-refuge zone of the fish would increase with increasing water transparency. We found that parasite prevalence did increase with decreasing UV exposure, however, only one lake differed in the number of parasites between the two zones of the fish. Very few studies have investigated the role of UV disinfecting fish of external parasites. Our findings are consistent with other epidemiological studies which suggest that as lakes continue to decrease in water transparency, the prevalence of parasites on Centrarchid fish (and other water borne pathogens and diseases of concern to humans and animals) may increase.
Authors: Isaac Smith, Nicole Berry, Addie Zeisler, Erin Overholt, Craig Williamson
Advisor: Craig Williamson, Biology
Graduate Advisor: Nicole Berry, Biology
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