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Aim In clear, cold-water lakes, ultraviolet radiation ( UV) and temperature are two important stressors that may prevent the establishment of aquatic invasive species by inhibiting the survival of sensitive early life history stages. In this study, we develop a UV-temperature response model to predict the establishment potential of a warmwater fish, largemouth bass ( Micropterus salmoides), in a large subalpine lake based on the ability of bass larvae to tolerate UV and temperature stress along a UV-temperature stress gradient. Location Lake Tahoe ( California/ Nevada, USA). Methods We compared the UV tolerance of largemouth bass larvae to that of the native redside minnow ( Richardsonius egregius) in outdoor UV exposure-response experiments. A UV-temperature response model for larval bass was developed that combined the experimentally derived UV exposure response from our outdoor experiments with a temperature response curve derived from the literature. We used the UV-temperature response model to predict reproductive success (i.e. larval survival) over the range of UV exposure and temperature conditions in nearshore Lake Tahoe. The model predictions were validated with in situ incubation experiments at nearshore locations. Results Non-native bass were significantly less UV tolerant than native redside minnows. The UV-temperature response model predicted that larval bass survival varies seasonally, spatially and over depth gradients in nearshore Lake Tahoe and is constrained by UV and temperature conditions. In situ incubation experiments confirmed model predictions. Main conclusions Our findings provide important insights into the potential for species invasion in clear, cold-water lakes that are experiencing significant changes in both temperature and transparency. The conceptual model and approach that we employ is a potentially powerful tool for exploring unanswered questions in invasion biology, including the role of alternate stable states in facilitating invasion and the potential for invasive species to promote 'invasional meltdown' through their impacts on water clarity and temperature. [ABSTRACT FROM AUTHOR]

Within Lake Tahoe (CA/NV), USA, multiple environmental stressors are present that can affect both native and nonnative fish species. Stressors include natural ultraviolet radiation (UVR) and polycyclic aromatic hydrocarbons (PAHs). Many PAHs, such as fluoranthene (FLU) are phototoxic to aquatic organisms in the presence of UVR. Decreasing levels of UVR due to eutrophication and increasing levels of PAHs due to recreational activities may combine to affect the relative ability of native versus nonnative fish species to survive in the lake. The objective of the present study was to examine the differential effects of exposure to different levels of UVR and phototoxic FLU in native and nonnative fish species. Responses to these changes in the native Lahontan redside minnow ( Richardsonius egregius) and the nonnative warm-water bluegill sunfish ( Lepomis macrochirus) were compared during toxicity tests, which were conducted in controlled outdoor exposures. Physiological defenses were also investigated in an attempt to elucidate ways each species may tolerate UVR and UVR + FLU exposures. It was determined that the native redside minnow is more tolerant to UVR and UVR + FLU exposure when compared to the nonnative bluegill. In addition, a natural UVR coping mechanism, increased pigmentation, is exhibited to a greater extent in the native redside. The present study will help determine the potential for a future successful invasion of the bluegill and similar species in Lake Tahoe and other oligotrophic, montane lakes that are susceptible to habitat alteration, nutrient inputs, and recreational activity. Environ. Toxicol. Chem. 2012; 31: 1129-1135. © 2012 SETAC [ABSTRACT FROM AUTHOR]

Predicting where species invasions will occur remains a substantial challenge in ecology, but identifying factors that ultimately constrain the distribution of potential invaders could facilitate successful prediction. Whereas ultraviolet radiation (UVR) is recognized as an important factor controlling species distribution and community composition, the role of UVR in a habitat invasibility context has not been explored. Here we examine how underwater UVR can regulate warm-water fish invasion. In Lake Tahoe, California and Nevada, USA, established populations of exotic bluegill sunfish (Lepomis macrochirus) are currently limited to turbid, low-UVR embayments. An in situ incubation experiment that manipulated incident UVR exposure of larval bluegill, combined with an assessment of UVR exposure levels in nearshore habitats around Lake Tahoe, demonstrates that UVR can mediate habitat invasibility. Our findings suggest that the susceptibility to invasion by UVR sensitive species may increase in transparent aquatic systems threatened by declining water quality, and they highlight the importance of abiotic factors as regulators of invasion risk in ecosystems. [ABSTRACT FROM AUTHOR]