Future directions

As levels of stratospheric ozone continue to decrease, future increases in UVR reaching the Earth's surface are predicted [88]. UVR has been shown to be damaging to many aquatic organisms from bacteria to fish [6-9], and UV avoidance behavior has been observed in several species [28-51]. Yet responses to future changes in the underwater UVR environment are largely unknown.

The presence of UV photoreceptors in such a wide variety of freshwater and marine organisms suggests that UV vision is prominent in aquatic ecosystems. Further experimentation is needed to identify potential UV photoreceptors as well as action spectra for behavioral responses to varying wavelengths of light. In addition, field experiments are needed to understand responses to natural solar radiation. As seen in the feeding experiments with rainbow trout [73], laboratory results may not always match those reported in the field. Interpreting responses of organisms to solar radiation may require an integration of scientists working in the fields of vision ecology, behavioral ecology, as well as bio-optics.

UVR is only one of many potential stressors acting on aquatic communities. Other stressors such as pH, temperature, competition, predation, and food limitation can also influence the vertical and seasonal abundance and distribution of aquatic organisms. UVR is likely to interact with these stressors through a variety of mechanisms. For example, high UVR levels in the surface waters of low DOC systems may force animals into deeper waters where habitats are suboptimal due to lower temperatures or greater risk of predation. Further investigation is needed to understand how UVR interacts with these other important abiotic and biotic stressors.

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