Biological Weighting Functions for Describing the Effects of Ultraviolet Radiation on Aquatic Systems

In order to evaluate the effects of ultraviolet radiation (UV; 280 400 nm) on aquatic ecosystems, and to predict the potential influence of enhanced ultraviolet-B radiation (UV-B; 280 320 nm) from ozone depletion, it is necessary to observe the effects of natural and experimentallyaltered UV on different biological and chemical systems, and to quantify measured responses as functions of irradiance and time. Because biological and chemical effects of UV are strongly dependent on wavelength, spectral weighting functions must be applied to relate experimental responses quantitatively to UV exposure, if the results are to have any use for predicting effects in nature. This is reality, not opinion. The fact is that if any biological or chemical effect is expressed as a function of radiant exposure for regimes with different spectral irradiance (i.e., different depths in the water column, times of day or year, or different artificial sources of UV), a weighting function is used, either explicitly or implicitly. An appropriate weighting function must be applied, therefore, or at least the uncertainties associated with the chosen weighting function should