Estimated Ultraviolet Radiation Doses in Wetlands in Six National Parks

Abstract

Ultraviolet-B radiation (UV-B, 280-320-nm wavelengths) doses were estimated for 1024 wetlands in six national parks: Acadia (Acadia), Glacier (Glacier), Great Smoky Mountains (Smoky), Olympic (Olympic), Rocky Mountain (Rocky), and Sequoia/ Kings Canyon (Sequoia). Estimates were made using ground-based UV-B data (Brewer spectrophotometers), solar radiation models, GIS tools, field characterization of vegetative features, and quantification of DOC concentration and spectral absorbance. UV-B dose estimates were made for the summer solstice, at a depth of 1 cm in each wetland. The mean dose across all wetlands and parks was 19.3 W-h m )2 (range of 3.4-32.1 W-h m )2 ). The mean dose was lowest in Acadia (13.7 W-h m )2 ) and highest in Rocky (24.4 W-h m )2 ). Doses were significantly different among all parks. These wetland doses correspond to UV-B flux of 125.0 lW cm )2 (range 21.4-194.7 lW cm )2 ) based on a day length, averaged among all parks, of 15.5 h. Dissolved organic carbon (DOC), a key determinant of water-column UV-B flux, ranged from 0.6 (analytical detection limit) to 36.7 mg C L )1 over all wetlands and parks, and reduced potential maximal UV-B doses at 1-cm depth by 1%-87 %. DOC concentration, as well as its effect on dose, was lowest in Sequoia and highest in Acadia (DOC was equivalent in Acadia, Glacier, and Rocky). Landscape reduction of potential maximal UV-B doses ranged from zero to 77% and was lowest in Sequoia. These regional differences in UV-B wetland dose illustrate the importance of considering all aspects of exposure in evaluating the potential impact of UV-B on aquatic organisms.

Removal of nonnative fish results in population expansion of a declining amphibian (mountain yellow-legged frog, Rana muscosa)

“…Their high detectability is a consequence of several factors. First, in the Sierra Nevada, water clarity in alpine lentic habitats is exceedingly high (Diamond et al, 2005) and habitats are structurally simple (e.g., lacking aquatic vegetation and submerged logs). Second, frogs spend the majority of the ice-free season on shore immediately adjacent to water and tadpoles are found primarily in near-shore shallows (Camp, 1917;Zweifel, 1955).…”

Phenotypic plasticity facilitates recurrent rapid adaptation to introduced predators

“…UV treatment beakers were placed 10.5 cm below 30 W, 36-inch Reptisun 5.0 UVB fluorescent lightbulbs (Zoo Med), and fans were used to ensure that UV treatment and control beakers retained the same 18°C temperature. The dose of UVB from these lamps was roughly 10% that at the lake surface during summer solstice, or equivalent to what Daphnia would experience ≈9 m below the water surface, according to estimates of UVB dose (27.9 W -h/m 2 ) and dissolved organic carbon attenuation coefficient (0.26) obtained from nearby Sequoia National Park (34). Opaque screens separated control and UV beakers.…”

Water clarity, maternal behavior, and physiology combine to eliminate UV radiation risk to amphibians in a montane landscape

“…As a result, we chose to use unweighted cumulative exposure (KJ·m −2 ·day) integrated across the UV-B range as the basis for comparing differences in exposure between sites. Previous risk assessments for amphibian breeding sites in midwestern US wetlands and US national parks also have used this maximum theoretical exposure (16,18) in the absence of a more mechanistic understanding of wavelength-specific damage rates.…”

“…A critical limitation preventing such analyses is the lack of quantitative data regarding actual UV-B exposures across the range of conditions experienced by individuals within a population, coupled to experimentally identified thresholds of lethal UV-B exposure. Although measuring cumulative exposure to UV-B over time at multiple sites in the field is currently limited by instrumentation and expense, site-level UV-B exposures have been estimated from the primary features of the terrestrial and aquatic environment that affect UV-B transmission, including geographic location, elevation, cloud cover, topographic and vegetative shading, and the attenuation of UV-B in water (16,18). However, an additional limitation of even these sophisticated models is the need to incorporate not only variation among sites, but also the variation in UV-B exposure among individuals within a site that may result from variation in individual behaviors (19,20).…”