MA9 Hazard Assessments for Near Coastal Ecosystems
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() Quantifying ultraviolet irradiance in estuarine tidal creek habitats: Relevance to the assessment of PAH phototoxicity.

Weinstein, J1, Diamond, S2, 1 The Citadel, Charleston, SC, US2 U.S. Environmental Protection Agency, Duluth, MN, US

ABSTRACT- Estuaries of the southeastern U.S. are characterized by diurnal tides, shallow depths, and expansive tidal creek/salt marsh habitats. These habitats not only serve an important nursery function for ecologically and commercially important species, but are also common repositories of PAH derived from upland development activities. Thus, tidal creeks habitats may be at risk for PAH phototoxicity. To better estimate this risk, solar UV irradiance measurements at various depths were performed approximately every two weeks during 2003 at the following three locations in coastal South Carolina: (1) Charleston Harbor Estuary, (2) James Island Creek, and (3) Leadenwah Creek. Significant seasonal variation in attenuation coefficients (Kd) occurred at all three sites, with values for both UV-A and UV-B being significantly lower (p<0.0001) in fall and winter compared to spring and summer. On a yearly basis, significant differences among the three sites were also evident. Yearly mean KdUVA and KdUVB were significantly lower at the Charleston Harbor site compared to that of both the Leadenwah Creek and James Island Creek sites (p=0.0023 and 0.0015, respectively). In addition to the seasonal survey, a daily survey of UV irradiance at various depths was performed at Leadenwah Creek on 27 June and 1 August 2003. UV irradiance at a depth of 10 cm exhibited a pattern generally similar to that observed at the surface, while UV irradiance at the bottom of the creek was a function of both tidal height and time of day. On both sampling days, KdUVA and KdUVB varied as a function of tidal height. The study results were used to develop (1) a preliminary risk assessment for larval grass shrimp (Palaemonetes pugio) based on published hazard data and (2) an environmentally-realistic laboratory light regime to be used for future assessments of both pelagic and benthic tidal creek organisms.

Key words: PAH, UV, Palaemonetes pugio, phototoxicity

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