HR: 0800h
AN: OS51C-1309    [Abstracts]
TI: Sunlight Damage To The Solitary Ascidian Chelyosoma productum
AU: * Flores, E
EM: eddyflores@hotmail.com
AF: Shannon Point Marine Center, 1900 Shannon Point Rd, Anacortes, WA 98221 United States
AB: Chelyosoma productum (Stimpson) is a temperate solitary ascidian commonly found in Puget Sound and the San Juan Archipelago, Washington, USA. Adult populations are restricted to deeper subtidal regions or shaded shallow-water habitats, such as docks in shaded marinas. C. productum adults have a thin translucent outer tunic that may provide very little if any protection from solar damage. I hypothesized that sunlight may be setting limits on the distribution of this species. Since adult ascidians are sessile and rely on earlier life stages for their distribution, all life stages of Chelyosoma productum were tested. In this study, I examined the effects of sunlight exposure in embryos, larvae, juveniles and adults of Chelyosoma productum. I isolated the PAR, UVA and UVB portions of the spectrum and exposed all life stages using natural sunlight. I also sampled shallow-water dock habitats to see how adult distributions were related to light exposure. The embryonic development in C. productum was negatively affected by any solar exposure. Most embryos exposed to UV light failed to develop normally and those that did could not subsequently settle. This species produces embryos of different colors; two (purple and brown) were observed in my experiments. Damage from light exposure differed between the color morphs. Overall, the brown morph was more tolerant of light exposure than was the purple morph across all life stages. The only exception to this general pattern was that purple embryos were remarkably resistant to light damage. The distribution of C. productum is restricted to areas with no direct solar exposure. However, even within shaded environments where they were abundant, subpopulations related to the color dimorphism were observed. The significance of the brown and purple pigments in embryos and larvae remains largely unknown. However, adults with brown eggs were found to be more prevalent in edge environments where there was higher light exposure. Purple individuals were limited to the darker, more shaded areas. There is strong evidence that natural sunlight not only affects the survival and development of early life history stages of Chelyosoma productum, but through these effects, influences adult distribution as well. Lethal and sublethal effects were evident for all life stages of this species. These results suggest that the distribution of C. productum may be largely controlled by light exposure. This conclusion raises interesting questions about the influence of light intensity and quality (wavelength) on the distribution, behavior, and survival of other benthic marine organisms.
DE: 4830 Higher marine organisms
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting