Effects of diet, temperature, salinity and season on wasting disease in ecologically important predatory sea stars
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This study investigates sea star wasting disease seen in ecologically important predatory sea stars on intertidal coasts of San Juan Island, Lopez Island and Orcas Island (Washington, United States). Three experiments were conducted to analyze the effects of diet, temperature, salinity on the vulnerability of sea stars to wasting disease. To test the hypothesis that higher pathogen-dosed food would result in heightened infection intensities and also different diet types would result in different infection intensities, we fed Pycnopodia helianthoides with healthy and pathogen-dosed clams and mussels separately. There is no significant difference in either different diet types or in different pathogen-dosed levels treatments to the prevalence of sea star wasting disease. To test the hypothesis that temperature influences the prevalence of sea star wasting disease, we kept P. helianthoides in normal temperature tanks and higher temperature tanks. The prevalence of sea star wasting disease was always higher in warmer temperature treatments. To test the hypothesis that lower salinity environment would lead to higher prevalence of sea star wasting disease, we kept P. helianthoides under normal and lower salinity treatments. More symptomatic sea stars were found in the lower salinity experiment group. Furthermore, disease effects showed seasonal changes in field surveys. Compared with survey data from last winter, sea stars showed higher prevalence of disease in late spring.