Insights into effects of salinity stress on the body-size spectrum of periphytic protozoan fauna in marine ecosystems

To evaluate the impacts of salinity stress on the community functioning of marine ecosystems, a 1-month bioassay was performed using periphytic protozoan fauna as the test organism community within a gradient of salinity 9, 19, 29 (control), 39, and 49 PSU. The samples of the test organism assemblage were collected from an intertidal zone of the Yellow Sea, northern China. In terms of both the frequency of occurrences and the probability density, the body-size spectrum of the test protozoan fauna was clearly shifted with the test scale of salinity variability. The significant changes occurred in the body-size distinctness measures, which followed a unique trend among salinity gradients. Furthermore, the body-size spectrum showed a significant departure from an expected pattern at 9 PSU. Therefore, it is suggested that the body-size spectrum of periphytic protozoan fauna may be used as a useful tool for evaluating the effects of salinity stress on community functioning in marine environments.