AME 82:299-306 (2019)  -  DOI: https://doi.org/10.3354/ame01898

ABSTRACT: The peritrich ciliate Epistylis sp. is commonly found attached to the dominant calanoid copepod Pseudodiaptomus stuhlmanni in the St Lucia Estuary, South Africa. A study was conducted to test if salinity interacted with temperature and turbidity to affect the survivorship of Epistylis sp. Two-way analysis of variance on ranks was conducted to test for the main and interaction effects of these parameters. There was no interaction between temperature and salinity, and temperature (15, 21 and 30°C) did not affect Epistylis sp. The survivorship of Epistylis sp. was however significantly and negatively affected by high salinity. Post hoc analyses revealed that the highest salinity level (25) was responsible for most of the Epistylis sp. mortalities. The survivorship of Epistylis sp. was significantly affected by the interaction between turbidity and salinity. High turbidity (1000 nephelometric turbidity units [NTU]) negatively affected survivorship across the entire salinity gradient (0 to 25), and high salinity (25) also generally resulted in low survivorship across the turbidity gradient of 50 to 1000 NTU. As the host P. stuhlmanni is more tolerant of high salinity and high turbidity, these findings suggest that these conditions can modulate epibiosis by limiting the prevalence and cover of Epistylis sp. in the St Lucia Estuary, particularly when salinity is high.

KEY WORDS: Ciliate epibiont · Copepod host · Physico-chemical drivers · St Lucia Estuary