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Past and present infestation of the stalked ciliate Zoothamnium sp. on copepods in the Klang Strait

Hao Chin Goh, Li Lee Chew, Chui Wei Bong, Ching Ching Ng, Ving Ching Chong*

*Corresponding author:

ABSTRACT: Ciliate-copepod epibiosis is a common but poorly understood phenomenon in the aquatic environment. This study investigated the prevalence of ciliate infestation on copepods in the Klang Strait, Straits of Malacca. We hypothesized that anthropogenic impacts in the strait increase ciliate epibiont infestation on copepods. Zooplankton samples collected exactly similar from 5 stations along an 18 km transect, 30 yr before ad after the Kapar power station (KPS) was established in 1985, were examined. The 5 stations including 1 impact station (I) and 4 control stations (C1–C4) were located from near KPS (I) through progressively offshore waters to C4. Ciliate epibionts on the copepods belonged to an unidentified Zoothamnium species. A total of 14 copepod species were infested by this ciliate. The highest infestation prevalence occurred in 5 key calanoid species: Paracalanus aculeatus, Acrocalanus gibber, Labidocera euchaeta, Parvocalanus crassirostris and Subeucalanus subcrassus. Before-After-Control-Impact-Pairs (BACI) analysis showed that the infestations were more prevalent at all stations in recent years compared to 30 years ago and were the lowest at or nearest the impact site. The prosome of the copepod was the most vulnerable body part to attachment by the ciliate. Generally, the density of infested copepods and their epibiont loads were positively correlated to copepod abundance. Only density of infested A. gibber showed significant positive relationships with water temperature, while in P. aculeatus the infested copepod density was significantly correlated to phytoplankton abundance after a lag of two months. We suggest that sea warming and eutrophication in recent years have increased ciliate-copepod epibiosis in Klang Strait.