Biological control of ciliate contamination in Chlamydomonas culture using the predatory copepod Acanthocyclops robustus

Abstract

Ciliates are a common but less-explored group of contaminants in microalgal cultures that feed on microalgae and can cause severe losses in productivity of cultures. The aim of this study was to evaluate the potential of biological control to eradicate ciliates from microalgal cultures. In lab-scale experiments, we used the carni- vorous cyclopoid copepod Acanthocyclops robustus as a biological control agent to eliminate the ciliate Sterkiella from cultures of the microalga Chlamydomonas. Our experiments showed that the copepod Acanthocyclops ro- bustus can consume up to 400 ciliates individual−1 day−1. Addition of 0.07 copepods mL−1 to a culture that was contaminated with 10 ciliates mL−1 resulted in a complete elimination of ciliates from the culture within 1 day and restored the algal biomass production at the level of a non-contaminated culture. Addition of copepods to a fresh Chlamydomonas culture did not cause a reduction in the microalgal biomass concentration, indicating that this copepod does not feed on Chlamydomonas. These laboratory-scale experiments indicate that copepods have potential to be used as a biological control agent to address the problem of contamination of large-scale mi- croalgal cultures by ciliates.