Persistence of bacterial-mediated anti-rotifer protection in preliminary outdoor cultivation trial for Microchloropsis salina

Outdoor algal cultivation systems are susceptible to a wide variety of deleterious species. In previously published studies, we observed protection using microbial consortia at laboratory scale cultures; Microchloropsis salina in the presence of microbial consortia were protected from grazing from the marine rotifer, Brachionus plicatilis. Our objective for the present work was to determine if this protection conferred by microbial consortia in controlled laboratory experiments would persist in an open, outdoor multi-liter cultivation system. We found that algal protection did persist as evidenced by the presence of fewer motile rotifers and decreased rotifer-associated egg counts for the consortia-treated outdoor cultures. Due to the low temperature and light conditions that reduced growth of the algae outdoors, we performed an indoor laboratory assay which also confirmed the persistence of algal protection. Lastly, the lower numbers of motile rotifers and fewer rotifer-associated eggs in the consortia-treated algal cultures suggests a possible protective mechanism by the consortia through interfering with the rotifer lifecycle or reproduction. These initial results support the possibility that low cost, prophylactic treatments with microbial consortia can protect algae from deleterious species in outdoor cultivation systems.