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Marine Ecology Progress Series

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MEPS 449:1-12 (2012)  -  DOI:

Influences of biofilm-associated ciliates on the settlement of marine invertebrate larvae

Jeff Shimeta*, Justin Cutajar, Matthew G. Watson, Thelma Vlamis

School of Applied Sciences, RMIT University, Melbourne, Victoria 3083, Australia

ABSTRACT: Settlement of benthic marine invertebrate larvae often limits recruitment, influencing the structure and dynamics of natural populations as well as biofouling of marine infrastructure, ship hulls, and aquaculture operations. Certain microbial components of substratum biofilms influence settlement (e.g. bacteria, diatoms), but the importance of biofilm protozoa has been unknown. We tested for effects of ciliates by comparing settlement and survival of common fouling invertebrates among 3 biofilm conditions: no biofilm, a purely bacterial biofilm, and a biofilm of bacteria and ciliates. With an assemblage of 7 ciliates (from Hypotrichia, Haptoria, and Scuticociliatia), the serpulid polychaete Galeolaria caespitosa showed a 44 to 49% average reduction in settlement rate compared to the purely bacterial biofilm, and post-settlement mortality increased 7-fold to 34%. In contrast, settlement and survival of the bryozoan Bugula neritina were unaffected. With a partially different assemblage of 11 ciliates (from Hypotrichia, Stichotrichia, Haptoria, Colpodida, and Scuticociliatia), settlement of the serpulid Pomatoceros taeniata more than doubled, whereas that of the blue mussel Mytilus galloprovincialis was reduced by 54% compared to the purely bacterial biofilm. The results could not be explained by ciliates changing the total abundance of biofilm bacteria. We hypothesize that mechanisms could include direct interactions between larvae and ciliates (physical interactions, interference from ciliates’ feeding currents, or responses to chemicals from ciliates), or indirect effects from ciliates altering the bacterial assemblage or its settlement cues. Such large and species-specific effects of ciliates on larval settlement and post-settlement mortality might impact invertebrate recruitment rates and species assemblages, especially because biofilm ciliates are highly variable over time and space.


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Cite this article as: Shimeta J, Cutajar J, Watson MG, Vlamis T (2012) Influences of biofilm-associated ciliates on the settlement of marine invertebrate larvae. Mar Ecol Prog Ser 449:1-12.

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