Abstract
Benthic marine invertebrates are naturally exposed to a broad array of potentially deleterious microorganisms, and they can exhibit either a broad spectrum or a selective activity against specific bacteria. It is well known that chemical defenses produced by invertebrates are efficient in preventing microbial colonization or infections; however, little is known about such defenses in Arctic invertebrates. To investigate the incidence of chemical defenses against bacteria in sessile or slow-moving marine invertebrates from the Arctic Beaufort Sea, organic extracts of 16 species (10 sponges, three soft corals, two bryozoans, and one holothurian) were tested for antimicrobial activity against six allopatric bacterial strains. Notably, most lipophilic fractions showed different degrees of activity, while none of the hydrophilic extracts of any of the invertebrate species tested in the study presented any antimicrobial activity. Ten out of 16 invertebrate species tested (62.5 %) inhibited growth of at least one bacterial strain at natural extract concentration. This indicates that antimicrobial defenses are a common trend among sessile or slow-moving marine benthic invertebrates from the Arctic.