Basibiont-epibiont communities in Maine: An invitation to expand understanding of facilitation by living habitats in marine ecosystems

Background/Question/Methods

: Because space in marine habitats is limited, particularly in productive marine environments, colonizing invaders may settle on biotic substrata (e.g., shells, seaweed, and other body structures). A number of invaders have been studied in recent years due to their intense impacts on native species; such invaders include the colonial ascidian Didemnum vexillum (on the native mussel Mytilus edulis) and the bryozoan Membranipora membranacea (on the native kelp species Laminaria spp.). What is not well understood, however, is the impact available space provided by basibionts has on community structure. A previous study, conducted by Lazzeri and Auker (in review), found that nonnative epibiont species do not preferentially settle only on non-native basibiont species, but that nonnative basibionts do support a less diverse community overall. These results are limited in scope due to their small geographic area in the Damariscotta Estuary within the Gulf of Maine, but there is room for further investigation of the question on how non-native basibionts structure communities. Using epibiont-basibiont assemblages collected from these sites, herein I ask the questions: 1) Does site or basibiont play a role in community similarity and 2) Are certain epibiont species more likely to be associated with one another across basibiont substrata?

Results/Conclusions

: The first question is answered using Bray-Curtis dissimilarity and is represented in a hierarchical cluster. I found that the sites most similar based on epibionts present are farthest from one another geographically. While this suggests that site location is not a factor, geographic expansion of this study may reveal site-dependent changes in community structure. However, there were similarities between epibiont assemblages by basibiont. For example, Mytilus edulis and Ciona intestinalis supported similar epibiont communities. The second question, answered through association analysis, conducted in R, showed no significant association between any pairs of epibionts (p >0.05). This research has promising potential for observing impacts of the interaction between invasion and epibiosis on community structure, and I invite collaboration in a wider geographic study to better understand the role of basibiont-epibiont relationships in habitat availability and facilitation of community growth and change.