COS 23-8
Intertidal turf algae: Redundant roles as foundation species?
Intertidal turf algae grow in short, dense mats that provide habitat for diverse epifaunal communities. The morphology of turf algae varies considerably, creating differences in habitat structure. We hypothesized that different types of turf algae would host different epifaunal communities, lending additive benefits to diversity. We surveyed four rocky intertidal sites along 600 km of the Oregon-northern California coast, collecting samples of calcareous coralline turfs and proximate non-calcareous fleshy turfs. We then compared the species composition and abundance of epifauna found in these two habitat types, as well as at the different sites. Since coralline algae are more vulnerable to ocean acidification than fleshy algae, coralline turf cover may decrease with an increase in pH stress. Examination of the distinctiveness of coralline turf epifaunal communities helps to address the broader consequences of ocean acidification impacts on calcifiers.
Results/Conclusions
Epifaunal communities differed between coralline turfs and fleshy turfs, but the effect size was small (MRBP, A = 0.056, p < 0.001). Blocked indicator species analysis revealed several taxa demonstrating high exclusiveness and frequency in coralline turfs: Leptasterias hexactis, Lacuna marmorata, Ianiropsis, and Anthopleura. However, most taxa were found in both habitats. This homogeneity in the epifaunal community may be explained by the small spatial scale of variation between habitat patches. Mobile epifauna may move across the habitat mosaic indiscriminately. Epifaunal communities were more distinct between sites (MRPP, A = 0.316, p < 0.001) than they were between turfs, suggesting greater sensitivity to large-scale environmental processes than to small-scale differences in turf habitat. The considerable overlap in epifaunal communities inhabiting coralline turfs and fleshy turfs suggests redundant roles as foundation species, providing some insurance against ocean acidification if fleshy turfs can act as a backup in case coralline turfs decline. Nevertheless, coralline turfs play other important community roles, e.g. providing recruitment substrate, for which there may not be backups.