Temporal and spatial variability in algal-invertebrate associations in benthic red algal communities, Monterey Bay, CA

Background/Question/Methods

Mechanisms that operate across spatial and temporal scales regulate distribution and abundance of available habitat and can influence abundance and diversity of associated fauna. The understory algal community in a kelp forest is comprised primarily of red algae, which provide important and highly complex habitat to a diverse community of small, mobile invertebrates that are, in turn, important food sources for kelp forest fishes. Morphological complexity of algae can influence the composition and abundance of associated fauna. Specifically I am to understand if mobile invertebrate assemblages are structured by algal composition and if so, how variations in assemblages influence these invertebrates. To understand spatial and temporal variability in red algae and how this translates to variability in associated invertebrates, I conducted benthic surveys and collections in 6 kelp forests along the Monterey Bay peninsula, CA from July-December 2011 and March 2012. Percent cover of red algae was quantified using UPC along transects. To determine abundance and composition of associated invertebrates at each site and for varying complexities of algal morphology, I collected 6 species of red algae that represent a range of algal morphologies from simple to complex. Associated invertebrates were removed and enumerated. Red algal coverage as well as abundance of the 6 algal species were compared among sites and by month.

Results/Conclusions

Cluster analysis shows that sites that are spatially close are also more similar in algal assemblages. The invertebrate composition associated with algal species and among sites was analyzed using multivariate approaches in PRIMER. Cluster analysis shows that invertebrate assemblages are more similar in sites that are spatially close. Additionally, invertebrate assemblages were significantly different by month showing temporal variability. Associations between the algal and invertebrate assemblages were significant in July and August 2011 and March 2012 but not in September and October 2012 showing temporal variability in the association. Three algal species appear to be significant drivers of these patterns indicating strong interactions that may be useful in future monitoring and predictions. The relationship between algal substrate and invertebrate community varied over space and time indicating that local drivers may have pronounced effects on the interactions between availability of habitat and structure of associated communities.