Molecular and Functional Ecology of Sponges and Their Microbial Symbionts

Sponge-microbe symbiotic interactions are important features of modern marine ecosystems. It is likely that these ancient partnerships are as old as the phylum Porifera. Powerful new tools have exposed remarkable microbial diversity within sponge tissues. We are now able to study the composition and structure of the microbial communities at unprecedented levels of resolution. We also recognize that the partnership cannot be disaggregated and should be considered as an integrated holobiont. New hypotheses (e.g., the sponge loop hypothesis) have opened exciting avenues for future experimental work that link holobiont performance from micro- to macro-perspectives. This type of research has taken on added significance given that our planet is experiencing accelerating rates of ocean warming and ocean acidification. It is essential that we examine how sponges respond to environmental stressors that are increasing in intensity and frequency. This review focuses on the molecular and functional ecology of sponge-based microbial symbioses. We discuss the coevolutionary processes that operate to generate partner specificity or to maintain promiscuous partnerships and consider reciprocal selective forces that shape the material exchanges that occur between the partners. We focus attention on the functional ecological role the holobiont plays in marine habitats. The role that the symbionts play in host physiology, and ultimately in the function of sponges on marine ecosystems, is also discussed. We stand to gain important basic information about symbiotic interactions through the detailed study of sponge-microbe interactions, but important practical lessons will be afforded to resource managers who are looking for strategies to protect aquatic habitats worldwide.Peer reviewe