UC San Diego

Methane seepage often generates precipitation of carbonate rocks, which host microbes and a diverse fauna. These rocks may also promote an interaction between seep and background communities that may last for centuries, providing hard substrate even after seepage ceases. I analyzed composition, density, and trophic structure of macrofaunal invertebrates on carbonate rocks at and surrounding Mound 12, a methane seep site off the coast of Costa Rica, to examine how species and trophic diversities respond to changes in seepage activity at different spatial and temporal scales. By sampling in situ carbonate rocks at active and transition sites, I observed declining density and a community shift from a gastropod dominance to more annelids and peracarid crustaceans under less seepage, while carbonates promoted an interaction between such communities functioning as hard substrate for attachment. Defaunated carbonates deployed for 7 years at active and transition sites indicated that grazers are amongst the most successful colonizers, although the community and its trophic structure were not able to fully recover. However, both seep and transition communities showed rapid response, persistence and recovery when carbonates were transplanted to sites with lesser/more seepage activity for 17 months. Finally, wood and bone deployed for 7 years at active and transition sites showed shared species indicating potential interaction between whale, wood, and seep ecosystems when in close proximity. This multi-experimental study offers insight on the resilience of macrofaunal communities and helps us predict community responses to disturbances in seepage activity that may result from growing anthropogenic interference on margins.