The influence of habitat-modifying fauna on the community ecology at deep cold-seeps in the Gulf of Mexico.

摘要

Cold seeps commonly occur on continental margins worldwide where hydrocarbons and reduced chemicals emerge from the seafloor. In the Gulf of Mexico, habitat-modifying fauna frequently dominate cold seep communities. Examples of these fauna include large aggregations of mussels and tubeworms as well as mobile animals such as burrowing spatangoid urchins. As seepage declines, cold-water corals settle on authigenic carbonate rock and eventually form large, long-lasting coral reefs that support diverse coral-associated fauna. In this dissertation, physical collections and nondestructive sampling tools such as image and GIS analyses were used to characterize newly discovered cold seep and coral communities as well as examine the mechanisms that influence the ecology of deep seeps. Chapters 2 and 3 examine interspecific interactions and habitat provision and modification by different foundation fauna, such as tubeworms, mussels and corals, which harbor unique communities. These fauna are long-lived, and have generally predictable successional trends that are similar to shallower seeps in the Gulf of Mexico. However, I also show that exceptions to these trends occur when small changes in seepage expression over time influence the recruitment and growth of the foundation fauna. In Chapter 4, I characterize a newly discovered type of seep community dominated by spatangoid urchins (Sarsiaster griegii), and provide evidence for the role of interspecific interactions as a strong influence on the community ecology of seep sediment infauna. I demonstrate that urchins act as habitat-modifying fauna whose activities influence sediment infauna community composition and structure, and contribute to high spatial heterogeneity in deep seep sediments. In these seep communities, the dominant megafauna influence the composition, structure, abundance and diversity of the associated community as a result of their physical structure, which provides a habitat resource and as a result of their activities. Facilitative interspecific interactions, particularly between habitat-modifying fauna and their associated communities, strongly contribute to the general patterns in the community ecology observed in these seep environments.