Recolonization of Deep-Water Hard-Substrate Communities: Potential Impacts From Oil and Gas Development

Many regions of the California, USA, outer continental shelf are subject to ongoing and planned oil and gas development, but there is very limited information on the recolonization and recovery of deep-water (e.g., 60-300 m) hard-substrate communities that may be affected by these activities. The purpose of this study was to summarize existing information on these communities, thereby aiding regulatory agencies and the scientific community in assessing potential impacts, and to determine whether additional studies may be necessary. Impacts from anchoring and increased sedimentation (e.g., from discharges of drilling muds and cuttings) are particularly likely. Sedimentation effects can be natural of human-induced, but habitat disruption from anchoring has few natural parallels. Disturbances from anchoring and sedimentation generally produce Type 1 and Type 2 patches (sensu Sousa 1985, Connell and Keough 1985), respectively. Recolonization and recovery of these patches in deep-water environments are expected to vary in accordance with current models of succession (i.e., inhibition, facilitation, and tolerance). However, inhibition responses likely will predominate in Type 1 patches, particularly high-relief (e.g., > 1 m) areas, where regrowth from the margins often is possible from sheet-like or mound-like forms such as those represented by many sponge taxa. In contrast, recovery of Type 2 patches, particularly low-relief (e.g., <1 m) areas, also may be influenced primarily by inhibition responses, but the relative lack of nearby colonizers suggests greater numbers of species interactions in accordance with facilitation and tolerance models. This is due to the greater stochastic component associated with recolonization by long-range larval dispersers. Recovery is expected to require a few to several years to accomplish for these deep-water hard-substrate communities. This is based on estimated times for recovery of slow-growing, generally long-lived taxa, such as some vase sponges and anemones characteristic of many high-relief areas, and the uncertainties of long-range recruitment coupled with variable sediment movement in many low-relief areas.