Emerging issues of environmental impact to deep-sea chemosynthetic petroleum seep communities

Continental slope chemosynthetic communities associated with hydrocarbon seeps off Louisiana and Texas are similar to communities associated with hydrothermal activity and polymetallic sulfide deposits. In each case potential environmental impact must be considered in conjunction with any plan to utilize the mineral resources. Unlike deep seafloor mining, which is still in the planning phase, progressively deeper petroleum production is now a reality. Therefore a higher priority should be assigned to determining the sensitivity of petroleum seep communities. On the basis of current knowledge, two opposing sensitivity models can be proposed. According to the first (which has been implicitly adopted by MMS), seep communities are robust with respect to impacts due to changing exposure to hydrocarbons. As such, no impact is to be expected from exploration and production if reasonable care is used.to avoid mechanical disturbance. According to the second, seep model, communities are specialized to a narrow geochemical window. Drilling and pumping which alter the subsurface flow of hydrocarbons may have a very major impact upon the continued existence of this window. It is anticipated that future research will contrast and test these two hypothetical models.