Megabenthic Invertebrates on Shell Mounds Under Oil and Gas Platforms Off California

摘要

Twenty-seven oil and gas platforms are located off the California coast, in waters up to 365 m deep. When a platform becomes uneconomical to operate for its original use, it faces decommissioning, a complex process involving state and federal agencies and requiring extensive environmental review. During their working lives, platforms accumulate a wealth of benthic and pelagic biota, becoming de facto artificial reefs. Species associated with the platforms may include economically important species, species of conservation importance, and even non-native species. Therefore, the environmental review required by decommissioning must consider the ecological impacts on the region of altering or removing each platform and its associated biota, as called for by the various decommissioning options. These options, which are summarized and discussed in OCS Study MMS 2003-032, range from complete removal of a platform, to partial removal, to toppling, and finally, no removal. The fishes associated with OCS platforms off California have been extensively studied and documented by OCS Studies MMS 99-0015 and 2003-032, and the platforms have been found to provide important habitat for the juveniles and adults of many species, including some overexploited, economically valuable rockfishes. Although there has long been interest in the platforms as sites of aquaculture of bivalves such as mussels and rock scallops (with at least one commercial venture), interest in the benthic invertebrate biota associated with the OCS platforms has generally lagged behind that of the fishes. This has changed recently, owing to (1) an increasing recognition of the functional significance beyond the usual predator/prey relationships of many sessile invertebrates of the types found on the platforms to fishes, and (2) because the platforms support a large biomass of sessile species, some of which might provide sustainable sources of marine natural products difficult or harmful to obtain in significant quantities from natural habitats.