BENTHIC INFAUNAL LONG-TERM RESPONSE TO OFFSHORE PRODUCTION PLATFORMS IN THE GULF-OF-MEXICO

Meiofaunal and macroinfaunal communities around three gas platforms on the continental shelf (29-157 m water depths) in the Gulf of Mexico w ere assessed for sublethal or persistent effects of chronic exposure t o contaminants associated with long-term production. Subsamples of box cores were collected from five distances (30-3000 m) along five radii from each platform during winter and spring in two years. In contrast with platforms in the North Sea, effects were very localized, extendin g to 100 m from the platforms. Total polychaete and nonselective depos it-feeding nematode density increased near platforms. Amphipod and har pacticoid abundance and diversity and harpacticoid reproductive succes s declined near platforms. Organic enrichment, contamination by toxica nts (e.g., heavy metals and hydrocarbons), and changes in sediment gra nulometry are confounded along the gradient of distance from platforms . However, the pattern of community change in both meiofauna and macro fauna around these gas production platforms follows an emerging paradi gm of response in which density increases of deposit-feeding polychaet es and nematodes indicate organic enrichment, while density declines o f harpacticoids and amphipods indicate toxicity.