Ecological investigations of petroleum production platforms in the central Gulf of Mexico – preliminary findings

Abstract

Southwest Research Institute is presently managing a relatively large program in offshore ecology for the Bureau of Land Management (BLM), Department of the Interior. The study involves university and private subcontractors representing several scientific disciplines. Project objectives .are to assess the long term cumulative effects of production platform operation on the outer continental shelf (OCS) environment, and further define their "artificial reef" effect. These results are then to be used in helping (1) formulate future research on the DeS, (2) indicate monitoring techniques and, (3) to review present "benchmark" studies. The study area covers a broad expanse of the Louisiana "oil patch" from the Mississippi delta, west 200 miles and offshore 100 miles. Twenty-four stations have been visited during late spring and late summer, 1978, and winter, 1979, with four platforms sampled as primary sites during each season, 16 as secondary sites in the late summer and four controls in each season. The program was designed by BLM to cover, as broadly as possible, all production types, ages and surrounding ecosystems normal to the northcentral Gulf of Mexico. Collections and analyses have included basic hydrography; hydrocarbons in water, sediments and biota; trace metals from similar samples; sediment physical characterization; benthic microbiology; benthic biota; histopathology in fish and invertebrates; and platform associated fouling organisms and fish. This paper presents data from initial sampling and gives observations of trends from a number of Principal Investigators doing the actual work. The major observation realized is that the Mississippi River overshadows man's activities in affecting the environment in that it overrides ocean water over a considerable area in the near shore during the summer months causing an oxygen decline and subsequent die off and emigration of organisms.