Georges Bank Benthic Infauna Monitoring Program -Year 1

Abstract

Concerns about the potential effects of oil and gas exploration on Georges Bank off the coast of Massachusetts led to the initiation of an intensive monitoring program in July, 1981. Sponsored by the Minerals Management Service of the Department of the Interior, the program includes benthic community analysis, as well as determination of the trace metal and hydrocarbon levels in sediments and biota, collected near, upcurrent and downcurrent of the drilling rigs. The benthic program includes seasonal collection of six replicate samples at each of 46 stations. Samples are collected with a 0.04m2modified Van Veen grab and are double live sieved through500 \mum and300 \mum screens. Twenty-nine stations are positioned in tight radial array around I rig at 80m. A second group of 3 stations are near a rig site at 145m. The remaining stations cover a broad expanse of the Bank and nearby areas of potential deposition of drilling materials. Results from the first 4 biological collections indicate little heterogeneity within stations, with good replication between samples.A strong relationship between faunal composition and both sediment type and depth is indicated by cluster analysis. Use of the300 \mum screen has resulted in the retention of all macroinfaunal components of each sample, including the newly settled and juvenile forms, as well as small-bodied species which are normally undersampled by larger screens.The capability of identifying the earliest juvenile stages of several species has enabled us to provide accurate counts of each species and to predict times of settlement. In general, no significant changes in benthic community structure which can be related to drilling activities have been detected during the first year of monitoring.