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2.1.5 



TEXAS AND LOUISIANA 

 SHELF ECOSYSTEMS STUDY 



Dr. Robert M. Avent 



Environmental Studies Staff 



Minerals Management Service 



Gulf of Mexico OCS Region 



INTRODUCTION 



The purposes of this presentation are threefold. First, it is necessary to describe the past ecosystems studies 

 funded by the Bureau of Land Management (BLM) and the Minerals Management Service (MMS). Second, 

 due to the new emphasis upon process studies, it is informative to examine past research approaches, successes, 

 and shortcomings. Third, against this background, the stage is set for participants' discussions on what new 

 ecosystems studies are appropriate, especially on the Texas and Louisiana outer continental shelf. 



With the requirements of the OCSLA in mind, (detailed in sections 2.1.1. and 2.1.2.) a number of questions are 

 in order. Among these are: 



How does one predict the consequences of the petroleum and sulfur mining industries? Can a predictive 

 capability be achieved, and if so, to what levels of accuracy? 



With respect to predicting consequences, what are the relative advantages in the "process" approach as 

 opposed to the "descriptive" approach? Which processes truly reflect a "healthy" environment and which 

 ones can be used to advantage in predicting anthropogenic impacts? 



• Once a balance of process and descriptive studies has been identified, exactly what are the relevant 

 scientific questions to be asked and which are possible to answer given technical, timing, and funding 

 constraints? 



How is an adequate study defined? How much data of what types are enough? 

 BRIEF HISTORY OF THE GULF OF MEXICO MARINE ECOSYSTEMS STUDIES PROGRAM 



Historically, marine ecosystems studies in the Gulf of Mexico have been descriptive, regional efforts stressing 

 inventories of habitats, living resources, and abiotic conditions. These have been designed variously to: define 

 faunal zonation patterns and the biotic similarities or dissimilarities among communities; describe and quantify 

 communities and habitats of special interest; identify and quantify the abiotic conditions which influence or 

 control those patterns; establish a baseline for future comparison; and detect anthropogenic change. 



Successful study design hinges on spatial and temporal variability and should allow an accurate view of all 

 variability found on the scale of sampling. Depending upon the expected biotic and abiotic conditions, 

 homogeneity, "zonation", patchiness, etc., one may adopt one or more spatial sampling designs. These include 

 high density mapping, spaced transect sampling, stratified random sampling, and habitat, depth, and site specific 

 sampling. Likewise, temporal design must consider the expected rapidity and frequency of change. Temporal 

 approaches include time-series sampling (e.g., day/night, monthly, seasonal, etc.), long-term monitoring, 

 opportunistic sampling (e.g., following hurricanes or mud slumps), and continuous in situ monitoring. All have 

 been used in the MMS programs at one time or another. 



The amount and type of sampling must be tailored to the characteristics and variability in a study area (e.g., the 

 distribution and abundance of diapirs and live bottom). While some BLM/MMS studies have relied mostly on 

 conventional at-sea sampling methodologies (trawls, grabs, hydrographic instrumentation, etc.), others have 

 required the deployment of manned submersibles, remotely operated vehicles (ROV's), side-scan sonar, 

 photographic sleds, divers, in situ instrumentation, or remote (satellite) technology. 



