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LONG-TERM MONITORING AT SELECTED ECOSYSTEM 

 SITES IN THE NORTHERN GULF OF MEXICO 



Dr. Rezneat M. Darnell 



Department of Oceanography 



Texas A&M University 



College Station, TX 77843 



3.3.1 Introduction - Limits of Monitoring and a Strawman 



Our purpose is to come up with a plan (or perhaps alternate plans) for a field research program for long-term 

 monitoring in the Gulf of Mexico which contributes to Minerals Management Service's (MMS) efforts to increase 

 the effectiveness of its Outer Continental Shelf (OCS) studies. This monitoring program would provide the 

 ecological basis for: 



understanding the natural ecological systems (their structure, function, and natural variation), and 



• understanding and interpreting potential human perturbations on the natural systems, particularly those 

 changes arising from oil and gas developments. 



In developing a plan which meets the above purposes, we are faced with the difficult task of drawing a 

 meaningful distinction between descriptive characterization and monitoring. Is it sufficient to create monitoring 

 programs simply by extending the time and space duration of existing characterizations? Or, does longer-term 

 monitoring call for a different set of questions, approaches, and analyses. 



Initially, we need to set some limits to the systems which we wish to monitor and then consider some of the most 

 appropriate aspects to study. First, monitoring should be limited to depositional environments (although hard 

 substrate environments should be considered) because this is the dominant habitat. Second, natural ecological 

 systems should be the primary focus of monitoring (although other systems such as biofouling communities and 

 impacted systems should be considered). Third, rather than attempt to monitor the full species inventory, key 

 process and/or species indicators of system condition will be the primary focus of monitoring. 



Since one of our purposes is to understand normal variation in parameters and causal relationships, monitoring 

 time must be suitable to that task. To reduce the ambiguity of the term "long-term" we have to set initial time 

 limits. Ideally, the temporal duration would be twice the periodicity of major low frequency events. In practice, 

 such a duration is difficult to determine due to our lack of familiarity of low frequency events (i. e., storms and 

 hurricanes, outflow of flood waters, major intrusion by the Gulf Loop Current, etc.). However, a long-term 

 monitoring program of a decade would capture two to three major storms and provide information of the 

 resulting variation. Setting the resolution of sampling (frequency within the 10 year program) must also be 

 determined somewhat arbitrarily since we know little about short-term variation. Initially, we could sample 

 quarterly, or according to the natural seasonal progression of events. 



Since our second purpose is to provide useful information on impacts, it is appropriate that the sampling duration 

 and frequency of this task also be considered. Here again, we are faced with poorly known long-term and 

 short-term sources of potential impact, detection, and interpretation of both chronic and episodic human-imposed 

 effects (especially those resulting from oil and gas activities). At least initially, it seems that a 10 year duration 

 might allow tracking of impacts associated with regional population/industrialization increases. The randomness 

 of short-term impacts, makes selection of an optimal frequency impossible. However, seasonal sampling might 

 serve to detect any residual changes up to three months after an impact. 



In order to avoid being too general in our conclusions, we should become fairly specific in our recommendations. 

 We should localize on regions and depths to be sampled, numbers and types of samples to be taken at each 

 station, and frequency of sampling. Although we cannot tell the agency how to do its job, our task is to provide 

 approaches, strategies, and guidelines which will be useful to the agency in its own deliberations. 



