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2 2 8 



MONITORING FOR SOFT BOTTOM EFFECTS 



Dr. Paul A. Montagna 



The University of Texas at Austin 



Marine Science Institute 



Port Aransas, TX 78373-1267 



It is very difficult to detect long-term impacts of oil and gas activities in the marine environment. Part of the 

 problem is in identifying and defining quantitative measures of impact. The most difficult aspect is to assess the 

 cumulative and chronic impacts of low-level effects. 



Three recent studies, California Monitoring ProgTam (CAMP), Group of Experts on Effects of Pollution 

 (GEEP), and SEEP have added substantially to our current knowledge on how to detect and measure impacts, 

 and are relevant to the purpose of this workshop. Each study defined potential impacts and implemented study 

 elements to detect those impacts. CAMP is a well-designed, long-term monitoring program on the California 

 continental shelf, and I will summarize the soft bottom studies to date. GEEP is a European study of a pollution 

 gradient which covered all aspects of the ecosystem. SEEP is a study of long-term chronic impact on benthic 

 processes at a southern California oil seep. I will review these programs and try to draw some conclusions and 

 perspectives on how to detect and measure long-term impacts. 



CAMP PROGRAM 



The CAMP program (Brewer, section 2.2.7) was conceived to determine the long-term impact of oil and gas 

 development and production in a pristine environment. The work is being performed by Battelle (the prime 

 contractor) and many subcontractors (I am the subcontractor for the meiofauna studies). Work at the hard 

 bottom site (south of Point Arguello) has progressed nicely. There were two cruises before spudding at Platform 

 Hildalgo in November 1987. There have been five cruises since then to perform long-term monitoring. 

 Unfortunately, work at the soft bottom site (west of Point Sal) has terminated after nine cruises. Platform Julius 

 was to be installed by Shell Western Exploration and Production in July 1987, but has been postponed until late 

 1992 or perhaps indefinitely. 



The objectives of the soft bottom program were to detect and measure long-term (or short-term) environmental 

 changes around oil and gas platforms in the Santa Maria Basin, and to determine whether the changes were 

 caused by drilling-related activities or were natural events. To achieve these objectives three null hypotheses were 

 formulated: (1) there are no differences in biological, chemical, or physical variables between platform and 

 comparison sites; (2) there are no changes in biological, chemical, or physical variables with time at the 

 monitoring sites; and (3) observed changes in biological, chemical, or physical variables at the monitoring sites 

 are not related to drilling-related events. 



The plan at the soft bottom site was to distinguish between local and regional effects. Regional stations were 

 selected to cover broad geographic and bathymetric zones, and to sample sites visited in an earlier reconnaissance 

 survey by Science Applications International Corp. We employed three transects with stations at depths of 90, 

 150, and 410 m. One additional station was added at 750 m to the central transect which is known locally as the 

 mud patch. This was added since it is apparently a depositional environment, and therefore the most likely area 

 to be impacted of any deeper sites. To determine near-field effects at the site of the platform a "Site Specific" 

 array was developed. We employed a semi-radial station pattern to determine near field impacts in any direction. 

 Concentric rings at 0.4, 1.0, and 2.0 km intervals were sampled to determine the spatial scale of detectable 

 impacts. This design was inspired by a successful monitoring program conducted on Georges Bank by Battelle 

 and the Woods Hole Oceanographic Institution. 



Sampling was designed to span 5 years. Sampling was to be performed three times annually for one year pre- 

 and post-spud, and then annually thereafter. Because of the drilling delays, we started sampling biannually in 

 May 1988, but cruises for the fourth and fifth year have been postponed indefinitely. 



