same period, drastically affected outer continental shelf (OCS) 

 operations. The increased concern and scrutiny resulting from these 

 high-profile accidents have led to greatly improved operating procedures 

 and technology, and importantly, to a reduced number of spills on the 

 OCS. 



All of the spills on the Texas-Louisiana shelf have been dwarfed by 

 the 1979-80 IXTOC blowout (3-3 million bbl) in the Bay of Campeche. 

 Some of this oil reached the Texas-Louisiana shelf, but in a highly 

 weathered state. An assessment of the impact of this event on the 

 Texas- Louisiana shelf is currently being prepared based upon present 

 studies being jointly conducted by NOAA and BLM. 



The effects of oil spills on gulf ecosystems have not been 

 determined with certainty. Surveys following the 1970 Chevron oil spill 

 did not establish detrimental effects, nor have other accidents resulted 

 in clear documentation of substantial impact. Mumphrey and Carlucci 

 (1978) state in their regional status report for the gulf coast that the 

 "short-term effects of oil spills include mortality and tissue damage to 

 fishes and invertebrates but experience has shown that a year after the 

 spills there is recovery of the biological resources." 



The issue of whether or not any (or all) of the above-described and 

 other petroleum spills have had an effect upon marine life in the Gulf 

 of Mexico is an important management concern. It will be important for 

 the reader to keep in mind that a number of terms are commonly used in 

 descriptions of possible spill effects. For example, "long-term" 

 effects are frequently differentiated from "short-term" effects in the 

 literature, as are the roughly equivalent categories "chronic" vs. 

 "acute." Typically, these expressions can be translated to mean either 

 that immediate, obvious kill of visually dominant organisms (e.g. 

 shorebirds, fish) occurred (short-term, acute) or that it did not, but 

 that more subtle, long-lasting, demographic-type effects are to be 

 anticipated in the form of reduced organism reproduction, lifespan, or 

 the like (long-term, chronic). It is not clear whether the two classes 

 of effects would best be considered a continuum as the occurrence of an 

 acute effect may not necessarily indicate that a long-term, chronic 

 problem will follow. For example, a massive kill of adults in a 

 population whose larval recruitment is density-independent (and in which 

 larvae are typically present in great excess) may not affect the size of 

 the next year class at all if at least enough adults survive to produce 

 young in adequate (if not excessive) numbers. This point has been amply 

 demonstrated for many benthic organisms, which usually produce many more 

 larvae than will survive to adulthood (Thorson 1966; Miliekovsky 1 971 ) - 

 On the other hand, species which rely upon more conservative 

 reproductive approaches to survival may be decimated by single 

 catastrophic incidents or by sublethal, chronic effects at particularly 

 sensitive periods in their life histories (Sarukhan 1979). 



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