Immediate Effects on Marine Communities 



Control Station 



October 16, 1969 Moderately Oiled 



Station 



September 22, 1969 



Number Number 



of of 



Species Individuals 

 (per square 

 meter) 



Heavily Oiled Station 

 September 25, 1969 



Source: Sanders, H.L., et al. IN PRESS. 

 Anatomy of an Oil Spill: Tfie West Falmouth 

 Study. (Submitted to EPA) 



What Were the 

 Immediate Effects 

 of the Oil Spill? 



Initial observations and samples 

 taken soon after the West Falmouth 

 spill revealed mass mortality in the ben- 

 thic communities. Bottom dwelling 

 species such as the lobster, tomcod 

 and scup washed up on the beaches, 

 indicating that subtidal benthic com- 

 munities had been impacted. To con- 

 firm this, the researchers trawled the 

 bottom off New Silver Beach in about 

 ten feet of water. The results of the 

 trawl were dramatic. The catch con- 

 sisted of several species of fish, 

 worms, crustaceans and other marine 

 invertebrates. About 95% of the 

 animals were dead, the rest, dying. 

 The results of this and similar observa- 

 tions prompted the initiation of a com- 

 prehensive study of the effects of the 

 West Falmouth spill on the benthos. 



The initial samples clearly demon- 

 strated the severity of the spill impact. 

 Compared to control areas, oiled areas 

 were reduced in both numbers of 

 species and densities of benthic 

 animals. This was true for both off- 

 shore and marsh sampling sites. When- 

 ever oil was found in the sediment, 

 there was mortality. The greater the 

 concentration of oil, the greater was 

 the observed mortality. Shortly after 

 the initial impact, an opportunistic or 

 "weed" species of worm called 

 Capitella capitata underwent an im- 

 pressive population explosion. Like 

 weeds on a cleared lot, the prolific and 

 resistant worm species took advantage 

 of the biological void created by the 

 spill at heavily oiled stations. In 

 February 1970, 99% of the individuals 

 at marsh Station IV were Capitella as 

 compared with the finding of no 

 Capitella at a similar non-oiled site 

 nearby. 



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