416 



6.2 Taxonomy 



The 0.3 mm screen was more efficient than the conventional 0.5 mm screen in 

 sampling several species of benthic invertebrates. Very small species such as the 

 polychaete Paradoneis new sp. A were retained almost exclusively on the 0.3 mm screen, 

 while efficiency of sampling of long, thin, smooth species like the amphipod Erichthonius 

 rubricornis was much greater with the 0.3 mm than the 0.5 mm screen. Recently settled 

 early life stages of many species of polychaetes and crustaceans also were sampled more 

 efficiently on the 0.3 mm screen. 



A total of 783 taxa of benthic invertebrates have been identified in the 

 samples analyzed to date. Seventy-four of these were epifaunal invertebrates or demersal 

 fish. The remainder were infaunal invertebrates. Polychaetes, represented by 306 

 species, were the most abundant group, and accounted for 39.1 percent of all taxa 

 identified. The polychaetes included at least 8 undescribed genera and 30 undescribed 

 species. Arthropods, represented by 159 species, accounted for 20.3 percent of all taxa 

 identified. Half of these were amphipods. There were at least two undescribed species. 

 Molluscs accounted for 16.6 percent of the fauna with 132 species, at least one of which 

 was a new species. The remaining 23.7 percent of the fauna included cnidarians, 

 echinoderms, oligochaetes, ectoprocts, etc. 



6.3 Abundance and Diversity 



The number of Individuals per O.Qtt m was high at most stations and varied 



seasonally. Densities were highest at Stations 5, 12, and 13, averaging approximately 



de 

 .2 



1,020, 870 and 1,200 individuals per O.Ct m , respectively. Lowest densities were at 



Stations 1 1 and 17, averaging between 100 and 200 individuals per 0.0k m 



Shannon-Wiener diversity was lowest at the shallow Stations <» and 10 and 

 highest at the deeper Stations 3, 16, and 17. The number of species per 1,000 individuals 

 was highest at regional stations at or below the 100 meter depth (mean 83-121 species per 

 1,000 individuals) and lowest at the shallow stations. 



6A Population Patterns; Regional Stations 



The most remarkable feature of the cluster analysis of the regional stations 

 was that all of the replicate samples of one station clustered with each other before 



