1976 and 1981. While Matta (1977) felt there were two other communities in 

 the deeper water, analysis of the 1981 data for species patterns showed there 

 was no distinct deeper water community. Considering the great similarity of 

 dominants, it is likely that cluster analysis of the 1976 data would produce 

 the same single community found in 1981. 



2. Sound Beach . 



a. Present conditions . The physical environment at the Duck sound beach 

 is characteristic of the low energy, low salinity, sandy sounds in the North 

 Carolina area. Sediments are virtually 100 percent sand with low organic and 

 carbonate contents. The grain size of sediments is consistent, being fine 

 sand. The water temperature was influenced by the air temperature. In 

 January the temperature was 0° Celsius with a 5- to 10-centimeter ice cover. 

 Temperatures higher than 24° Celsius do occur in the summer due to the 

 shallowness of the sound system. Matta (1977) recorded 35° Celsius in 

 July 1976. The salinity during the study increased from about 3 to 8 parts 

 per thousand, reflecting the sensitivity of the system to the prevailing 

 drought conditions. The fauna that inhabits these low salinity, shallow-water 

 areas has to be able to cope with temperature extremes encountered during 

 winter and summer. While not diverse, the fauna is generally a mixture of 

 the eury-tolerant freshwater and estuarine species. Shifts in the balance 

 between these forms are determined by what appears only slight shifts in 

 salinity, on the order of 5 parts per thousand (Tenore, 1972; Diaz, 1977; 

 Boesch, 1977). 



Oligochaetes, polychaetes, chironomids, and at times amphipods or 

 mollusks are the dominant taxa in the low salinity areas in temperate 

 estuarine systems along the North and South American and the European coasts 

 (Tenore, 1972; Leppakoski, 1975; Diaz, 1977, 1980). Within any one of these 

 major taxonomic groups there are generally only one or two species dominant in 

 any particular area. In the Duck sound the dominants were Limnodrilus spp. 

 (very likely all L. hoffmeisteri from several mature specimens examined), an 

 oligochaete, Laeonereis eulveri and SooleooZepides viridis , both polychaetes, 

 Polypedilum sp. , a chironomid, and Lepidactylus dystious, an amphipod. While 

 the clam Rangia auneata is a dominant in the deeper water sampled, it was not 

 a dominant in the shallow water sampled. These four dominants accounted for 

 21 percent of all taxa and 71 percent of all occurrences (Table 23). 



The Genus Limnodrilus contains the most widely distributed and eury- 

 tolerant species of oligochaetes known (Brinkhurst and Cook, 1974, 

 Diaz, 1980). At Duck, North Carolina, Limnodrilus spp. was the top numerical 

 dominant on every collection date, reaching densities as high as 24,870 per 

 square meter and averaging 2,290 per square meter for the entire study. While 

 many Limnodrilus species can be pollution indicators, particular L. 

 hoffmeisteri , which is likely the only species at Duck (Brinkhurst and Cook, 

 1974), their presence at Duck does not indicate a degraded environment. At 

 Duck the Limnodrilus spp. is part of a low salinity community in a physically 

 controlled environment. They are well adapted to salinity (Diaz, 1980) and 

 temperature (Kennedy, 1966) stress. Through the course of the study, the 

 size of the Limnodrilus spp. was always small with very few mature specimens. 

 This is likely a result of the salinity, which is very close to their maximum 

 reported field tolerance (Diaz, 1980). 



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