35 



SIMPER results compliment the comparisons of taxonomic composition and NMDS 

 results. In 1990 the constructed intertidal flat and reference sites were distinguished 

 primarily by higher densities of oligochaetes, the polychaetes Fabricia sabella , Pygospio 

 elegans , and the amphipod Gammarus oceanicus at the reference site, and Polydora 

 quadrilobata at the constructed flat (Table 3-13). After 1990, oligochaetes, specifically 

 Tectadrilus gabriella , contributed greatly to overall site dissimilarity and was always more 

 abundant at the reference site. Tubificoides benedini , another oligochaete, was also 

 generally more abundant at the reference site and was one of the five taxa contributing 

 strongly to dissimilarity in 1992 and 1994. The amphipod Corophium volutator , another 

 taxon making a large contribution to dissimilarity, was always most abundant at the 

 dredged material site. The polychaete Polydora quadrilobata was most abundant at the 

 constructed flat in 1990 and again m 1998. The remaining taxa among the top five taxa 

 contributing to dissimilarity in any given year were inconsistent in their distributions, i.e., 

 diey would be most abundant at the constructed flat one year and at the reference area in 

 another. For instance, the polychaete Exogene hebes was most abundant at the constructed 

 flat in 1991, but in preceding and subsequent years it was most abundant at the reference 

 site. 



In summary, taxonomic composition, NMDS, and SIMPER results indicate that 

 taxonomic strucmre of the Sheep Island constructed flat assemblage was slightly but 

 persistently different from that of the reference area. Differences arose from the relative 

 abundance of a few dominant taxa, the most important of which were the oligochaetes 

 Tectadrilus gabriella and Tubificoides benedini at the reference site and the amphipod 

 Corophium volutator at the constructed flat. Relative abundances of the remaining 

 dominant taxa were inconsistent or contributed little to taxonomic similarity. 



Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine 



