30 



3.3.1.2 Taxonomic Composition 



A total of 90 taxa was collected at the Sheep Island sites between 1990 and 1998: 

 64 at the constructed intertidal flat and 81 at the reference site (Appendix Table 2). 

 Species composition was similar with 49 of the 90 taxa being present at both sites. A 

 total of twenty five taxa were classified as dominants, i.e., they constituted 1% or 

 more of total numerical abundance or were present in 50% or more of the samples 

 (Tables 3-11; 3-12). None of the dominants were found exclusively at either site. 



The most abundant organism was the amphipod Corophium volutator . Reaching a 

 maximum density of 28,000 animals/m^ in 1992, it was generally most abundant and 

 comprised the greatest proportion of the constructed flat assemblage (Appendix Table 2; 

 Table 3-11; Table 3-12). Next in importance were the oligochaetes Tectidrilus gabriella 

 and Tubificoides benedini . Tectidrilus was the more abundant of the two but its relative 

 importance varied among years: in 1991 and 1992 it was more than twice as numerous as 

 Tubificoides benedini at the constructed flat, but precisely the opposite was true in 1998. 

 Tectidrilus populations at the reference site were at least twice as dense as Tubificoides 

 populations in 1991, 1994, and 1998. The polychaete Capitella sp., the fourth most 

 abundant taxon, was generally more numerous at the reference area than at the constructed 

 flat and was one of the most commonly occurring taxa at both sites. Densities of the fifth 

 most abundant taxon, the amphipod Gammams oceanicus, varied widely between sites and 

 over time. Highest densities of this species occurred at the constructed flat in 1998 when 

 abundances were over 19,000/m^ (Appendix Table 2). Of the ten most abundant taxa the 

 remaining five were polychaetes: Exogene hebes , Streblospio benedicti , Fabricia sabella , 

 Pygospio elegans, and Polydora ligni . 



Taxonomic composition of the sites was also compared using Nonmetric 

 Multidimensional Scaling (NMDS). As previously noted, differences in the level of 

 taxonomic detail between data from 1990 and the remaining sample collections required 

 two separate sets of comparisons: one between 1990 and 1991 data and a second 

 comparing 1991-1998 collections. NMDS of the 1990-1991 data separated both sites by 

 year but not by great degrees indicating small but persistent differences in species 

 composition (Figure 3-18). Similar results were obtained from NMDS of the 1991-1998 

 data indicating small but persistent differences among sites (Figure 3-19). 



Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine 



