Executive Summary 



Rocky Intertidal Studies 



The rocky intertidal sampling program was designed to assess potential biological perturbation from 

 operation of Units 1 and 2 and construction of Unit 3, and to provide base-line data that would permit 

 prediction and assessment of potential impact from Unit 3 operation. Attached plant and animal species 

 on local rocky shores were identified, temporal and spatial patterns of occurrence and abundance of these 

 benthic species were examined, and physical and biological factors that induce variability were identified. 

 This report includes data from the initial 3-unit operational period. Qualitative algal collections, quantitative 

 studies of intertidal organisms, recolonization studies, and Ascophyllum nodosum studies were performed 

 to EvSsess impact, and are summarized below. 



The local flora, as characterized by qualitative algal collections, has shown consistent spatial and temporal 

 patterns of distribution during MNPS operation. Overall, 160 algal species have been identified since the 

 inception of the monitoring program in 1979, consisting of 75 reds, 40 browns, and 45 greens. In the 

 3-unit operational period to date, 128 species have been found; 59 reds, 33 greens, and 36 browns. 

 Divisional proportions and seasonal distributions have not changed during 3-unit operation. 



Anlilhamnionella floccoswn and Neinalion helminthoides have been identified only in the 3-unit operational 

 period, but their occurrence is related to sporadic distribution rather than power-plant operation. Species 

 composition at Fox Island-Exposed under 3-unit operating conditions continues to resemble that found 

 under 2-unit, 2-cut conditions. 



Quantitative studies show intertidal zonation patterns typical of rocky shores throughout New England, 

 with the high intertidal dominated by barnacles, the mid intertidal by barnacles and fucoids, and the low 

 intertidal dominated by Chondrns crispus, a perennial red alga. The abundances of these major components 

 of local rocky shore communities var>' over time and space. Variations are predictable and explainable in 

 terms of seasonality, degree of exposure, intertidal height, inter- and intraspecific competition, and life-history 

 of the organisms. Changes to communities have been minor, indicating stable environmental conditions 

 during MNPS operation. 



An exception to the local stability was the development of a community dominated by opportunistic 

 ephemeral algae after the opening of the second quarry cut in August 1983 at Fox Island-Exposed (I'E), 

 the station closest to the discharges. This change was attributed to thermal incursion and water temperatures 

 in excess of 28 °C. High water temperatures in late summer 1984 were responsible for the elimination of 

 the perennial algae, Chondi-us rrispw;, A.scophylhtm nodosum and Funis vesiculosus from the low intertidal 

 at FE. Codium fragile, a large green alga, became and remains a dominant component of the EE 

 community. However, Fucus has recolonizcd the mid intertidal zone at EE; its persistence is evidence of 

 stability at a hew level. 



Recolonization studies, performed during 2-utiit operation, allowed isolation and identification of some 

 factors that influence the structure of local rocky intertidal communities. Recolonization was influenced 

 by time of year in which denuding occurred, and related to degree of exposure and intertidal height, e.g.. 



Executive Summary 



