EFFECTS OF REDUCED TEMPERATURES 437 



plant were further delineated and coded with colored plastic tape. 

 Length measurements in June and through most of the growing 

 season, therefore, represent the average of 200 tips. Mortality 

 gradually reduced the number of plants and tips by the following 

 June, but there were rarely fewer than 20 tips per site. Data were 

 averaged for the last two stressed years (1973—1974 and 

 1974—1975) and were presented individually for subsequent years 

 (see Fig. 3). The data for Foxbird Island during the stressed years 

 represent only the lengths for 1973—1974 since viable apexes were 

 not formed in 1974. The 95% confidence limits were used to 

 distinguish differences among years at each site. The survivorship of 

 plants and apical tips was determined concurrently with growth 

 measurements. 



RESULTS 



Environmental Parameters 



Two significant changes have occurred since the initial period of 

 surface discharge into Bailey Cove. First, the Cowseagan Narrows 

 causeway, a major impediment to water flow in and out of 

 Montsweag Bay, was removed during the fall of 1974. Second, the 

 cooling-water discharge was relocated and released through a 

 multiport diffuser in May 1975. Both alterations contributed to 

 changes in environmental conditions in Montsweag Bay. Extinction 

 coefficient patterns were excellent indicators of the construction 

 activities involved in these changes (Fig. 2). Throughout construction 

 phases sediments were continually resuspended into the water 

 column. The surface discharge into Bailey Cove additionally in- 

 creased turbidity at the Foxbird Island and Young Point sites. 

 Except after storms, turbidity values have decreased since the 

 diffuser became operational but are slightly higher than preoperation 

 values (Vadas, Keser, and Rusanowski, 1976; Vadas, Keser, and 

 Larson, 1977). 



Salinities increased and generally, with the exception of Foxbird 

 Island and Young Point, became less variable throughout the bay, 

 e.g., Bailey Point (Fig. 2) and (Vadas, Keser, and Larson, 1977). 

 Higher salinities were caused by increased flushing and exchange with 

 higher salinity waters. The relatively damped amplitude in salinity 

 fluctuations in Montsweag Bay, however, does not approach that of 

 most control sites, e.g., Hodgson Island (Fig. 2). Reduced tempera- 

 tures at experimental sites were the direct result of cooler waters 

 entering the bay and of rapid heat dissipation with the diffuser. 



