A Gompertz growth curve was fitted to 

 Ascophyllum length data using non-linear regres- 

 sion methods (PROC NLIN, SAS Institute Inc. 

 1985). The growth curve parameters were com- 

 pared among years and stations using 2-sample 

 t-tests (a = 0.05). Ascophyllum mortality data are 

 presented as number of surviving base tags (plants) 

 and tip tags (apices); Unit 3 operational data 

 (1986-87) are plotted against the mean and range 

 of pre-op data (1979-1986). Because of the total 

 elimination of Ascophyllum from the original Fox 

 Island Ascophyllum station in 1984 and establish- 

 ment of a new study site, pre-op data from Fox 

 Island excludes the 1984-85 season, and separates 

 1985-86 (FN) from 1979-84 (FL). 



Results and Discussion 



Temperature 



Since Unit 3 began operation, ambient water 

 temperatures (measured at the MNPS cooling 

 water intakes) have ranged from 2.0 °C (16 Feb- 

 ruary 1987) to 22.1 °C (17 and 18 August 1987). 

 These values are typical of those reported in past 

 years, when minima generally occurred in January- 

 February (1-3 °C) and maxima in August- 

 September (20-22 °C). These temperatures were 

 recorded at a depth of about 3 m below Mean 

 Low Water; insolation of shallow water near the 

 rocky intertidal sampling stations raised summer 

 maxima 2-3 °C, and in winter, slush/ice formed 

 in near-shore shallows. 



Effluent water temperatures, measured at the 

 discharge quarry cuts, were dependent on reactor 

 power level and cooling water flow (see Introduc- 

 tion to this report). The designed temperature 

 rise above ambient AT was 12 °C for 3-unit, full 

 power operation, but AT was less when a unit 

 was shut down and its unheated effluent diluted 

 the discharge of the operating units. 



The hydrodynamics of the 3-unit thermal plume, 

 and its behavior at various tidal stages, are de- 

 scribed more fully in the Hydrothermal Studies 

 section of this report. Briefly, the 3-unit plume 



extends into Twotree Island Channel, where it is 

 subject to tidal flushing. This is different from 

 the 2-unit/2-cut plume, that produced elevated 

 water temperatures along the shore between the 

 cuts and the southwest tip of Fox Island, regardless 

 of tidal stage. The effects of the 2-unit effluent 

 were summarized in NUSCO (1987). 



The exposure of local rocky shores to the full 

 power 3-unit plume, therefore, varies with tidal 

 stage, as well as distance from the discharges. On 

 an ebbing tide, as water moves out of Long Island 

 Sound, the plume is deflected to the east, across 

 Fox Island. At the original experimental 

 Ascophyllum station (FL, Fig. 2), ca. 75 m east 

 of the discharges, the plume elevated water tem- 

 perature 7-9 °C; temperatures remained elevated 

 for 10-11 hours per tidal cycle. However, tem- 

 peratures dropped close to ambient levels for 1-2 

 hours during maximum tidal flooding, as the 

 plume was deflected to the west, and the heated 

 water was displaced. 



At FE, ca. 100 m from the discharges, water 

 temperatures were elevated for 9-10 hours per 

 tidal cycle and peaked at 6-8 °C above ambient; 

 ambient water temperatures occurred for 2-3 

 hours, around the time of high tide. At the new 

 experimental Ascophyllum station (FN, Fig. 2), 

 250 m from the discharges around the tip of Fox 

 Island, maximum water temperature elevation was 

 4-5 °C above ambient, only during the ebbing 

 tidal stage. 



Maximum flood tide deflected the full power, 

 3-unit plume to the west. At high tide, water 

 temperatures 4 °C above ambient were recorded 

 at MP, ca. 250 m west of the discharges. At this 

 station, there was also a 2-3 °C increase above 

 ambient at the time of low slack water, as the 

 plume spread laterally (cf. Hydrothermal Studies). 



The plume characteristics described above are 

 representative of full power, full cooling water 

 flow; because of scheduled and unscheduled shut- 

 downs, these conditions existed for less than 50% 

 of the Unit 3 operational period to date. Specif- 

 ically, we have not seen consistent full power 



Rocky Intertidal Studies 



15 



