leum gas torch. All recolonization transects were 

 sampled monthly in the same manner as described 

 for undisturbed transects. In the pre-op period, 

 denudings were performed in April 1979, and 

 again in September 1981 at the same transects, to 

 determine the effect that seasonality of denuding 

 would have on recolonization. Autumn denudings 

 (September 1986) were re-established in the Unit 

 3 operational period, to assess possible 3-unit ef- 

 fects on recolonization. 



Exclusion cages 



To investigate the effects of grazing and preda- 

 tion on recolonization rates and patterns, nine 

 areas were selected at each of the recolonization 

 stations, three areas in each of three tide zones. 

 In each area, two 20 cm x 20 cm patches were 

 cleared and burned; one was covered with a stain- 

 less steel mesh cage (20 cm x 20 cm x 5 cm, 3 

 mm mesh), the second left as a control. Each 

 month the percent cover of colonizing organisms 

 was determined. The effect that season of denud- 

 ing had on rates and patterns of recolonization 

 was also determined. The pre-op series of exclu- 

 sion cage experiments began in April 1979, June 

 1980, September 1981, and December 1982; each 

 area was re-burned 15 months after the previous 

 denuding. The exclusion cage studies were re- 

 established in December 1987 to determine the 

 effects of grazing and predation on recolonization 

 under 3-unit operating conditions. Results from 

 these studies will be presented in future armual 

 reports. 



Ascophyllum nodosum Studies 



Growth and mortality of populations of the 

 perennial brown alga, Ascophyllum nodosum, were 

 studied at two control stations (GN, 5.5 km west 

 of the discharge and WP, 1.5 km east of the 

 discharge. Fig. 1) and an experimental station 

 (FL, ca. 75 m east of the original Millstone quarry 

 cut. Fig. 2) from 1979-1984. Ascophjllum was 

 eliminated from FL in summer 1984, its loss at- 

 tributed to elevated water temperatures resulting 

 from the thennal plume of two operating units 

 discharging through two quarry cuts (NUSCO 



1985). In spring 1985 a second experimental 

 Ascophyllum station (FN) was established between 

 FE and FS (Fig. 2, ca. 250 m from the quarry 

 discharges, northeast of the Fox Island-Exposed 

 sampling site). Following the loss of plants from 

 FL, FN supported the Ascophyllum population 

 nearest the discharges. 



Ascophyllum plants were measured at monthly 

 intervals from April, after the onset of new vesicle 

 formation, until the following April. Fifty plants 

 at each station were marked with a numbered 

 plastic tag at the base of each plant, and five 

 apices were marked on each plant with colored 

 cable ties. Linear growth was determined by mea- 

 surements made from the top of the most recently 

 formed vesicle to the apex of the developing axis, 

 or apices if branching had occurred. Vesicles were 

 not large enough to be tagged in April or May, 

 so five tips were measured on each of 50 randomly 

 chosen Ascophyllum plants, and monthly mea- 

 surements of tagged plants began in June. Lost 

 tags were not replaced, and the pattern of loss 

 was used as a measure of mortality. Loss of the 

 entire plant was assumed when the base tag and 

 tip tags were missing. Tip survival was determined 

 in terms of remaining tip tags. 



Temperature 



Water temperatures were obtained from the 

 EDAN (Envirormiental Data Acquisition Net- 

 work) system which continually records a variety 

 of environmental parameters and reports at 

 15-minute intervals. Ambient water temperatures 

 were recorded by sensors in Unit 1 and 2 intake 

 bays, and effluent water temperatures by sensors 

 in the quarry cuts. Temperatures at FE, MP, and 

 the experimental Ascophyllum stations (Fl, and 

 FN) were measured over several tidal cycles with 

 a portable thermistor and strip chart recorder. 

 During 1987, solid-state data loggers were de- 

 ployed at several sites in the Millstone area to 

 record water temperatures under differing power 

 plant operating levels; these data were incorpo- 

 rated into models of regimes to which rocky 

 intertidal stations in the vicinity of the MNPS 

 discharge were exposed. 



Rocky Intertidal Studies 



13 



