abundance in Zone 2 ranged between 60-85% 

 (1986, 3-unit denuding) and 50-70% (1981, 2-unit 

 denuding) in the recolonization transects and be- 

 tween 60-80% (1986) and 45-70% (1981) in the 

 undisturbed transects (Fig. 9). In terms of bar- 

 nacle abundance, recovery of the mid intertidal 

 zone occurs in less than a year, soon after first 

 settlement; populations in the recolonization 

 transects were equal in abundance to those in 

 nearby undisturbed transects. 



Recent barnacle abundance patterns in the 

 recolonization transects at FE, while similar to 

 those of FE undisturbed areas (Fig. 9, FE), were 

 different from those of other stations and also 

 different from those seen at FE following the au- 

 tumn 1981 denuding. Barnacle coverage decreased 

 to < 5% in both the recolonization and undis- 

 turbed transects by September 1987. Some species 

 (e.g., Mylilus and Codium, noted in the previous 

 section) outcompeted barnacles for available sub- 

 strata in late summer. Again, these differences 

 were associated with the opening of the second 

 quarry cut, not Unit 3 start-up. 



Fucus 



Local Fucus recolonization was not evident untU 

 the spring following the autumn denudings. Fucus 

 (mostly Fucus vesiculosus) settled in spring and 

 rapid growth was evident in summer (Fig. 10). 

 Recovery of the Fucus population to undisturbed 

 levels following the autumn 1981 denuding (2-unit 

 operation) took from 15-36 months (Fig. 10; 

 NUSCO 1984, 1985). Following the autumn 

 1 986 denuding, recovery was faster; by September 

 1987, Fucus abundance in the recolonization 

 transects approached or exceeded that in the un- 

 disturbed transects at each station but FS. Even 

 at FS, the Fucus cover 12 months after the 1986 

 denuding (25%) was much more extensive than 

 12 months after the 1981 denuding (2%). The 

 difference between Fucus recolonization after the 

 1981 and 1986 denudings was attributed to year- 

 to-year variability in Fucus zygote settlement and 

 survival, as the pattern was consistent throughout 

 the study area. 



After the 1986 autumn denuding, major groups 

 of species recolonized at different rates and pat- 

 terns, dependent on several factors such as life- 

 history stages. Simpler, faster-growing, opportun- 

 istic algal species are initially superior in coloni- 

 zation to the more complex, slower-growing per- 

 ennial species. Denuded areas near local estab- 

 lished communities were most rapidly colonized 

 by ephemeral species, characterized by having 

 long reproductive seasons, rapid growth rates, 

 high productivity, and simple thallus forms (Littler 

 and Murray 1974; Connell 1975; Littler and Littler 

 1980). Because of their availability, ephemerals 

 always initiated the sequence of recolonization in 

 all intertidal zones at exposed and sheltered sam- 

 pling sites. Balanus and Fucus settled next in 

 spring, and achieved peak abundance in summer. 

 Chondrus, because of competition with Fucus 

 (and removal of Chondrus holdfasts when the area 

 was denuded), recolonizes at a slow rate, and may 

 require more than 30 months to recover (cf. 1981 

 autumn denuding, NUSCO 1985, 1986). Contin- 

 ued monitoring of recolonization transects will 

 track the recovery rates of these major intertidal 

 species during the 3-unit operational period. 



Ascophyllum nodosum Studies 



Since 1979, the rocky intertidal monitoring pro- 

 gram has included studies of Ascophyllum 

 nodosum, a large perennial alga that is abundant 

 in the low and mid intertidal areas locally. 

 Ascophyllum has been studied extensively through- 

 out its range, and its vegetative and reproductive 

 phenology is well documented (David 1943; Printz 

 1959; Baardseth 1970a; Sundene 1973; Mathieson 

 et al. 1976; Wilce et al. 1978). Ascophyllum 

 growth rate has been shown to be sensitive to 

 water temperature changes, especially increases to 

 ambient temperature (Vadas et al. 1976, 1978; 

 Stromgren 1977; Wilce et al. 1978; Keser and 

 Foertch 1982). Because of the alga's response to 

 water temperature change and its mode of linear 

 growth, it has been used to evaluate the thermal 

 effects of power plants in New England (e.g., 

 Maine Yankee, Pilgrim) and is an important 

 biomonitoring tool in the MNPS rocky intertidal 

 program. Extensive discussions of local 



Rocky Intertidal Studies 



45 



