operation during periods of maximum ambient 

 water temperature. Various combinations of op- 

 erating units, varying water flow, and changing 

 meteorological conditions affect the behavior of 

 the thermal plume, and the degree to which the 

 plume affects intertidal communities. The gener- 

 alized temperature regimes provide a physical 

 framework for interpreting the biological responses 

 of rocky intertidal plants and animals discussed 

 in the following sections. 



Qualitative Studies 



NIJEL qualitative studies were designed to iden- 

 tify algal species present in intertidal and shallow 

 subtidal areas in the vicinity of MNPS throughout 

 the year, and to characterize their spatial and tem- 

 poral distribution patterns. Changes in these pat- 

 terns, i.e. differences in species composition among 

 stations or years, may indicate environmental 

 changes and require assessment of whether the 

 changes were related to construction or operation 

 of MNPS. Floristic analyses have been used in 

 similar environmental impact assessments, e.g., 

 Wilce et al. (1978) and NAI (1984). 



A rich and diverse flora occupies the rocky 

 intertidal monitoring area, relative to other areas 

 of Long Island Sound. Overall, 128 species (ex- 

 cluding blue-greens and diatoms) have been iden- 

 tified in the Unit 3 operational period, but not 

 all species were found at any one station, nor 

 were they found in any one collection period. 

 Qualitative algal collections for the 3-unit moni- 

 toring period are presented as number of stations 

 at which each species was found in any given 

 month, and as number of months each species 

 was found at any given station (Table 1). 



Fucua vesiciihxus is the only alga that was col- 

 lected in every month at every station during 

 3-unit operation, although Chondnis c.rlspus and 

 Ascophyllum nodosum were ubiquitous at all sites 

 except Fox Island-Exposed (dissimilarities be- 

 tween the flora at FE and those at other stations 

 will be discussed in a later section). Other species 



(e.g., Ceramium ruhnim, Uka lactuca, Codium 

 fragile), while not ubiquitous, were common 

 throughout the area, throughout the sampling pe- 

 riod. 



Of the 128 bentliic algal species found in the 

 3-unit period, several were site-specific (Table 1), 

 such as Laminaha digitata at TT, Fucus spiralis 

 at BP, and Agardhiella subulata at FEi. In addi- 

 tion, some species were characteristically rare at 

 a particular station, such as Corallina officinalis 

 at ON. The local flora also showed seasonal 

 trends. Some examples of temporal differences 

 include Bangia atropurpurea, Dumontia contorta, 

 and Monostroma spp. as most common in winter- 

 spring, Leathesia diffornns, Pctalonia fascia, and 

 Scytosiphon lomenlaria in spring-summer, 

 Champia parvula and Giffordia milchelliae in 

 summer-autumn, and Spcrmothamnion repens and 

 Sphacelaria cirrosa in autumn-winter (Table 1). 

 Spring collections were typically richest and winter 

 collections were poorest. These patterns were 

 noted in the pre-op flora as well (NUSCO 1987). 



Some local species exhibit no apparent spatial 

 or temporal pattern of occurrence, i.e., they are 

 not characteristic of a particular station or season 

 but occur sporadically among sampling sites. 

 Sporadic occurrence of many algal species ac- 

 counts for the fact that algae collected in any one 

 year will comprise only a portion of the total 

 flora, represented by aggregated collections since 

 1979. The presence of infrequent or occasional 

 species also explains why new species are added 

 to the overall species list each year. For example, 

 A ntithamnionella floccosum and Nemalion 

 hehninlhoidcs were newly recorded in the Unit 3 

 period. Antithamnionella was found througliout 

 the period at 6 out of 9 stations (generally at 

 exposed sites) and Nemalion only once, in .luly 

 at HP. (^lonversely, some rare and small epiphytic 

 algal species that had been reported between 

 March 1979 (when this sampling program began) 

 and February 1986 (the last sampling month of 

 the pre-op period) have not yet been found in 

 the 3-unit operational period. 



16 



