germlings (Knight and Parke 1950; Keser and Larson 1984). Typically, these germlings do not grow under 

 an established Fucus canopy. However, if an area in the mid intertidal is cleared (e.g., by ice-scour), Fucus 

 zygotes settle and grow into a new canopy, composed of plants of similar age. As these plants mature, 

 they become increasingly susceptible to epiphytism (Menge 1975), storm damage and ice-scouring 

 (Mathieson et al. 1982; Chock and Mathieson 1983). These processes tend to remove many plants at 

 once; plant loss opens new substrata for colonization, and the cycle of Fucus abundance is maintained (cf. 

 Schonbeck and Norton 1980; Keser and Larson 1984). 



The decrease in Fucus cover at FE from 1980 through 1983 was another example of a cyclic pattern 

 in abundance. However, thermal impact resulting from water temperatures in excess of 28 °C interrupted 

 the Fucus population cycle at FE. The increase predicted after a settlement of germlings in spring 1984 

 failed to occur after thermal incursion and subsequent germling mortality. 



Fucus cover also decreased at MiUstone Point, the station second closest to the MNPS discharges. 

 This decline may represent the descending portion of the same type of abundance cycle seen at FE, or it 

 may reflect a direct or indirect thermal effect. A direct effect might relate to the thermal tolerance of 

 Fucus; an indirect effect might be related to the observed increase in abundance of Liltorina littorea at 

 MP, and concomitant increase in grazing pressure on newly settled Fucus germlings. Other researchers 

 have shown that high grazer densities can retard Fucus recolonization for several years (Lubchenco 1983; 

 Keser and I.^rson 1984). 



Chondrus crispw; is the dominant alga in low intertidal (Zone 3) and shallow subtidal areas near 

 MNPS, as it is throughout New England, the Canadian Maritimes, and Northern Europe (Mathieson and 

 Prince 1973). Chondrus populations were stable at all NUEL study sites, both within and among years 

 (Fig. 8). The decline in abundance seen at FE after the opening of the second quarry cut was due to 

 water temperatures in excess of 28 °C which eliminated Chondrus from FE in September 1984. 



lypically, Chondrus is host to a variety of ephemeral epiphytic algae. In our area, the dominant 

 epiphytes on Chondrus are Monostroma pulchrum, Polysiphonia harveyi, and P. novae- angliae. These algae 

 have distinct seasonal peaks of abundance (Fig. 8), with Monostroma occurring in spring and Polysiphonia 

 in late summer-autumn. Some researchers have reported that shading by epiphytes is harmful to the 



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