wrap used as a tip tag, or between the tip tag and the growing apex. To determine if the causes of 

 mortality differed between stations, tip mortality was examined in two ways: as surviving tapes, and as 

 surviving tapes with at least one viable apex (Figs. 22 and 23). Ix)ss of tip tags implies mechanical removal 

 and immediate loss of plant material. Loss of viable apices and/or damage to the apical cell implies a 

 potential loss of biomass due to lack of growth. 



Factors that contribute to Ascophyllum mortality include epiphytization (e.g., by Pofysiphonia lanosa, 

 Ceramium ruhrum, Ec.tocarpus siliculosm) and grazing (especially by Littorina oblusata). Both of these 

 processes increase the likelihood of breakage during storms. Thermal stress was evident only at Fl, < 1 

 month after the opening of the second quarry cut, and in the following year, tagged Ascophyllum plants 

 were eliminated from FL by September 1984. 



Since 1979, Ascophyllum plant loss averaged ca. 60% and tip loss ca. 80% (NUSCo 1986). In general, 

 there was much year-to-year variability in plant and tip mortality. Prior to the opening of the second 

 quarry cut, mortality was never associated with proximity to the MNPS discharge. Maintenance of stable 

 populations, despite high measures for loss of plant material, is an indication of both the high degree of 

 productivity of Ascophyllum, and the importance of this plant in contributing to the detrital pool of the 

 marine ecosystem. Similar conclusions, and similar rates of mortality have been reported by other 

 researchers in New England (Vadas et al. 1976; Wilce et al. 1978). 



Ascophyllum is not expected to recolonize at FL, even though conditions may be favorable for most 

 of each year. Since repopulation involves long-term survival of individuals (as discussed earlier for 

 Chondrus), even short-term exposure to lethal water temperatures in summer prevents Ascophyllum recovery. 

 The substratum previously occupied by Ascophyllum in this area will continue to be dominated by 

 ephemeral algae. We must emphasize, however, the localized scale of this impact, i.e., less than 150 m of 

 shoreline. Sampling of populations more distant to the discharge will continue to provide information to 

 the rocky intcrtidal monitoring program. In particular, analyses of growth during ,3-unit operation permits 

 determination of whether thermal effects may be seen over a larger area. 



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