was a contributor to tip loss at both the control and experimental 

 stations. Littorinid snails, particularly Llttorina obtusata , are 

 present tliroughout the year and have been seen to damage bladders and 

 axes (Foertch et al. 1982; NUSCo I9H2; Steneck and Watlinp, 1982). 



There has continued to be a great deal of year-to-year variability 

 in both plant and tip mortalities between stations. The lack of pattern 

 ill mortality, concurrent with the consistency of relative growth rates, 

 implies that neither loss of plant material nor damage to apical cells 

 was associated with proximity to the thermal discharge. It would seem 

 that natural variability in environmental growing conditions is the 

 major influence on both plant and tip mortality. 



Ascophy llum plants are not found in the immediate vicinity of the 

 thermal discharge (ca. 25 m to each side), and plants nearest the 

 effluent occur in scattered clumps; individuals are stunted and heavily 

 epiphytized. However, the experimental area is only 70 m from the 

 discharge; plants grow in extensive populations and show enhanced growth 

 and similar mortality rates, relative to the control stations. 



In August 1983, a new discharge canal was opened, ca. 20 m nearer 

 the experimental area than was the old one. In light of the indications 

 that Ascophyllum plants at the Fox Island station may be approaching 

 their physiological limits (e.g., increased epiphytism last year, growth 

 pattern noted this year), it will be particularly interesting to compare 

 population parameters from the past four years to those of future 

 growing seasons. 



In summary, As copyllum nodosum has proven to be an ideal research 

 tool for monitoring the effects of the thermal discharge from KNPS . The 

 growth studies show a direct biological response to an environmental 

 impact; the mortality studies show that, over the last four years, the 

 impact has not stressed the Asco phyl lum population beyond its ability to 

 compensate. These studies, in conjunction with the other facets of the 

 Rocky Shore program, demonstrate that effects of two Unit operation in 

 the intertidal region are restricted to areas in close proximity to the 

 discharge, and that detrimental changes to the local rocky intertidal 

 community have not been seen. 



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