range of temperatures for optimal growth of Ascophyllum. Average tip length and growth rate were 

 significantly greater at FL than at the control sites. 



When two units were operating, with discharge through two quarry cuts, as in the 1984-1985 growing 

 season, water temperature averaged 12-13 °C warmer than at the control sites, resulting in high initial 

 growth at FL in April-June (Fig. 20a). In July, temperatures exceeded 25 °C and growth rate at FL 

 decreased sharply (Fig. 20b); in July some tagged plants had tiny bladders and many lateral proliferations. 

 By August, water temperatures exceeded 28 °C and Ascophyllum plants died at FL. Ascophyllum at GN 

 and WP had a predictable epiphyte flora and appeared healthy. Other researchers have related increased 

 water temperatures to physiological stress. Chock and Mathieson (1979) found the maximum net 

 photosynthesis for summer Ascophyllum nodosum plants to occur at temperatures between 18-21 °C with 

 a "conspicuous decrease" beyond 24 °C. Thermal injury to Ascophyllum was determined between 30-35 

 °C (Kanwisher 1966), while enhancement at 22 °C, gradual demise at 26 "C, and complete thalJus 

 destruction at temperatures above 30 °C was modelled by Vadas et al. (1978). 



A second Fox Island station was established in April 1985, following the loss of Ascophyllum at FL 

 in 1984. This new station was located at the first available Ascophyllum population around Fox Island- 

 Exposed, approximately 200 m from the discharges (Fig. 2); water temperature at FN was 0-2 °C warmer 

 than at controls in spring 1985 (with only two units in operation). Ascophyllum growth at FN was higher 

 than at the control sites from April to May, but for the remainder of the growth season neither average 

 tip length nor growth rate differed significantly between FN and GN (Fig. 21). 



Temperature measurements made during periods when Unit 3 was testing its circulating water pumps 

 in summer of 1985 (thereby increasing effluent volume) indicate that during 3-unit operation, FN will be 

 exposed to water temperatures 2-3 °C above ambient. Thermal plume predictions indicate that WP may 

 also be exposed to warmer water. Comparison of Ascophyllum growth under 3-unit operating conditions 

 to data collected during 2-unit operation will permit assessment of the extent of the plume. 



Mortality 



Ascophyllum mortality, determined as thallus breakage, is a response to mechanical and environmental 

 stress. Thallus breakage could occur above the base tag, either between the base tag and the colored tie 



51 



