Mnrch or ApriJ , the swelling hns clcveloperl Into a vesicle, or air 

 bladder, and a new tip has formed beyond the bladder. Subsequent growth 

 occurs only between the apex and bladder, so tip elongation can be 

 determined by monthly measurements of the distance from bladder to tip. 

 This report presents data from April 1982 through April 1983. For 

 the fourth consecutive year, growth (measured as total tip length) was 

 highest at the experimental station. Fox Island (Fig. 6a). Average tip 

 length at Fox Island was 145 mm in April 1983; at Giants Neck and UTiite 

 Point, tip lengths averaged 114 and 112 mm, respectively. This past 

 growing season was the best since Ascophyllum monitoring was begun in 

 1979; total tip length at Fox Island was ca. 10 mm longer than in 

 1979-80 (previously the best season), and ca. 30-35 mm longer at tne 

 control stations. The difference in response to apparently favorable 

 growing conditions between experimental and control plants may indicate 

 an upper limit to growth for Ascopliyllum in our area, ca. 15 cm/yr. 



Support for this hypothesis is seen in Figure 6b, where 1982-83 

 Ascophyllum growth is represented as monthly length increments. In past 

 years, the increased length at Fox Island has been attributed to "a 

 higher initial growth rate in early spring and an extended growing 

 season through November" (NUSCo 1983) . This was apparent in the past 

 growing season as well (Fig. 6), but the peak in growth rate that 

 occurred between September and October at Giants Neck and White Point 

 was not seen at Fox Island. Peak ambient surface water temperatures of 

 ca. 21 °C occur in early September; Baardseth (1970) reports that 

 geographical distribution of Ascophyllum is limited by maximum summer 

 temperatures of 22-23°C. Our studies show that (depending on power 

 plant operating level and tidal flow) the water temperature at Fox 

 Island is 2-3°C warmer than at the reference stations; it seems likely 

 that in early autumn, water temperature near the power plant discharge 

 exceeded the optimum temperature for growth. A temperature probe was 

 placed near the Fox Island plants in early January 1984, so future 

 reports should include accurate water temperatures. 



Regardless of the actual temperature values, the slight thermal 

 input at Fox Island has consistently, over the last four growing seasons, 

 evidenced itself as enhanced growth of Ascophyllum tips. It would seem 

 that year to year variability is primarily due to slight natural 

 fluctuations in environmental growing conditions (Vadas et al. 1978). 



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