Ascophyllum nodosum Studies 



Growth 



Since 1979, the rocky intertidal monitoring program has included studies of Ascophyllum nodosum, a 

 large perennial alga that is abundant in the low and mid intertidal areas locally, as well as throughout 

 New England, the Canadian Maritimes, and Northern Europe. Ascophyllum has been studied extensively 

 throughout its range, and its vegetative and reproductive phenology is well documented (David 1943; 

 Printz 1959; Baardseth 1970a; Sundene 1973; Mathicson et al. 1976; Wilce et al. 1978). Ascophyllum 

 growth rate has been shown to be sensitive to water temperature changes, especially increases to ambient 

 temperature (Vadas et al. 1976, 1978; Stromgren 1977; Wilce et al. 1978; Keser and Foertch 1982). Because 

 of the alga's response to water temperature change and its mode of linear growth, this alga is an important 

 biomonitoring tool in the rocky intertidal program. Details of growth and mortality of local Ascophyllum 

 are summari/xd below. 



From April 1979 through May 1983, Ascophyllum plants (tips) at Fox Island grew significantly longer 

 than those at White Point or Giants Neck (Fig. 18a); data from the reference stations did not vary between 

 themselves. In the year representative of this growth pattern, 1982-1983, Ascophyllum tips grew longer 

 because of the 2-3 "C AT at FL under single quarry cut conditions (see Temperature Data section), 

 showing a higher growth rate earlier in spring and an extended growing season in late autumn (Fig. 18b). 

 Tlie increased tip length at FF resulted from faster growth from April to July. Growth rate during the 

 remainder of the year was similar to growth rates at the control stations. Annual growth was similar to 

 growth recorded for Ascophyllum populations throughout its geographical range (cf. Vadas et al. 1976, 

 1978; Stromgren 1977, 1983; Wilce et al. 1978; Keser and Foertch 1982). 



During the 1983-1984 growing season, FL water temperatures were 2-3 °C above ambient from April 

 to luly, and average tip length was significantly longer at FI, than at the control sites (Fig. 19a). After 

 August 1983 when the second quarry cut opened and only one unit was in operation, the water temperature 

 at V'V, rose to 7-9 °C above ambient and plants were exposed to a maximum temperature of about 27 °C. 

 Growth rate at FF decreased sharply from August to October when temperatures decreased (Fig. 19b); 

 tissue damage and some deformed tips were observed. When both units were operating in spring 1984, 

 elevated water temperatures (12-13 °C above ambient, ca. 20 °C at the end of April 1984) were within the 



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