GROWTH AND ECOLOGY OF Spartina alterniflora 421 



in 60% of the marsh was related to the destruction of the rhizome 

 system, which had metabohzed its reserves and was unable to 

 produce viable shoots in the spring of 1974 and 1975. 



In May 1975 the thermal discharge into Bailey Cove from the 

 Maine Yankee Atomic Power Company (MYAPCO) was discon- 

 tinued, and 2 months later the discharge was diverted into a 

 multiport diffuser system in the main channel of Montsweag Bay. 

 This paper analyzes the growth and potential recovery of this 

 previously stressed population of Spartina. 



SITE AND METHODS 



We studied two populations of Spartina in Montsweag Bay from 

 spring 1975 to August 1977. Populations were located in Bailey 

 Cove, which was previously stressed by a surface thermal discharge, 

 and in Causeway Marsh, a control area located 3 km north of the 

 power plant (Fig. 1). Detailed descriptions of Bailey and Causeway 

 marshes are available elsewhere (Vadas et al., 1976). 



Ten randomly selected quadrats ('/i^m^) at each site were 

 sampled for aboveground biomass in July and August 1975 and 1977 

 and monthly from May to October 1976. Because of the disruptive 

 nature of biomass collections, limited sampling was performed in 

 1975 and 1977 to minimize damage to previously stressed plants. In 

 1975 and 1977 samples were taken during previously established 

 peak biomass periods (Vadas et al., 1976). Sampling in Bailey Marsh 

 was stratified since only 40% of the marsh contained Spartina. Four 

 samples were taken at random in areas containing plants, and six 

 were taken in cireas devoid of plants. Plants were cut v^th shears at 

 the surface of the mud and were transported to the laboratory, 

 where they were washed, counted, measured, and dried to a constant 

 weight at 70° C. Salinities and temperatures were measured monthly 

 over mud flats adjacent to each marsh during high tide at depths of 

 0.15 m (surface) and 3.0 m (bottom) with a salinomete]^ 

 thermometer. Light extinction coefficients were determined with a 

 Secchi disc (Holmes, 1970). Incident solar radiation was measured 

 with a pyreheliometer at MYAPCO. 



After removal of the causeway in the fall of 1974, the average 

 tidal range increased by 0.34 m, reflecting greater water flow in and 

 out of Montsweag Bay. The average high tide was 0.06 m higher, and 

 the average low tide 0.27 m lower. The resultant average tidal range, 

 2.88 m, exposed an additional 109 to 158 ha of mud flat during each 

 tide (Anonymous, 1975). 



