GROWTH AND ECOLOGY 



OF Spartina alterniflora IN MAINE 



AFTER A REDUCTION IN THERMAL STRESS 



M. KESER,* B. R. LARSON,* R. L. VADAS,t and W. McCARTHY* 

 *Department of Botany and Plant Pathology, and fDepartment of Botany and 

 Plant Pathology and Oceanography and Zoology, University of Maine, 

 Orono, Maine 



ABSTRACT 



When a surface thermal discharge was relocated through a diffuser system in May 

 1975, the thermal impact on a previously stressed and moribund population of 

 Spartina alterniflora in Montsweag Bay, Maine, was terminated. Post-stress 

 growth and recovery were examined over three growing seasons. Plant biomass 

 and density were lowest in 1975 because of continued surface discharge into 

 Bailey Cove during the winter and early growing season of 1975. In 1976 and 

 1977, however, biomass and density increased slightly and shoot grovirth 

 returned to prestress levels, as indicated by size-frequency distributions. The 

 partial recovery of Spartina resulted from viable patches of plants and rhizomes 

 in ~40% of the study area. In relation to previous values, biomass declined in the 

 control marsh during this 3-year period. The decline was attributed to increased 

 salinity, greater tidal amplitude, and decreased summer temperatures resulting 

 from the removal of a causeway between the mainland and Westport Island in 

 the fall of 1974. 



Spartina alterniflora, which dominates extensive coastal areas of 

 eastern North America (Teal, 1962; Redfield, 1972), is generally 

 considered eurytopic and relatively insensitive to aquatic stresses 

 (Young, 1974; Adams, 1963; Anderson, 1969). Populations near 

 their northern limit of distribution are not as tolerant as others, 

 however, and, when they were exposed to thermal stress in Maine, 

 they were affected adversely and collapsed within 2.5 years (Vadas, 

 Keser, Rusanowski, and Larson, 1976). The disappearance of plants 



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