GROWTH AND ECOLOGY OF Spartina alterniflora 431 



similar findings by Nixon and Oviatt (1973) in Rhode Island were 

 confounded additionally by negative correlations between salinity 

 and nutrient levels which masked the causes of variability. High 

 soil— sediment salinities have also been implicated in reduced growth 

 in Spartina (Mooring, Cooper, and Seneca, 1971; Broome, Wood- 

 house, and Seneca, 1973). 



The idea that the decrease in biomass at Causeway was caused by 

 increased salinity is supported by the lack of correlation between 

 biomass and temperature. Despite the apparent correlation between 

 increasing temperatures and biomass from 1972 to 1974 (Vadas 

 et al., 1976), warmer temperatures in 1976 did not result in higher 

 than normal biomass estimates. This suggests that the growth of 

 Spartina in Maine is not wholly temperature dependent, but rather 

 that temperature and salinity, and perhaps other factors, act in 

 concert to control growth. 



The decline in biomass at Bailey Marsh during the thermal- 

 discharge phase, however, was attributed directly to increased 

 temperatures. Direct surface discharge continued until May 2, 1975, 

 and resulted in the lowest recorded biomass estimates for August 

 (Fig. 5). Biomass increased slightly in 1976 and 1977, suggesting that 

 the thermal stress and apparent shock has been alleviated and that 

 the marsh may be returning to more stable (prestress) conditions. 



SUMMARY 



During the first year of diffuser operation, the biomass and shoot 

 density of Spartina at Bailey Marsh continued to decline. In 1976 

 and 1977 the decline, which was associated with the previous 

 thermal stress on the rhizome system, was arrested, and recovery was 

 evident. 



The biomass, plant density, and flowering of Sparf ma at Causeway 

 Marsh (control) decreased after the Cowseagan Narrows causeway 

 was removed in the fall of 1974. These declines were attributed to 

 increased tidal amplitude and salinities and decreased temperatures 

 during the growing season. Light was not considered important since 

 changes in incoming solar radiation were not evident and since 

 turbidity had decreased from 1975 to 1977. 



The most noticeable effect of the thermal effluent was the 

 reduction in coverage of Spartina in Bailey Marsh. Approximately 

 60% of the study area was devoid of plants. Colonization by seeds or 

 rhizomes had not occurred as of 1977. Examination of rhizomes in 

 the area showed them to be badly decomposed. Redfield (1972) 



