Eelgrass is a perennial, and grows during winter, but plants in 

 shallow water (<1 ra MLW) are functional annuals because they are killed 

 by ice scouring, freezing, or other stresses (Phillips et al. 1983; 

 Robertson and Mann, 1984) . Plants exposed to these conditions typically 

 have a high incidence of flowering. There have been reports of 

 genetically determined annual populations (Keddy and Patriquin, 1978; 

 Keddy, 1987) , but evidence for this hypothesis is not conclusive (Gagnon 

 et al., 1980; Phillips et al., 1983). 



Eelgrass grows in diverse habitats ranging from anoxic muds in 

 poorly flushed areas to sand and gravel bottoms with current velocities 

 up to 1.2-1.5 m s"^ (2.3-2.9 kt; Fonseca et. al. 1982a, 1983; Pregnall 

 et al., 1984). The morphology of eelgrass shows considerable plasticity 

 in growth in response to physical energy of the environment and nutrient 

 content of sediments (Kenworthy and Fonseca, 1977; Phillips et al, 1983; 

 Short, 1983; Thayer et al . , 1984). For example, plants growing in 

 shallow, wave-swept bottoms tend to have short narrow leaves, grow in 

 high densities (>1000 shoots m~^) , and produce dense root and rhizome 

 clusters; whereas plants growing in deeper water have longer broader 

 leaves, grow in lower densities (<200 m~^) , and produce less root and 

 rhizome material. 



Eelgrass beds are maintained and expand by vegetative lateral 

 shoots and by recruitment of new seedlings. Because most shoots in a 

 bed may be derived from vegetative growth of a few plants, it is often 

 stated that eelgrass beds are large clonal populations. Bare areas not 

 adjacent to existing eelgrass beds are colonized almost completely by 



