THE RELATIVE IMPORTANCE OF SULFATE AVAILABILITY IN THE GROWTH OF SPARTINA-ALTERNIFLORA AND SPARTINA CYNOSUROIDES

The marsh cordgrass Spartina alterniflora Loisel. dominates temperate coastal marshes on the Atlantic coast of North America, and it is an a ggressive invader in other coastal wetlands around the world. However, it also flourishes at much lower salinities, extending well into the mesohaline region of major estuaries such as Chesapeake Bay. This spec ies survives even in oligohaline marshes, usually disappearing in the natural environment at salinities below about 2 parts per thousand. Th e possibility that this distribution is related to sulfate limitation was investigated in a long-term greenhouse experiment. Sulfate uptake kinetics were first determined for S. alterniflora. The long-term grow th response to four different concentrations of sulfate was then evalu ated for S. alterniflora and for Spartina cynosuroides (L.) Roth, a lo w salinity species of overlapping distribution. Growth indices include d the total number of leaves, total leaf length, and the relative grow th rate of shoots and of whole plants. Spartina alterniflora responded positively to increasing sulfate concentration; however, S. cynosuroi des did not exhibit a growth response. These results suggest that S. a lterniflora distribution in oligohaline marshes is limited by sulfate supply, and that the plant may have an uncommonly high sulfate require ment.