Using sediment alginate amendment as a tool in the restoration of Spartina alterniflora marsh

Growth and survival of transplanted vegetation for salt marsh restoration can be greatly affected by edaphic conditions. We investigated the potential for an organic carbon sediment amendment, alginate, to enhance establishment and growth of Spartina alterniflora transplants, as well as colonization by macroinvertebrates commonly associated with S. alterniflora (Uca sp. and Littoraria irrorata). Plots were established in a bare mud area previously inhabited by S. alterniflora, and transplant rhizospheres were either treated with alginate or left unamended as controls. Growth of transplanted S. alterniflora and colonization by Uca sp. and L. irrorata were evaluated over portions of three growing seasons. Within the first month post-transplantation, a nonsignificant trend toward greater live stem density emerged, but disappeared completely by week ten. Both Uca sp. and L. irrorata densities were significantly greater in the alginate treatment compared to the control only during the first ten weeks post-transplantation. However, the initial organic content of the sediment in the transplant area was more than twice that in the adjacent natural marsh. Therefore, our findings suggest that a threshold level of sediment organic matter above which alginate addition does not confer an advantage on transplanted S. alterniflora may exist, and the conditions under which amendments are most beneficial to transplanted S. alterniflora should be determined.