Investigations into the effects of environmental and physical variables on the growth of natural and transplanted populations of Ruppia maritima L. s.l. in the Galveston Bay System, Texas

Abstract

The effects of sixteen environmental and physical variables on the growth of six natural populations and on the establishment and growth of transplanted populations of widgeon grass, Ruppia maritima L. s.l., were evaluated in the Galveston Bay System, Texas. Growth differences in natural populations among different basin morphologies and tidal regimes were examined. Sediment texture influenced the percent cover of widgeon grass the greatest of the variables studied. High silt content and low sand content in the sediments resulted in greater percent cover of widgeon grass than sediments with low silt and high sand content. Water temperature significantly influenced the stem lengths of widgeon grass; warm temperatures stimulated longer plant lengths, while cold water temperatures resulted in reduced stem lengths. Marshes and tidal habitats exhibited perennial growth patterns of widgeon grass as compared to annual growth patterns found in ponds, lakes, and semitidal habitats. Ponds, lakes, and semitidal habitats generally had significantly higher percent cover and stem lengths than marshes and tidal habitats; except in periods of drought. The effects of sixteen environmental and physical variables on the growth and establishment of transplanted widgeon grass, Ruppia maritima L. s.l., in the Galveston Bay System, were analyzed. Growth differences between different transplant spacings (1 meter, 0.5 meters and 0.25 meters) also were studied. Various fetch distances had the greatest significant influence on the establishment and growth of transplanted widgeon grass. Greater fetch distances resulted in reduced growth of transplants due to increased wave action that the transplants were subjected to. There was no significant difference in widgeon grass growth among the transplant spacings. In conclusion, I found that widgeon grass can be successfully transplanted onto submerged bare sediments in areas of low fetch distances. Transplanting widgeon grass into internal open water areas designed with low fetch distances in saltmarsh restoration projects can increase habitat diversity and function. Efforts should concentrate on designing suitable habitat into restoration plans rather than transplanting large quantities of plant material.