Factors Affecting Restoration of Halodule wrightii to Galveston Bay, Texas

Abstract

Experimental restoration of Halodule wrightii (shoalgrass) to its former range on Galveston Island, Texas, began in April 1994. We tested the effects of site, planting density, water depth, and fertilizer addition on survival and growth through June 1996. Temperature, salinity, light transmittance, turbidity, and sediment properties at two restoration sites, Redfish Cove and Snake Island Cove, were similar to those in naturally occurring grassbeds in nearby Christmas Bay. Halodule survival, coverage, and new shoot densities were affected by site (significantly higher at Redfish Cove than at Snake Island Cove, which eventually failed), by planting density (significantly higher when planted on 0.25-m or 0.5-m centers rather than on 1.0-m centers), and by water depth (significantly higher when planted in relatively shallow water). Propagation (spreading from transplant units) was significantly greater from 0.25-m or 0.5-m center plantings but was not consistently affected by site or water depth. Fertilizer enhanced propagation but not survival. After two years, Redfish Cove produced belowground biomass similar to that observed in Christmas Bay, but aboveground biomass remained significantly less. Snake Island Cove plant mortality in September 1995 may have been presaged by low root-rhizome carbohydrate levels observed in October 1994, but causes remain unknown. Further restoration of Halodule to Galveston Bay is possible at selected sites, but structural equivalency will take longer than two growing seasons to achieve.

Do nutrient availability and plant density limit seagrass colonization in the Baltic Sea?

“…Similarly, Olesen & Sand-Jensen (1994a) found Zostera patch mortality to be restricted to newly recruited patches with <32 shoots, which was interpreted as due to lack of mutualistic protection. In a restoration experiment similar to ours, Sheridan et al (1998) found that seagrass (Halodule wrightii) survival, coverage and new shoot density was increased by high plant density. Positive effects of plant density on seagrass colonization appear to be similar across different regions and species.…”

“…For established meadows, numerous studies have shown that seagrass growth is limited by the availability of N or P resources in the sediment porewater (reviewed by Short 1987. Very few studies have indicated a lack of nutrient limitation (but see critique by Worm et al 2000), and artificial fertilization has been recommended for seagrass transplantation and restoration (Kenworthy & Fonseca 1992, Sheridan et al 1998. Based on comparisons of 4 uptake and growth studies, nitrogen limitation of Zostera growth was suggested to occur generally below concentrations of 100 pm01 NH4+ 1-' porewater (Dennison et al 1987).…”

Growth of newly settled red drum Sciaenops ocellatus in different estuarine habitat types

“…Our study site was Christmas Bay, Texas, in the Galveston Bay system (~1420 km 2 ); this small satellite bay (~26 km 2 ) contains most of the remaining (~113 ha) seagrass meadows (primarily Halodule wrightii ) within the estuary (Pulich & White 1991, Sheridan et al 1998. The dominant shoreline vegetation is Spartina alterniflora, and other major habitat types include oyster reefs and sandy nonvegetated bottom.…”

Habitat Use Patterns of Newly Settled Southern Flounder, Paralichthys lethostigma, in Aransas–Copano Bay, Texas

“…Evaluating density patterns of fishes in these ecosystems is important for the conservation and proper management of fish stocks. In addition, given the decline of available habitat in many estuaries, a comparative evaluation of fish use of various habitat types is needed (Short and Wyllie-Echeverria 1996;Sheridan et al 1998).…”