Post-mortem ecosystem engineering by oysters creates habitat for a rare marsh plant.
Oysters are ecosystem engineers in marine ecosystems, but the functions of oyster shell deposits in intertidal salt marshes are not well understood. The annual plant Suaeda linearis is associated with oyster shell deposits in Georgia salt marshes. We hypothesized that oyster shell deposits promoted the distribution of Suaeda                 linearis by engineering soil conditions unfavorable to dominant salt marsh plants of the region (the shrub Borrichia frutescens, the rush Juncus roemerianus, and the grass Spartina alterniflora). We tested this hypothesis using common garden pot experiments and field transplant experiments. Suaeda                 linearis thrived in Borrichia                 frutescens stands in the absence of neighbors, but was suppressed by Borrichia                 frutescens in the with-neighbor treatment, suggesting that Suaeda                 linearis was excluded from Borrichia                 frutescens stands by interspecific competition. Suaeda                 linearis plants all died in Juncus                 roemerianus and Spartina                 alterniflora stands, regardless of neighbor treatments, indicating that Suaeda                 linearis is excluded from these habitats by physical stress (likely water-logging). In contrast, Borrichia frutescens, Juncus                 roemerianus, and Spartina                 alterniflora all performed poorly in Suaeda                 linearis stands regardless of neighbor treatments, probably due to physical stresses such as low soil water content and low organic matter content. Thus, oyster shell deposits play an important ecosystem engineering role in influencing salt marsh plant communities by providing a unique niche for Suaeda linearis, which otherwise would be rare or absent in salt marshes in the southeastern US. Since the success of Suaeda                 linearis is linked to the success of oysters, efforts to protect and restore oyster reefs may also benefit salt marsh plant communities.
Department of Biology and Biochemistry, University of Houston, Houston, TX 77204, USA. hguo4@uh.edu
Hongyu
H
Guo
Steven C
SC
Pennings
D060105:Animal Shells; D000818:Animals; D019663:Chenopodiaceae / Q000502:physiology; D017753:Ecosystem; D005845:Georgia; D019684:Magnoliopsida; D010125:Ostreidae; D006109:Poaceae; D012987:Soil; D053833:Wetlands
D012987:Soil