In Georgia coastal marshes, the annual marsh plant Suaeda linearis is usually found in association with oyster shell deposits. Dense piles of oyster shells in the marsh support low densities of dominant salt marsh plants but are the primary location where we find S. linearis. We hypothesized that in oyster shell deposits, abiotic stresses (e.g. lower soil water content due to faster drainage) would decrease densities of marsh plants, therefore, lowering competition and enabling the relatively drought-resistant S. linearis to survive. In contrast, in regular marsh soils with lower water stress levels, S. linearis would be more suppressed by competition from other species. To test these hypotheses, we conducted greenhouse experiments using S. linearis and two high marsh dominant species, Borrichia frutescens and Juncus roemerianus.

Results/Conclusions

The oyster shell media had the lowest water content, while the soil media had the highest. All plant species tested grew poorly in oyster shells versus high-marsh soil.  However, S. linearis was least suppressed by its competitors when planted in the oyster shell media, and the competitive pressure of S. linearis on B. frutescens and J. roemerianus was the highest in the oyster shell media. We conclude that oyster deposits represent a refuge for S. linearis from competition with other marsh plants.