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Good Crab, Bad Crab
Citation:
Wigand, C. Good Crab, Bad Crab. Presented at New England Estuarine Research Society (NEERS), Groton, CT, October 16 - 18, 2014.
Impact/Purpose:
Climate change and nutrient enrichment can have adverse effects on New England salt marshes, and coupled with these effects are crab-plant interactions. We examined the effect of two common crab species (Uca pugilator, Sesarma reticulatum) on plants and the marsh system subject to rising tides. An understanding of these crab-plant interactions will inform restoraction and climate adaptation actions which are part of the EPA-ORD Safe and Healthy Communities research plans.
Description:
Are crabs friends or foes of marsh grass, benefit or detriment to the salt marsh system? We examined Uca pugilator (sand fiddler) and Sesarma reticulatum (purple marsh crab) with Spartina patens (salt marsh hay) at two elevations (10 cm below MHW and 10 cm above MHW) in mesocosms with a marsh soil matrix, and a semidiurnal tidal cycle with Narragansett Bay water. While the purple marsh crab had significant negative effects on the salt marsh hay productivity at both elevations, the sand fiddler had positive effects on the plants at the high elevation, and apparently kept macroalgae blooms in check at the low elevations. Our results support published reports of the purple marsh crab as one potential cause of marsh dieback at sites where there are large populations of this crab species. The response of the marsh system to sand fiddlers was positive, which may bode well for some northern New England marsh systems where there are recent reports of fiddler crab movement into marsh areas previously devoid of these crabs. Future work will examine the nitrogen cycling in the plant/crab mesocosms, and the effect of the crabs on greenhouse gas emissions. With impacts of climate change (e.g., accelerated sea level rise; warming water temperatures) reported in many New England salt marshes, it is important to better understand plant-animal interactions and effects crabs have on the marsh system.