Effects of a Beach Nourishment Project in Jamaica Bay, New York, on Horseshoe Crab ( Limulus polyphemus ) Spawning Activity and Egg Deposition

Restoration of horseshoe crab spawning habitats through beach nourishment may be considered as a potential strategy to enhance reproductive success in areas where estuarine beaches have been lost to coastal erosion and development. The US Army Corps of Engineers performed a beach nourishment project at Plumb Beach (Jamaica Bay, Brooklyn, NY) in 2012 to stabilize the shoreline. While the addition of sand was done to protect infrastructure, it created an opportunity to examine the responses of American horseshoe crabs ( Limulus polyphemus ) to beach nourishment using a BACI (before-after control impact) design. During Spring 2012, before beach nourishment, horseshoe crabs made minimal use of the highly degraded western section of Plumb Beach in comparison to a nearby reference site, as quantified by numbers of spawning adults at high tide and densities of horseshoe crab eggs in core samples. In the first post-nourishment field season (Spring 2013), there was no detectable increase in horseshoe crab spawning activity on the newly restored beach. In 2014 and 2015, the density of spawning females began to increase at the nourished beach, although their numbers and especially the density of horseshoe crab eggs remained much lower than at the reference site. Three years after beach nourishment, differences in sediments texture (mean grain diameter, percent gravel, sorting, skewness, and hardness) were still evident between the nourishment and reference sites. Our results suggest that (1) at this site, beach nourishment appeared to bring about only slow increases in horseshoe crab spawning density after several seasons and (2) subtle differences in beach geomorphology over relatively short distances can be detected by horseshoe crabs and may underlie their selection of specific nesting sites.