Improvement of genetic health and diversity of Zostera marina (eelgrass) in Barnegat Bay, New Jersey ten years after Hurricane Sandy: Support for the “storm stimulus” hypothesis

Hurricane Sandy struck the New York metropolitan region on October 29, 2012. The storm severely impacted the physical state of Barnegat Bay, New Jersey with its heavy storm surge, affecting many forms of benthic life and ripping up extensive beds of Zostera marina. Pre-Sandy studies of the genetic status of Z. marina in Barnegat Bay indicated low levels of heterozygosity and high levels of inbreeding. This present study examines the long-term effects of Hurricane Sandy on the eelgrass meadows of New Jersey. Heterozygosity analysis (mean Ho= 0.482 ± 0.013 and mean He= 0.498± 0.009) of the five Barnegat populations studied suggest an improvement in diversity from pre-Sandy values of 2008. Mean inbreeding levels (overall Fis = 0.077 ± 0.034) also indicated reduced inbreeding, and the fixation index (overall mean pairwise Fst = 0.064 ±0.006) suggested increased connectivity between populations with low levels of differentiation. Although we found no indication of bottlenecks in the last 2–3 years, by employing m-ratio calculations, there was strong evidence for long-term, historical bottlenecks in all populations, potentially due to the mass wasting disease epidemic in the 1930s. Unexpectantly, the post-Sandy genetic health and diversity of Z. marina in Barnegat Bay appears to have improved since it was last surveyed in 2008, supporting the “Storm Stimulus” hypothesis.