POSTER: Seasonal variation in mangrove tree crab (Aratus pisonii) population characteristics along a salinity gradient within the Imperial River – Estero Bay watershed
Research Mentor: Dr. Brian Bovard
Additional Authors: 
Abstract:
Abstract: Mangrove tree crabs are considered ecosystem engineers to mangrove forests impacting energy flow by forming links between trophic levels in mangrove food webs (Kristensen, 2008; Macintosh et al., 2002). Although they are common throughout southwest Florida, relatively little is known about their natural history and role in mangrove ecosystem. The effects that climate change has on mangroves are very well understood however, this cannot be said for the most common macrofauna found in the ecosystem. The aim of this study was to identify wet season variations of mangrove tree crab (Aratus pisonii) population characteristics throughout a salinity gradient between Imperial River and Estero Bay, Bonita Springs. Crabs were observed and captured from June 2021 to October 2021. A total of 537 individuals were captured, comprising of 226 females, 188 males and 123 egg-bearing females. In this study, salinity was the greater contributor to population variation compared to air and water temperature however this may be due to the small spatial scale of the Imperial River-Estero Bay ecosystem. No crabs were found in the freshwater river sites, and the highest number of crabs observed and captured occurred in the Site closest to te Gulf of Mexico. Salinity is significantly correlated with carapace width, number of observable crabs and number of ovigerous females found. Site 5 with close proximity to the Gulf of Mexico was the only location with a male biased population and sexual dimorphism with statistically larger females which are both uncommon. An egg-bearing female seasonality pattern was observed using the number of ovigerous females where they occur through the summer, peaked in September and drastically decreases to almost zero in October. All the results from this study indicate variations in mangrove tree crab population morphology on a relatively small spatial scale. Understanding the relationship of mangrove tree crabs and local salinities can help determine how climate-induced salinity changes could affect man grove tree crab population and distribution.