PS 19-55 - Multiple stressors in a Caribbean dwarf mangrove ecosystem

Wednesday, August 10, 2016
ESA Exhibit Hall, Ft Lauderdale Convention Center
Ryann E. Rossi1, Stephanie K. Archer2 and Craig A. Layman1, (1)Applied Ecology, North Carolina State University, Raleigh, NC, (2)Fisheries and Oceans Canada, Nanaimo, BC, Canada

Mangroves are foundation species in coastal ecosystems providing an estimated US $1.6 billion in ecosystem services worldwide. These services range from providing essential nursey habitat for marine organisms to land accretion and carbon sequestration. Unfortunately, mangrove forests are declining as a result of myriad factors, many related to human activity. Although human activities are the driving cause of mangrove loss globally, natural factors result in mangrove loss. Here, we present a case study from Abaco, The Bahamas in which dwarf Red Mangroves (Rhizophora mangle) are dying on a large scale. Initial data suggest that prior to death these dwarf R.mangle are stressed by multiple factors, including a fungal plant pathogen, herbivory, and altered abiotic conditions (e.g., hyper-salinity). In order to determine how each of these factors contribute to the die-off we are using a series of empirical experiments. Herbivore exclusion cages were placed on live dwarf mangroves to examine effects of herbivory on mangrove health in the die-off region. Next, disease incidence surveys were completed in the die-off area and infected leaf samples were collected and sequenced for fungal DNA. A simulated grazing experiment was conducted in dwarf mangroves to determine if there is an interaction between herbivory and pathogen.


Our initial results show that there is a trend of decreased herbivory in the caged dwarf mangrove treatments, however, the experiment is ongoing. We have identified a potential fungal pathogen, a Pestalotiopsis species, on infected mangrove leaves from DNA sequencing. Though, Koch’s postulate experiments are ongoing to confirm pathogen identity and virulence. The simulated grazing experiment results show a trend of increased lesion development on cut leaves suggesting a potential interaction between grazing damage and fungal infection. Future work will incorporate how hyper-saline conditions in the presence and absence of both the plant pathogen and herbivore contribute to mangrove health. ­­­