Voss, Joshua

Coral reef ecosystems worldwide are threatened by disease, anthropogenic damage, and climate change. Recently mesophotic coral ecosystems MCEs have been discovered and characterized as continuations of shallow reefs below traditional SCUBA depths. Because MCEs appear to be sheltered from many of the stressors known to affect shallow reefs, Glynn 1996 originally proposed that deeper reefs may act as a refuge for coral species by providing larvae to nearby shallow reefs. My dissertation research will address key questions that underlie this theory and advance our knowledge of coral ecology and physiology at mesophotic depths. including: 1 How well are MCEs connected to shallow reefs, and 2 Can corals adapt their morphology and gene expression to match changing environmental stimuli? Microsatellite based analysis of genetic connectivity will be complemented by morphometric analyses of corallite phenotypic plasticity and gene expression profiling in the dominant coral species, Montastraea cavernosa. MCEs in the Flower Garden Banks and Pulley Ridge have been surveyed and sampled using both ROVs and technical diving in 2011-2013, with additional expeditions planned for 2014-2015. A reciprocal transplant experiment on Carrie Bow Cay, Belize will assess the physiological and morphological plasticity of M. cavernosa in shallow and mesophotic environments. This project will address the influences of both environment and genotype control on coral’s potentially plastic responses. Additionally, this research is designed to provide data for improved regional management of mesophotic coral reef ecosystems and to strengthen collaborative marine research through NOAA’s Cooperative Institute for Ocean Exploration, Research, and Technology CIOERT.

The unique coral reef at St. Lucie Reef (Stuart, FL) persists despite environmental variability from extensive freshwater discharges, summer upwelling, and thermal
instability. By examining the symbiotic zooxanthellae, or Symbiodinium, that reside
in corals, we can gain insight to coral physiology impacted by local stressors. Two
scleractinian corals, Montastraea cavernosa and Pseudodiploria clivosa were sampled
over 1.5 years, including both wet and dry seasons. Zooxanthellae were isolated and
quantitatively characterized using standard measurements and molecular techniques.
Both coral species varied in zooxanthellae biomass, where Pseudodiploria clivosa had
Higher cell densities and chlorophyll concentrations than Montastraea cavernosa. Over
time, these parameters varied, but were not significantly altered by fresh water discharge events. Symbiodinium diversity and abundance were identified by ITS2 region amplification and next-generation sequencing .Novel associations between Symbiodinium and each coral explained the observed physiological differences. The symbioses remained stable throughout and could indicate local adaptation for St. Lucie Reef corals.