Coral reef: linking microbiome to physiology and resilience.
Understanding the link between the microbiome and coral physiology is paramount. We are investigating the local adaption of coral microbiome that occurs at different reef zones (inner or outer reefs) and the resilience of corals to bleaching stress. The inner reef is closer to the coast and generally has more variable environmental conditions, such as higher temperature, nutrient and sedimentation range compared with the outer reef, which is influenced by the ocean. The microbes from the inner reef therefore will be modified by the higher environmental variability, whereas the outer reef microbiome will be more stable. We hypothesize that the more flexible microbiome will be associated with a coral phenotype that is more resilient to changes in condition, such as temperature.
We are conducting collaborative research experiment in Bermuda to test this hypothesis. To date we have collected the coral microbiomes from the two reef zones and identified that there are major differences in both the taxa and function of the microbes. The differences in the coral associated microbiomes is not driven by the water column microbes, which is distinctive in both locations.
The corals were collected from each zone and placed under temperature stress in an aquarium situation. As predicted the inner reef corals were more resilient to thermal stress, compared with the outer reef corals. The microbiome of the coral during the experiment are now being sequenced. This research is being led by Lais Lima, a Ph.D. student.
The Dinsdale Lab also has had the opportunity to collaborate with researchers internationally and perform microbial analysis off the coast of Bahia, Brazil. We worked with local researchers to assess the health of the reefs through a variety of metrics from fish counts to microbial identification. We have shown changes in microbial community composition corresponding to anthropogenic pressure across reefs. As coral reefs decline, the benthic community transitions from corals to algae and the biomass shifts from higher trophic levels, sharks, to bacteria and viruses. We hypothesize the change in benthic cover is influencing the proportion of heterotrophic bacteria in the water column. We have measured this change by looking at the water column directly over areas of reef dominated by one benthic organism and small mesocosm experiments. We find that at a small reef scale benthic organisms influence water column microbes and are assembling genomes from metagenomes to identify super-heterotrophs implicated in coral disease. These interactions over a small spatial scale can be modeled to represent the whole reef mosaic.