Abstract
Coral reefs are in decline worldwide. In response to this habitat loss, there are efforts to grow, outplant, and restore corals in many regions. The physical oceanographic habitat of corals—such as sea temperature, waves, ocean currents, and available light—is spatially heterogeneous. We therefore hypothesize that outplant location may affect microbiomes, and ultimately, coral health and restoration success. We evaluated the influence of the physical oceanographic habitat on microbes in wild Porites astreoides and Siderastrea siderea. Tissue samples were collected at four Florida reefs in March, June, and September of 2015. We estimated oceanographic conditions from moored instruments, diver observations, remote sensing data, and numerical models. We analyzed microbiomes using amplicon 16S rRNA high-throughput sequencing data. We found microbial alpha-diversity negatively correlated with in situ sea temperature (which represented both the annual cycle and upwelling), as well as modeled alongshore currents, in situ sea-level, and modeled tide. Microbial beta-diversity correlated positively with significant wave height and alongshore currents from models, remotely-sensed relative turbidity, and in situ temperature. We found that archaea from the order Marine Group II decrease with increases in significant wave height, suggesting that this taxon may be influenced by waves. Also, during times of high wave activity, the relative abundance of bacteria from the order Flavobacteriales increases, which may be due to resuspension and cross-shelf transport of sediments. We also found that bacteria from the order SAR86 increase in relative abundance with increased temperature, which suggests that this taxon may play a role in the coral microbiome during periods of higher temperature. Overall, we find that physical oceanographic variability correlates with the structure of these coral microbiomes in ways that could be significant to coral health.
Highlights
Coral reefs face numerous environmental and biological challenges, especially in a changing climate
We aimed to identify the impacts of the physical oceanographic habitat—in particular, turbidity, temperature, waterflow, and bathymetry—on coral microbiomes
We found that increases in tide height, sea-level, sea temperature, and modeled alongshore currents were associated with declines in microbial Shannon diversity and/or evenness (Fig. 5)
Summary
Coral reefs face numerous environmental and biological challenges, especially in a changing climate. Understanding how the physical habitat—such as temperature variability, light, and water flow—interacts with biological factors in corals has important implications for managing these sensitive ecosystems. Environmental factors such as wind and surface ocean waves can contribute to the spatial morphology of coral reefs over time. Coral larval dispersion and settlement rates are affected by hydrodynamic variability, which impacts gene flow and the genetic diversity of coral reefs (Baums, Paris & Chérubin, 2006; Serrano et al, 2014; Serrano et al, 2016)
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