Voss, J. D. | Search bioRxiv

bioRxiv2022

A meta-analysis of the stony coral tissue loss disease microbiome finds key bacteria in lesions and unaffected tissue of diseased colonies

Stony coral tissue loss disease (SCTLD) has been causing significant whole colony mortality on reefs in Florida and the Caribbean. The cause of SCTLD remains unknown, with limited concurrence of SCTLD-associated bacteria among studies. We conducted a meta-analysis of SSU 16S ribosomal RNA gene datasets generated by 16 field and laboratory SCTLD studies to find consistent bacteria associated with SCTLD across disease zones (vulnerable, endemic, and epidemic), coral species, coral compartments (mucus, tissue, and skeleton), and disease states (apparently healthy colony tissue [AH], and unaffected [DU] and lesion [DL] tissue from diseased colonies). We also evaluated bacteria in seawater and sediment, which may be sources of SCTLD transmission. Although AH colonies in endemic and epidemic zones harbor bacteria associated with SCTLD lesions, and aquaria and field samples had distinct microbial compositions, there were still clear differences in the microbial composition among AH, DU, and DL in the combined dataset. Alpha diversity between AH and DL was not different; however, DU showed increased alpha diversity compared to AH, indicating that, prior to lesion formation, corals may undergo a disturbance to the microbiome. This disturbance may be driven by Flavobacteriales, which were especially enriched in DU. While Rhodobacterales and Peptostreptococcales-Tissierellales were prominent in structuring microbial interactions in DL. Peptostreptococcales-Tissierellales specifically may contribute to lesion progression through an alpha-toxin. We provide a consensus of SCTLD-associated bacteria both prior to and during lesion progression and identify how these taxa vary across studies, coral species, coral compartments, seawater, and sediment.

microbiology↗

bioRxiv2018

Montastraea cavernosa corallite structure demonstrates ‘shallow-only’ and ‘depth-generalist’ morphotypes across shallow and mesophotic depth zones in the Gulf of Mexico

This study assessed morphological variation in corallite structure of the depth-generalist coral Montastraea cavernosa across shallow and mesophotic coral ecosystems in the Gulf of Mexico (GOM). Among eight corallite metrics examined, corallite diameters were smaller and spacing was greater in mesophotic corals as compared to shallow corals. Additional corallite variation, including greater corallite height of mesophotic samples, were hypothesized to be photoadaptive responses to low light environments. Although comparison of shallow and mesophotic M. cavernosa was the initial objective of the study, multivariate analyses revealed two distinct morphotypes able to be identified by the significant variation in corallite spacing with >90% accuracy. A shallow-only morphotype was characterized by larger, more closely-spaced corallites, while a depth-generalist type exhibited smaller, further-spaced corallites. The depth-generalist morphotype comprised the majority of mesophotic M. cavernosa colonies sampled from sites in the northwest GOM including the Flower Garden Banks (FGB), Bright Bank, and McGrail Bank. A combination of both morphotypes were found at shallow depths in the FGB. Conversely, in the southeast GOM, the shallow-only morphotype was observed in shallow Dry Tortugas. Mesophotic M. cavernosa at Pulley Ridge were comparable to the shallow-only morphotype in terms of corallite spacing but shared morphological similarities with mesophotic corals for other measured characters, likely representing a hybrid morphology. The variable presence of the morphotypes across sites likely indicates a genotypic influence on corallite morphology, as there was a slight, but significant, impact of morphotype on genetic differentiation within the FGB. Patterns of increased algal symbiont (Symbiodiniaceae) density and chlorophyll concentration were retained in the depth-generalist morphotype even at shallow depths, suggesting multiple photoadaptive strategies between morphotypes. Despite the observed polymorphism in shallow and mesophotic M. cavernosa, the implications for these morphological differences in coral physiology and fitness are not fully known, although some evidence suggests skeletal optical properties may influence bleaching resilience.

ecology↗