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1. Space-filling and benthic competition on coral reefs

   https://doi.org/10.7717/peerj.11213  

   George, Emma E. ; Mullinix, James A. ; Meng, Fanwei ; Bailey, Barbara A. ; Edwards, Clinton ; Felts, Ben ; Haas, Andreas F. ; Hartmann, Aaron C. ; Mueller, Benjamin ; Roach, Ty N. F. ; et al ( June 2021 , PeerJ)

   Reef-building corals are ecosystem engineers that compete with other benthic organisms for space and resources. Corals harvest energy through their surface by photosynthesis and heterotrophic feeding, and they divert part of this energy to defend their outer colony perimeter against competitors. Here, we hypothesized that corals with a larger space-filling surface and smaller perimeters increase energy gain while reducing the exposure to competitors. This predicted an association between these two geometric properties of corals and the competitive outcome against other benthic organisms. To test the prediction, fifty coral colonies from the Caribbean island of Curaçao were rendered using digital 3D and 2D reconstructions. The surface areas, perimeters, box-counting dimensions (as a proxy of surface and perimeter space-filling), and other geometric properties were extracted and analyzed with respect to the percentage of the perimeter losing or winning against competitors based on the coral tissue apparent growth or damage. The increase in surface space-filling dimension was the only significant single indicator of coral winning outcomes, but the combination of surface space-filling dimension with perimeter length increased the statistical prediction of coral competition outcomes. Corals with larger surface space-filling dimensions (D_s> 2) and smaller perimeters displayed more winning outcomes, confirming the initial hypothesis. We propose that the space-filling property of coral surfaces complemented with other proxies of coral competitiveness, such as life history traits, will provide a more accurate quantitative characterization of coral competition outcomes on coral reefs. This framework also applies to other organisms or ecological systems that rely on complex surfaces to obtain energy for competition.

    

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2. Microbiome diversity and metabolic capacity determines the trophic ecology of the holobiont in Caribbean sponges

   https://doi.org/10.1038/s43705-022-00196-3  

   Lesser, Michael P. ; Pankey, M. Sabrina ; Slattery, Marc ; Macartney, Keir J. ; Gochfeld, Deborah J. ( November 2022 , ISME Communications)

   Sponges are increasingly recognized as an ecologically important taxon on coral reefs, representing significant biomass and biodiversity where sponges have replaced scleractinian corals. Most sponge species can be divided into two symbiotic states based on symbiont community structure and abundance (i.e., the microbiome), and are characterized as high microbial abundance (HMA) or low microbial abundance (LMA) sponges. Across the Caribbean, sponge species of the HMA or LMA symbiotic states differ in metabolic capacity, as well as their trophic ecology. A metagenetic analysis of symbiont 16 S rRNA and metagenomes showed that HMA sponge microbiomes are more functionally diverse than LMA microbiomes, offer greater metabolic functional capacity and redundancy, and encode for the biosynthesis of secondary metabolites. Stable isotope analyses showed that HMA and LMA sponges primarily consume dissolved organic matter (DOM) derived from external autotrophic sources, or live particulate organic matter (POM) in the form of bacterioplankton, respectively, resulting in a low degree of resource competition between these symbiont states. As many coral reefs have undergone phase shifts from coral- to macroalgal-dominated reefs, the role of DOM, and the potential for future declines in POM due to decreased picoplankton productivity, may result in an increased abundance of chemically defended HMA sponges on tropical coral reefs.

    

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3. 2D and 3D coral models imaged in Curaçao: George, Mullinix, et al PeerJ 2021

   https://doi.org/10.5061/dryad.5x69p8d2x  

   George, Emma E. ; Mullinix, James A. ; Meng, Fanwei ; Bailey, Barbara A. ; Edwards, Clinton ; Felts, Ben ; Haas, Andreas F. ; Hartmann, Aaron ; Mueller, Benjamin ; Roach, Ty F. ; et al ( January 2021 , Dryad)

   Abstract from the article associated with the dataset: George, Mullinix, et al PeerJ 2021. Reef-building corals are ecosystem engineers that compete with other benthic or- ganisms for space and resources. Corals harvest energy through their surface by photosynthesis and heterotrophic feeding, and they divert part of this energy to defend their outer colony perimeter against competitors. Here, we hypothesized that corals with a larger space-filling surface and smaller perimeters increase energy gain while reducing the exposure to competitors. This predicted an association between these two geometric properties of corals and the competitive outcome against other benthic organisms. To test the prediction, fifty coral colonies from the Caribbean island of Curac ̧ao were rendered using digital 3D and 2D reconstructions. The surface areas, perimeters, box-counting dimensions (as a proxy of space-filling property), and other geometric properties were extracted and analyzed with respect to the percentage of the perimeter losing or winning against competitors based on the coral tissue apparent growth or damage. The increase in surface space-filling dimension was the only significant single indicator of coral winning outcomes, but the combination of surface space-filling dimension with perimeter length increased the statistical prediction of coral competition outcomes. Corals with larger surface space-filling dimensions (Ds > 2) and smaller perimeters displayed more winning outcomes, confirming the initial hypothesis. We propose that the space-filling property of coral surfaces complemented with other proxies of coral competitiveness, such as life history traits, will provide a more accurate quantitative characterization of coral competition outcomes on coral reefs. This framework also applies to other organisms or ecological systems that rely on complex surfaces to obtain energy for competition. For the compressed files: - Reconstruction of the split file can be accomplished by issuing the command cat *.tar.bz2*part-a* > 3D_model_stl_data.tar.bz2 - Unzipping the compressed files can be accomplished by issuing the command tar -jxvf *.tar.bz2 

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4. Severe hurricanes increase recruitment and gene flow in the clonal sponge Aplysina cauliformis

   https://doi.org/10.1111/mec.17307  

   Segura‐García, Iris ; Olson, Julie B. ; Gochfeld, Deborah J. ; Brandt, Marilyn E. ; Chaves‐Fonnegra, Andia ( March 2024 , Molecular Ecology)

   Upright branching sponges, such asAplysina cauliformis, provide critical three‐dimensional habitat for other organisms and assist in stabilizing coral reef substrata, but are highly susceptible to breakage during storms. Breakage can increase sponge fragmentation, contributing to population clonality and inbreeding. Conversely, storms could provide opportunities for new genotypes to enter populations via larval recruitment, resulting in greater genetic diversity in locations with frequent storms. The unprecedented occurrence of two Category 5 hurricanes in close succession during 2017 in the U.S. Virgin Islands (USVI) provided a unique opportunity to evaluate whether recolonization of newly available substrata on coral reefs was due to local (e.g. re‐growth of remnants, fragmentation, larval recruitment) or remote (e.g. larval transport and immigration) sponge genotypes. We sampledA. cauliformisadults and juveniles from four reefs around St. Thomas and two in St. Croix (USVI). Using a 2bRAD protocol, all samples were genotyped for single‐nucleotide polymorphisms (SNPs). Results showed that these major storm events favoured sponge larval recruitment but did not increase the genetic diversity ofA. cauliformispopulations. Recolonization of substratum post‐storms via clonality was lower (15%) than expected and instead was mainly due to sexual reproduction (85%) via local larval recruitment. Storms did enhance gene flow among and within reef sites located south of St. Thomas and north of St. Croix. Therefore, populations of clonal marine species with low pelagic dispersion, such asA. cauliformis, may benefit from increased frequency and magnitude of hurricanes for the maintenance of genetic diversity and to combat inbreeding, enhancing the resilience of Caribbean sponge communities to extreme storm events.

    

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5. Transmission studies and the composition of prokaryotic communities associated with healthy and diseased Aplysina cauliformis sponges suggest that Aplysina Red Band Syndrome is a prokaryotic polymicrobial disease

   https://doi.org/10.1093/femsec/fiab164  

   Monti, Matteo ; Giorgi, Aurora ; Easson, Cole G. ; Gochfeld, Deborah J. ; Olson, Julie B. ( December 2021 , FEMS Microbiology Ecology)

   Aplysina cauliformis, the Caribbean purple rope sponge, is commonly affected by Aplysina Red Band Syndrome (ARBS). This transmissible disease manifests as circular lesions with red margins and results in bare spongin fibers. Leptolyngbya spp. appear to be responsible for the characteristic red coloration but transmission studies with a sponge-derived isolate failed to establish disease, leaving the etiology of ARBS unknown. To investigate the cause of ARBS, contact transmission experiments were performed between healthy and diseased sponges separated by filters with varying pore sizes. Transmission occurred when sponges were separated by filters with pore sizes ≥ 2.5 μm, suggesting a prokaryotic pathogen(s) but not completely eliminating eukaryotic pathogen(s). Using 16S rRNA gene sequencing methods, 38 prokaryotic taxa were significantly enriched in diseased sponges, including Leptolyngbya, whereas seven taxa were only found in some, but not all, of the ARBS-affected sponges. These results do not implicate a single taxon, but rather a suite of taxa that changed in relative abundance with disease, suggesting a polymicrobial etiology as well as dysbiosis. As a better understanding of dysbiosis is gained, changes in the composition of associated prokaryotic communities may have increasing importance for evaluating and maintaining the health of individuals and imperiled coral reef ecosystems.

    

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