Publications by authors named "Marilyn E Brandt"

Article Synopsis
  • Upright branching sponges like Aplysina cauliformis are essential for coral reef habitats but are vulnerable to damage from storms, which can lead to increased fragmentation and inbreeding.
  • The occurrence of two Category 5 hurricanes in 2017 in the U.S. Virgin Islands allowed researchers to study the impact of storms on sponge recolonization and genetic diversity by analyzing samples from multiple reefs.
  • Findings revealed that storms favored sponge larval recruitment and sexual reproduction over clonality, leading to lower-than-expected fragmentation rates, while also enhancing gene flow, which may help combat inbreeding and support the genetic diversity of Caribbean sponge populations.
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Article Synopsis
  • * The study investigates how various coral species and their algal symbionts respond to SCTLD by analyzing gene expression profiles from a transmission experiment.
  • * Key findings show that SCTLD infection increases expression of specific genes linked to the breakdown of algal symbionts and that the disease's severity varies depending on the type of symbiotic algae present.
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Emerging diseases can have devastating consequences for wildlife and require a rapid response. A critical first step towards developing appropriate management is identifying the etiology of the disease, which can be difficult to determine, particularly early in emergence. Gathering and synthesizing existing information about potential disease causes, by leveraging expert knowledge or relevant existing studies, provides a principled approach to quickly inform decision-making and management efforts.

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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 the limited concurrence of SCTLD-associated bacteria among studies. We conducted a meta-analysis of 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 colony health states (apparently healthy colony tissue (AH), and unaffected (DU) and lesion (DL) tissue from diseased colonies).

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Infectious diseases are an increasing threat to coral reefs, resulting in altered community structure and hindering the functional contributions of disease-susceptible species. We exposed seven reef-building coral species from the Caribbean to white plague disease and determined processes involved in (i) lesion progression, (ii) within-species gene expression plasticity, and (iii) expression-level adaptation among species that lead to differences in disease risk. Gene expression networks enriched in immune genes and cytoskeletal arrangement processes were correlated to lesion progression rates.

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Article Synopsis
  • Stony coral tissue loss disease (SCTLD) is a severe illness affecting about 50% of Caribbean coral species, prompting a study on its microbial community response in US Virgin Islands (USVI) corals.
  • The researchers tested six coral species with varying susceptibility to SCTLD and analyzed the microbial communities in their mucus and tissue layers before and after disease exposure.
  • Findings revealed that while the microbiomes were similar among species post-disease acquisition, distinct patterns emerged based on species and habitat, with mucus potentially serving as an early indicator of disease presence.
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Symbiotic relationships range from parasitic to mutualistic, yet all endosymbionts face similar challenges, including evasion of host immunity. Many symbiotic organisms have evolved similar mechanisms to face these challenges, including manipulation of the host's transforming growth factor-beta (TGFβ) pathway. Here we investigate the TGFβ pathway in scelaractinian corals which are dependent on symbioses with dinoflagellates from the family Symbiodiniaceae.

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Bioerosion, the removal of calcium carbonate from coral frameworks by living organisms, influences a variety of reef features, from their topographic complexity to the net balance of carbonate budgets. Little is known, however, about how macroborers, which bore into reef substrates leaving traces greater than 0.1 mm diameter, are distributed across coral reefs, particularly reef systems with high (>50%) stony coral cover or at mesophotic depths (≥30 m).

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It is suspected that land cover alteration on the southern coast of St. Thomas, USVI has increased runoff, degrading nearshore water quality and coral reef health. Chronic and acute changes in water quality, sediment deposition, and coral health metrics were assessed in three zones based upon perceived degree of human influence.

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Energetic responses of zooxanthellate reef corals along depth gradients have relevance to the refugia potential of mesophotic coral ecosystems (MCEs). Previous observations suggested that MCEs in the Caribbean are thermally buffered during the warmest parts of the year and occur within or just below the chlorophyll maximum, suggesting abundant trophic resources. However, it is not known if mesophotic corals can maintain constant energy needs throughout the year with changing environmental and biological conditions.

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Article Synopsis
  • Deeper coral reefs are believed to offer protection from thermal stress and bleaching due to lower temperatures and reduced light exposure, challenging the deep reef refugia hypothesis.
  • Over two thermal stress events studied, mesophotic reefs (30-75 m deep) showed a decline in bleaching threshold temperatures with depth, contradicting the idea that deeper reefs are safer from climate impacts.
  • The findings suggest that cooler depths do not provide immunity against climate change, indicating that both deep and shallow coral reefs are similarly vulnerable to rising sea temperatures.
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Natural and anthropogenic factors may influence corals' ability to recover from partial mortality. To examine how environmental conditions affect lesion healing, we assessed several water quality parameters and tissue regeneration rates in corals at six reefs around St. Thomas, US Virgin Islands.

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White plague (WP)-like diseases of tropical corals are implicated in reef decline worldwide, although their etiological cause is generally unknown. Studies thus far have focused on bacterial or eukaryotic pathogens as the source of these diseases; no studies have examined the role of viruses. Using a combination of transmission electron microscopy (TEM) and 454 pyrosequencing, we compared 24 viral metagenomes generated from Montastraea annularis corals showing signs of WP-like disease and/or bleaching, control conspecific corals, and adjacent seawater.

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Coral disease is playing a significant role in structuring today's coral reef communities. While monitoring programs document declines associated with coral disease, there is a lack of tools that can test hypotheses of disease incidence and control. Here, we describe a modeling tool developed to test hypotheses about the spread and impact of white plague disease in diverse coral populations distributed across heterogeneous reef landscapes.

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Recent outbreaks of coral bleaching and disease have contributed to substantial declines in the abundance of reef-building coral. Significant attention has been paid to both phenomena in order to determine their effect on reef trajectories. Although each is positively correlated with high temperatures, few studies have explored the potential links between bleaching and disease.

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