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1. Geographically driven differences in microbiomes of Acropora cervicornis originating from different regions of Florida’s Coral Reef

   https://doi.org/10.7717/peerj.13574  

   Williams, Sara D. ; Klinges, J. Grace ; Zinman, Samara ; Clark, Abigail S. ; Bartels, Erich ; Villoch Diaz Maurino, Marina ; Muller, Erinn M. ( January 2022 , PeerJ)

   Effective coral restoration must include comprehensive investigations of the targeted coral community that consider all aspects of the coral holobiont—the coral host, symbiotic algae, and microbiome. For example, the richness and composition of microorganisms associated with corals may be indicative of the corals’ health status and thus help guide restoration activities. Potential differences in microbiomes of restoration corals due to differences in host genetics, environmental condition, or geographic location, may then influence outplant success. The objective of the present study was to characterize and compare the microbiomes of apparently healthy Acropora cervicornis genotypes that were originally collected from environmentally distinct regions of Florida’s Coral Reef and sampled after residing within Mote Marine Laboratory’s in situ nursery near Looe Key, FL (USA) for multiple years. By using 16S rRNA high-throughput sequencing, we described the microbial communities of 74 A. cervicornis genotypes originating from the Lower Florida Keys ( n  = 40 genotypes), the Middle Florida Keys ( n  = 15 genotypes), and the Upper Florida Keys ( n  = 19 genotypes). Our findings demonstrated that the bacterial communities of A. cervicornis originating from the Lower Keys were significantly different from the bacterial communities of those originating from the Upper and Middle Keys even aftermore »these corals were held within the same common garden nursery for an average of 3.4 years. However, the bacterial communities of corals originating in the Upper Keys were not significantly different from those in the Middle Keys. The majority of the genotypes, regardless of collection region, were dominated by Alphaproteobacteria, namely an obligate intracellular parasite of the genus Ca. Aquarickettsia . Genotypes from the Upper and Middle Keys also had high relative abundances of Spirochaeta bacteria. Several genotypes originating from both the Lower and Upper Keys had lower abundances of Aquarickettsia , resulting in significantly higher species richness and diversity. Low abundance of Aquarickettsia has been previously identified as a signature of disease resistance. While the low- Aquarickettsia corals from both the Upper and Lower Keys had high abundances of an unclassified Proteobacteria, the genotypes in the Upper Keys were also dominated by Spirochaeta . The results of this study suggest that the abundance of Aquarickettsia and Spirochaeta may play an important role in distinguishing bacterial communities among A. cervicornis populations and compositional differences of these bacterial communities may be driven by regional processes that are influenced by both the environmental history and genetic relatedness of the host. Additionally, the high microbial diversity of low- Aquarickettsia genotypes may provide resilience to their hosts, and these genotypes may be a potential resource for restoration practices and management.« less
2. Twenty years of change in benthic communities across the Belizean Barrier Reef

   https://doi.org/10.1371/journal.pone.0249155  

   Alves, Catherine ; Valdivia, Abel ; Aronson, Richard B. ; Bood, Nadia ; Castillo, Karl D. ; Cox, Courtney ; Fieseler, Clare ; Locklear, Zachary ; McField, Melanie ; Mudge, Laura ; et al ( January 2022 , PLOS ONE)

   Coen, Loren D. (Ed.)

   Disease, storms, ocean warming, and pollution have caused the mass mortality of reef-building corals across the Caribbean over the last four decades. Subsequently, stony corals have been replaced by macroalgae, bacterial mats, and invertebrates including soft corals and sponges, causing changes to the functioning of Caribbean reef ecosystems. Here we describe changes in the absolute cover of benthic reef taxa, including corals, gorgonians, sponges, and algae, at 15 fore-reef sites (12–15m depth) across the Belizean Barrier Reef (BBR) from 1997 to 2016. We also tested whether Marine Protected Areas (MPAs), in which fishing was prohibited but likely still occurred, mitigated these changes. Additionally, we determined whether ocean-temperature anomalies (measured via satellite) or local human impacts (estimated using the Human Influence Index, HII) were related to changes in benthic community structure. We observed a reduction in the cover of reef-building corals, including the long-lived, massive corals Orbicella spp. (from 13 to 2%), and an increase in fleshy and corticated macroalgae across most sites. These and other changes to the benthic communities were unaffected by local protection. The covers of hard-coral taxa, including Acropora spp., Montastraea cavernosa , Orbicella spp., and Porites spp., were negatively related to the frequency of ocean-temperature anomalies.more »Only gorgonian cover was related, negatively, to our metric of the magnitude of local impacts (HII). Our results suggest that benthic communities along the BBR have experienced disturbances that are beyond the capacity of the current management structure to mitigate. We recommend that managers devote greater resources and capacity to enforcing and expanding existing marine protected areas and to mitigating local stressors, and most importantly, that government, industry, and the public act immediately to reduce global carbon emissions.« less
3. Predator-permanence hypothesis in time: Community dynamics in a seasonally flooded wetland

   https://doi.org/10.1086/721960  

   Ruehl, Clifton B. ; Pintar, Matthew R. ; Trexler, Joel C. ( January 2022 , Freshwater Science)

   The predator-permanence hypothesis predicts that as hydroperiod increases in lentic ecosystems, biotic interactions—mainly predation—replace physical factors like drying as the main determinant of community structure and population dynamics. We propose that the same transition occurs over time in seasonally flooded ecosystems that are connected to permanent water bodies. To test for evidence of successional changes that are similar to spatial changes in the relative importance of drying and predation, we used a 12-y time series of snail density, predator density, and water depth at 4 sites arranged along a nutrient gradient in a subtropical, seasonally flooded wetland, the Florida Everglades, USA. The rate of change in snail population size was negatively correlated with their density at all 4 sites, suggesting that density-dependent factors such as resource limitation regulate snail dynamics. The strength of the relationship varied among sites such that when water depth changes were less important, snail population size was more important in predicting changes in snail population size. At the site that consistently had the greatest snail density, crayfish density negatively affected the rate of snail population change, suggesting that crayfish predation may limit snail population growth in areas with more or higher-quality resources that support larger snailmore »populations. Tethering studies were also conducted, which revealed higher snail mortality in the wet season, primarily because crushing predators (e.g., molluscivorous fishes) were more common at that time and added to the chronic mortality by entry-based predators (e.g., crayfish, which access snails through their aperture). In summary, 3 of the sites resembled temporary or permanent fishless ponds where snail populations were primarily structured by abiotic factors, intraspecific competition, and invertebrate predators (e.g., crayfish) during the wet season, whereas 1 site showed evidence that snail populations were also influenced by molluscivorous fish. This temporal change in importance of water permanence factors to fish that affected population dynamics supports the spatial pattern proposed by the predator-permanence hypothesis.« less
4. The coral symbiont Candidatus Aquarickettsia is variably abundant in threatened Caribbean acroporids and transmitted horizontally

   https://doi.org/10.1038/s41396-021-01077-8  

   Baker, Lydia J. ; Reich, Hannah G. ; Kitchen, Sheila A. ; Grace Klinges, J. ; Koch, Hanna R. ; Baums, Iliana B. ; Muller, Erinn M. ; Thurber, Rebecca Vega ( August 2021 , The ISME Journal)

   The symbiont “CandidatusAquarickettsia rohweri” infects a diversity of aquatic hosts. In the threatened Caribbean coral,Acropora cervicornis,Aquarickettsiaproliferates in response to increased nutrient exposure, resulting in suppressed growth and increased disease susceptibility and mortality of coral. This study evaluated the extent, as well as the ecology and evolution ofAquarickettsiainfecting threatened corals,Ac. cervicornis, andAc. palmataand their hybrid (“Ac. prolifera”).Aquarickettsiawas found in all acroporids, with coral host and geographic location impacting the infection magnitude. Phylogenomic and genome-wide single-nucleotide variant analysis ofAquarickettsiafound phylogenetic clustering by geographic region, not by coral taxon. Analysis ofAquarickettsiafixation indices suggests multiple sequential infections of the same coral colony are unlikely. Furthermore, relative to other Rickettsiales species,Aquarickettsiais undergoing positive selection, with Florida populations experiencing greater positive selection relative to other Caribbean locations. This may be due in part toAquarickettsiaproliferating in response to greater nutrient stress in Florida, as indicated by greater in situ replication rates in these corals.Aquarickettsiawas not found to significantly codiversify with either the coral animal or the coral’s algal symbiont (Symbiodinium“fitti”). Quantitative PCR analysis showed that gametes, larvae, recruits, and juveniles from susceptible, captive-reared coral genets were not infected withAquarickettsia. Thus, horizontal transmission ofAquarickettsiavia coral mucocytes or an unidentified host is more likely. The prevalence ofAquarickettsiainAc. cervicornisandmore »its high abundance in the Florida coral population suggests that coral disease mitigation efforts focus on preventing early infection via horizontal transmission.

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5. Large-scale invasion of western Atlantic mesophotic reefs by lionfish potentially undermines culling-based management

   https://doi.org/DOI 10.1007/s10530-016-1358-0  

   Andradi-Brown, Dominic A. ; Vermeij, Mark J. ; Slattery, Marc ; Lesser, Michael ; Bejarano, Ivonne ; Appeldoorn, Richard ; Goodbody-Gringley, Gretchen ; Chequer, Alex D. ; Pitt, Joanna M. ; Eddy, Corey ; et al ( January 2017 , Biological invasions)

   The detrimental effects of invasive lionfishes (Pterois volitans and Pterois miles) on western Atlantic shallow reefs are well documented, including declines in coral cover and native fish populations, with disproportionate predation on critically endangered reef fish in some locations. Yet despite individuals reaching depths[100 m, the role of mesophotic coral ecosystems (MCEs; reefs 30–150 m) in lionfish ecology has not been addressed. With lionfish control programs in most invaded locations limited to 30 mby diving restrictions, understanding the role of MCEs in lionfish distributions remains a critical knowledge gap potentially hindering conservation management. Here we synthesise unpublished and previously published studies of lionfish abundance and body length at paired shallow reef (0–30 m) and MCE sites in 63 locations in seven western Atlantic countries and eight sites in three Indo-Pacific countries where lionfish are native. Lionfish were found at similar abundances across the depth gradient from shallow to adjacent MCEs, with no difference between invaded and native sites. Of the five invaded countries where length data were available three had larger lionfish on mesophotic than shallow reefs, one showed no significant difference, while the fifth represented a recently invaded site. This suggests at least some mesophotic populations may represent extensionsmore »of natural ontogenetic migrations. Interestingly, despite their shallow focus, in many cases culling programs did not appear to alter abundance between depths. In general, we identify widespread invasive lionfish populations on MCE that could be responsible for maintaining high densities of lionfish recruits despite local shallow-biased control programs. This study highlights the need for management plans to incorporate lionfish populations below the depth limit of recreational diving in order to address all aspects of the local population and maximise the effectiveness of control efforts.« less