ABSTRACT Coral and oyster reefs have declined greatly due to anthropogenic stressors. Low recruitment rates from larvae hamper recovery of these important ecosystems. Although much is known about factors affecting larval settlement, a detailed understanding of their swimming and substrate selection behaviour is lacking. Here, we present an approach to study coral and oyster larval behaviour in unprecedented detail, using a high resolution camera, choice chambers and behavourial analysis software. From second-by-second spatial data, we extracted variables such as swimming pattern, swimming speed and distance travelled using larvae between 0.2 and 3 mm in length. We applied this to larvae of the Caribbean brooding coral Favia fragum and show they locate their major settlement cue, coralline algae, within 90 min when placed in a choice chamber. Oyster (Ostrea edulis) larvae exhibited reduced swimming speed with age, suggesting pre-settlement behaviour. With the presented real-time high resolution tracking approach we can address new questions related to the behaviour of coral, oyster and other marine larvae, with applications in ecology, aquaculture and coastal engineering. Most notable is future development of “flypaper” substrates with cues to promote larval settlement on reefs, to aid restoration efforts.
Abstract Evolutionary tradeoffs between life-history strategies are central to animal evolution. However, because microbes can influence aspects of host physiology, behavior, and resistance to stress or disease, changes in animal-microbial symbioses have the potential to mediate life-history tradeoffs. Scleractinian corals provide a highly biodiverse and data-rich host system to test this idea, made more relevant by increases in coral disease outbreaks as a result of anthropogenic changes to climate and reef ecosystems. Identifying factors that determine coral disease susceptibility has therefore become a focus for reef conservation efforts. Using a comparative approach, we tested if coral microbiomes correlate with disease susceptibility across 425 million years of coral evolution by combining a cross-species coral microbiome survey (the “Global Coral Microbiome Project”) with long-term disease prevalence data at multiple sites. Interpreting these data in their phylogenetic context, we show that microbial dominance and composition predict disease susceptibility. We trace this dominance-disease association to a single putatively beneficial bacterial symbiont, Endozoicomonas, whose relative abundance in coral tissue explained 30% of variation in disease susceptibility and 60% of variation in microbiome dominance across 40 coral genera. Conversely, Endozoicomonas abundances in coral tissue strongly correlated with high growth rates. These results demonstrate that the evolution of microbial symbiosis in corals correlates with both disease prevalence and growth rate. Exploration of the mechanistic basis for these findings will be important for our understanding of how microbial symbiosis influences animal life-history tradeoffs, and in efforts to use microbes to increase coral growth or disease resistance in-situ.
ABSTRACTThe populations of native iguanas in the Caribbean Lesser Antilles are threatened by the wide occur-rence and spread of non-native iguanas. Until recently, competitive hybridization was not believed tothreaten the Saba Green Iguana, a subpopulation ofIguana iguana(Linnaeus, 1758) from the island ofSaba. However, the arrival of non-native iguanas has put the native population at risk, leading to achange in the conservation status of the Saba Green Iguana to Critically Endangered, according toguidelines from the International Union for the Conservation of Nature. Here, we generated the com-plete mitogenome of the Saba Green Iguana using Oxford Nanopore long-read technology. The mito-genome is 16,626 bp long and has 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and acontrol region (1194 bp). Noteworthy, this is only the second published mitogenome for theIguanaiguanaspecies complex, despite the known high intraspecific genetic variation.
Abstract Coral reefs are some of the most diverse and valuable ecosystems worldwide. Since the 1970’s the coral populations of Acropora spp. around Bonaire Island have been declining due to White Band Disease (WBD) and due to heavy storms and hurricanes (i.e., hurricane Lenny in 1999). Acropora cervicornis is one of the species selected as restoration target because its critically endangered status according to the IUCN red list and its ecological value as reef builder. Promoting genetic diversity is key to aid the recovery of degraded populations and give this species higher chance to survive in the long-term. In this study, we measure growth and healing, as phenotypic traits of propagated corals to assess the different genotype performance in the nursery phase. Linear length and tissue regeneration have been monitored for 8 weeks for 10 different genotypes (n=5), respectively with in situ measurement and image analysis. The preliminary results suggest that some individual fragments can grow up to one centimeter per week and achieve complete tissue regeneration from cutting and handling damage in 15 days. Being able to determinate the differences in performance from various coral genotypes can help nursery based coral restoration to be more performant. Indeed, selecting coral genotypes that can grow and regenerate faster is a considerable advantage for coral restoration practitioners that could therefore optimize their outplanting efforts.
Saba Bank, a submerged atoll in the Caribbean Sea with an area of 2,200 km2 , has attained international conservation status due to the rich diversity of species that reside on the bank. In order to assess the role of Saba Bank as a potential reservoir of diversity for the surrounding reefs, we examined the population genetic structure, abundance and health status of two prominent benthic species, the coral Montastraea cavernosa and the sponge Xestospongia muta. Sequence data were collected from 34 colonies of M. cavernosa (nDNA ITS1- 5.8S-ITS2; 892 bp) and 68 X. muta sponges (mtDNA I3-M11 partition of COI; 544 bp) on Saba Bank and around Saba Island, and compared with published data across the wider Caribbean. Our data indicate that there is genetic connectivity between populations on Saba Bank and the nearby Saba Island as well as multiple locations in the wider Caribbean, ranging in distance from 100s–1000s km. The genetic diversity of Saba Bank populations of M. cavernosa (π = 0.055) and X. muta (π = 0.0010) was comparable to those in other regions in the western Atlantic. Densities and health status were determined along 11 transects of 50 m2 along the south-eastern rim of Saba Bank. The densities of M. cavernosa (0.27 ind. m-2, 95% CI: 0.12–0.52) were average, while the densities of X. muta (0.09 ind. m-2, 95% CI: 0.02–0.32) were generally higher with respect to other Caribbean locations. No disease or bleaching was present in any of the specimens of the coral M. cavernosa, however, we did observe partial tissue loss (77.9% of samples) as well as overgrowth (48.1%), predominantly by cyanobacteria. In contrast, the majority of observed X. muta (83.5%) showed signs of presumed bleaching. The combined results of apparent gene flow among populations on Saba Bank and surrounding reefs, the high abundance and unique genetic diversity, indicate that Saba Bank could function as an important buffer for the region. Either as a natural source of larvae to replenish genetic diversity or as a storehouse of diversity that can be utilized if needed for restoration practices.
Marine organism are often kept, cultured, and experimented on in running seawater aquaria. However, surprisingly little attention is given to the nutrient composition of the water owing through these systems, which is generally assumed to equal
in situ conditions, but may change due to the presence of biofouling organisms. Signi cantly lower bacterial abundances and higher inorganic nitrogen species (nitrate, nitrite, and ammonium) were measured in aquarium water when biofouling organisms were present within a 7-year old inlet pipe feeding a tropical reef running seawater aquaria system, compared with aquarium water fed by a new, biofouling-free inlet pipe. These water quality changes are indicative of the feeding activity and waste production of the suspension- and lter-feeding communities found in the old pipe, which included sponges, bivalves, barnacles, and ascidians. To illustrate the physiological consequences of these water quality changes on a model organism kept in the aquaria system, we investigated the in uence of the presence and absence of the biofouling community on the functioning of the lter-feeding sponge Halisarca caerulea, by determining its choanocyte ( lter cell) proliferation rates. We found a 34% increase in choanocyte proliferation rates following the replacement of the inlet pipe (i.e., removal of the biofouling community). This indicates that the physiological functioning of the sponge was compromised due to suboptimal food conditions within the aquarium resulting from the presence of the biofouling organisms in the inlet pipe. This study has implications for the husbandry and performance of experiments with marine organisms in running seawater aquaria systems. Inlet pipes should be checked regularly, and replaced if necessary, in order to avoid excessive biofouling and to approach in situ water quality.
In this study I assessed the extent of sedimentation and contamination by human enteric bacteria Enterococci on the reefs of Bonaire, Netherlands Antilles as well as the relationship of these factors to the prevalence of coral disease and bleaching. Largely the effects of sedimentation and enteric bacteria from wastewater run-off in Bonaire have been relatively unknown. Because of the lack of wastewater treatment in Bonaire, runoff contamination by sewage and nutrient fluxes is common. Assessment sites for this study were chosen based on the intensity of nearby anthropogenic activity. These sites were defined as “More Impacted” (MI, n=2) and “Less Impacted” (LI, n=2). Water and sediment samples were acquired at 12 m on a weekly basis for the assessment of enterococcal concentration using the Enterolert™ fluorescing substrate system and determination of sediment particle size distributions. In addition, the frequency of coral disease and extent of coral bleaching were assessed using Coral Point Count software on data acquired along two 10 m video transect lines laid at 12m for each site over 4 weeks. Overall sediment particle size analysis yielded statistically significant differences between LI and MI particle size distributions, with more fine grained sediments at MI sites and more coarse grained sediments at LI sites. Finer grains suggest greater human impact. Enteric bacteria were found at several sites over time and their concentrations show a positive correlation between human presence and higher bacteria counts. Bleaching and disease did not show any correlation with sediment particle sizes or presence of enteric bacteria.
In 2004, as part of a GEF funded project entitled “Coral Reef Targeted Research and Capacity Building” (CRTR), to assess the current status and future of these important communities, six groups of researchers looked at different aspects of the dynamics and degradation of coral reefs worldwide (i.e. Coral diseases, bleaching, connectivity, remote sensing. One of these groups, the Coral Disease Working Group (CDWG), assessed the number, prevalence, distribution, impacts and host range of coral diseases and their spatial and temporal variability in the wider Caribbean.
Curacao was selected as one of six localities spread over the Caribbean, and one of two southern localities. Results presented here represent our preliminary approach and surveys in Curacao. Surveys were done in permanently marked transects using the CARICOMP sampling protocol. Overall, coral diseases in these sites had, on average, a relatively low prevalence (5.74 ± 3.7%) at the community level (all colonies from all species included). Curacao was the second country with higher disease prevalence of the 6 countries visited across the Caribbean during the Summer-Fall of 2005, the weight of this prevalence coming from one of the two sites surveyed on the island. The most common diseases observed were dark spots syndrome (DSS), white plague type II (WP-II) and secondary infections by ciliates. Noteworthy was the lack of bleaching in these two reef localities and in general, in the Netherland Antilles when most of the eastern, northern and western were suffering the worst bleaching event on record for the Caribbean. Bleached colonies were only mild paling patterns and the overall prevalence was below 1.0 %. Octocoral diseases were almost two times more prevalent (9.6 ± 16.9%) than coral diseases in Curacao.