Recent publications in Marine Science & Aquaculture
Barramundi (Lates calcarifer) is a tropical finfish species rapidly growing in popularity for aquaculture production. However, sperm quality tests have yet to be adapted to enable selection of highly fertile male broodstock in this species. Accordingly, in this study advanced tools were optimized to evaluate barramundi sperm function to facilitate the future study of male fertility and address some of the reproductive constraints currently observed in captive-bred broodstock. Sperm morphology data were used to calibrate and validate automated sperm counting and motility detection by computer-assisted sperm analysis (CASA; AndroVision, Minitube). Several parameters were examined to determine the optimum settings for accurate CASA sperm counting and were compared to manual haemocytometer methods including: sample dilution (1:1000, r = 0.87), minimum number of fields (n = 4, CV = 7.5%), and the effect of motile vs. immotile spermatozoa on automated counting (no effect, r = 0.99, P < .001). Assays for cell viability and DNA damage were also validated for barramundi spermatozoa using 70 °C heat-treated controls and a 5-point intact:damaged dilution curve (r = 0.98, P < .001), and DNase-treated sperm controls, respectively. Data from these optimized assessments indicated high variation between individuals for each parameter assessed and the presence of high rates of DNA and membrane damage in sperm samples tested. Further research building upon this preliminary sperm quality data, is required to identify the cause of DNA and membrane damage in barramundi spermatozoa and understand any potential relationships with paternal performance in commercial spawns.
Fuller, Zachary L., Mocellin, Veronique J. L., Morris, Luke A., Cantin, Neal, Shepherd, Jihanne, Sarre, Luke, Peng, Julie, Liao, Yi, Pickrell, Joseph, Andolfatto, Peter, Matz, Mikhail, Bay, Line K., and Przeworski, Molly (2020) Population genetics of the coral Acropora millepora: toward genomic prediction of bleaching. Science, 369 (6501). eaba4674.
INTRODUCTION Coral reefs worldwide are suffering losses at an alarming rate as a result of anthropogenic climate change. Increased seawater temperatures, even only slightly above long-term maxima, can induce bleaching—the breakdown of the symbiotic relationship between coral hosts and their intracellular photosynthetic dinoflagellates from the family Symbiodiniaceae. Because these symbionts provide the majority of energy required by the coral host, prolonged periods of bleaching can eventually lead to the death of the colony. In the face of rapidly increasing temperatures, new conservation strategies are urgently needed to prevent future mass losses of coral cover, and these benefit from an understanding of the genetic basis of bleaching. RATIONALE Bleaching responses vary within and among coral species; in the reef-building coral Acropora millepora, a commonly distributed species across the Indo-Pacific, these differences have been shown to be at least partly heritable. In principle, therefore, interindividual differences in bleaching should be predictable from genomic data. Here, we demonstrate the feasibility of using a genomics-based approach to predict individual bleaching responses and suggest ways in which this can inform new strategies for coral conservation. RESULTS We first generated a chromosome-scale genome assembly as well as whole-genome sequences for 237 samples collected at 12 reefs distributed across the central Great Barrier Reef during peak bleaching in 2017. We showed that we can reliably impute genotypes in low-coverage sequencing data with a modestly sized reference haplotype panel, demonstrating a cost-effective approach for future large-scale whole-genome sequencing efforts. Very little population structure was detected across the sampled reefs, which was likely the result of the broadcast spawning mode of reproduction in A. millepora. Against this genomic background, we detected unusually old variation at the heat-shock co-chaperone sacsin, which is consistent with long-term balancing selection acting on this gene. Our genomic sequencing approach simultaneously provides a quantitative measure of bleaching and identifies the composition of symbiont species present within individual coral hosts. Testing more than 6.8 million variants for associations with three different measures of bleaching response, no single site reached genome-wide significance, indicating that variation in bleaching response is not due to common loci of large effect. However, a model that incorporates genetic effects estimated from the genome-wide association data, genomic data on relative symbiont species composition, and environmental variables is predictive of individual bleaching phenotypes. CONCLUSION Understanding the genetics of heat and bleaching tolerance will be critical to predict coral adaptation and the future of coral reef ecosystems under climate change. This knowledge also supports both conventional management approaches and the development of new interventions. Our work provides insight into the genetic architecture of bleaching response and serves as a proof of principle for the use of genomic approaches in conservation efforts. We show that a model based on environmental factors, genomic data from the symbiont, and genome-wide association data in the coral host can help distinguish individuals most tolerant to bleaching from those that are most susceptible. These results thus build a foundation toward a genomic predictor of bleaching response in A. millepora and other coral species.
Wei, Yujie, Lin, Dongdong, Xu, Zhanning, Gao, Xiaoman, Zeng, Chaoshu, and Ye, Haihui (2020) A possible role of crustacean cardioactive peptide in regulating immune response in hepatopancreas of mud crab. Frontiers in Immunology, 11. 711.
Crustacean cardioactive peptide (CCAP), a cyclic amidated non-apeptide, is widely found in arthropods. The functions of CCAP have been revealed to include regulation of heart rate, intestinal peristalsis, molting, and osmotic pressure. However, to date, there has not been any report on the possible involvement of CCAP in immunoregulation in crustaceans. In this study, a CCAP precursor (designated as Sp-CCAP) was identified in the commercially important mud crab Scylla paramamosain, which could be processed into four CCAP-associated peptides and one mature peptide (PFCNAFTGC-NH2). Bioinformatics analysis indicated that Sp-CCAP was highly conserved in crustaceans. RT-PCR results revealed that Sp-CCAP was expressed in nerve tissues and gonads, whereas the Sp-CCAP receptor gene (Sp-CCAPR) was expressed in 12 tissues of S. paramamosain, including hepatopancreas. In situ hybridization further showed that an Sp-CCAPR-positive signal is mainly localized in the F-cells of hepatopancreas. Moreover, the mRNA expression level of Sp-CCAPR in the hepatopancreas was significantly up-regulated after lipopolysaccharide (LPS) or polyriboinosinic polyribocytidylic acid [Poly (I:C)] challenge. Meanwhile, the mRNA expression level of Sp-CCAPR, nuclear transcription factor NF-kappa B homologs (Sp-Dorsal and Sp-Relish), member of mitogen-activated protein kinase (MAPK) signaling pathway (Sp-P38), pro-inflammatory cytokines factor (Sp-TNFSF and Sp-IL16), and antimicrobial peptide (Sp-Lysozyme, Sp-ALF, Sp-ALF4, and Sp-ALF5) in the hepatopancreas were all up-regulated after the administration of synthetic Sp-CCAP mature peptide both in vivo and in vitro. The addition of synthetic Sp-CCAP mature peptide in vitro also led to an increase in nitric oxide (NO) concentration and an improved bacterial clearance ability in the hepatopancreas culture medium. The present study suggested that Sp-CCAP signaling system might be involved in the immune responses of S. paramamosain by activating immune molecules on the hepatopancreas. Collectively, our findings shed new light on neuroendocrine-immune regulatory system in arthropods and could potentially provide a new strategy for disease prevention and control for mud crab aquaculture.
Nordborg, F. Mikaela, Jones, Ross J., Oelgemöller, Michael, and Negri, Andrew P. (2020) The effects of ultraviolet radiation and climate on oil toxicity to coral reef organisms – a review. Science of the Total Environment, 720. 137486.
Oil pollution remains a significant local threat to shallow tropical coral reef environments, but the environmental conditions typical of coral reefs are rarely considered in oil toxicity testing and risk assessments. Here we review the effects of three environmental co-factors on petroleum oil toxicity towards coral reef organisms, and show that the impacts of oil pollution on coral reef taxa can be exacerbated by environmental conditions commonly encountered in tropical reef environments. Shallow reefs are routinely exposed to high levels of ultraviolet radiation (UVR), which can substantially increase the toxicity of some oil components through phototoxicity. Exposure to UVR represents the most likely and harmful environmental co-factor reviewed here, leading to an average toxicity increase of 7.2-fold across all tests reviewed. The clear relevance of UVR co-exposure and its strong influence on tropical reef oil toxicity highlights the need to account for UVR as a standard practice in future oil toxicity studies. Indeed, quantifying the influence of UVR on toxic thresholds of oil to coral reef species is essential to develop credible oil spill risk models required for oil extraction developments, shipping management and spill responses in the tropics. The few studies available indicate that co-exposure to elevated temperature and low pH, both within the range of current daily and seasonal fluctuations and/or projected under continued climate change, can increase oil toxicity on average by 3.0- and 1.3-fold, respectively. While all three of the reviewed environmental co-factors have the potential to substantially increase the impacts of oil pollution in shallow reef environments, their simultaneous effects have not been investigated. Assessments of the combined effects of oil pollution, UVR, temperature and low pH will become increasingly important to identify realistic hazard thresholds suitable for future risk assessments over the coming century.
Valero-Rodriguez, J.M., Swearer, S.E., Dempster, T., de Nys, R., and Cole, A.J. (2020) Evaluating the performance of freshwater macroalgae in the bioremediation of nutrient-enriched water in temperate environments. Journal of Applied Phycology, 32. pp. 641-652.
Algal bioremediation can significantly improve the quality of wastewater by assimilating nutrients. However, the efficiency and stability of this approach depends on identifying suitable algae based on their biomass productivity and ability to outcompete less desirable algae. Here, we compare the productivity and competitive ability of three taxa of filamentous macroalgae under the seasonal light and temperature conditions experienced in temperate environments, including extremes of heat and cold. Specific growth rate was greatest for the tropical isolate of Oedogonium under summer conditions (36–40%; P < 0.05); however, it had lower growth under cooler (autumn, winter) conditions than the temperate algae of Stigeoclonium and Hyalotheca. Overall, Stigeoclonium and Hyalotheca had the most stable production across all treatments. A 5-week competition experiment found that each algae grew fastest in monoculture compared with bi-culture and poly-culture treatments. While all three genera showed a considerable level of competitive dominance depending on algae composition and environmental conditions, no single genus outperformed all others under all conditions. Oedogonium was dominant in warmer conditions, Stigeoclonium in cooler conditions (> 90% for both) and, in its absence, Hyalotheca also dominate over Oedogonium. Our results suggest that rather than finding an optimal taxon for all four seasons, the best decision for maximising stable biomass production will require either seasonal rotation of algae, or bi-cultures of the most dominant ones. Further, prioritising competition over production when selecting freshwater algae for wastewater bioremediation is likely to prove the most successful strategy.
Neveux, Nicolas, Nugroho, A.A., Roberts, D.A., Vucko, M.J., and de Nys, R. (2020) Selecting extraction conditions for the production of liquid biostimulants from the freshwater macroalga Oedogonium intermedium. Journal of Applied Phycology. (In Press)
Liquid biostimulants made from macroalgae have traditionally been based on the processing of brown seaweeds collected from the wild. In this study, liquid extracts were produced from the freshwater green macroalga Oedogonium intermedium, cultivated in a land-based system. The first part of the study was aimed at selecting extraction conditions to maximize the liquid yield and the recovery of soluble solids from Oedogonium biomass, which resulted in the selection of a biomass-to-solvent ratio of 5% (w/v), an extraction time of 4 h, and a temperature of 70 °C. These extraction conditions were used in the second part of the study to assess the effect of extraction solvent, across the whole pH range, on root growth of tomato and mung bean seedlings. Root growth of tomato seedlings was highest for the acid extract prepared with 0.05 M HCl, and the alkali extract prepared with 0.01 M KOH. Therefore, these two extracts were further tested in a mung bean assay to determine their auxin-like activity, and were also analyzed to determine their elemental and hormone profiles. The selected acid and alkali extracts, at concentrations of 10% and 2–10% (v/v), respectively, had an auxin-like activity equivalent to 5 × 10−5 M indole-3-butyric acid, with the alkali extract having the highest concentration of auxins (120 ng IAA g−1 dry weight). This study highlights the potential of O. intermedium for the production of liquid extracts with biostimulant activity.
Jones, K., Burgess, G., Budd, A.M., Huerlimann, R., Mashkour, N., and Ariel, E. (2020) Molecular evidence for horizontal transmission of chelonid alphaherpesvirus 5 at green turtle (Chelonia mydas) foraging grounds in Queensland, Australia. PLoS ONE, 15 (1). e0227268.
Fibropapillomatosis (FP) is a marine turtle disease recognised by benign tumours on the skin, eyes, shell, oral cavity and/or viscera. Despite being a globally distributed disease that affects an endangered species, research on FP and its likely causative agent chelonid alphaherpesvirus 5 (ChHV5) in Australia is limited. Here we present improved molecular assays developed for detection of ChHV5, in combination with a robust molecular and phylogenetic analysis of ChHV5 variants. This approach utilised a multi-gene assay to detect ChHV5 in all FP tumors sampled from 62 marine turtles found at six foraging grounds along the Great Barrier Reef. Six distinct variants of ChHV5 were identified and the distribution of these variants was associated with host foraging ground. Conversely, no association between host genetic origin and ChHV5 viral variant was found. Together this evidence supports the hypothesis that marine turtles undergo horizontal transmission of ChHV5 at foraging grounds and are unlikely to be contracting the disease at rookeries, either during mating or vertically from parent to offspring.
Chin, A., Rigby, C., Short, A., and White, W.T. (2020) Verified records of Kuhl's devil ray (Mobula kuhlii) in the Solomon Islands from citizen scientists. Pacific Conservation Biology, 26. pp. 100-101.
Citizen science provides valuable information about species distributions. The Shark Search Indo-Pacific project received photographs of devil rays (Mobula spp.) from the Solomon Islands that were identified as Kuhl’s devil ray (Mobula kuhlii). These records represent new knowledge about the range and distribution of a poorly known species in an undersampled region.
Kyne, Peter M., Jabado, Rima W., Rigby, Cassandra L., Dharmadi, , Gore, Mauvis A., Pollock, Caroline M., Herman, Katelyn B., Cheok, Jessica, Ebert, David A., Simpfendorfer, Colin A., and Dulvy, Nicholas K. (2020) The thin edge of the wedge: extremely high extinction risk in wedgefishes and giant guitarfishes. Aquatic Conservation: marine and freshwater ecosystems, 30 (7). pp. 1337-1361.
The process of understanding the rapid global decline of sawfishes (Pristidae) has revealed great concern for their relatives, the wedgefishes (Rhinidae) and giant guitarfishes (Glaucostegidae), not least because all three families are targeted for their high-value and internationally traded 'white' fins. The objective of this study was to assess the extinction risk of all 10 wedgefishes and six giant guitarfishes by applying the International Union for Conservation of Nature (IUCN) Red List Categories and Criteria, and to summarize the latest understanding of their biogeography and habitat, life history, exploitation, use and trade, and population status. Three of the 10 wedgefish species had not been assessed previously for the IUCN Red List. Wedgefishes and giant guitarfishes have overtaken sawfishes as the most imperilled marine fish families globally, with all but one of the 16 species facing an extremely high risk of extinction through a combination of traits: limited biological productivity; presence in shallow waters overlapping with some of the most intense and increasing coastal fisheries in the world; and overexploitation in target and by-catch fisheries, driven by the need for animal protein and food security in coastal communities and the trade in meat and high-value fins. Two species with very restricted ranges, the clown wedgefish (Rhynchobatus cooki) of the Malay Archipelago and the false shark ray (Rhynchorhina mauritaniensis) of Mauritania, may be very close to extinction. Only the eyebrow wedgefish (Rhynchobatus palpebratus) is not assessed as Critically Endangered, with it occurring primarily in Australia where fishing pressure is low and some management measures are in place. Australia represents a 'lifeboat' for the three wedgefish and one giant guitarfish species occurring there. To conserve populations and permit recovery, a suite of measures will be required that will need to include species protection, spatial management, by-catch mitigation, and harvest and international trade management, all of which will be dependent on effective enforcement.
Grant, Michael I., Smart, Jonathan J., Rigby, Cassandra L., White, William T., Chin, Andrew, Baje, Leontine, and Simpfendorfer, Colin A. (2020) Intraspecific demography of the silky shark (Carcharhinus falciformis): implications for fisheries management. ICES Journal of Marine Science, 77 (1). pp. 241-255.
The silky shark (Carcharhinus falciformis) is one of the most heavily fished tropical shark species globally, and currently there is increasing concern for its conservation status. However, large differences and ambiguity in life history parameter estimates among regions complicates its conservation and fisheries management. Using a Leslie matrix model that incorporated stochastic effects, we analysed the intraspecific demography of C. falciformis using available life history data from seven regions. Among regions, large differences were observed in generation time and age-specific reproductive contributions. Carcharhinus falciformis generally had low resilience to fishing mortality (F) throughout its distribution. Age-at-first-capture and age-at-last-capture management approaches resulted in substantial differences among regions. This was largely influenced by age-at-maturity. However, in scrutinizing some regional life history studies, it is likely that sampling design and methodological differences among regions have resulted in inaccuracies in life history parameter estimates and subsequent demographic attributes. This implies that age and life-stage-dependent management approaches using these possibly inaccurate life history parameters may be inappropriate. We suggest that a greater emphasis needs to be placed on eliminating human sources of error in elasmobranch life history studies to ensure management for wide-ranging species, such as C. falciformis, is most effective.
Barton, Jonathan A., Bourne, David G., Humphrey, Craig, and Hutson, Kate S. (2020) Parasites and coral-associated invertebrates that impact coral health. Reviews in Aquaculture. (In Press)
Globally coral reefs are in decline, largely driven by local anthropogenic pressures combined with broader cumulative impacts from climate change. Coral aquaculture will play an important role in active reef restoration and attempts to preserve some semblance of coral reefs in highly impacted areas. Achieving maximum growth and survivorship of cultured corals is necessary to achieve optimal results. This is not possible without the study of coral pests and diseases which can be detrimental to coral health. Here we review the complex relationships between corals and their associated symbiotic organisms, identify invertebrates that may harm the corals and suggest known management techniques in captivity. Groups considered included acoels (Xenacoelomorpha: Acoela), digeneans (Trematoda: Digenea), polyclads (Rhabditophora: Polycladida), gastropods (Mollusca: Gastropoda), decapods (Malacostraca: Decapoda), copepods (Hexanauplia: Copepoda) and pyrgomatids (Cirripedia: Pyrgomatidae). There are few empirically validated management techniques for coral pests, particularly in terms of large-scale aquaculture, emphasizing the need for further directed research in this area. Information generated through the ornamental trade and hobbyists is valuable to inform future research direction targeted towards captive coral husbandry, reef ecosystem management and restoration strategies.
Anderson, R Charles, Herrera, Miguel, Ilangakoon, Anoukchika D., Koya, K.M., Moazzam, M., Mustika, Putu L., and Sutaria, Dipani N. (2020) Cetacean bycatch in Indian Ocean tuna gillnet fisheries. Endangered Species Research, 41. pp. 39-53.
Pelagic gillnet (driftnet) fisheries account for some 34% of Indian Ocean tuna catches. We combined published results from 10 bycatch sampling programmes (1981−2016) in Australia, Sri Lanka, India and Pakistan to estimate bycatch rates for cetaceans across all Indian Ocean tuna gillnet fisheries. Estimated cetacean bycatch peaked at almost 100 000 ind. yr−1 during 2004−2006, but has declined by over 15% since then, despite an increase in tuna gillnet fishing effort. These fisheries caught an estimated cumulative total of 4.1 million small cetaceans between 1950 and 2018. These bycatch estimates take little or no account of cetaceans caught by gillnet but not landed, of delayed mortality or sub-lethal impacts on cetaceans (especially whales) that escape from gillnets, of mortality associated with ghost nets, of harpoon catches made from gillnetters, or of mortality from other tuna fisheries. Total cetacean mortality from Indian Ocean tuna fisheries may therefore be substantially higher than estimated here. Declining cetacean bycatch rates suggest that such levels of mortality are not sustainable. Indeed, mean small cetacean abundance may currently be 13% of pre-fishery levels. None of these estimates are precise, but they do demonstrate the likely order of magnitude of the issue. Countries with the largest current gillnet catches of tuna, and thus the ones likely to have the largest cetacean bycatch are (in order): Iran, Indonesia, India, Sri Lanka, Pakistan, Oman, Yemen, UAE and Tanzania. These 9 countries together may account for roughly 96% of all cetacean bycatch from tuna gillnet fisheries across the Indian Ocean.
Sheaves, Marcus, Abrantes, Katya, Barnett, Adam, Benham, Claudia, Dale, Patricia, Mattone, Carlo, Sheaves, Alison, Waltham, Nathan, and Bradley, Michael (2020) The consequences of paradigm change and poorly validated science: the example of the value of mangroves to fisheries. Fish and Fisheries. (In Press)
Accuracy in representing, communicating and reporting science is critical to the translation of science into knowledge. Any lack of accuracy degrades the quality and reliability of consequent decisions. One common cause of inaccuracy is the use of superseded paradigmatic concepts with a lack of careful validation. This leads to evidentiary dissonance (an apparent abundance of evidence with little basis in actual reported scientific findings). We illustrate the nature and consequences of evidentiary dissonance using the example of estimates of the value of mangroves to fisheries, which are key motivators of decision‐making around land‐use activities in mangroves systems, mangrove restoration and disturbance offset initiatives. Causes include the use of inappropriate or inaccurate data and inadequate support for reasoning used to develop estimates of fisheries value. Evidentiary dissonance in linking estimates to scientific understanding has produced a citable and cited body of work with tenuous foundations in current ecological understanding, and a body of literature that is likely to lead to unrealistic expectations, misdirected and wasted resources, and perverse management outcomes.
Martins, A. P. B., Heupel, M. R., Bierwagen, S. L., Chin, A., and Simpfendorfer, C. (2020) Diurnal activity patterns and habitat use of juvenile Pastinachus ater in a coral reef flat environment. PLoS ONE, 15 (2). e0228280.
Stingrays are thought to play important ecological roles in coral reef ecosystems. However, little is known about juvenile stingray movement patterns and habitat use in coral reefs. This study used active acoustic telemetry to determine fine-scale diel movement patterns and habitat use of juvenile cowtail stingrays (Pastinachus ater) in a coral reef flat environment. Seven cowtail stingrays (4 males and 3 females) were manually tracked between April and December 2016. Each individual was tracked over 2 days, generating a total of 14 active tracks ranging from 4.91 to 9 h. Specimens moved at an average speed of 2.44 m min-1 ± 0.87 SE, with minimum distances travelled ranging from 546 to 1446 m. Tracking data showed that juvenile cowtail stingrays move in response to tidal cycles, moving faster and in straighter pathways during incoming and outgoing tides. Juvenile cowtail stingrays also showed a strong affinity to sand flat areas and mangrove edge areas. These areas provide food resources and potential refuges for juvenile rays to avoid predators. Coral reef flats were identified as secondary refuge for juveniles during the lowest tides. Future research is necessary to fully unveil the major drivers of juvenile cowtail stingray seasonal and ontogenetic movement patterns and habitat use within coral reef flat environments. This information is important to establish a full understanding of juvenile cowtail stingray ecology, but could also improve management and conservation policies.
O'Brien, Paul A., Tan, Shangjin, Yang, Chentao, Frade, Pedro R., Andreakis, Nikolaos, Smith, Hillary A., Miller, David J., Webster, Nicole S., Zhang, Guojie, and Bourne, David G. (2020) Diverse coral reef invertebrates exhibit patterns of phylosymbiosis. ISME Journal: multidisciplinary journal of microbial ecology. (In Press)
Microbiome assemblages of plants and animals often show a degree of correlation with host phylogeny; an eco-evolutionary pattern known as phylosymbiosis. Using 16S rRNA gene sequencing to profile the microbiome, paired with COI, 18S rRNA and ITS1 host phylogenies, phylosymbiosis was investigated in four groups of coral reef invertebrates (scleractinian corals, octocorals, sponges and ascidians). We tested three commonly used metrics to evaluate the extent of phylosymbiosis: (a) intraspecific versus interspecific microbiome variation, (b) topological comparisons between host phylogeny and hierarchical clustering (dendrogram) of host-associated microbial communities, and (c) correlation of host phylogenetic distance with microbial community dissimilarity. In all instances, intraspecific variation in microbiome composition was significantly lower than interspecific variation. Similarly, topological congruency between host phylogeny and the associated microbial dendrogram was more significant than would be expected by chance across all groups, except when using unweighted UniFrac distance (compared with weighted UniFrac and Bray-Curtis dissimilarity). Interestingly, all but the ascidians showed a significant positive correlation between host phylogenetic distance and associated microbial dissimilarity. Our findings provide new perspectives on the diverse nature of marine phylosymbioses and the complex roles of the microbiome in the evolution of marine invertebrates.
McLeod, I.M., Bostrom Einarsson, L., Creighton, C., D'Anastasi, B., Diggles, B., Dwyer, P.G., Firby, L., Le Port, A., Luongo, A., Martinez-Baena, F., McOrrie, S., Heller-Wagner, G., and Gillies, C.L (2020) Habitat value of Sydney rock oyster (Saccostrea glomerata) reefs on soft sediments. Marine and Freshwater Research, 71 (7). pp. 771-781.
Estimates of the ecological and economic value of ecosystems can provide important information for the prioritisation of conservation and restoration actions. Oyster reefs that were once common in temperate coastal waters have now been largely degraded or lost. Oyster reefs provide a suite of ecological services, including habitat and a food supply for a range of other species. In Australia, there is growing interest in oyster reef restoration, but there are knowledge gaps with regard to their structure and habitat value. Here, we describe the structure of eight remnant Sydney rock oyster (Saccostrea glomerata) reefs and estimate the density, biomass, productivity and composition of mobile macroinvertebrate and infaunal communities associated with them. The oyster reefs had a distinct assemblage of macroinvertebrates, with fivefold higher density of larger ($2 mm) macroinvertebrates, fivefold higher biomass and almost fivefold higher productivity, than that of adjacent bare sediments. The productivity of infaunal communities was twice as high under oyster reefs than in adjacent bare sediments. Therefore, S. glomerata reef restoration is likely to provide important habitat for macroinvertebrate communities and boost local secondary production.
Barton, Jonathan A., Humphrey, Craig, Bourne, David G., and Hutson, Kate S. (2020) Biological controls to manage Acropora-eating flatworms in coral aquaculture. Aquaculture Environment Interactions, 12. pp. 61-66.
Coral aquaculture is expanding to supply the marine ornamental trade and active coral reef restoration. A common pest of Acropora corals is the Acropora-eating flatworm Prosthiostomum acroporae, which can cause colonial mortality at high infestation densities on Acropora spp. We investigated the potential of 2 biological control organisms in marine aquaria for the control of P. acroporae infestations. A. millepora fragments infested with adult polyclad flatworms (5 flatworms fragment(-1)) or single egg clusters laid on Acropora skeleton were cohabited with either sixline wrasse Pseudocheilinus hexataenia or the peppermint shrimp Lysmata vittata and compared to a control (i.e. no predator) to assess their ability to consume P. acroporae at different life stages over 24 h. P. hexataenia consumed 100% of adult flatworms from A. millepora fragments (n = 9; 5 flatworms fragment(-1)), while L. vittata consumed 82.0 +/- 26.36% of adult flatworms (mean +/- SD; n= 20). Pseudocheilinus hexataenia did not consume any Prosthiostomum acroporae egg capsules, while L. vittata consumed 63.67 +/- 43.48% (n = 20) of egg capsules on the Acropora skeletons. Mean handling losses in controls were 5.83% (shrimp system) and 3.50% (fish system) of flatworms and 2.39% (fish system) and 3.50% (shrimp system) of egg capsules. Encounters between L. vittata and P. hexataenia result in predation of P. acroporae on an Acropora coral host and represent viable biological controls for reducing infestations of P. acroporae in aquaculture systems.
Taylor, Brett M., Benkwitt, Cassandra E., Choat, Howard, Clements, Kendall D., Graham, Nicholas A.J., and Meekan, Mark G. (2020) Synchronous biological feedbacks in parrotfishes associated with pantropical coral bleaching. Global Change Biology, 26 (3). pp. 1285-1294.
Biological feedbacks generated through patterns of disturbance are vital for sustaining ecosystem states. Recent ocean warming and thermal anomalies have caused pantropical episodes of coral bleaching, which has led to widespread coral mortality and a range of subsequent effects on coral reef communities. Although the response of many reef-associated fishes to major disturbance events on coral reefs is negative (e.g., reduced abundance and condition), parrotfishes show strong feedbacks after disturbance to living reef structure manifesting as increases in abundance. However, the mechanisms underlying this response are poorly understood. Using biochronological reconstructions of annual otolith (ear stone) growth from two ocean basins, we tested whether parrotfish growth was enhanced following bleaching-related coral mortality, thus providing an organismal mechanism for demographic changes in populations. Both major feeding guilds of parrotfishes (scrapers and excavators) exhibited enhanced growth of individuals after bleaching that was decoupled from expected thermal performance, a pattern that was not evident in other reef fish taxa from the same environment. These results provide evidence for a more nuanced ecological feedback system-one where disturbance plays a key role in mediating parrotfish-benthos interactions. By influencing the biology of assemblages, disturbance can thereby stimulate change in parrotfish grazing intensity and ultimately reef geomorphology over time. This feedback cycle operated historically at within-reef scales; however, our results demonstrate that the scale, magnitude, and severity of recent thermal events are entraining the biological responses of disparate communities to respond in synchrony. This may fundamentally alter feedbacks in the relationships between parrotfishes and reef systems.
Salles, Océane C., Almany, Glenn R., Berumen, Michael L., Jones, Geoffrey P., Saenz-Agudelo, Pablo, Srinivasan, Maya, Thorrold, Simon R., Pujol, Benoit, and Planes, Serge (2020) Strong habitat and weak genetic effects shape the lifetime reproductive success in a wild clownfish population. Ecology Letters, 23 (2). pp. 265-273.
The relative contributions of environmental, maternal and additive genetic factors to the Lifetime reproductive success (LRS) determine whether species can adapt to rapid environmental change. Yet to date, studies quantifying LRS across multiple generations in marine species in the wild are non-existent. Here we used 10-year pedigrees resolved for a wild orange clownfish population from Kimbe Island (PNG) and a quantitative genetic linear mixed model approach to quantify the additive genetic, maternal and environmental contributions to variation in LRS for the self-recruiting portion of the population. We found that the habitat of the breeder, including the anemone species and geographic location, made the greatest contribution to LRS. There were low to negligible contributions of genetic and maternal factors equating with low heritability and evolvability. Our findings imply that our population will be susceptible to short-term, small-scale changes in habitat structure and may have limited capacity to adapt to these changes.
Smallhorn-West, Patrick, Garvin, J.B., Slayback, D.A., DeCarlo, T.M., Gordon, S.E., Fitzgerald, S.H., Halafihi, T., Jones, G.P., and Bridge, T.C.L. (2020) Coral reef annihilation, persistence and recovery at Earth's youngest volcanic island. Coral Reefs. (In Press)
The structure and function of coral reef ecosystems is increasingly compromised by multiple stressors, even in the most remote locations. Severe, acute disturbances such as volcanic eruptions represent extreme events that can annihilate entire reef ecosystems, but also provide unique opportunities to examine ecosystem resilience and recovery. Here, we examine the destruction, persistence and initial recovery of reefs associated with the hydro-magmatic eruption that created Earth's newest landmass, the Hunga Tonga-Hunga Ha'apai volcanic island. Despite extreme conditions associated with the eruption, impacts on nearby reefs were spatially variable. Importantly, even heavily affected reefs showed signs of rapid recovery driven by high recruitment, likely from local refuges. The remote location and corresponding lack of additional stressors likely contribute to the resilience of Hunga's reefs, suggesting that in the absence of chronic anthropogenic stressors, coral reefs can be resilient to one of the largest physical disturbances on Earth.
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