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Tsai CH, Sweatman HPA, Thibaut LM, Connolly SR. Volatility in coral cover erodes niche structure, but not diversity, in reef fish assemblages. Sci Adv 2022; 8:eabm6858. [PMID: 35704577 PMCID: PMC9200288 DOI: 10.1126/sciadv.abm6858] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 05/02/2022] [Indexed: 05/26/2023]
Abstract
The world's coral reefs are experiencing increasing volatility in coral cover, largely because of anthropogenic environmental change, highlighting the need to understand how such volatility will influence the structure and dynamics of reef assemblages. These changes may influence not only richness or evenness but also the temporal stability of species' relative abundances (temporal beta-diversity). Here, we analyzed reef fish assemblage time series from the Great Barrier Reef to show that, overall, 75% of the variance in abundance among species was attributable to persistent differences in species' long-term mean abundances. However, the relative importance of stochastic fluctuations in abundance was higher on reefs that experienced greater volatility in coral cover, whereas it did not vary with drivers of alpha-diversity. These findings imply that increased coral cover volatility decreases temporal stability in relative abundances of fishes, a transformation that is not detectable from static measures of biodiversity.
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Affiliation(s)
- Cheng-Han Tsai
- College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia
- Australian Institute of Marine Science, Townsville MC, QLD 4810, Australia
- Australian Research Council Centre of Excellence for Coral Reef Studies, Townsville, QLD 4811, Australia
| | | | - Loïc M. Thibaut
- School of Mathematics and Statistics, University of New South Wales, Sydney, NSW 2052, Australia
- Centre for Population Genomics, Garvan Institute of Medical Research and UNSW Sydney, Sydney, NSW, Australia
- Centre for Population Genomics, Murdoch Children’s Research Institute, Melbourne, VIC, Australia
| | - Sean R. Connolly
- College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia
- Australian Research Council Centre of Excellence for Coral Reef Studies, Townsville, QLD 4811, Australia
- Smithsonian Tropical Research Institute, Panama, Republic of Panama
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Madin EMP, Madin JS, Harmer AMT, Barrett NS, Booth DJ, Caley MJ, Cheal AJ, Edgar GJ, Emslie MJ, Gaines SD, Sweatman HPA. Latitude and protection affect decadal trends in reef trophic structure over a continental scale. Ecol Evol 2020; 10:6954-6966. [PMID: 32760504 PMCID: PMC7391320 DOI: 10.1002/ece3.6347] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 04/17/2020] [Indexed: 01/02/2023] Open
Abstract
The relative roles of top-down (consumer-driven) and bottom-up (resource-driven) forcing in exploited marine ecosystems have been much debated. Examples from a variety of marine systems of exploitation-induced, top-down trophic forcing have led to a general view that human-induced predator perturbations can disrupt entire marine food webs, yet other studies that have found no such evidence provide a counterpoint. Though evidence continues to emerge, an unresolved debate exists regarding both the relative roles of top-down versus bottom-up forcing and the capacity of human exploitation to instigate top-down, community-level effects. Using time-series data for 104 reef communities spanning tropical to temperate Australia from 1992 to 2013, we aimed to quantify relationships among long-term trophic group population density trends, latitude, and exploitation status over a continental-scale biogeographic range. Specifically, we amalgamated two long-term monitoring databases of marine community dynamics to test for significant positive or negative trends in density of each of three key trophic levels (predators, herbivores, and algae) across the entire time series at each of the 104 locations. We found that trophic control tended toward bottom-up driven in tropical systems and top-down driven in temperate systems. Further, alternating long-term population trends across multiple trophic levels (a method of identifying trophic cascades), presumably due to top-down trophic forcing, occurred in roughly fifteen percent of locations where the prerequisite significant predator trends occurred. Such alternating trophic trends were significantly more likely to occur at locations with increasing predator densities over time. Within these locations, we found a marked latitudinal gradient in the prevalence of long-term, alternating trophic group trends, from rare in the tropics (<5% of cases) to relatively common in temperate areas (~45%). Lastly, the strongest trends in predator and algal density occurred in older no-take marine reserves; however, exploitation status did not affect the likelihood of alternating long-term trophic group trends occurring. Our data suggest that the type and degree of trophic forcing in this system are likely related to one or more covariates of latitude, and that ecosystem resiliency to top-down control does not universally vary in this system based on exploitation level.
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Affiliation(s)
- Elizabeth M. P. Madin
- Department of Biological SciencesMacquarie UniversitySydneyNSWAustralia
- School of Life SciencesUniversity of Technology SydneySydneyNSWAustralia
- Hawai'i Institute of Marine BiologyUniversity of Hawai'iKane'oheHIUSA
| | - Joshua S. Madin
- Department of Biological SciencesMacquarie UniversitySydneyNSWAustralia
- Hawai'i Institute of Marine BiologyUniversity of Hawai'iKane'oheHIUSA
| | - Aaron M. T. Harmer
- Department of Biological SciencesMacquarie UniversitySydneyNSWAustralia
- School of Natural and Computational SciencesMassey UniversityAucklandNew Zealand
| | - Neville S. Barrett
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTASAustralia
| | - David J. Booth
- School of Life SciencesUniversity of Technology SydneySydneyNSWAustralia
| | - M. Julian Caley
- School of Mathematical SciencesQueensland University of TechnologyBrisbaneQLDAustralia
- Australian Research Council Centre of Excellence for Mathematical and Statistical FrontiersThe University of MelbourneParkvilleVICAustralia
| | | | - Graham J. Edgar
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTASAustralia
| | | | - Steven D. Gaines
- Bren School of Environmental Science and ManagementUniversity of CaliforniaSanta BarbaraCAUSA
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Emslie MJ, Cheal AJ, MacNeil MA, Miller IR, Sweatman HPA. Reef fish communities are spooked by scuba surveys and may take hours to recover. PeerJ 2018; 6:e4886. [PMID: 29844998 PMCID: PMC5971101 DOI: 10.7717/peerj.4886] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 05/11/2018] [Indexed: 11/20/2022] Open
Abstract
Ecological monitoring programs typically aim to detect changes in the abundance of species of conservation concern or which reflect system status. Coral reef fish assemblages are functionally important for reef health and these are most commonly monitored using underwater visual surveys (UVS) by divers. In addition to estimating numbers, most programs also collect estimates of fish lengths to allow calculation of biomass, an important determinant of a fish’s functional impact. However, diver surveys may be biased because fishes may either avoid or are attracted to divers and the process of estimating fish length could result in fish counts that differ from those made without length estimations. Here we investigated whether (1) general diver disturbance and (2) the additional task of estimating fish lengths affected estimates of reef fish abundance and species richness during UVS, and for how long. Initial estimates of abundance and species richness were significantly higher than those made on the same section of reef after diver disturbance. However, there was no evidence that estimating fish lengths at the same time as abundance resulted in counts different from those made when estimating abundance alone. Similarly, there was little consistent bias among observers. Estimates of the time for fish taxa that avoided divers after initial contact to return to initial levels of abundance varied from three to 17 h, with one group of exploited fishes showing initial attraction to divers that declined over the study period. Our finding that many reef fishes may disperse for such long periods after initial contact with divers suggests that monitoring programs should take great care to minimise diver disturbance prior to surveys.
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Affiliation(s)
- Michael J Emslie
- Australian Institute of Marine Science, Townsville, QLD, Australia
| | - Alistair J Cheal
- Australian Institute of Marine Science, Townsville, QLD, Australia
| | - M Aaron MacNeil
- Department of Biology, Dalhousie University, Halifax, NS, Canada
| | - Ian R Miller
- Australian Institute of Marine Science, Townsville, QLD, Australia
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Osborne K, Thompson AA, Cheal AJ, Emslie MJ, Johns KA, Jonker MJ, Logan M, Miller IR, Sweatman HPA. Delayed coral recovery in a warming ocean. Glob Chang Biol 2017; 23:3869-3881. [PMID: 28485822 DOI: 10.1111/gcb.13707] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 03/11/2017] [Accepted: 03/14/2017] [Indexed: 05/13/2023]
Abstract
Climate change threatens coral reefs across the world. Intense bleaching has caused dramatic coral mortality in many tropical regions in recent decades, but less obvious chronic effects of temperature and other stressors can be equally threatening to the long-term persistence of diverse coral-dominated reef systems. Coral reefs persist if coral recovery rates equal or exceed average rates of mortality. While mortality from acute destructive events is often obvious and easy to measure, estimating recovery rates and investigating the factors that influence them requires long-term commitment. Coastal development is increasing in many regions, and sea surface temperatures are also rising. The resulting chronic stresses have predictable, adverse effects on coral recovery, but the lack of consistent long-term data sets has prevented measurement of how much coral recovery rates are actually changing. Using long-term monitoring data from 47 reefs spread over 10 degrees of latitude on Australia's Great Barrier Reef (GBR), we used a modified Gompertz equation to estimate coral recovery rates following disturbance. We compared coral recovery rates in two periods: 7 years before and 7 years after an acute and widespread heat stress event on the GBR in 2002. From 2003 to 2009, there were few acute disturbances in the region, allowing us to attribute the observed shortfall in coral recovery rates to residual effects of acute heat stress plus other chronic stressors. Compared with the period before 2002, the recovery of fast-growing Acroporidae and of "Other" slower growing hard corals slowed after 2002, doubling the time taken for modest levels of recovery. If this persists, recovery times will be increasing at a time when acute disturbances are predicted to become more frequent and intense. Our study supports the need for management actions to protect reefs from locally generated stresses, as well as urgent global action to mitigate climate change.
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Affiliation(s)
- Kate Osborne
- Australian Institute of Marine Science, Townsville MC, QLD, Australia
| | - Angus A Thompson
- Australian Institute of Marine Science, Townsville MC, QLD, Australia
| | - Alistair J Cheal
- Australian Institute of Marine Science, Townsville MC, QLD, Australia
| | - Michael J Emslie
- Australian Institute of Marine Science, Townsville MC, QLD, Australia
| | - Kerryn A Johns
- Australian Institute of Marine Science, Townsville MC, QLD, Australia
| | - Michelle J Jonker
- Australian Institute of Marine Science, Townsville MC, QLD, Australia
| | - Murray Logan
- Australian Institute of Marine Science, Townsville MC, QLD, Australia
| | - Ian R Miller
- Australian Institute of Marine Science, Townsville MC, QLD, Australia
| | - Hugh P A Sweatman
- Australian Institute of Marine Science, Townsville MC, QLD, Australia
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Babcock RC, Dambacher JM, Morello EB, Plagányi ÉE, Hayes KR, Sweatman HPA, Pratchett MS. Assessing Different Causes of Crown-of-Thorns Starfish Outbreaks and Appropriate Responses for Management on the Great Barrier Reef. PLoS One 2016; 11:e0169048. [PMID: 28036360 PMCID: PMC5201292 DOI: 10.1371/journal.pone.0169048] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 12/09/2016] [Indexed: 11/22/2022] Open
Abstract
The crown-of-thorns starfish Acanthaster planci (COTS) has contributed greatly to declines in coral cover on Australia's Great Barrier Reef, and remains one of the major acute disturbances on Indo-Pacific coral reefs. Despite uncertainty about the underlying causes of outbreaks and the management responses that might address them, few studies have critically and directly compared competing hypotheses. This study uses qualitative modelling to compare hypotheses relating to outbreak initiation, explicitly considering the potential role of positive feedbacks, elevated nutrients, and removal of starfish predators by fishing. When nutrients and fishing are considered in isolation, the models indicate that a range of alternative hypotheses are capable of explaining outbreak initiation with similar levels of certainty. The models also suggest that outbreaks may be caused by multiple factors operating simultaneously, rather than by single proximal causes. As the complexity and realism of the models increased, the certainty of outcomes decreased, but key areas that require further research to improve the structure of the models were identified. Nutrient additions were likely to result in outbreaks only when COTS larvae alone benefitted from nutrients. Similarly, the effects of fishing on the decline of corals depended on the complexity of interactions among several categories of fishes. Our work suggests that management approaches which seek to be robust to model structure uncertainty should allow for multiple potential causes of outbreaks. Monitoring programs can provide tests of alternative potential causes of outbreaks if they specifically monitor all key taxa at reefs that are exposed to appropriate combinations of potential causal factors.
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Affiliation(s)
- Russell C. Babcock
- CSIRO Oceans and Atmosphere, Brisbane, Qld, Australia
- School of Plant Biology, University of Western Australia, Crawley, WA, Australia
| | | | | | | | - Keith R. Hayes
- CSIRO Computational Informatics, Castray Esplanade, Hobart, TAS, Australia
| | - Hugh P. A. Sweatman
- Australian Institute of Marine Science, PMB 3, Townsville MC, Qld, Australia
| | - Morgan S. Pratchett
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD, Australia
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Emslie MJ, Logan M, Williamson DH, Ayling AM, MacNeil MA, Ceccarelli D, Cheal AJ, Evans RD, Johns KA, Jonker MJ, Miller IR, Osborne K, Russ GR, Sweatman HPA. Expectations and Outcomes of Reserve Network Performance following Re-zoning of the Great Barrier Reef Marine Park. Curr Biol 2015; 25:983-92. [PMID: 25819564 DOI: 10.1016/j.cub.2015.01.073] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2014] [Revised: 12/16/2014] [Accepted: 01/30/2015] [Indexed: 11/25/2022]
Abstract
Networks of no-take marine reserves (NTMRs) are widely advocated for preserving exploited fish stocks and for conserving biodiversity. We used underwater visual surveys of coral reef fish and benthic communities to quantify the short- to medium-term (5 to 30 years) ecological effects of the establishment of NTMRs within the Great Barrier Reef Marine Park (GBRMP). The density, mean length, and biomass of principal fishery species, coral trout (Plectropomus spp., Variola spp.), were consistently greater in NTMRs than on fished reefs over both the short and medium term. However, there were no clear or consistent differences in the structure of fish or benthic assemblages, non-target fish density, fish species richness, or coral cover between NTMR and fished reefs. There was no indication that the displacement and concentration of fishing effort reduced coral trout populations on fished reefs. A severe tropical cyclone impacted many survey reefs during the study, causing similar declines in coral cover and fish density on both NTMR and fished reefs. However, coral trout biomass declined only on fished reefs after the cyclone. The GBRMP is performing as expected in terms of the protection of fished stocks and biodiversity for a developed country in which fishing is not excessive and targets a narrow range of species. NTMRs cannot protect coral reefs directly from acute regional-scale disturbance but, after a strong tropical cyclone, impacted NTMR reefs supported higher biomass of key fishery-targeted species and so should provide valuable sources of larvae to enhance population recovery and long-term persistence.
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Affiliation(s)
- Michael J Emslie
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, Townsville, QLD 4810, Australia.
| | - Murray Logan
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, Townsville, QLD 4810, Australia
| | - David H Williamson
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia; College of Marine and Environmental Sciences, James Cook University, Townsville, QLD 4811, Australia
| | - Anthony M Ayling
- Sea Research, 20 Rattray Avenue, Hideaway Bay, QLD 4800, Australia
| | - M Aaron MacNeil
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, Townsville, QLD 4810, Australia
| | - Daniela Ceccarelli
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia
| | - Alistair J Cheal
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, Townsville, QLD 4810, Australia
| | - Richard D Evans
- Department of Parks and Wildlife, 17 Dick Perry Avenue, Kensington, Perth, WA 6151, Australia; Oceans Institute, University of Western Australia, Crawley, WA 6009, Australia
| | - Kerryn A Johns
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, Townsville, QLD 4810, Australia
| | - Michelle J Jonker
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, Townsville, QLD 4810, Australia
| | - Ian R Miller
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, Townsville, QLD 4810, Australia
| | - Kate Osborne
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, Townsville, QLD 4810, Australia
| | - Garry R Russ
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia; College of Marine and Environmental Sciences, James Cook University, Townsville, QLD 4811, Australia
| | - Hugh P A Sweatman
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, Townsville, QLD 4810, Australia
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Affiliation(s)
- Loïc M. Thibaut
- School of Marine and Tropical Biology, and ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811 Australia
| | - Sean R. Connolly
- School of Marine and Tropical Biology, and ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811 Australia
| | - Hugh P. A. Sweatman
- Australian Institute of Marine Science, PMB 3, Townsville MC, Queensland 4810 Australia
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Wilson SK, Burgess SC, Cheal AJ, Emslie M, Fisher R, Miller I, Polunin NVC, Sweatman HPA. Habitat utilization by coral reef fish: implications for specialists vs. generalists in a changing environment. J Anim Ecol 2007; 77:220-8. [PMID: 18081778 DOI: 10.1111/j.1365-2656.2007.01341.x] [Citation(s) in RCA: 193] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
1. The impact of environmental disturbance and habitat loss on associated species is expected to be dependent on a species' level of specialization. We examined habitat use and specialization of coral reef fish from the diverse and ecologically important family Pomacentridae, and determined which species are susceptible to declines in coral cover due to disturbance induced by crown-of-thorns seastar (COTS, Acanthaster planci L.). 2. A high proportion of pomacentrid species live in association with live coral as adults (40%) or juveniles (53%). Adults of many species had strong affiliations with branching corals, while juveniles favoured plating growth forms, reflecting the sizes of refuge provided by coral types. 3. Juveniles of species that associated with coral had narrower niche breadths than adult conspecifics, due to associations with specific coral types. The especially high coral association and narrower niche breadth of juveniles suggest that the presence of live coral is crucial for many species during early life history, and that disturbance-induced coral loss may have serious flow-on effects on adult abundance. 4. Microhabitat availability was a poor predictor of fish species abundance. Significant correlations between coverage of coral types and abundance of five adults and two juvenile species were detected; however, these relationships explained <35% and <10% of the variation in abundance of adult and juvenile species, respectively. 5. Niche breadth explained 74% of the variation in species' mean response to coral decline and it is clear that disturbance has a greater impact on resource specialists, suggesting that increasing frequency and intensity of coral loss will cause reef fish communities to become dominated by habitat generalists at the expense of coral-dwelling specialists.
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Affiliation(s)
- Shaun K Wilson
- School of Marine Science & Technology, University of Newcastle, Newcastle-upon-Tyne, NE1 7RU, UK.
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Sweatman HPA. A Field Study of the Predatory Behavior and Feeding Rate of a Piscivorous Coral Reef Fish, the Lizardfish Synodus englemani. COPEIA 1984. [DOI: 10.2307/1445051] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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