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The Great Barrier Reef and its catchments. Primary COTS outbreaks tend to occur 

The Great Barrier Reef and its catchments. Primary COTS outbreaks tend to occur 

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Article
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In this paper, we postulate a unique environmental triggering sequence for primary outbreaks of crown-of-thorns starfish (COTS, Acanthaster planci) on the central Great Barrier Reef (GBR, Australia). Notably, we extend the previous terrestrial runoff hypothesis, viz. nutrient-enriched terrestrial runoff→elevated phytoplankton 'bloom' concentrations...

Citations

... Collectively, and when coupled with high rates of self-recruitment (Wooldridge & Brodie, 2015), this would suggest that higher densities of putative predators, ranging from planktivorous fishes that feed on gametes and/or larvae (Cowan et al., 2016;Cowan et al., 2017;Cowan et al., 2020) to larger benthic feeding fishes within no-take marine reserves (Emslie et al., 2015;Emslie et al., 2020), may serve to suppress populations and perhaps even prevent localized population irruptions. However, explicit research is required to establish the relative importance of different predatory species and at different life-stages, based on their capacity to regulate larval supply, settlement, and post-settlement survivorship of COTS. ...
Article
• Spatial and temporal stochasticity in the abundance and population dynamics of crown-of-thorns starfish (COTS; Acanthaster spp.) highlight the critical need for improved knowledge of demographic variability within and among populations. • This study compared the prevalence (proportion of individuals) and severity (extent of damage) of injuries in adult COTS between contrasting fisheries management zones in Australia's Great Barrier Reef, explicitly testing whether injuries are more prevalent or severe on reefs where fishing is not permitted. • Prevalence of sublethal injuries was significantly higher for COTS collected from reefs within Marine National Park Zones, where fishing is effectively prohibited, versus Conservation Park Zones or Habitat Protection Zones, where fishing is permitted, but regulated. This finding is consistent with the notion that predation rates on COTS are higher within reef habitats where fishing is prohibited, presumably due to the bigger size or higher abundance of predatory fishes. • Severity was predominantly low among the injured starfish and there was no significant difference between management zones. Nevertheless, there was a higher frequency of individuals with between one and three injured arms in no-take reefs compared to those from reefs that were open to fishing. • Prevalence and severity of sublethal injuries was higher in medium-sized COTS (11–30 cm diameter) compared to larger COTS (>30 cm diameter). • This study adds to existing evidence that established networks of marine reserves can have benefits beyond conservation and fisheries management, including potential reductions in the likelihood of devastating population irruptions of COTS and mitigation of further coral loss.
... Elevated food supply (Brodie et al., 2005), anthropogenic eutrophication of seawater (Lucas, 1973;Birkeland, 1982;Fabricius et al., 2010), reduced predation pressure due to overfishing (Cowan et al., 2016) have been associated with increased larval survival. Notably, the geographical dispersal of COTS plays an important role in the formation of secondary outbreaks of COTS (Pratchett, 2005;Yasuda et al., 2009;Wooldridge and Brodie, 2015;Tusso et al., 2016), given that the duration of the planktonic larval stage (PLS) ranges between 9 and 42 days . Weak or variable longshore currents may promote strong larval retention or limited dispersal, which are likely to give rise to primary outbreaks (Pratchett, 2005;Wooldridge and Brodie, 2015). ...
... Notably, the geographical dispersal of COTS plays an important role in the formation of secondary outbreaks of COTS (Pratchett, 2005;Yasuda et al., 2009;Wooldridge and Brodie, 2015;Tusso et al., 2016), given that the duration of the planktonic larval stage (PLS) ranges between 9 and 42 days . Weak or variable longshore currents may promote strong larval retention or limited dispersal, which are likely to give rise to primary outbreaks (Pratchett, 2005;Wooldridge and Brodie, 2015). However, strong directional longshore currents increase the likelihood of inter-reef dispersal, which leads to outbreaks once they become established (Wooldridge and Brodie, 2015). ...
... Weak or variable longshore currents may promote strong larval retention or limited dispersal, which are likely to give rise to primary outbreaks (Pratchett, 2005;Wooldridge and Brodie, 2015). However, strong directional longshore currents increase the likelihood of inter-reef dispersal, which leads to outbreaks once they become established (Wooldridge and Brodie, 2015). The multiple factors that lead to increased COTS larval survival rates remain unclear, and they may show spatial differences among distinct areas in the Indo-Pacific region. ...
Article
Full-text available
The coral-eating crown-of-thorns starfish (COTS; Acanthaster spp.) play a major role in coral reef degradation in the Indo-Pacific region. However, the impacts of environmental factors on the phylogenetic and genetic characteristics of COTS in the northern Indo-Pacific convergence region remains unclear. We used mitochondrial DNA (mtDNA) and microsatellite markers to analyze the phylogenetic relationship, demographic history, genetic diversity and genetic structure of COTS in the South China Sea (SCS) and explored the impact of environmental factors on historical population expansion, genetic differentiation and larval dispersal. There was a clear signature of a population expansion in the SCS using the mtDNA marker. According to microsatellite loci analysis, COTS have high genetic diversity in the SCS. STRUCTURE analysis indicated that COTS in the Pacific Ocean can be divided into four subgroups: the SCS, Western Pacific, Pacific equatorial current affected zone, and Pacific insular atolls populations in the Pacific Ocean. F st-statistical analysis revealed positive correlations between the F st values and geographic isolation for all sampling sites. Additionally, there were no clear associations between the F st values and chlorophyll a concentrations among coral reefs in the SCS; however, there were significant positive associations between the F st values and particulate organic carbon (POC) concentrations within small geographic distances. These results suggest that COTS underwent historical population expansion after the Last Glacial Maximum, possibly followed by coral population expansion. The genetic structure of COTS populations may have been shaped by distinct nutrient concentrations, particularly those of POC, over small geographic distances. Moreover, ocean currents provide a potential dispersal mechanism for COTS larvae in the SCS. This study demonstrates that environmental and oceanographic factors play important roles in shaping the genetic characteristics and larval dispersal of COTS populations in the northern Indo-Pacific convergence region.
... As such, there are several specific research questions that have been posed to assess current limitations and potential advances in the methods used to sample and monitor COTS, across all life stages (Table 6). Management actions to minimize fishing impacts (largely through the increasing establishment of no-take marine protected areas) and to improve water quality (by minimizing runoff of sediments, nutrients, and pollutants) also attract continued attention, because they represent no-regret strategies that contribute to the increased resilience of reef ecosystems (e.g., Fabricius et al., 2010;McCook et al., 2010;Wooldridge and Brodie, 2015) and may ultimately moderate the incidence or severity of population irruptions of COTS (Sweatman, 2008;Wooldridge and Brodie, 2015;Westcott et al., 2020). There is some evidence linking the reduction of fishing pressure via the establishment of no-take marine reserves to the effective suppression of population irruptions of COTS (Dulvy et al., 2004;Sweatman, 2008;Vanhatalo et al., 2016). ...
... As such, there are several specific research questions that have been posed to assess current limitations and potential advances in the methods used to sample and monitor COTS, across all life stages (Table 6). Management actions to minimize fishing impacts (largely through the increasing establishment of no-take marine protected areas) and to improve water quality (by minimizing runoff of sediments, nutrients, and pollutants) also attract continued attention, because they represent no-regret strategies that contribute to the increased resilience of reef ecosystems (e.g., Fabricius et al., 2010;McCook et al., 2010;Wooldridge and Brodie, 2015) and may ultimately moderate the incidence or severity of population irruptions of COTS (Sweatman, 2008;Wooldridge and Brodie, 2015;Westcott et al., 2020). There is some evidence linking the reduction of fishing pressure via the establishment of no-take marine reserves to the effective suppression of population irruptions of COTS (Dulvy et al., 2004;Sweatman, 2008;Vanhatalo et al., 2016). ...
Article
Abstract. Crown-of-thorns sea stars (Acanthaster sp.) are among the most studied coral reef organisms, owing to their propensity to undergo major population irruptions, which contribute to significant coral loss and reef degradation throughout the Indo-Pacific. However, there are still important knowledge gaps pertaining to the biology, ecology, and management of Acanthaster sp. Renewed efforts to advance understanding and management of Pacific crown-of-thorns sea stars (Acanthaster sp.) on Australia’s Great Barrier Reef require explicit consideration of relevant and tractable knowledge gaps. Drawing on established horizon scanning methodologies, this study identified contemporary knowledge gaps by asking active and/or established crown-of-thorns sea star researchers to pose critical research questions that they believe should be addressed to improve the understanding and management of crown-of-thorns sea stars on the Great Barrier Reef. A total of 38 participants proposed 246 independent research questions, organized into 7 themes: feeding ecology, demography, distribution and abundance, predation, settlement, management, and environmental change. Questions were further assigned to 48 specific topics nested within the 7 themes. During this process, redundant questions were removed, which reduced the total number of distinct research questions to 172. Research questions posed were mostly related to themes of demography (46 questions) and management (48 questions). The dominant topics, meanwhile, were the incidence of population irruptions (16 questions), feeding ecology of larval sea stars (15 questions), effects of elevated water temperature on crown-of-thorns sea stars (13 questions), and predation on juveniles (12 questions). While the breadth of questions suggests that there is considerable research needed to improve understanding and management of crown-of-thorns sea stars on the Great Barrier Reef, the predominance of certain themes and topics suggests a major focus for new research while also providing a roadmap to guide future research efforts
... Eutrophication can result in reef degradation and overall reduced coral biodiversity; increased vulnerability of corals to thermal stress leading to coral bleaching (Burkepile et al., 2020;Wooldridge, 2009); increased presence of macroalgae (which can effect coral diversity and/or coral larval recruitment) (D' Angelo and Wiedenmann, 2014); and physical reef damage from the coral eating Crown-of-Thorns starfish (CoTS) (Brodie et al., 2019) is considered one of the major causes of coral death in the GBR (Brodie et al., 2019;De'Ath et al., 2012;Osborne et al., 2011). CoTS outbreaks are estimated to have increased from one in 50-80 years to one every 15 years and these outbreaks may be associated with increased phytoplankton availability (on which larvae feed) because of excess nutrients (Fabricius et al., 2010;Pratchett et al., 2017;Wooldridge and Brodie, 2015). ...
Article
Measuring stream pollutant loads across the Great Barrier Reef (GBR) catchment area (GBRCA) is challenging due to the spatial extent, climate variability, changing land use and evolving land management practices, and cost. Thus, models are used to estimate baseline pollutant loads. The eWater Source modelling framework is coupled with agricultural paddock scale models and the GBR Dynamic SedNet plugin to simulate dissolved inorganic nitrogen (DIN) generation and transport processes across the GBRCA. Catchment scale monitoring of flow and loads are used to calibrate the models, and performance is assessed qualitatively and quantitatively. Modelling indicates almost half (47%) of the total modelled DIN load exported to the GBR lagoon is from the Wet Tropics, and almost half of the total modelled DIN load is from sugarcane areas. We demonstrate that using locally developed, customised models coupled with a complementary monitoring program can produce reliable estimates of pollutant loads.
... The transport of dissolved nutrients in sediments is a major concern in the Wet Tropics. It exacerbates eutrophication in adjacent waterways and the Reef and increases numbers of Crown of Thorns starfish, the larvae from which can rapidly grow in nutrient-rich waters, causing significant damage to coral reefs (Wooldridge & Brodie, 2015). Over the last 27 years, coral cover has declined by 50% for the entire GBR and by 70% along the central and southern GBR (Kroon et al., 2016). ...
Article
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Poor water quality caused by intensive sugarcane farming has been among the main causes of coastal degradation around the Great Barrier Reef (GBR). Despite regulations and incentives, water quality in the GBR has yet to reach government targets, and there is an urgent need to investigate alternative management approaches. In this study, we have employed a social-ecological approach to understand farmers' attitudes to existing nutrient and sediment management approaches, assess farmers' perceptions of managing coastal wetlands to ameliorate agricultural run-off, and propose how these findings could inform integrative policy development for the GBR. We conducted semi-structured interviews with sugarcane farmers in the Wet Tropics to understand perceptions of ecosystem services, coastal wetlands and industry challenges. We linked our analysis of key issues of concern to farmers with broader environmental and land use issues and have outlined future policy considerations in the face of socio-economic and climatic change. Our conclusions emphasise the need to rethink future land tenure in low-lying areas of North Queensland, the importance of considering ecosystem services provided by coastal wetlands in policy models and the need for a payments for ecosystem services (PES) model to safeguard the future of the GBR.
... It produces carbon dioxide during production and degradation. Fourthly, the direct or indirect consumption of fossil fuels (mainly agricultural diesel oil) used by the agricultural machinery; fifthly, in agricultural production, ploughing has broken the soil organic carbon pool, and a large amount of organic carbon is lost to the air, resulting in carbon emissions; sixthly, carbon release from indirect consumption of fossil fuels by electricity during irrigation [19]. ...
Article
Full-text available
With the change of social economic system and the rapid growth of agricultural economy in China, the amount of agricultural energy consumption and carbon dioxide emissions has increased dramatically. Based on the estimation of agricultural carbon dioxide emissions from 1991 to 2018 in China, this paper uses EKC model to analyze economic growth and agricultural carbon dioxide emissions. The Kaya method is used to decompose the factors affecting agricultural carbon dioxide emissions. The experimental results show that there is a co-integration relationship between economic growth and the total intensity of agricultural carbon emissions, and between economic growth and the intensity of carbon emissions caused by five types of carbon sources: fertilizer, pesticide, agricultural film, agricultural diesel oil and tillage. Economic growth is the main driving factor of agricultural carbon dioxide emissions. In addition, technological progress has a strong role in promoting carbon emission reduction, but it has a certain randomness. However, the impact of energy consumption structure and population size on carbon emissions is not obvious.
... Environmental conditions, such as elevated phytoplankton concentrations and low current velocities, potentially combined with a lack of predators, are thought to contribute to the initiation of COTS outbreaks (e.g. K. E. Fabricius, Okaji, & De'ath, 2010;Sweatman, 2008;Wooldridge & Brodie, 2015). However, the relative contribution of each of these drivers to the dynamics of COTS is still debated (R. C. Babcock, Milton, & Pratchett, 2016;Morgan S. Pratchett, Caballes, et al., 2017). ...
Technical Report
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The NESP COTS Regional Scale Modelling work aimed to build on two existing advanced coral-COTS community models (CoCoNet and ReefMod-GBR) which have been widely tested and used on the GBR. The goal of this work was to incorporate descriptions of the management processes implemented in the Expanded COTS Control Program, and to assess the performance of a range of alternative regional strategies on outbreak dynamics.
... The COTS spawning period is mainly from November to February , which coincides with this period. The strongest correlation between water quality and COTS outbreaks has been found in the COTS initiation area, also called the 'initiation box' between Cairns and Lizard Island (Logan et al., 2014;Wooldridge & Brodie, 2015; Figure 4). This area of periodic nutrient enrichment linked to river discharge from the Wet Tropics rivers is believed to be the initiation point of the four historic waves of COTS outbreaks in the GBR (Wooldridge & Brodie, 2015). ...
... The strongest correlation between water quality and COTS outbreaks has been found in the COTS initiation area, also called the 'initiation box' between Cairns and Lizard Island (Logan et al., 2014;Wooldridge & Brodie, 2015; Figure 4). This area of periodic nutrient enrichment linked to river discharge from the Wet Tropics rivers is believed to be the initiation point of the four historic waves of COTS outbreaks in the GBR (Wooldridge & Brodie, 2015). It has recently been suggested that nutrient levels on mid-shelf reefs are sufficiently elevated during flood plumes to also promote the spread of secondary outbreaks . ...
... xiii The debate over whether more frequent COTS outbreaks in the central GBR are partially caused by nutrient runoff from agricultural activities in the Wet Tropics and Burdekin regions is unresolved Wooldridge & Brodie, 2015) and other factors including the loss of the predators on various life stages of COTS may also influence outbreaks. It has been demonstrated that oceanographic conditions associated with the ENSO cycle (Hock et al., 2014) may also play a part in this region, and Wooldridge & Brodie (2015) have also confirmed that both nutrient enrichment from river runoff and connectivity due to ENSO conditions are important in initiating outbreaks. ...
Preprint
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Synthesis report on most recent research on crown-of-thorns starfish, innovations on monitoring outbreaks and improving efficiency of management strategies, to control COTS outbreaks on the Great Barrier Reef
... Reduced water quality in inshore areas of the GBR Marine Park is a result of the increased loads of fine sediment, nutrients, and pesticides discharged from land use changes in the GBR catchment (Brodie and Fabricius, 2008;Kroon et al., 2012). Specifically, terrestrially-sourced dissolved inorganic nitrogen (DIN) may be linked to increased frequency of CoTS through proliferation of phytoplankton as larval food (Fabricius et al., 2010;Wooldridge and Brodie, 2015;Brodie et al., 2017), and to increased susceptibility of scleractinian coral to bleaching and disease prevalence (Wooldridge and Done, 2009;Wiedenmann et al., 2013;Morris et al., 2019). River runoff reduces WQ by affecting parameters such as light availability and salinity, which are drivers of reef health (De'ath and Fabricius, 2008;Fabricius et al., 2013Fabricius et al., , 2016. ...
Article
Full-text available
Coral bleaching, cyclones, outbreaks of crown-of-thorns seastar, and reduced water quality (WQ) threaten the health and resilience of coral reefs. The cumulative impacts from multiple acute and chronic stressors on "reef State" (i.e., total coral cover) and "reef Performance" (i.e., the deviation from expected rate of total coral cover increase) have rarely been assessed simultaneously, despite their management relevance. We evaluated the dynamics of coral cover (total and per morphological groups) in the Central and Southern Great Barrier Reef over 25 years, and identified and compared the main environmental drivers of State and Performance at the reef level (i.e. based on total coral cover) and per coral group. Using a combination of 25 environmental metrics that consider both the frequency and magnitude of impacts and their lagged effects, we find that the stressors that correlate with State differed from those correlating with Performance. Importantly, we demonstrate that WQ metrics better predict Performance than State. Further, inter-annual dynamics in WQ (here available for a subset of the data) improved the explanatory power of WQ metrics on Performance over long-term WQ averages. The lagged effects of cumulative acute stressors, and to a lesser extent poor water quality, correlated negatively with the Performance of some but not all coral groups. Tabular Acropora and branching non-Acropora were the most affected by water quality demonstrating that group-specific approaches aid in the interpretation of monitoring data and can be crucial for the detection of the impact of chronic pressures. We highlight the complexity of coral reef dynamics and the need of evaluating Performance metrics in order to prioritise local management interventions.
... 16.9°S)dubbed the 'CoTS outbreak initiation zone'(Fig. 1a;Pratchett et al. 2014;Wooldridge and Brodie 2015). Monthly samples (around the middle of each month, except for December, which was sampled at the end of the first week for each spawning season) of 10-68 starfish were collected from reefs between Palfrey and South Island in the Lizard Island group(Fig. ...
Article
Full-text available
Population outbreaks of the coral-eating crown-of-thorns starfish (CoTS) have resulted in extensive coral mortality on reefs in the Indo-Pacific region and is considered one of the major contributors of significant declines in coral cover in Australia’s Great Barrier Reef (GBR). Effective management of CoTS outbreaks rely on improved understanding of the drivers of individual and population-level differences in reproductive patterns, particularly those factors that may contribute to step-changes in reproductive success, such as the timing and synchronicity of spawning. This study investigated gametogenesis and spawning patterns in a persistent population of CoTS at one reef within the putative initiation zone where outbreaks appear to start in the GBR. We examined variation in the progression of gametogenesis and spawning patterns over two distinct spawning seasons (2013–2014, 2014–2015), using a variety of methods: macroscopic examination of gonads, assessment of monthly changes in the gonadosomatic index, analysis of histological sections of ovaries and testes, and comparison of the size-frequency distribution of oocytes. These methods yielded consistent results, which revealed striking variation in the timing of maturation and gamete release between two summer spawning seasons, possibly depending on local environmental conditions. The optimal temperature for gametogenesis and spawning occurred when seawater temperature exceeded 28 ℃. Gradual increases in temperature (to > 28 ℃) over spawning months in 2013–2014 caused ‘batch/dribble’ spawning, while abrupt increases in temperature in 2014–2015 caused synchronous ‘all-at-once’ spawning. During more rapid warming events in the typical summer spawning period, CoTS may exhibit greater synchronicity in their reproductive capacity, which may help seed outbreaks. This work advances our understanding of the mechanisms surrounding periodic fluctuations in CoTS densities and improves predictions on how this corallivorous predator will respond to environmental perturbations due to climate change.