Impacts of turbidity on corals: The relative importance of light limitation and suspended sediments

Bessell-Browne, Pia; Negri, Andrew P.; Fisher, Rebecca; Clode, Peta L.; Duckworth, Alan; Jones, Ross

doi:10.1016/j.marpolbul.2017.01.050

Cited by 125 publications

(77 citation statements)

References 69 publications

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“…Basing thresholds on the probability of a target mortality provides an effective means of accounting for environmental uncertainty that would be difficult to achieve through conventional methods based on observed mortality. The approach could also be applied to other sublethal indices of coral health, such as mucus production (Bessell‐Browne, Negri, et al., ) and bleaching (Bessell‐Browne, Fisher, Duckworth, & Jones, ) or aggregate indices of coral condition (Ferrigno et al., ).…”

Section: Discussionmentioning

confidence: 99%

Accounting for environmental uncertainty in the management of dredging impacts using probabilistic dose–response relationships and thresholds

Fisher

Walshe

Bessell-Browne

et al. 2017

Journal of Applied Ecology

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Dredging and related activities are common across nearshore marine environments, potentially threatening nearby ecosystems. Regulatory frameworks are essential for minimizing environmental impacts, yet rely heavily on a sound understanding of how ecosystems will respond to environmental stressors, and the thresholds that delineate benign and harmful conditions. Here, we use novel statistical approaches and mathematical tools to account for uncertainty in deriving in situ dose–response relationships and thresholds for the environmental management of dredging, based on estimates of the probability of non‐zero mortality of corals during a dredging campaign at Barrow Island, Western Australia. Using modified receiver operating characteristic curves, we derive thresholds with explicit Type I and Type II errors rates, across the full range of primary stress pathways and exposure dimensions (intensity, frequency and duration). Monitoring coral health and mortality can be expensive and water quality indicators are often used to supplement direct receptor monitoring during dredging management. We found strong relationships between coral mortality and a range of water quality exposure metrics, lending support to the use of water quality metrics as management tools for protecting corals during dredging. Metrics based on sediment deposition were more statistically powerful than those based on either light or turbidity, but may be more difficult to implement in practice. Thresholds reflecting aversion to a false sense of security in environmental protection or aversion to the costs of false alarms varied substantially for all exposure metrics examined. Synthesis and applications. Strategies for managing environmental harm under uncertainty are critical to achieving an informed risk‐weighted balance between environmental protection outcomes and development costs. Our study demonstrates the complexities of how communities respond to variable environmental exposure across a range of pressures in time and space, and the value of integrating probabilistic approaches in environmental management to account for that complexity and its associated uncertainty. Coral mortality was strongly related to a range of water quality exposure metrics associated with dredging activities, and regulatory thresholds based on water quality can provide a solid and cost‐effective foundation for protecting corals during dredging. The probabilistic dose–response relationships and thresholds presented here are the first to be derived from in situ data using dredging related coral mortality and represent a step forward in integrating formal decision science approaches into environmental management.

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Section: Discussionmentioning

confidence: 99%

Accounting for environmental uncertainty in the management of dredging impacts using probabilistic dose–response relationships and thresholds

Fisher

Walshe

Bessell-Browne

et al. 2017

Journal of Applied Ecology

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“…Several pathways or mechanisms that underlie sediment impacts have been proposed to explain the biological effects on marine species, including a reduction in light availability (Bessell‐Browne, Negri, et al, ), an elevation in suspended sediment concentrations (Jones et al, ) and an increase in the rate of sedimentation (Jones, Ricardo, & Negri, ). A decrease in light penetration has frequently been perceived as the most influential proximate stressor on autotrophs (Jones et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…However, reduction in light availability can also disrupt foraging activities or decrease the foraging efficacy of heterotrophic organisms that rely on visual cues to detect prey (Kjelland, Woodley, Swannack, & Smith, ; Wenger, Johansen, & Jones, ). The detrimental impacts of constrained light availability have mostly been measured in corals (Bessell‐Browne, Negri, et al, ), seagrass (Erftemeijer & Robin Lewis, ), macroalgae (Eriksson & Johansson, ) and fish assemblages (Kjelland et al, ). Light attenuation may also exacerbate abiotic conditions, with negative effects on marine biota (Ban, Graham, & Connolly, ; Bessell‐Browne, Negri, et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…The detrimental impacts of constrained light availability have mostly been measured in corals (Bessell‐Browne, Negri, et al, ), seagrass (Erftemeijer & Robin Lewis, ), macroalgae (Eriksson & Johansson, ) and fish assemblages (Kjelland et al, ). Light attenuation may also exacerbate abiotic conditions, with negative effects on marine biota (Ban, Graham, & Connolly, ; Bessell‐Browne, Negri, et al, ).…”

Section: Introductionmentioning

confidence: 99%

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A meta‐analysis reveals global patterns of sediment effects on marine biodiversity

Magris

Ban

2019

Global Ecol Biogeogr

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Aim Sediment disturbances are important threats affecting marine biodiversity, but the variety of biological responses has not yet been synthesized. Here, we collate all available information to compare the extent of impacts across different taxonomic groups, habitat types and pathways of impact (light attenuation, suspended sediment and sedimentation). Location Global. Time period Data collected from 1979 to 2017. Major taxa studied Corals, fishes, seagrasses, sponges, macroalgae, ascidians, bryozoans, crustaceans, echinoderms, molluscs and polychaetes. Methods We used meta‐analyses to evaluate the effects of sediments across 842 observations found in 110 publications. We also evaluated some of the biological and methodological factors that could explain the variable effects observed in different studies. Results We found a significant negative effect of sediments on behavioural responses of species, reproduction and recruitment processes, the morphology of organisms, physiology, community abundance and diversity, and species interactions. In contrast, the overall effect on the abundance of individual species was statistically non‐significant and there was a strong positive effect on abundance for sponge and polychaete species. Many individual studies described physiological effects on coral reefs, but the effects on the diversity of soft‐bottom and coral reef communities were particularly detrimental. Phototrophic species were generally more negatively impacted by sediments than heterotrophs, driven by strong physiological responses in crustose coralline algae and seagrasses. Additionally, species with limited mobility were more vulnerable to sediment disturbances than highly mobile species. Sedimentation alone triggered more consistently negative effects on most biological responses than light depletion and suspended sediments. We found evidence for increased impacts on community diversity when more than one pathway of impact was present, indicating that these disturbances can disrupt whole ecosystems. Main conclusions Our meta‐analysis provided, for the first time, strong quantitative support of negative effects of sediments on marine biodiversity. Taxonomic groups, habitat types and life‐history characteristics were most influential in determining the biological responses to sediment disturbances, highlighting the importance of an ecosystem‐based approach when fully accounting for the impacts of sediments.

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“…However, the ability of extended periods of low light to induce bleaching (in the absence of heat stress) is well documented (Bessell-Browne et al 2017). Photoacclimation to decreased light involves the upregulation of protein synthesis for the manufacture of additional photosynthetic pigments (Falkowski and Raven 2007) and is thus energetically costly (Raven 1984).…”

Section: Discussionmentioning

confidence: 99%

Coral responses to temperature, irradiance and acidification stress: linking physiology to satellite remote sensing

Mason¹

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The success of the symbiosis of scleractinian corals with dinoflagellates of the genus Symbiodinium is highly dependent on the availability of sufficient, but not excess, light for photosynthesis. After decades of fundamental research into the effect of light on the coral-dinoflagellate symbiosis, an important practical application is emerging in remote monitoring of bleaching at coral reefs. Coral bleaching that originates with the dysfunction of photosynthesis can be either photoacclimatory, a controlled adjustment in response to environmental change, or it can be associated with photodamage, an uncontrolled response to environmental change. It is the latter that tends to lead to severe bleaching events that decrease the rate of carbon fixation, generate excessive oxygen radicals and may ultimately lead to coral death if unfavourable conditions persist. Current best practice methods for the prediction of coral bleaching use water temperature as detected via satellite, and predict the onset of coral bleaching accurately, but not the percent of corals bleached at a reef or the extent of the ensuing mortality.Due to its central role in causing photodamage, the use of light level (in addition to temperature) as a predictive variable may improve the accuracy of predictions of coral bleaching severity. The rate of photoacclimation affects the duration of elevated stress following an increase or decrease in incident light level and so it is potentially important for predicting the severity of coral bleaching.As coral reef management practitioners aim to predict bleaching and bleaching-induced mortality at entire reef locales, which are typically composed of a multi-species coral community, differences in coral physiological responses are of importance in designing accurate prediction methods. The interaction of high light and high temperature with a third stressor, ocean acidification, may influence coral bleaching, as ocean acidification changes oceanic chemical parameters that are key to cellular mechanisms of homeostasis and to dinoflagellate photosynthesis.Using multiple-stressor aquarium experiments, I investigated the photoacclimation rate in corals, differences in response to light and temperature stress among coral species, and the interaction of light, temperature and ocean acidification on coral bleaching onset and severity (at the colony scale). My investigation of photoacclimation (via 24 days of exposure to a large increase, a moderate increase, and a large decrease in light) in Acropora muricata and mounding Porites spp.indicated that the direction of light change and the water temperature influenced photoacclimation duration. However, the exact patterns were specific to the variable used to measure photoacclimation (for instance, changes in net areal photosynthesis, or changes in quantum 2 efficiency of photosystem II), with important ramifications for the development of a combined light and temperature bleaching prediction method.I investigated species-specific physiological responses in A. mu...

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Impacts of turbidity on corals: The relative importance of light limitation and suspended sediments

Cited by 125 publications

References 69 publications

Accounting for environmental uncertainty in the management of dredging impacts using probabilistic dose–response relationships and thresholds

Accounting for environmental uncertainty in the management of dredging impacts using probabilistic dose–response relationships and thresholds

A meta‐analysis reveals global patterns of sediment effects on marine biodiversity

Coral responses to temperature, irradiance and acidification stress: linking physiology to satellite remote sensing

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