Responses of corals to chronic turbidity

Jones, Ross; Giofre, Natalie; Luter, Heidi M.; Neoh, Tze Loon; Fisher, Rebecca; Duckworth, Alan

doi:10.1038/s41598-020-61712-w

Cited by 54 publications

(48 citation statements)

References 76 publications

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“…trap silt and fine sand. Smothering of corals by sediment has been shown to preferentially occur on encrusting and foliose (but not branching) growth forms under periods of chronic sedimentation (Jones et al, 2020). Singapore's coral communities are dominated by encrusting, massive and foliose forms, whereas branching species (e.g., Acropora spp.)…”

Section: Discussionmentioning

confidence: 99%

Light Limitation and Depth-Variable Sedimentation Drives Vertical Reef Compression on Turbid Coral Reefs

et al. 2020

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Turbid coral reefs experience high suspended sediment loads and low-light conditions that vertically compress the maximum depth of reef growth. Although vertical reef compression is hypothesized to further decrease available coral habitat as environmental conditions on reefs change, its causative processes have not been fully quantified. Here, we present a high-resolution time series of environmental parameters known to influence coral depth distribution (light, turbidity, sedimentation, currents) within reef crest (2–3 m) and reef slope (7 m) habitats on two turbid reefs in Singapore. Light levels on reef crests were low [mean daily light integral (DLI): 13.9 ± 5.6 and 6.4 ± 3.0 mol photons m–2 day–1 at Kusu and Hantu, respectively], and light differences between reefs were driven by a 2-fold increase in turbidity at Hantu (typically 10–50 mg l–1), despite its similar distance offshore. Light attenuation was rapid (KdPAR: 0.49–0.57 m–1) resulting in a shallow euphotic depth of <11 m, and daily fluctuations of up to 8 m. Remote sensing indicates a regional west-to-east gradient in light availability and turbidity across southern Singapore attributed to spatial variability in suspended sediment, chlorophyll-a and colored dissolved organic matter. Net sediment accumulation rates were ∼5% of gross rates on reefs (9.8–22.9 mg cm–2 day–1) due to the resuspension of sediment by tidal currents, which contribute to the ecological stability of reef crest coral communities. Lower current velocities on the reef slope deposit ∼4 kg m2 more silt annually, and result in high soft-sediment benthic cover. Our findings confirm that vertical reef compression is driven from the bottom-up, as the photic zone contracts and fine silt accumulates at depth, reducing available habitat for coral growth. Assuming no further declines in water quality, future sea level rise could decrease the depth distribution of these turbid reefs by a further 8–12%. This highlights the vulnerability of deeper coral communities on turbid reefs to the combined effects of both local anthropogenic inputs and climate-related impacts.

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Section: Discussionmentioning

confidence: 99%

Light Limitation and Depth-Variable Sedimentation Drives Vertical Reef Compression on Turbid Coral Reefs

et al. 2020

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“…Light penetration changes after hurricane events can affect seagrasses [11] and other light-dependent organisms like corals. Previous research shows that coral photo-physiology is altered by light availability [25,52]. García-Sais and collaborators (2017) studied K d 490 and Chl-a trends over individual coral reefs in Puerto Rico using L2 and L3 imagery from SeaWiFS and MODIS Aqua satellite data [10].…”

Section: Discussionmentioning

confidence: 99%

Water Quality Anomalies following the 2017 Hurricanes in Southwestern Puerto Rico: Absorption of Colored Detrital and Dissolved Material

et al. 2020

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Absorption of colored dissolved organic matter or detrital gelbstoff (aCDOM/ADG) and light attenuation coefficient (Kd490) parameters were studied at La Parguera Natural Reserve in southwestern Puerto Rico, before and following Hurricanes Irma (6–7 September) and María (20–21 September) in 2017. Water quality assessments involving Sentinel 3A ocean color products and field sample data was performed. The estimated mean of ADG in surface waters was calculated at >0.1 m−1 with a median of 0.05 m−1 and aCDOM443 ranged from 0.0023 to 0.1121 m−1 in field samples (n=21) in 2017. Mean ADG443 values increased from July to August at 0.167 to 0.353 m−1 in September–October over Turrumote reef (LP6) with a maximum value of 0.683 m−1. Values above 0.13 m−1 persisted at offshore waters off Guánica Bay and over coral reef areas at La Parguera for over four months. The ADG443 product presented values above the median and the second standard deviation of 0.0428 m−1 from September to October 2017 and from water sample measurement on 19 October 2017. Mean Kd490 values increased from 0.16 m−1 before hurricanes to 0.28 right after Hurricane Irma. The value remained high, at 0.34 m−1, until October 2017, a month after Hurricane María. Analysis of the Sentinel (S3) OLCI products showed a significant positive correlation (rs = 0.71, p = 0.0005) between Kd490_M07 and ADG_443, indicating the influence of ADG on light attenuation. These significant short-term changes could have ecological impacts on benthic habitats highly dependent on light penetration, such as coral reefs, in southwestern Puerto Rico.

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“…For example, turbidity-induced light reductions can result in reduced coral recruitment and diversity (Fabricius, 2005). Similarly, prolonged exposure to 'dark' (low to no light) conditions during high turbidity (e.g., near dredging locations) can cause sub-lethal bleaching in some corals (Bessell-Browne et al, 2017a;Bessell-Browne et al, 2017b) while others were able to adjust to combination of low light levels (2.3 mol photons m -2 d -1 ) and elevated suspended sediment concentrations (Jones et al, 2020). Other examples include increased coral bleaching during high irradiance in the presence of thermal stress (Leahy et al, 2013) and compromised seagrass survival during limited light levels and high nutrient conditions (McKenzie et al, 2010).…”

Section: The Ecological Importance Of Benthic Lightmentioning

confidence: 99%

A benthic light index of water quality in the Great Barrier Reef, Australia

Canto¹,

Fabricius²,

Logan³

et al. 2020

Preprint

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Good water quality is essential to the health of marine ecosystems, yet current metrics used to track water quality in the Great Barrier Reef are not strongly tied to ecological outcomes. There is a need for a better water quality index (WQI). Benthic light, the amount of light reaching the seafloor, is critical for coral and seagrass health and is strongly affected by water quality. It therefore represents a strong candidate for use as a water quality indicator. Here, we introduce a new index based on remote sensing benthic light (bPAR) from ocean colour. Resulting bPAR index timeseries, based on the extent to which the observed bPAR fell short of the locally-and seasonally-specific optimum, showed strong spatial and temporal variability, which was consistent with the dynamics that govern changes in water clarity in the Great Barrier Reef. Our new index is ecologically relevant, responsive to changes in light availability and provides a robust metric that may complement current Great Barrier Reef water quality metrics.

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Responses of corals to chronic turbidity

Cited by 54 publications

References 76 publications

Light Limitation and Depth-Variable Sedimentation Drives Vertical Reef Compression on Turbid Coral Reefs

Light Limitation and Depth-Variable Sedimentation Drives Vertical Reef Compression on Turbid Coral Reefs

Water Quality Anomalies following the 2017 Hurricanes in Southwestern Puerto Rico: Absorption of Colored Detrital and Dissolved Material

A benthic light index of water quality in the Great Barrier Reef, Australia

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