Monsoon variability of ultraviolet radiation (UVR) attenuation and bio-optical factors in the Asian tropical coral-reef waters

Mizubayashi, Keiko; Kuwahara, Victor S.; Segaran, Thirukanthan Chandra; Kassim, Zaleha; Effendy, A.W.M.; Kushairi, M.R.M.; Toda, Tatsuki

doi:10.1016/j.ecss.2013.04.002

Cited by 16 publications

(11 citation statements)

References 59 publications

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“… 6 reported that FDOM accounts for 70–95% of the total UV attenuation in surface waters. Since FDOM efficiently protects the labile cells of microorganisms and corals from harmful UV radiation, FDOM is considered to be a key factor in sustaining the coral ecosystem 3 , 4 , 6 , 29 . Additionally, high DOC concentrations are another major threat to coral reefs 30 , 31 .…”

Section: Resultsmentioning

confidence: 99%

“…In particular, it absorbs harmful UV and visible radiation with a short wavelength 2 . Thus, the abundance of FDOM in the surface water influences optical conditions in aquatic environments 3 . It has been reported that FDOM contributes significantly to coastal ecosystems in terms of optically dependent components, such as the growth of coral reefs, juvenile fish, and photosynthesis 4 – 8 .…”

Section: Introductionmentioning

confidence: 99%

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Inputs of humic fluorescent dissolved organic matter via submarine groundwater discharge to coastal waters off a volcanic island (Jeju, Korea)

Kim

2017

Sci Rep

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The abundance of fluorescent dissolved organic matter (FDOM) in the surface ocean plays a critical role in the growth of marine microorganisms and corals by affecting the optical properties (i.e., the penetration of UV radiation) of seawater. In general, it is known that rivers are the main source of FDOM to surface ocean waters. Here, however, we show that the concentrations of FDOM in coastal seawater off a volcanic island, Jeju, Korea, are dependent primarily on submarine groundwater discharge (SGD). Based on a significant correlation between 222Rn and salinity in seawater, fresh groundwater was found to be the main source of groundwater as well as fresh water in the bay. The addition of dissolved organic carbon (DOC) and protein-like FDOM to the bay via SGD was generally negligible or negative. However, SGD enhanced the inventory of humic-like FDOM (FDOMH) in seawater by 2–3 times over all seasons, with conservative behavior of FDOMH in bay seawater. These results suggest that SGD-driven fluxes of FDOM regulate its inventory in seawater and consequently play a significant role in determining the optical properties of coastal waters off islands and associated coastal ecosystems (i.e., corals).

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Inputs of humic fluorescent dissolved organic matter via submarine groundwater discharge to coastal waters off a volcanic island (Jeju, Korea)

Kim

2017

Sci Rep

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“…In particular, several UVR and nutrient levels can occur in a reef during a thermal stress event. Nutrient level can vary with the eutrophication status of the reef, but also with rainfalls, floods, or local biological activity depleting nutrients from surface waters [ 16 , 17 ], while UVR level reaching a coral colony depends on the local shading, the surface orientation, the cloud cover or the depth at which corals grow [ 18 , 19 ]. Results from previous studies showed different responses to the combination of thermal stress with UVR [ 20 , 21 , 22 , 23 , 24 , 25 ] or with nutrient enrichment [ 14 , 26 , 27 ], depending on the environmental context, as well as the quality and severity of the stress.…”

Section: Introductionmentioning

confidence: 99%

Effects of ultraviolet radiation and nutrient level on the physiological response and organic matter release of the scleractinian coral Pocillopora damicornis following thermal stress

et al. 2018

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Understanding which factors enhance or mitigate the impact of high temperatures on corals is crucial to predict the severity of coral bleaching worldwide. On the one hand, global warming is usually associated with high ultraviolet radiation levels (UVR), and surface water nutrient depletion due to stratification. On the other hand, eutrophication of coastal reefs increases levels of inorganic nutrients and decreases UVR, so that the effect of different combinations of these stressors on corals is unknown. In this study, we assessed the individual and crossed effects of high temperature, UVR and nutrient level on the key performance variables of the reef building coral Pocillopora damicornis. We found that seawater warming was the major stressor, which induced bleaching and impaired coral photosynthesis and calcification in all nutrient and UVR conditions. The strength of this effect however, was nutrient dependent. Corals maintained in nutrient-depleted conditions experienced the highest decrease in net photosynthesis under thermal stress, while nutrient enrichment (3 μM NO3- and 1 μM PO4+) slightly limited the negative impact of temperature through enhanced protein content, photosynthesis and respiration rates. UVR exposure had only an effect on total nitrogen release rates, which significantly decreased under normal growth conditions and tended to decrease also under thermal stress. This result suggests that increased level of UVR will lead to significant changes in the nutrient biogeochemistry of surface reef waters. Overall, our results show that environmental factors have different and interactive effects on each of the coral’s physiological parameters, requiring multifactorial approaches to predict the future of coral reefs.

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“…In coral reefs specifically, CDOM exerts a major control over the attenuation of UV radiation (Dunne & Brown 1996, Otis et al 2004, Zepp et al 2008, Kuwahara et al 2010, and reefs off Peninsular Malaysia have been shown to receive significant inputs of terrigenous CDOM (Kuwahara et al 2010, Bowers et al 2012. Mizubayashi et al (2013) further showed that this terrigenous CDOM input is correlated with changes in UV and PAR attenuation off north-eastern Malaysia. Our data thus provide further evidence of the importance of CDOM in controlling the light environment of coral reefs, but also demonstrate that the spectral distribution of PAR is affected.…”

Section: Impact Of Terrigenous Cdom On Light Availabilitymentioning

confidence: 96%

“…That terrigenous, as opposed to marine, CDOM can significantly affect the underwater light environment in the sea has been recognised in regions where the CDOM pool is predominantly terrestrial (Blough et al 1993, Kjeldstad et al 2003, Kowalczuk et al 2006, Hessen et al 2010, Mizubayashi et al 2013, Cherukuru et al 2014). However, CDOM in coastal waters often consists of a mixture of marine and terrigenous CDOM in proportions that can vary strongly spatially and temporally.…”

Section: Introductionmentioning

confidence: 99%

Dissolved organic matter from tropical peatlands impacts shelf sea light availability on coral reefs in the Singapore Strait, Southeast Asia

Martin

Sanwlani

Lee

et al. 2021

Preprint

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Shelf seas provide valuable ecosystem services, but their productivity and ecological functioning depend critically on sunlight transmitted through the water column. Anthropogenic reductions in underwater light availability are thus recognized as a serious threat to coastal habitats. The flux of strongly light-absorbing coloured dissolved organic matter (CDOM) from land to sea may have increased world-wide, but how this has altered the availability and spectral quality of light in shelf seas remains poorly known. Here, we present time-series data from the Sunda Shelf in Southeast Asia, where the monsoon-driven reversal in ocean currents supplies water enriched in CDOM from tropical peatlands for part of the year, resulting in 5–10-fold seasonal variation in light absorption by CDOM. We show that this terrigenous CDOM can dominate underwater light absorption at wavelengths up to 500 nm, and shift in the underwater irradiance spectrum towards longer wavelengths. The seasonal presence of terrigenous CDOM also causes the depth of 10% light penetration to shoal by 1–5 m, or 10–45%. We further estimate that on average 0.6 m, or 25%, of this terrigenous CDOM-mediated shoaling might be attributable to the enhanced loss of dissolved organic matter caused by peatland disturbance. We show that the seasonal change in the light environment is correlated with photo-acclimation by phytoplankton, and infer that terrigenous CDOM likely contributes to limiting the depth distribution of photosynthetic corals. Our results thus reveal an ecologically important but largely overlooked impact of human modifications to carbon fluxes that is likely becoming increasingly important in coastal seas.

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Monsoon variability of ultraviolet radiation (UVR) attenuation and bio-optical factors in the Asian tropical coral-reef waters

Cited by 16 publications

References 59 publications

Inputs of humic fluorescent dissolved organic matter via submarine groundwater discharge to coastal waters off a volcanic island (Jeju, Korea)

Inputs of humic fluorescent dissolved organic matter via submarine groundwater discharge to coastal waters off a volcanic island (Jeju, Korea)

Effects of ultraviolet radiation and nutrient level on the physiological response and organic matter release of the scleractinian coral Pocillopora damicornis following thermal stress

Dissolved organic matter from tropical peatlands impacts shelf sea light availability on coral reefs in the Singapore Strait, Southeast Asia

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