Temporal variation of light availability in coastal benthic habitats : effects of clouds, turbidity, and tides

Anthony, Kenneth R.N., Ridd, Peter V., Orpin, Alan R., Larcombe, Piers, and Lough, Janice (2004) Temporal variation of light availability in coastal benthic habitats : effects of clouds, turbidity, and tides. Limnology and Oceanography, 49 (6). pp. 2201-2211.

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We analyzed the contributions of clouds, turbidity, and tides to variations in irradiance and predicted benthic primary productivity on a coastal coral reef over a period of 2 yr (2001–2002). At 1.5 m below lowest astronomical tide (3.8-m tidal range), attenuation by suspended solids (turbidity) accounted for 74–79% of the total annual variation in irradiance, clouds for 14–17%, and tides for 7–10%. With increasing depth, the contribution from turbidity to irradiance variation increased asymptotically toward 95%. Fourier (spectral) analyses indicated that the benthic irradiance regime followed strong 8-week periodicities and weaker 2–4-week periodicities. The 8-week cycle was driven primarily by turbidity and secondarily by clouds and matches the periodicity of the intraseasonal Madden–Julian atmospheric oscillation. The weaker 3–4-week irradiance cycle was driven by turbidity; the 2-week cycle was driven by tides and, to a lesser extent, clouds. Comparisons of the benthic irradiance pattern with predictions of physiologically optimal irradiance levels (parameter Ek) for the coral Turbinaria mesenterina suggested that corals at the site alternate between states of potential light limitation and light stress, with a 2–8-week periodicity caused mainly by variations in turbidity. The effect of external sources of light reduction, such as episodic runoff events, on the energetics of benthic primary producers is likely to vary critically with the timing of such events.

Item ID: 1524
Item Type: Article (Research - C1)
ISSN: 1939-5590
Keywords: primary productivity, benthic, irradiance, coral reefs, clouds, tides, turbidity
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Reproduced with permission from American Society of Limnology and Oceanography.

Date Deposited: 31 May 2007
FoR Codes: 04 EARTH SCIENCES > 0405 Oceanography > 040503 Physical Oceanography @ 100%
SEO Codes: 96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961102 Physical and Chemical Conditions of Water in Coastal and Estuarine Environments @ 100%
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