Coseismic canyon flushing reveals how earthquakes drive canyon development and deep-sea sediment dispersal on active margins.

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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 E k ) 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.

(after 18 ka) deep-sea sedimentation along the Hikurangi subduction margin (New Zealand): Characterisation, timing and origin of turbidites. Marine Geology, Elsevier, 2012Elsevier, , 295-298, pp.51-76. <10.1016Elsevier, /j.margeo.2011.002>.

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The delivery, flux and fate of terrigenous sediment entering the Great Barrier Reef lagoon has been a focus of recent studies and represents an ongoing environmental concern. Wave‐induced bed stress is the most significant mechanism of sediment resuspension in the Great Barrier Reef, and field data and mathematical modelling indicates that the combined effects of short‐period wind waves, longer period swell waves, and tidal and wind‐driven currents can often exceed the critical bed stress for resuspension. Suspended‐sediment concentrations at 20 m water depth indicate resuspension seldom occurs on the middle shelf under normal wave conditions. Non‐cyclonic turbidity events are generally confined to the inner shelf. The wave climate in the southern sector of the central Great Barrier Reef lagoon is the most erosive, and resuspension of outer shelf sediments was hindcast for recorded cyclones. Wind‐driven, longshore currents are fundamental to the northward movement of sediment, and the annual northward mass flux from embayments undergoing resuspension in the Burdekin region is estimated to be one order of magnitude larger than the mass of sediment introduced by a moderate flood plume. Strong onshore winds are estimated to generate significant three‐dimensional bottom return currents on approximately 30–70 days per year, forming a potentially significant offshore‐directed sediment flux during high suspended‐sediment concentration events on the inner shelf.

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