Research ArticleOCEANOGRAPHY

Nutrient-supplying ocean currents modulate coral bleaching susceptibility

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Science Advances  21 Aug 2020:
Vol. 6, no. 34, eabc5493
DOI: 10.1126/sciadv.abc5493
  • Fig. 1 Early summer upwelling in the Red Sea.

    SST difference between the August minimum and the June maximum reveals the influence of upwelling. Blue colors indicate upwelling, which is mostly restricted to the southeastern Red Sea. Thin contours indicate climatological SSH anomalies, which show a persistent anti-cyclonic eddy in the central Red Sea that acts as a barrier to the northward propagation of the upwelling waters. Thick black line shows the 100-m isobath that defines the shelf edge. Yellow and orange boxes show the locations of surveys and coral coring, respectively. Inset time series shows the climatology (black) of SST between 1982 and 2015 (gray) in the Farasan Banks, revealing the early summer decrease in SST due to upwelling.

  • Fig. 2 Coral core evidence of past bleaching events.

    (A) Computerized tomography (CT) images reveal annual high (light) and low (dark) density bands and anomalous high-density stress bands or partial mortality scars (white arrows). Stress bands are weak, moderate, or strong based on the intensity of the high-density anomaly. (B) Dating the stress bands or partial mortality scars with the annual banding patterns reveals a timeline of past bleaching events. The thin gray line shows the number of cores in the dataset per year. Scale bars, 1 cm.

  • Fig. 3 Coral bleaching in response to a combination of heat and nutrient stress.

    (A) SST during the 4 years with stress bands in the Farasan Banks (1982, 1995, 2002, and 2015). Declines in SST from June to August (shading toward lower left) indicate early summer upwelling, and SST above the dashed black line indicates anomalously warm summers (shading toward upper right) above the MMM. (B) Summary of heat stress (DHW) and nutrients (DIN) for all years 1982–2015 in the Farasan Banks. (C) Spatial distribution of maximum DHW during 2015 (colors) and locations of either coral cores (eastern coast, i.e., Farasan Banks) or visual surveys (western coast, i.e., Sudan). The map corresponds to the area indicated by the yellow box in Fig. 1. The inset histograms show the relative distribution of maximum DHW (°C-weeks) per site on each side of the Red Sea. Contours show the June to August 2015 SST change, which indicates that upwelling (negative values) was constrained primarily to the Farasan Banks area. (D and E) Characteristic reefs with high live coral cover in Sudan (D) and recently dead corals with skeletons still intact in the Farasan Banks. Photo credits: (D) Darren Coker, King Abdullah University of Science and Technology; (E) Morgan Bennett-Smith, King Abdullah University of Science and Technology.

Supplementary Materials

  • Supplementary Materials

    Nutrient-supplying ocean currents modulate coral bleaching susceptibility

    Thomas M. DeCarlo, Laura Gajdzik, Joanne Ellis, Darren J. Coker, May B. Roberts, Nicholas M. Hammerman, John M. Pandolfi, Alison A. Monroe, Michael L. Berumen

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