Coral Reefs

, Volume 31, Issue 3, pp 763–763

Raised reef on Larak suggests Acropora dominance on the ‎Persian Gulf coral reefs since the Pleistocene

Authors

    • Netherlands Centre for Biodiversity Naturalis
    • Iranian National Institute for Oceanography
  • B. Riegl
    • National Coral Reef Institute, Oceanographic Center, Nova Southeastern University

DOI: 10.1007/s00338-012-0908-x

We show hitherto undescribed raised coral frameworks exposed at the NE coast of Larak (Iran), a salt diapir island, located in the Strait of Hormuz, Persian Gulf (Fig. 1a). The entire outcropping section is ~7 m thick. At least two fossil reef sequences were recognized, separated by clastic sediment layers: one near mean sea level (MSL) and the other one >4 m above MSL, the upper 2.5 m of which consist mostly of Acropora plates of the clathrata/downingi group (Fig. 1 b–d). Preliminary U/Th, 14C dates are problematic but suggest an upper Pleistocene age ranging from 30 to 150 ka. This is comparable to similar outcrops at nearby Hormoz and Qeshm (Bruthans et al. 2006). Outcrops suggest several consecutive layers of Acropora dominance, comparable to the situation in the modern Gulf until recently, but not yet reported from other known raised deposits in the region (Pirazzoli et al. 2004; Bruthans et al. 2006).
https://static-content.springer.com/image/art%3A10.1007%2Fs00338-012-0908-x/MediaObjects/338_2012_908_Fig1_HTML.jpg
Fig. 1

a Overview of the outcrop. bc Details of Acropora tables in growth position. d Acropora dominance continues to the very top of the section, where it becomes obscured by heavier diagenesis

The Larak outcrop allows us for the first time to clearly establish that Acropora has been a dominant member of Persian Gulf coral assemblages since the Pleistocene. While Acropora remain common in the northern Gulf, rapidly recurring bleaching events caused their abrupt decline in the southern Gulf (Riegl et al. 2011). Their dire situation in the southern Gulf may herald an interruption of long-term ecological persistence of Acropora dominance. This is eerily similar to the situation observed in the Caribbean (Pandolfi and Jackson 2006).

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© The Author(s) 2012