Title: WHY DO CORAL REEFS THRIVE IN ICEHOUSE WORLD CLIMATES? CLUES FROM LARGER BENTHIC FORAMINIFERS

Abstract: In the past 25 years, foraminifers that host algal endosymbionts (aka large benthic forams or LBF) have become widely used as bioindicators for carbonate-depositional environments, both fossil and modern. This is particularly true for Amphistegina, which is nearly circumtropical in modern oceans and has a long fossil record. They exhibit bleaching, induced by photo-oxidative stress similar to bleaching in zooxanthellate (Z-) corals, though responding more directly to photic stress. Yet though Z-corals have declined dramatically on the offshore reefs of Florida, LBF have continued to thrive in the clearest offshore habitats. The highest coral cover is now on patch reefs, where LBF populations tend to be low or highly variable. The Cenozoic fossil record provides clues to this divergence. During the Eocene, when global temperatures and atmospheric CO2 were higher than pre-Industrial modern levels, LBF were important producers of carbonate buildups; Z-corals typically occupied mesophotic conditions, either deeper or at reduced water transparency. A long-recognized paradox of Z-corals is that, despite requiring warm-water to thrive and build substantial reefs, coral reefs became prominent with the onset of Icehouse World climates. By their production of calcite rather than aragonite, and by hosting a diversity of symbiont taxa, the LBF provide additional models of how organisms with potential to hypercalcify respond to environmental conditions and especially to changes in the suites of conditions, useful to the study of reefs in the past, present and future.

Authors: Hallock P, Mateu-Vicens G, Pomar L

Presentation: Poster (#292)

Session: 25

Date: 06/21/16

Time: 18:15 - 19:45

Location: Poster/Exhibit Hall

Back