[Coral-List] coral bleaching

[Eugene Shinn]

Regarding our recent discussions concerning coral bleaching and 
temperature here is something I thought would be relevant for readers of 
the list. It is well known that the Florida Keys were once a coral reef 
as were many elevated Pleistocene age coral reefs around the planet. 
They had to be formed when sea level was several meters above present. 
They did not grow in air. They grew during what is known as isotope 
stage 5e. The newest information suggests that was 129-116 thousand 
years ago. Most scientists agree the higher sea level at that time was 
due to melting polar ice and therefore Earth was likely warmer that 
today's temperature. If bleaching today is due to warm temperatures, 
then coral growth that produced those elevated stage 5e coral reefs 
should have bleached. We have no way of knowing for sure, but it is 
evident that those 5e reefs did produce what is now land in many places 
including the Florida Keys. If there was bleaching back then it is clear 
those corals did not go extinct until sea level dropped and left them 
high and dry. As readers know, sea level dropped as much as 120 meters 
when those reefs were left high and dry. Sea level then began rising as 
it is doing now. Was the higher sea level during stage 5e caused by 
higher CO2 levels? If so, what caused the high CO2 levels? There were no 
automobiles or fossil fuel power plants back then. The CO2 could have 
been expelled by a warming sea but what caused the sea to warm? Could 
whatever cause the sea to warm be what is causing today's warming? I 
thought these questions would be relevant subjects for discussion by 
members of the coral-list. Gene