Guest essay by Eric Worrall

New Scientist has discovered that bleaching is a mechanism by which coral protects itself from abrupt warming (or cooling). But if global warming hits 2C, somehow all the coral will know it is time to die.

Corals swap in heat-resistant algae to better cope with global warming

ENVIRONMENT 17 May 2021

By  Karina Shah

Some corals can swap out the algae that live inside their tissues for different strains that are more heat tolerant – and these coral species have a better chance of surviving global climate change in the coming decades.

When sea temperatures are too high, corals expel the microscopic algae living in their tissues. This is what occurs during coral bleaching. Losing algae in this way is harmful for the corals because the algae normally provide oxygen for them and remove their waste products. However, marine biologists have previously discovered that when some corals are exposed to warmer temperatures, they can swap the algae inside their tissues for strains that have a higher thermal tolerance.

The researchers found that the coral species that are able to swap their algae for more heat-resistant strains are more likely to survive until 2100 by resisting bleaching. But this was only the case in scenarios in which greenhouse gas emissions are kept low and ocean warming is restricted to below 2°C.

Read more: https://www.newscientist.com/article/2277726-corals-swap-in-heat-resistant-algae-to-better-cope-with-global-warming/

The abstract of the study;

Quantifying global potential for coral evolutionary response to climate change

Cheryl A. LoganJohn P. DunneJames S. RyanMarissa L. Baskett & Simon D. Donner 

Abstract

Incorporating species’ ability to adaptively respond to climate change is critical for robustly predicting persistence. One such example could be the adaptive role of algal symbionts in setting coral thermal tolerance under global warming and ocean acidification. Using a global ecological and evolutionary model of competing branching and mounding coral morphotypes, we show symbiont shuffling (towards taxa with increased heat tolerance) was more effective than symbiont evolution in delaying coral-cover declines, but stronger warming rates (high emissions scenarios) outpace the ability of these adaptive processes and limit coral persistence. Acidification has a small impact on reef degradation rates relative to warming. Global patterns in coral reef vulnerability to climate are sensitive to the interaction of warming rate and adaptive capacity and cannot be predicted by either factor alone. Overall, our results show how models of spatially resolved adaptive mechanisms can inform conservation decisions.

Read more: https://www.nature.com/articles/s41558-021-01037-2

One thing I’m curious about, how do all the corals know its time to die, when average global temperature reaches 2C above pre-industrial? With large contiguous reefs like the Great Barrier Reef in Australia, there is a substantial difference between the average sea temperature of the cool southern end of the reef, and water temperatures in the tropical far North. Yet somehow a death signal manages to propagate across all these hugely varied biomes, like a kind of coral telepathy.

Do I need the /sarc tag?

via Watts Up With That?

2021 May 18