Corals under climate change

Welcome to this year’s BIOL 301L blog. My name is Keisha and I am one of the Teaching Assistants for this year’s Marine Ecology and Evolution Lab. I am currently a Ph. D. student in Zoology in the Coral Reef Ecology Lab (Point Lab) at the Hawaii Institute of Marine Biology under the advisement of Dr. Paul Jokiel.

My research interests focus on the effects of anthropogenic stressors on coral reef ecology, particularly I am interested in how corals will be impacted by our changing climate. Currently, I am examining the interactions between increased temperature, ocean acidification, and increased solar irradiance on coral calcification (i.e. growth) and bleaching.

My experimental setup at the Hawaii Institute of Marine Biology

My experimental setup at the Hawaii Institute of Marine Biology
Photo Credit : Keisha Bahr

Our climate is changing at an alarming rate. The changes that are occurring in our climate are a result of increased carbon dioxide and other heat-trapped gases in the atmosphere, causing the Earth to warm. Along with global warming, the increased amount of carbon dioxide in the atmosphere has dissolved within our oceans causing the acidity of the ocean to increase (i.e. pH of the ocean is decreasing). This phenomenon is called ocean acidification. Nearly 40% of the carbon dioxide that is released by us into the atmosphere dissolves into the ocean, rivers, and lakes. With the increase in these emissions into the atmosphere, scientists project a wide range of impacts including sea level rise; melting of snow and ice; more severe heat, fire, and drought events; and more storms, rainfall, and floods. Moreover, the effects of climate change and ocean acidification potentially have negative effects of marine life.

Today, corals are one of the most ecologically and economically important ecosystems on Earth. An estimated 85% of the United States’ reef area is located within the Hawaiian Archipelago, which was recently valued at $33.57 billion dollars annually. Coral reef communities within the Hawaiian Islands are of particular concern because there is a high proportion of native and unique marine organisms only found in Hawaii. These organisms are a major component as well as dominant engineers of the world’s most isolated coral reef ecosystem.

Corals under climate change pressure are experiencing warmer water temperatures and more acidic water. Corals are very sensitive to temperature changes, where 1-2º C above the normal summer maximum can led to coral bleaching. Coral bleaching occurs with the corals’ algal symbiont (algal that live in the corals’ cells) is expelled from the coral. This event can be exteremly detrimental for coral, as the algal symbionts provide up to 90% of the corals diet. Without these symbionts, the coral can starve.

Check out this video on coral bleaching:

The other obstacle corals face in our changing climate is ocean acidification. The increasing acidity in the ocean hinders the corals’ ability to grow its carbonate skeleton. With slower calcification rates (i.e. growth rates) in our coral reefs, the reefs become more fragile in structure and more vulnerable to erosion.

My research aims to identify how corals in Hawaii will respond to climate change and ocean acidification. As part of my research, I am investigation the single effects,  interactions, and multiple effects of climate change stressors (i.e. temperature, solar irradiance, and carbon dioxide).

I am currently investigating the following questions:
1. Do corals respond differently to one stressor in comparison to another?
2. How do corals respond to multiple climate change stressors?
3. When are corals most vulnerable to climate change?

Here are a few parting thoughts:




Bridge TCL, Hughes TP, Guinotte JM, and P Bongaerts. 2013. Call to protect all coral reefs. Nature Climate Change.

Cesar HSJ, and P van Beukering. 2004. Economic Valuation of the Coral reefs of Hawaii. Pacific Science. 58 (2): 231-242

Hoegh-Guldberg O, Mumby PJ, Hooten AJ, Steneck RS, Greenfield P, Gomez E, and ME Hatziolos. 2007. Coral reefs under rapid climate change and ocean acidification. Science. 318(5857): 1737-1742.

Gattuso J.-P., Allemand D. and M. Frankignoulle. 1999. Photosynthesis and calcification at cellular, organismal and community levels in coral reefs: a review on interactions and control by carbonate chemistry. American Zoologist 39(1):160-183.

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This entry was posted on Tuesday, January 21st, 2014 at 10:58 pm and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.