DREW HARVELL: The oceans-- for thousands of years, we have depended upon their vast resources to provide us sustenance essential to daily life. Even today, half of the world's population lives within 100 kilometers of a coastline. And 2/3 of the world's largest cities are found near a coast.
With all these people, it is not, probably, surprising that over the last 20 years, we have begun to see evidence that these valuable ocean ecosystems are under stress.
Hi, my name is Drew Harvell. I'm a professor in the Department of Ecology and Evolutionary Biology at Cornell, where I teach and study the biology of the oceans.
I'm particularly interested in the health of coral reefs. Recently, we detected that the occurrence of disease in ocean animals, particularly those found on coral reefs, are increasing. I would like to share with you an exciting new international project at Cornell that is letting us target innovative research to management solutions on coral reefs.
Now, coral reefs are among the most important ocean ecosystems. Although they occupy only a tenth of a percent of the ocean surface and are predominantly in tropical environments, coral reefs house an incredible diversity of species, rivaling that of tropical rain forests.
These fragile ecosystems provide us with valuable global services. And just consider what would happen if we had no reefs to provide these services. First, coral reefs provide coastal communities with barriers from storms, as we observed after the tsunami in December of 2004.
Second, they provide critical habitat for tens of thousands of different animals, including many commercial fish that communities depend on for sustenance. We've also found some organisms within the reef synthesize natural products that could be useful as medicines, and there are many more to discover.
Third, the diversity and inherent beauty of coral reefs is such that recreational diving provides critical income for thousands of coastal communities worldwide.
Now unfortunately, in the past few decades, we've seen the health of these ecosystems declining rapidly. Over 85% of countries with significant coral communities have experienced damage. While there are many human and natural influences affecting coral reef health, I will focus on three.
First, global climate change is causing increases in the ocean's temperature. When things get too hot in the tropics, corals undergo a process we call bleaching. If this lasts too long, the coral can die. Higher temperatures may also stimulate the growth of bacteria that cause disease.
Second, overfishing can affect coral communities. Many fish eat green algae that can grow over the coral surface-- so they essentially clean the coral. When the fish populations drop, the algae grows out of control and coral can die. And, of course, dynamite fishing is used in some Indo-Pacific reefs, and it destroys the reef in addition to all the fish-- small and large.
Third, the addition of nutrients and sediments-- especially as runoff from the coast-- can also change the balance of reef ecosystems. As nutrients enter the system, algae and microorganisms grow better and can cover and kill coral.
We think all these factors are contributing to the increase in coral disease by making corals more susceptible to infection, in the same way that we become more susceptible to illness when we are overtired or stressed.
But before we can fully understand the issues facing coral reefs today, we need to understand the organisms that make up coral reefs. In the next section, we take a closer look at the colonial animals of the reef.
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Over the last 20 years we have observed coral reefs declining at an alarming rate. What is causing this catastrophe and what can be done to prevent further damage?
This study room examines the causes of coral reef decline, including increasing ocean temperatures, overfishing, and runoff from coastal areas. The room describes research on coral disease and how coral organisms resist disease. The research is being conducted by graduate students, undergraduate students, and researchers, who describe their work in their own words.
This video is part 1 of 10 in the Coral Reef Sustainability series.