**Some challenging vocabulary**
There is no longer any shadow of a doubt about the impact of global warming on coral reefs. A rise of a few degrees in sea surface temperature induces the expulsion of essential microscopic algae which live in symbiosis with the coral. This process is the cause of coral bleaching and is well known to scientists, but few large-scale studies have dealt with its effects on the structure of communities of hundreds of species of reef-colonizing fish.
Coral die-offs—caused by a process known as bleaching—tend to look as bland and lifeless, in contrast to the vibrant rainbow colors of thriving coral. Bleached coral reefs usually appear as an endless stretch of white coral and eventually turn to dead brown coral.
Coral bleaching and associated mortality not only have negative impacts on coral communities, but they also impact fish communities and the human communities that depend on coral reefs and associated fisheries for livelihoods and wellbeing.
Bleaching often leads to coral death, and is a stress response to two key factors: increasing ocean acidity, caused by uptake of carbon dioxide from the atmosphere, and a rise in ocean temperature. It's all too apparent that ecosystems near bleached corals tend to collapse, but the reasons why are not fully understood.
Guerrero and his fellow trainees hope to join a 33-member team of first-response divers called Guardians of the Reef. The divers are part of an ambitious pilot project to rehabilitate a stretch of battered coral reefs along Mexico’s Caribbean coast, in the tourism-dependent state of Quintana Roo that includes the resort hubs of Cancun and Playa del Carmen, as well as smaller cities like Puerto Morelos.
"Oil spills are an environmental disaster. When crude oil is spilled into the sea, it affects more than the water in that particular location. This Web site presents information about what happens when an oil spill occurs. What steps are taken to lessen the spread of oil? How is the impact accessed? A photo journal of the Exxon Valdez oil spill in 1989 shows the damage that occurred. Many animated pages on this site illustrate what happens to the oil, where it goes, how coastlines are affected, and how wind speed influences the way the oil moves."
The open oceans are the world’s largest ecosystems, vital to everyone, owned by no-one. Traversed by whales, sharks, turtles, tuna and albatross and home to mysterious deep-sea creatures, these are the true wilds of our planet.