Census of Marine Life identifies risks, threats and impact of man

by Jeni Bone on 3 Aug 2010 The Mediterranean Sea is in danger of losing its abundant mix of flora and fauna, ranked as the most threatened sea on Earth, according to a landmark scientific survey released yesterday.

The Med, a favourite boating playground and home to millions of people who glean a livelihood from its waters, is the most under threat of the 20 ocean areas examined during the decade-long study of biodiversity.

The Mediterranean is among the five most generously endowed ocean zones, with an estimated 17,000 species ranging from microscopic, single-cell algae to loggerhead sea turtles and bluefin tuna. Only oceans around Japan and Australia boast a greater variety of aquatic life.

Drawing on the work of hundreds of scientists, the 'Census of Marine Life' is the largest global research programme on marine diversity ever undertaken. Results were rendered into more than a dozen studies published in the peer-reviewed journal PLoS ONE.

Habitat loss, pollution and overfishing have already take a heavy toll on the Med, the planet's largest enclosed sea, and now climate change is exerting an impact, the study found. The exhaustive study estimates that the world's oceans are home to more than 230,000 species, with many more likely to be discovered and some to become extinct before we locate them!

The Mediterranean also has nearly three times as many invasive species when compared to the second-most infested region. The depletion of tuna and other top ocean predators, for example, has helped drive a jellyfish explosion disruptive of aquatic food chains and the region's tourism. Some of those unwelcome invertebrates, such as the American comb-jelly, have come from afar. After hitching a ride in the ballast water of oil tankers in the early 1980s, the comb-jelly spread up into the Black and Caspian seas, outcompeting native species all along the way.

From Antarctica to the tropics, the Census uncovered thousands of previously unknown marine creatures across the planet, and confirmed that there are hundreds of thousands, perhaps more than a million, yet to be discovered.

But at the same time the Mediterranean, encircled by dense concentrations of humanity and visited by 200 million tourists each year, was shown to be suffering from decades, centuries and even millennia of exploitation.
Pollution along with rampant coastal development have decimated many habitats critical to marine diversity, including seagrass meadows and coral reefs.

The most important threat looming on the horizon is increasing water temperatures and acidification brought on by global warming, the studies found.

Given than an estimated 75 percent of the region's deep-water species are still unknown, it seems probable some will disappear before they can be identified.