NIWAThe census hits the seabed: starfish among corals and other invertebratesNIWA
On October 4, at the Royal Society in London, a group of biologists presented the final results of the Marine Life Census, the broadest research program on sea life. For 10 years, 2,700 researchers from 80 countries conducted 568 expeditions, finding at least 1,200 previously unknown species. They are now estimating the number of marine plants, invertebrates, fish and other vertebrates at 230 thousand. Some 33 thousand of these live in the seas around Australia while another 33 thousand live off the coast of Japan, one of the richest in terms of biological diversity.
Brazil, one of the leaders when it comes to biodiversity on land, with some 20 percent of the life forms found on Earth, holds only a modest position in this survey, with 9,101 species of marine organisms, or 4 percent of the total. This is the first time that stock was taken, though perhaps not fully, of Brazilian marine biodiversity, previously assessed only by means of occasional studies, concentrated in the country’s South and Southeast and limited to a few groups of animals found on beaches or shallow waters.
Most of the marine species on the Brazilian coast also exist in the Caribbean, which has one of the highest levels of biodiversity in the world, with 12 thousand species. “Because it is one of the extremes of the Sea of Thetis, the Caribbean holds more species than the western South Atlantic,” says Tavaris. At the other extreme of Thetis, the primitive ocean that lay between the continents 280 million years ago, are Australia and New Caledonia, which are also rich in marine diversity.
Still, Brazilian seas might harbor a fair amount of wealth not yet discovered. “Our marine biodiversity, has been inadequately assessed and very underestimated, to put it mildly,” states the zoologist and researcher Marcos Tavares, the deputy director of the Zoology Museum at the University of São Paulo (USP). He based his conclusion on the ramification of the species that he is helping to create for just one group of crustaceans, with 2,500 species in the Americas and 700 in Brazil. In previous surveys, the experts only had samples of South Atlantic crustaceans that inhabited the beaches and mangrove swamps, underestimating the biological diversity of the Brazilian coast’s eight thousand kilometers.
In the light of genetics
Today, more detailed examinations are showing that species previously regarded as a single one are actually several. “Before, there was only one species of the Chaceon quinquidens red crab, over half a meter long with its legs stretched out and found from Canada to Argentina. Now there are five different species, because what we regarded before as one species has been studied better and samples from different regions have been examined better,” says Tavares, who took part in the reclassification effort, along with researchers from the Smithsonian Institute in the United States. One of the jars on his desk contains a yellowish crab with black pincers found on the coast of Rio Grande do Sul state. “We used to think that it was one more species shared with the Caribbean, but today we know it is found only in Brazil,” he says.
At a marine biodiversity workshop held at FAPESP in September, Antonio Solé-Cava, a researcher from the Institute of Biology at the Federal University of Rio de Janeiro (UFRJ) explained that his team has advanced substantially in differentiating species, complementing the traditional morphological descriptions with genetic analyses. As a result, they have found that angel sharks, fished fairly heavily in Rio Grande do Sul state, were actually three species rather than one. The most important lobster in the Caribbean and in Brazil in commercial terms turned out to be two species, one from each region. Two types of sponges of the Placospongia genus are now eight, four of which are yet to be named and described. Assessing the dimensions of the diversity of sea life forms is essential, among other reasons, to drive the search for medical drugs inspired in compounds extracted from marine organisms: beings that were previously regarded as belonging to the same species may yield substances that are different from the one sought.
The number of marine species may still grow, although engaging in scientific activities in the sea is difficult and expensive. “It’s far easier to organize an expedition to the farthest corners of the Amazon region that to take one to sea,” states Tavares. “Collecting on sandy beaches is much simpler; you only need a spade, plastic bag, sieve and bucket, but even so our beaches haven’t been studied much,” says Cecília Amaral, from the State University of Campinas (Unicamp). “On the high seas, besides needing a boat and big pieces of equipment, collection is far more difficult, time consuming and expensive.” Another difficulty is that marine environments can change quickly because of strong winds or human activities.
The collecting efforts of the program Evaluation of the Sustainable Potential of Living Resources in the Exclusively Brazilian Economic Zone – Revizee, the broadest Brazilian marine diversity survey ever conducted, reached down into depths as great as 1.5 thousand meters at some points along the Brazilian coast. Now these collection efforts are going even deeper: in September and October of last year, four Brazilian researchers took part in one of the Mar-Eco: South Atlantic expeditions and brought back 976 samples of crustaceans, mollusks, worms and corals that live as much as 4 thousand meters below the surface.
Integrated into the Marine Life Census , Mar-Eco:South Atlantic brought together teams from nine domestic and seven foreign research institutions interested in learning how the Meso-Oceanic range of mountains, 14 thousand kilometers long and rising 2 thousand meters high as from the seabed , separates the marine species of the eastern and western Atlantic. According to José Angel Alvarez Perez, a researcher from the University of Vale do Itajaí (Univali) and the coordinator of the Latin American team, the conclusions as to the wealth of the deep seas and the effect of the mountain range should be ready in early 2011, when another expedition is due to leave.
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