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Leatherback turtle and jellyfish

19/07/2006 Ecological networks have well defined patterns. A study by a group of Spanish researchers from the Universidad Pompeu Fabra appears on the front cover of this week's Nature. Relationships between organisms are highly complex. Darwin recognized this in his metaphor of a "tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth". They may be complex, but the researchers conclude that they're not so complex that we can't understand them.

"All interactions can be visualized as ecological networks, in which species are linked together, either directly or indirectly through intermediate species. Ecological networks, although complex, have well defined patterns that both illuminate the ecological mechanisms underlying them" The effect of eliminating a species can be disastrous for an ecosystem, as a cascade extinction can be unleashed and the ecosystem can collapse.

An example is the decimation of leatherback turtles in the Mediterranean and elsewhere and the massive increase in their favourite prey, jellyfish. The leatherback turtle provides natural ecological control of jellyfish populations. Overabundance of jellyfish may reduce fish populations as jellyfish can feed on fish larvae and reduce population growth of commercially important fish. Hence, the presence of leatherback turtles benefits fish, fisheries and people. This collapse of ecosystems has important consequences for the world's biodiversity which many scientists believe is threatened at the same level as during previous mass extinctions. In the case of the oceans some researchers have said we are fishing them back to an almost Precambrian sea (-600 million years ago) in which vertebrate animals are almost entirely absent: a totally altered ecosystem. See also El Mundo

27/11/2006 Scientists stress importance of turtles in contolling jellyfish swarms (Ambientum)