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Bones of seabirds reveal how dramatically food chain in the oceans

Bones of seabirds reveal how dramatically food chain in the oceans What can drive a dead Fulmar Hawaiian, skilled hunter marine fish reveal about life under water? With research focused on the content of specific isotopes in the bones of seabirds, we can observe a drastic change of the structure of their food, which is a response to the loss of large fish off the coast.

Hawaiian petrel (Pterodroma sandwichensis) is an endangered species endemic to the Hawaiian archipelago. Spends most of its life in the air when restlessly circling above the waves, waiting for prey. According to the results of research conducted at Michigan State University (MSU), shows that over the last decade has seen a significant transformation in food preferences of these great pilots. Over time he began to collect food that is in the food pyramid rather at the lower levels. How such a conclusion scientists reached?

"Changes in the food following an analysis of the bone samples of the dead, and indeed long dead fulmars," says Peggy Ostrom, a zoologist from MSU. "We start by comparing nitrogen isotopes N14 and N15. Very simply, we can say that the higher up the food chain will be laid feeding, the greater the content of nitrogen isotopes in bone eater. "Were used to analyze the bones collected in stone nesting cavities on the cliffs, and 17,000 historical fragments of bone, provided Smithsonianovým Institute.

"High levels of nitrogen isotopes measured in the bones of the old 1-4000 years suggest that at the time Shearwaters focused their attention on large and hearty fish that were in the food pyramid above," says Ostrom. "Around the fifties of the last century, the onset of intensive fishing, but we can observe a rapid decline of these isotopes. "Why is it that Shearwaters suddenly began to focus on smaller fish and crustaceans? Researchers from MSU believe that the relatively sudden change in diet has a lot to do with the effects of human factors: industrial fishing.

According to Ostrom is the alarming findings: "It is only a threat to one particular type of intensive fishing, but the shift pressure to other bar food pyramid. When a group of fish will result in capture, small, and it affects a number of other species, perhaps the entire food chain in the ocean ecosystem. "

The article was published on the 13th 5th ScienceDaily Server 2013 under the name "Seabird Bones Reveal Changes in Open-Ocean Food Chain" .



Author: Radomir Dohnal
Source: Ecomonitor.cz



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