'Jellyfish Joyride' A Threat To The Oceans

ScienceDaily — Early action could be crucial to addressing the problem of major increases in jellyfish numbers, which appears to be the result of human activities.

New research led by CSIRO Climate Adaptation Flagship and University of Queensland scientist, Dr Anthony Richardson, presents convincing evidence that this ’jellyfish joyride’ is associated with over-fishing and excess nutrients from fertilisers and sewage.

“Dense jellyfish aggregations can be a natural feature of healthy ocean ecosystems, but a clear picture is now emerging of more severe and frequent jellyfish outbreaks worldwide,” Dr Richardson says.

“In recent years, jellyfish blooms have been recorded in the Mediterranean, the Gulf of Mexico, the Black and Caspian Seas, the Northeast US coast, and particularly in Far East coastal waters.

“The most dramatic have been the outbreaks in the Sea of Japan involving the gargantuan Nomura jellyfish which can grow up to 2 m in diameter and weigh 200 kg.”

The new research, by Dr Richardson and colleagues at the University of Miami, Swansea University and the University of the Western Cape, has been published in the international journal; Trends in Ecology and Evolution, in time for World Oceans Day on 8 June.

“Fish normally keep jellyfish in check through competition and predation but overfishing can destroy that balance,” Dr Richardson says. “For example, off Namibia intense fishing has decimated sardine stocks and jellyfish have replaced them as the dominant species.”

Climate change may favour some jellyfish species by increasing the availability of flagellates in surface waters – a key jellyfish food source. Warmer oceans could also extend the distribution of many jellyfish species.

“Mounting evidence suggests that open-ocean ecosystems can flip from being dominated by fish, to being dominated by jellyfish,” Dr Richardson says “This would have lasting ecological, economic and social consequences.

“We need to start managing the marine environment in a holistic and precautionary way to prevent more examples of what could be termed a ‘jellyfish joyride’.”

Journal reference:

1. Richardson et al. The jellyfish joyride: causes, consequences and management responses to a more gelatinous future. Trends in Ecology & Evolution, 2009; 24 (6): 312 DOI: 10.1016/j.tree.2009.01.010

Adapted from materials provided by CSIRO Australia.

SHARKS KILL PEOPLE - Through Methyl Mercury Poisoning

Ok, granted, the title of this article is a little over the top I confess. The fact of the matter is we as people are much more dangerous to sharks than they are to us...unless we eat them. Shark meat has some of the highest concentrations of methyl mercury know to cause birth defects and neurological problems.

The consequences of such a poisoning are for an infant mental development disturbances and for an adult heavy damage to the central nervous system. These express themselves by headache, memory difficulties or depressions." Besides kidney damages, cancer and massive damages of the brain threatens.

For a long time it was assumed and now it is certain: Shark meat is poisonous!! By a new method of analysis, patented by Professor Klaus Heumann of the University of Mainz (Germany), alarming concentrations of methyl mercury were found in shark steaks.

A study - given by the shark protection organization Sharkproject - proved that there is up to 1400 microgram of methyl mercury per kilogram blue shark steak. These are 420 microgram of methyl mercury in a normal 300 gram shark steak portion and this is 60 times more than a 70 kg heavy consumer per day may have.
The danger value is 0.1 microgram per kilogram body weight and day. This value was specified by EPA (Environmental Protection Agency) in a toxicologist committee and is considered as new international standard. A consumer might take only 5 gram blue shark steak or 12.7 gram of smoked rock salmon (smoked dogfish) per day. Each higher dose can have serious consequences.

Methyl mercury is most dangerous for the human body. Toxicologist Dr. Hermann Kruse of the University of Kiel (Germany) explains why: "It is one of the biologically most active and most dangerous poisons for humans. In addition methyl mercury is a "Trojan horse" which can pass easily each protection barrier as to the separation mechanism between the blood circulation of a mother and her unborn child as well as the blood-brain barrier of each adult.

Who thinks that a smoked rock salmon (smoked dogfish) or a small blue shark steak from the food discounter now and then is not precarious is wrong because the half-life of methyl mercury is high. The human organism needs 60 to 80 days to halve the poison concentration in the body.

But not only sharks are affected by this heavy metal load. The same applies to all large predatory fish who take up the poison over their natural food chain. For example also tuna and swordfish count for this.

The management of the German fish restaurant chain North Sea already reacted to the arguments of the animal conservationist organization and wants to go completely without any shark products. These results also would have to alarm now the food branch and the Ministries of Health.
Best would be if everyone stopped immediately buying and consuming all kind of shark products and stopped the consumption of tuna and swordfish.

(Source: "Tauchen"-Magazine and Sharkproject)

Great Pacific Garbage Patch in the News