Giant manta rays also appear to exhibit a high degree of plasticity or variation in terms of their use of depths within their habitat. Manta rays use many different types of feeding strategies, such as barrel rolling (doing somersaults over and over again) and creating feeding chains with other mantas to maximize prey intake. When feeding, mantas hold their cephalic fins in an “O” shape and open their mouths wide, creating a funnel that pushes water and prey through their mouth and over their gill rakers. Manta rays primarily feed on planktonic organisms such as euphausiids, copepods, mysids, decapod larvae, and shrimp, but some studies have noted their consumption of small and moderately sized fish as well. The timing of these visits varies by region and seems to correspond with the movement of zooplankton, current circulation and tidal patterns, seasonal upwelling, seawater temperature, and possibly mating behavior.Īlthough the giant manta ray tends to be solitary, they aggregate at cleaning sites and to feed and mate. The dose received from background radiation on the island was found to be between 2.4 mSv/year and 4.5 mSv/year (the lower rate is the same as natural background radiation).The giant manta ray is a migratory species and seasonal visitor along productive coastlines with regular upwelling, in oceanic island groups, and near offshore pinnacles and seamounts. But eating many over a long period of time without having taken remedial measures might result in radiation doses higher than internationally agreed safety levels." The main radiation risk would be from the food: eating locally grown produce, such as fruit, could add significant radioactivity to the body.Eating coconuts or breadfruit from Bikini Island occasionally would be no cause for concern. although the residual radioactivity on islands in Bikini Atoll is still higher than on other atolls in the Marshall Islands, it is not hazardous to health at the levels measured. The special International Atomic Energy Agency (IAEA) Bikini Advisory Group determined in 1997 that "It is safe to walk on all of the islands. The Bikini Atoll was entered into the list of UNESCO World Heritage sites on August 2010. The United States provided $150 million as a settlement for damages caused by the nuclear testing program. It was not uncommon for women to experience faulty pregnancies, miscarriages, stillbirths and damage to their offspring as a result of the nuclear testing on Bikini. In 1978, however, the islanders were removed again when strontium-90 in their bodies reached dangerous levels after a French team of scientists did additional tests on the island. In 1968 the United States declared Bikini habitable and started bringing a small group of Bikinians back to their homes in the early 1970s as a test. Preceding the nuclear tests, the indigenous population was relocated to Rongerik Atoll, though during the Castle Bravo detonation in particular some members of the population were exposed to nuclear fallout. Between 19, twenty-three nuclear devices were detonated at Bikini Atoll, beginning with the Operation Crossroads series in the summer of 1946. Following the end of World War II, Bikini came under the control of the United States as part of the Trust Territory of the Pacific Islands until the independence of the Marshall Islands in 1986.
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