A team of researchers from the University of Valencia (UV) has found that 34% of ultraviolet radiation filters through under beach umbrellas. According to a new study, umbrellas intercept the full direct flow that comes from the Sun, but not the diffused radiation that penetrates through from the sides.

"We have proven that irradiance (radiation incidence per unit of surface area) that reaches the ground covered by an umbrella is 34% of the total," says José Antonio Martínez-Lozano, co-author of the study and coordinator of the Research Group of Solar Radiation in UV.

To carry out the project, which was published recently in the journal Photochemistry and Photobiology, the team positioned an ultraviolet ray sensor on the base of a canvas umbrella painted blue and white, with a radius of 80cm and height of 1.5 metres.

"The umbrella intercepts the direct radiation that comes from the Sun, but part of the diffused radiation, which makes up approximately 60% of the total, reaches the sensor from the sky not covered by the umbrella," explains Martínez-Lozano.

The results show that canvas has a very high capacity for absorbing radiation, "with only 5% transmissivity," but this does not prevent diffused ultraviolet radiation from penetrating through on the sides.

In addition, the team has developed a geometric model to obstruct the sky to calculate the irradiance that is received on the different horizontal and vertical planes under the umbrella. In the case of horizontal irradiance, the values that the model provides coincide with those registered experimentally with only a relative error of 3%.

In this way, and using various configurations of sky, ground and umbrella, the researchers have been able to simulate the real situation of people, who do not always remain lying down under sunshades, as they often tend to rise, sit or stand up.

Protection against skin cancer

Scientists believe that this study can help to gain a better understanding of the epidemiology of some skin cancers. An excess of ultraviolet radiation is not only related to the appearance of melanoma, it is also connected to sunburn, photoageing, many eye disorders -especially cataracts-, weakness of the immune system and DNA damage.

The earth's atmosphere is a natural barrier that reduces the harmful effects of UV rays, but experts recommend the use of others such as umbrellas, pieces of clothing, hats with a brim over 7cm, sunglasses with protection and sun creams. They also recommend reducing the exposure time and avoiding hours when the sun is at its highest (between midday and 4pm local time).

In any case, rational use of ultraviolet rays also has beneficial effects for human health, as they help to treat dermatological disorders and form vitamin D3. Some studies even highlight its properties for limiting hypertension and reducing the appearance of certain internal cancers, such as prostrate cancer.

Text and Photo by SINC

How does a female penguin choose a mate? Courtship calls help females decide which males are likely to be devoted dads, says a study in the journal Behaviour.

Antarctic penguins come on land for just a few short months each summer to breed and raise their chicks. Raising a family in the coldest place on earth is no small feat. Adelie penguins pull it off by tag-team parenting, the researchers explained. Males and females take turns incubating the eggs and guarding the chicks while their mate forages for food.

Males arrive first to claim a territory and build a nest. When the females arrive, the males serenade prospective mates by throwing their heads back, pointing their beaks to the sky, and emitting a series of hoarse trills and squawks.

"They're not musical calls -- they sound like a cross between a donkey and a stalled car," said author Emma Marks of the University of Auckland. Penguin calls may not be music to our ears, but to penguin females they hold clues to a male's paternal potential, Marks and colleagues report.

After choosing a mate the female lays two eggs and returns to sea, leaving the male alone to tend the egg until she returns to take the next shift. For the first two weeks penguin dads do the bulk of babysitting duty without breaking to eat. By relying on stored fat reserves, father penguins can lose more than 20% of their body weight over the course of the summer breeding season, the researchers said.

"It's a pretty arduous task, especially for the males," said Marks. "If a male doesn't have enough fat to last these fasts, he may have to abandon the eggs and go to sea before the female can make it back. So it's imperative that the female pick a male in good condition," she added.

The researchers wanted to know how courtship calls help a penguin female choose the father of her chicks. "We knew that females preferred some males over others. But we didn't know what traits females were using to choose a good mate," said co-author Dianne Brunton of Massey University in New Zealand.

"If she chooses a male with a particular kind of call, does she have a better chance of successfully raising chicks?" Marks asked.

To find out, Marks traveled to Antarctica's remote Ross Island, summer home to half a million Adelie penguins. Over the course of the next three months she weighed dozens of males and recorded their calls with a handheld microphone. She also noted how successful they were at attracting mates and raising chicks.

When the researchers examined the calls, they found that steady frequency over the longest part of the call -- an extended chattering in the middle of the male's display -- best predicts male buffness and breeding success. "It's as if females are listening to the stability of the call," said Marks.

Males with more consistent pitch were snatched up more quickly. These males were also heavier and more successful at raising chicks, the researchers found. "The fat surrounding the male's voice box changes what his call sounds like," said Brunton. "We don't yet know the physiological mechanism for call production, but body fat appears to stabilize their calls," Marks added.

By listening to male courtship calls, a female can tell how fat a male is and what kind of father he'll be, Brunton explained. Fatter males make better fathers because they have the energy reserves to endure long fasts, so are less likely to leave the nest and desert their chicks.

"A fat male is a good choice for a female because males do so much of the offspring care," said Brunton. "They're able to incubate the eggs for longer and use up their fat stores, while skinny males aren't able to do that."

The researchers also wondered if males were always honest about their potential as caring fathers, or merely bluffing to attract a mate. "What if the guy calls, and it turns out he's a skinny bird pretending to be a fat bird, making himself sound better than he really is?" said Marks.

"Females can't judge how fat a male is just by looking at him," said Brunton. "How fat he looks depends on how he's standing and how fluffed up his feathers are."

A male who lies about his paternal commitment might increase his chances of passing on his genes, said co-author Allen Rodrigo, Director of the National Evolutionary Synthesis Center in Durham, North Carolina. For that reason, females are likely to be on the lookout for the most honest indicators of paternal potential, he explained.

As penguin dads lost weight over the chick-rearing season, their calls changed too, Marks found. "So a skinny male is unlikely to be able to pretend he's a big fat male. He can't fake it," said Marks.

Text by National Evolutionary Synthesis Center Photo by Emma Marks

Newly detected rising sea levels in parts of the Indian Ocean, including the coastlines of the Bay of Bengal, the Arabian Sea, Sri Lanka, Sumatra and Java, appear to be at least partly a result of human-induced increases of atmospheric greenhouse gases, says a study led by the University of Colorado at Boulder.

The study, which combined sea surface measurements going back to the 1960s and satellite observations, indicates anthropogenic climate warming likely is amplifying regional sea rise changes in parts of the Indian Ocean, threatening inhabitants of some coastal areas and islands, said CU-Boulder Associate Professor Weiqing Han, lead study author. The sea level rise -- which may aggravate monsoon flooding in Bangladesh and India -- could have far-reaching impacts on both future regional and global climate.

The key player in the process is the Indo-Pacific warm pool, an enormous, bathtub-shaped area of the tropical oceans stretching from the east coast of Africa west to the International Date Line in the Pacific. The warm pool has heated by about 1 degree Fahrenheit, or 0.5 degrees Celsius, in the past 50 years, primarily caused by human-generated increases of greenhouse gases, said Han.

"Our results from this study imply that if future anthropogenic warming effects in the Indo-Pacific warm pool dominate natural variability, mid-ocean islands such as the Mascarenhas Archipelago, coasts of Indonesia, Sumatra and the north Indian Ocean may experience significantly more sea level rise than the global average," said Han of CU-Boulder's atmospheric and oceanic sciences department.

A paper on the subject was published in Nature Geoscience. Co-authors included Balaji Rajagopalan, Xiao-Wei Quan, Jih-wang Wang and Laurie Trenary of CU-Boulder, Gerald Meehl, John Fasullo, Aixue Hu, William Large and Stephen Yeager of the National Center for Atmospheric Research in Boulder, Jialin Lin of Ohio State University, and Alan Walcraft and Toshiaki Shinoda of the Naval Research Laboratory in Mississippi.

While a number of areas in the Indian Ocean region are showing sea level rise, the study also indicated the Seychelles Islands and Zanzibar off Tanzania's coastline show the largest sea level drop. Global sea level patterns are not geographically uniform, and sea rise in some areas correlate with sea level fall in other areas, said NCAR's Meehl.

The Indian Ocean is the world's third largest ocean and makes up about 20 percent of the water on Earth's surface. The ocean is bounded on the west by East Africa, on the north by India, on the east by Indochina and Australia, and on the south by the Southern Ocean off the coast of Antarctica.

The patterns of sea level change are driven by the combined enhancement of two primary atmospheric wind patterns known as the Hadley circulation and the Walker circulation. The Hadley circulation in the Indian Ocean is dominated by air currents rising above strongly heated tropical waters near the equator and flowing poleward, then sinking to the ocean in the subtropics and causing surface air to flow back toward the equator.

The Indian Ocean's Walker circulation causes air to rise and flow westward at upper levels, sink to the surface and then flow eastward back toward the Indo-Pacific warm pool. "The combined enhancement of the Hadley and Walker circulation form a distinct surface wind pattern that drives specific sea level patterns," said Han.

The international research team used several different sophisticated ocean and climate models for the study, including the Parallel Ocean Program -- the ocean component of NCAR's widely used Community Climate System Model. In addition, the team used a wind-driven, linear ocean model for the study.

"Our new results show that human-caused changes of atmospheric and oceanic circulation over the Indian Ocean region -- which have not been studied previously -- are the major cause for the regional variability of sea level change," wrote the authors in Nature Geoscience.

Han said that based on all-season data records, there is no significant sea level rise around the Maldives. But when the team looked at winter season data only, the Maldives show significant sea level rise, a cause for concern. The smallest Asian country, the Maldives is made up of more than 1,000 islands -- about 200 of which are inhabited by about 300,000 people -- and are on average only about five feet above sea level.

The complex circulation patterns in the Indian Ocean may also affect precipitation by forcing even more atmospheric air down to the surface in Indian Ocean subtropical regions than normal, Han speculated. "This may favor a weakening of atmospheric convection in the subtropics, which may increase rainfall in the eastern tropical regions of the Indian Ocean and increase drought in the western equatorial Indian Ocean region, including east Africa," Han said.

The new study indicates that in order to document sea level change on a global scale, researchers also need to know the specifics of regional sea level changes that will be important for coastal and island regions, said NCAR's Hu. Along the coasts of the northern Indian Ocean, seas have risen by an average of about 0.5 inches, or 13 millimeters, per decade.

"It is important for us to understand the regional changes of the sea level, which will have effects on coastal and island regions," said Hu.

Text by University of Colorado at Boulder Graphic by Reto Stockli, NASA Earth Observatory

Rising levels of antidepressants in coastal waters could change sea-life behavior and potentially damage the food-chain, according to a new study.

Research into the behavior of shrimps exposed to the antidepressant fluoxetine, showed that their behavior is dramatically affected. The shrimps are five times more likely to swim toward the light instead of away from it -- making them more likely to be eaten by fish or birds, which could have devastating effects on the shrimp population.

"Crustaceans are crucial to the food chain and if shrimps' natural behavior is being changed because of antidepressant levels in the sea this could seriously upset the natural balance of the ecosystem," said Dr Alex Ford from the University of Portsmouth's Institute of Marine Sciences.

"Much of what humans consume you can detect in the water in some concentration. We're a nation of coffee drinkers and there is a huge amount of caffeine found in waste water, for example. It's no surprise that what we get from the pharmacy will also be contaminating the country's waterways."

The research is published in the journal Aquatic Toxicology. The study found that the shrimps' behavior changes when they are exposed to the same levels of fluoxetine found in the waste water that flows to rivers and estuaries as a result of the drugs humans excrete in sewage.

Dr Ford's research was motivated by a species of parasite which can alter the behavior of aquatic creatures through changing serotonin levels within the brains of the organisms. Serotonin is a neuro-hormone found in many animals, including humans, known to control types of behavior, such as modulating mood and decreasing anxiety.

Drugs to combat depression in humans are often designed to target levels of serotonin which led to the question of whether they could also alter the behavior of marine organisms.

Dr Ford said: "Effluent is concentrated in river estuaries and coastal areas, which is where shrimps and other marine life live -- this means that the shrimps are taking on the excreted drugs of whole towns."

Prescriptions for antidepressants have risen rapidly in recent years, according to the Office for National Statistics. In 2002, there were 26.3 million antidepressant prescriptions handed out by doctors in England and Wales -- yet the environmental effect of pharmaceuticals in sewage has been largely unexplored.

Dr Ford is hoping to carry out future research on a number of other prescribed drugs on the market known to affect serotonin.

Head of the School of Biological Sciences, Professor Matt Guille, said: "Dr Ford has conducted some beautifully simple research, which potentially shows huge ecological consequences. I hope it will lead the way for further study of prescribed drugs and other substances impacting on the country's marine-life."

Text and Photo by University of Portsmouth

Just like people in a bar or other noisy location, North American right whales increase the volume of their calls as environmental noise increases; and just like humans, at a certain point, it may become too costly to continue to shout, according to marine and acoustic scientists.

"The impacts of increases in ocean noise from human activities are a concern for the conservation of marine animals like right whales," said Susan Parks, assistant professor of acoustics and research associate, Applied Research Laboratory, Penn State. "The ability to change vocalizations to compensate for environmental noise is critical for successful communication in an increasingly noisy ocean."

Right whales are large baleen whales that often approach close to shore. They may have been given the name because they were the right whales to hunt as they are rich in blubber, slow swimming and remain afloat after death. Consequently, whalers nearly hunted these whales to extinction. Currently right whales are monitored to determine the health and size of the population. The northern and southern right whales are on the endangered species list.

"Right whale upcalls are used extensively for passive acoustic monitoring in conservation efforts to protect this endangered species," said Parks.

Whales produce upcalls, sometimes called contact calls, when they are alone or in the process of joining with other whales. An upcall begins low and rises in pitch. It is the most frequent call produced by right whales.

Parks and her colleagues, Mark Johnson and Peter L. Tyack, Woods Hole Oceanographic Institution and Douglas Nowacek, Duke University, looked at short-term modifications of calling behavior of individual North Atlantic right whales in varying environmental noise situations. They report their results in Biology Letters.

The researchers' data came from right whales tagged with acoustic suction cup tags. They listened to tag recordings from seven male and seven female whales totaling 107 calls. The tags recorded from 2 to 18 calls each. The team looked at received level, duration and fundamental frequency of the calls, and they compared background noise levels with the call-received levels of the individual calls. Noise below 400 Hertz dominated the recorded background noise. These frequencies overlap with the frequencies of right whale upcalls. Much of the increase in background ocean noise in right whale habitat is believed to be due to commercial shipping.

It appears that right whales increase the amplitude, or the energy in their calls, directly as background noise levels increase without changing the frequency. This suggests that right whales can maintain the signal to noise ratio of their calls in moderate levels of ocean noise.

"To our knowledge, this is the first evidence for noise-dependent amplitude modification of calls produced by a baleen whale," said Parks.

Changing calling patterns can, however, incur costs including increased energy expenditure, alteration of the signal and the information it contains, and increased predatory risks. With increased noise the effective communication range for feeding or mating will shrink and stress levels on individual animals may rise.

"Whether they can maintain their communication range in noisier environments still needs to be tested," said Parks. "Ocean sound levels will probably continue to increase due to human activities and there is a physical limit to the maximum source level that an animal can produce."

Another implication for potential changes in whale calls is that upcalls are the whale calls that conservationists use to monitor right whale populations. They do this using automated acoustic sensors that are looking for specific parameters to tease out the whale calls from other noises.

The research team cautions that "Variability of call parameters also can reduce the effectiveness of detection algorithms and should be taken into account when calculating the probability of detection in different habitats."

Text and Photo by Penn State

Scientists have just returned from a voyage with samples of rare animals and more than 10 possible new species in a trip which they say has revolutionized their thinking about deep-sea life in the Atlantic Ocean.

One group of creatures they observed -- and captured -- during their six weeks in the Atlantic aboard the RRS James Cook is believed to be close to the missing evolutionary link between backboned and invertebrate animals.

Using the latest technology they also saw species in abundance that until now had been considered rare.

Researchers were also surprised to discover such diversity in habitat and marine life in locations just a few miles apart.

Scientists were completing the last leg of MAR-ECO -- an international research program, part of the Census of Marine Life, which is enhancing our understanding of the occurrence, distribution and ecology of animals along the Mid-Atlantic Ridge between Iceland and the Azores.

The University of Aberdeen is leading the UK contribution to the project which involves scientists from 16 nations. Key collaborators in the UK include Newcastle University and the National Oceanography Centre.

During more than 300 hours of diving -- using Isis the UK's deepest diving remotely operated vehicle (ROV) to depths of between 700m right down to 3,600m -- researchers surveyed flat plains, cliff faces and slopes of the giant mountain range that divides the Atlantic Ocean into two halves, east and west.

The research was focused in two areas -- beneath the cold waters north of the Gulf Stream and the warmer waters to the south.

Professor Monty Priede, Director of the University of Aberdeen's Oceanlab, said: "We were surprised at how different the animals were on either side of the ridge which is just tens of miles apart.

"In the west the cliffs faced east and in the east the cliffs faced west. The terrain looked the same, mirror images of each other, but that is where the similarity ended. It seemed like we were in a scene from Alice Through the Looking Glass.

"In the north-east, sea urchins were dominant on the flat plains and the cliffs were colorful and rich with sponges, corals and other life.

"In the north-west, the cliffs were dull gray bare rock with much less life. The north-west plains were the home of deep-sea enteropneust acorn worms. Only a few specimens, from the Pacific Ocean, were previously known to science.

"These worms are members of a little-known group of animals close to the missing link in evolution between backboned and invertebrate animals.

"The creatures were observed feeding and leaving characteristic spiral traces on the sea floor.

"They have no eyes, no obvious sense organs or brain but there is a head end, tail end and the primitive body plan of back-boned animals is established. One was observed showing rudimentary swimming behavior.

"By the end of the expedition three different species were discovered each with a different color, pink, purple and white with distinctly different shapes."

Using the remotely operated vehicle, high quality complete specimens of all three different-coloured species were captured and will be sent to specialists for further investigations.

Sea cucumbers, or holothurians, normally seen crawling incredibly slowly over the flat abyssal plains of the ocean floor, were found on steep slopes, small ledges and rock faces of the underwater mountain range.

Researchers were also surprised to see that they were very able and fast moving swimmers and unique video sequences were recorded of swimming holothurians.

Professor Priede said: "This expedition has revolutionized our thinking about deep-sea life in the Atlantic Ocean. It shows that we cannot just study what lives around the edges of the ocean and ignore the vast array of animals living on the slopes and valleys in the middle of the Ocean.

"Using new technology and precise navigation we can access these regions and discover things we never suspected existed."

Dr Andrey Gebruk, Shirshov Institute, Moscow, said: "We were surprised how species, elsewhere considered rare, were found in abundance on the Mid Atlantic Ridge and we were finding new species up to the last minute of the last dive in the voyage."

Text by Census of Marine Life Photo by David Shale

University of Leeds scientists have created the first convincing robotic fish that shoals will accept as one of their own. The innovation opens up new possibilities for studying fish behavior and group dynamics, which provides useful information to support freshwater and marine environmental management, to predict fish migration routes and assess the likely impact of human intervention on fish populations.

"We've proven it's possible to use robotic fish to study relationships between individuals and shoal dynamics as well as the behavior of individual fish," says PhD student Jolyon Faria who led the experiments. "In the past, we had to watch a shoal and change environmental conditions to see how that affected behavior. Because the robotic fish is accepted by the shoal, we can use it to control one or several individuals, which allows us to study quite complex situations such as aggressive, cooperative, anti-predator and parental behavior."

The computer controlled replica -- dubbed Robofish by its creators John Dyer, Dr Dean Waters and Natalie Holt -- is a plaster cast model of a three-spined stickleback with an acetate fin, painted to mimic the coloration and markings of a real fish. The scientists needed to prove that Robofish was accepted into the group sufficiently for the fish to respond to the robot like a normal shoal member.

"Although Robofish looked like a stickleback to us, we weren't sure whether the other fish would see it in the same light," explained Jolyon. "We also thought there might be a problem with the smell, as fish use chemical cues in the water to identify other shoal members. In the end, Robofish was accepted straight away -- though we did trial various models until we found one that worked the best."

Robofish was placed in a tank with either single fish or a group of ten, and then programmed to follow a set path at a slightly faster speed than normal fish. The aim was to see if Robofish could tempt other fish to leave the tank's refuge area and convince its companions to make a 90 degree turn.

Single fish left the refuge much sooner if Robofish instigated the move than they would on their own, though groups of fish left quite quickly without other motivation. Robofish was able to persuade both single fish and groups to make a turn. However, the longer time the fish spent in the tank, the less likely they were to display shoaling activity either on their own or in response to Robofish.

"Because Robofish moved faster and without stopping and tended to be at the front or on the edge of the shoal, the other fish saw it as bold and definite in its actions, which encouraged them to follow," said Jolyon. "The fish were more easily influenced by a bolder member when they were nervous in new surroundings. Once they'd got used to the tank, they moved round quite happily to explore the tank, rather than moving in unison as they did at the start."

The experiments -- funded through the Biotechnology and Biological Sciences Research Council and the Engineering and Physical Sciences Research Council -- have also allowed the researchers to answer a long-standing question of group dynamics: whether an individual's ability to influence a group is dependent on how close together its members are. In fact, when Robofish turned, its nearest neighbor did turn first, but it made no difference whether they were 9cm or 33cm away from the robot. Most models of group dynamics are based on the assumption that the closer you are to your neighbor the more influence you have, but this study has added weight to the argument that relative, rather than metric distance, is more important.

Text and Photo by University of Leeds

The dreaded giant freak wave that can appear on the open sea out of nowhere, can now for the first time be theoretically calculated and modeled: researchers at the Ruhr- Universitt Bochum and the University of Ume, Sweden have developed a new statistical model for non-linear, interacting waves in computer simulations. It explains how the water-wave system evolves, behaves and, above all, how it stabilizes itself. The model is also suitable for the calculation of other "extreme occurrences" - for example on the stock market - or more complex phenomena in plasma physics. Bochum's physicist Prof. Padma Kant Shukla and his Swedish colleague Prof. Bengt Eliasson report on their findings in Physical Review Letters.

Pioneers of the giant freak wave
Shukla and Eliasson already managed to simulate how the giant freak wave occurs on the computer four years ago. If two or more waves meet at a certain relatively small angle, they can progressively "amplify" each other. Two non-linear interacting waves therefore act very differently to a single wave which shows normal instabilities and breaks up into several small waves, which then run diagonally to each other. Two non-linear waves, however, cause the water to behave in a new way, for example, the emergence of downright "wave packets" with amplitudes three times higher than that of a single wave. Buoyed by strong currents and powerful - opposing - winds, the giant wave can continuously build up from there.

Bundled energy
With their new statistical model, the scientists have now succeeded in taking another crucial step towards explaining this freak wave: it results from combined non-linear effects in the wave-to-wave interaction and the dispersion of the "wave packets" in a certain direction. This causes the energy of the water to be concentrated "in a narrow band across a confined wavelength spectrum", and with sudden, large amplitude. The actual instability of individual waves is "saturated" through the broadening of the wave spectrum, thus the water-wave system temporarily stabilizes itself. This behavior is typical for the localized giant wave, the researchers explain. Their calculations tally with observations from experiments in large water tanks. "These show that long-crested water waves, i.e. groups of waves propagating in approximately the same direction, have an increased tendency to evoke extreme events," said Shukla and Eliasson.

A step towards prediction
The fact that the giant wave is no "sailor's yarn" has been known at least since the cruise liner Queen Elizabeth 2 encountered such a freak wave in 1995. The damage to passenger and cargo ships, but also for example to oil platforms at sea can be considerable. Shukla and Eliasson's statistical model is a contribution to being able to predict freak waves in certain regions - for example in the North Atlantic or the Mediterranean - and providing early warning in future. The deeper physical understanding of the giant wave and statistical calculation would have to be combined with new, improved methods of observation, the researchers say.

Text by Ruhr-Universitaet-Bochum Photo by NASA

University of Rhode Island Pharmacy Professor Bongsup Cho knows there are cancer-causing chemicals in diesel fumes and cigarette smoke.

The biomedical scientist also knows that some of the same chemicals are found in the gooey tar balls that are being produced as a result of the oil spill in the Gulf of Mexico, which began April 20 when a rig exploded and caught fire.

But what he and other scientists have little knowledge of is the long-range impact of the spill on humans and wildlife at the cellular level.

Cho studies the effects of environmental toxins such as cigarette smoke, diesel fumes and charred meat on DNA mutation as potential triggers for cancer.

For close to 20 years, the National Institutes of Health and the American Cancer Society have funded Cho's research on mechanistic understanding of DNA damage and its consequences on mutation and repair. "Such research is crucial in the development of effective strategies for chemoprevention and drug development, as well as risk assessment," he said.

Cho said the saturated hydrocarbons found in crude oil, such as methane, hexane and octane, evaporate quickly once in the ocean because they have low boiling points.

"These are the chemicals that can cause the respiratory problems in people involved in cleanup operations, but they are not the ones necessarily known as carcinogens," Cho said.

In many cases, these volatile organic compounds evaporate quickly when exposed to sunlight and heat. "Most would evaporate before people would suffer effects from them," Cho said.

But the tar balls and remaining thick ooze washing ashore and into marshes cause more worry for Cho.

"The tar balls contain the non-volatile, benzene-like, heavily unsaturated hydrocarbons with high boiling points," Cho said. "That's where there are a lot of toxins, such as benzo[a]pyrene. This is a known human carcinogen, and it is used as a biomarker to detect human exposure to toxins."

The researcher said a carcinogen usually has mutagenic and teratogenic effects on cells, meaning it can cause mutations in DNA and cause birth defects.

A study of the blood of individuals who worked on the Exxon Valdez cleanup following the spill in March of 1989 found DNA damage in those subjects. "DNA damage in certain functionally important areas of the genome can be a precursor to various human cancers," Cho said.

While individuals can get sick when volatile organic compounds evaporate, they would have to absorb the non-volatile compounds through ingestion or actual physical contact, he added.

"It has been reported that the size of the Gulf oil spill is unprecedented, much greater than that of the the (land mass) of New England area combined. You have to wonder about the fate of the crude oil that has not come ashore and recovered and what long term effects such toxins will have on the food chain," Cho said. "The pollutants from these toxins are going to be there for a long time."

Cho is worried about another phenomena from the spill-- the orange sheen seen on the surface of the gulf.

"That orange sheen is a result of a chemical reaction involving the sun, the crude oil and the oil dispersants," Cho said. "But nobody knows what's in that color and how toxic the chemicals are. Companies keep the chemical makeup of the dispersants secret.

"Crude oil, like diesel fuel and cigarette smoke, contain thousands of chemicals, and we have studied only a few, so the big worry is the unknown activity of those chemicals we have not studied. According to the recent Cancer Advisory Board report to President Barack Obama, Americans are constantly exposed to chemicals. There are 80,000 of them, and we only know a little about them."

Text and Photo by University of Rhode Island

The latest image of Pacific Ocean sea surface heights from the NASA/European Ocean Surface Topography Mission/Jason-2 oceanography satellite, dated June 11, 2010, shows that the tropical Pacific has switched from warm (red) to cold (blue) during the last few months.

The blue area in the center of the image depicts the recent appearance of cold water hugging the equator, which the satellite measures as a region of lower-than-normal sea level. Remnants of the El Nino warm water pool, shown here in red and yellow, still linger north and south of the equator in the center of the image.

The image shows sea surface height relative to normal ocean conditions. Red (warmer) areas are about 10 centimeters (4 inches) above normal. Green areas indicate near-normal conditions. Purple (cooler) areas are 14 to 18 centimeters (6 to 7 inches) below normal. Blue areas are 5 to 13 centimeters (2 to 5 inches) below normal.

"The central equatorial Pacific Ocean could stay colder than normal into summer and beyond. That's because sea level is already about 10 centimeters [4 inches] below normal, creating a significant deficit of the heat stored in the upper ocean," said JPL oceanographer and climatologist Bill Patzert. "The next few months will reveal if the current cooling trend will eventually evolve into a long-lasting La Nina situation."

A La Nina is essentially the opposite of an El Nino. During a La Nina, trade winds in the western equatorial Pacific are stronger than normal, and the cold water that normally exists along the coast of South America extends to the central equatorial Pacific. La Ninas change global weather patterns and are associated with less moisture in the air, resulting in less rain along the coasts of North and South America. They also tend to increase the formation of tropical storms in the Atlantic.

"For the American Southwest, La Ninas usually bring a dry winter, not good news for a region that has experienced normal rain and snowpack only once in the past five winters," said Patzert.

Text and Graphic by NASA/Jet Propulsion Laboratory