Monday, October 29, 2012

Dead Sea Diving

The Dead Sea has such a high saline content
that pillars of salt form near its banks.

Lying on the border of Israel and Jordan, the Dead Sea is a one of the best-known examples of a hypersaline lake. With a salinity of 33.7 percent, it is more than ten times saltier that the ocean. And at 377 meters deep, it’s also the world’s deepest hypersaline lake. 
   The Jordan River used to feed fresh water into the Dead Sea, but in the 1950s it was diverted to supply drinking water to Israel and Jordan instead. This lowered the lake’s water level, and it continues to drop more each year. Water levels have fallen by more than 25 meters over the last 40 years. Since the basin has no outlet, water only escapes by evaporation, leaving behind salt and other minerals. Over time, this made the Dead Sea much saltier than ocean water.
   Fish can’t survive in the Dead Sea, but it’s not totally lifeless. Extremophiles—organisms adapted to live in extreme conditions such as high temperature or salinity—do live in the Dead Sea. Salt-loving microbes known as halophiles can survive and thrive in the lake.
   In 2010, researchers from Ben-Gurion University found several giant craters at depths of 30 meters spewing fresh water and brimming with bacteria at the bottom of the otherwise barren lake. The craters were covered with thick layers of a new microbial species that live near fresh water plumes that shoot from underwater springs.
   Reaching the springs is a bit of a challenge. Divers carry about 40 kg of weight to lower their buoyancy enough to sink, since the salty water is so dense it makes you float. They also must wear full face masks to protect their eyes and mouths. Getting Dead Sea water in your eyes could cause blindness and swallowing it would cause choking and possibly suffocation.
   The bacteria they found were similar to what you’d find living in a regular saltwater ocean. These bacteria use both sunlight and sulfides to survive. Not only have the organisms evolved in such a harsh environment, the bacteria can cope with sudden changes in salinity as fresh water and saltwater currents swirl around the springs.
   Normally, highly salt-adapted bacteria die when placed in fresh water, and fresh water bacteria die when they come in contact with salt water. Researchers claim that being able to live in both environments is something very unexpected and deserves further study. 

Saturday, October 20, 2012

The Evolution of Sight

The compound eye of the Arctic krill is highly evolved
for such a small creature.

Our vision is based upon a very small sliver of the electromagnetic (EM) spectrum. Humans can sense EM radiation between the wave lengths of 380 nm and 750 nm, ranging from violet through red. We cannot see, however, all the electromagnetic chatter that is happening around us outside the visible range. We’re bathed in an ocean of electromagnetic waves all day, every day. There is nothing qualitatively different about the visible portion of the spectrum compared to radio waves or ultraviolet waves, for example; it’s just that we can sense some waves (which we call light), yet have no awareness outside this narrow range.
   There’s a very good reason for this—it’s not just a coincidence. It’s because of the way light attenuates in water. Attenuation is the physical property that describes the gradual decrease in intensity of electromagnetic radiation as it travels through a medium—in this case sea water. When the Sun’s rays reaches the surface of the ocean, visible light is absorbed at the longest wavelengths, red and orange, first. Blue and violet wavelengths reach deeper into the water column, which is why deep-ocean water appears blue.
The attenuation (decibels/meter) of EM radiation in water as a function of wavelength (nm). EM attenuation in water drops six orders of magnitude just around the visual range.
   Now expand this concept to the entire spectrum of EM radiation. Species began to evolve eyes during the Cambrian explosion (about 540 million years ago), while life was still confined to the sea. Eyes developed sensitivity to the 380-750 nm range because that band of EM radiation travels through water with an attenuation 1,000 orders of magnitude lower than that of adjacent wavelengths. Being able to see in deeper water provided an evolutionary advantage, so the earliest animals developed sensitivity in the portion of the spectrum that reached the greatest depth. During this time the eye developed rapidly. After creatures began to move onto land, there was no evolutionary incentive to see a larger portion of the spectrum because every other organism also saw in this range.
A Trilobite fossil with the eye structure outlined in red.
   Sight gave predators the ability to find prey, triggering an evolutionary arms race where animals either evolved or died. Trilobites possessed highly-advanced compound eyes that gave them a competitive advantage in both finding food and avoiding predators. It’s no surprise that trilobites thrived during the Cambrian explosion to become one of the most diverse and successful classes of all the early animals, roaming the oceans of the world for the next 270 million years. Continual adaptation during the Cambrian explosion was needed in order to maintain relative fitness amongst all the other species that were evolving at the same time. This is known as the Red Queen Effect, a term taken from Lewis Carroll’s Through the Looking-Glass where Alice and the Red Queen are running yet not getting anywhere: 
   “Well, in our country,” said Alice, still panting a little, “you’d generally get to somewhere else—if you run very fast for a long time, as we’ve been doing.”
   “A slow sort of country!” said the Queen. “Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!”

Monday, October 15, 2012

The Antarctic Paradox

A phytoplankton bloom off the
coast of Argentina.

Recently I wrote about how the population of Antarctic krill has dropped by 80% over the last 40 years. I have to admit, I was feeling a bit depressed after writing that column. It seems that the natural world is forever being drop-kicked at the expense of progress. But are the two competing worlds forever destined to be in conflict? Maybe not.
   Let’s look a little closer at the problem of declining krill numbers. It’s paradoxical that there are vast areas of the Southern Ocean that contain plenty of nutrients to support phytoplankton growth, the primary food source for krill, yet we don’t see the growth that would normally be expected. These low-plankton regions near Antarctica are called HNLC areas because the have High Nutrient yet Low Chlorophyll.
   The main reason for this is a lack if iron in the water. Iron is an element that is required in trace amounts for photosynthesis to take place, but it is insoluble in sea water, making it a limiting nutrient for plankton growth.
   Over the last 20 years, there has been considerable research into the problem and it has been shown that phytoplankton growth can be stimulated by adding iron. Usually such iron fertilization occurs naturally by ocean current upwellings, wind-born dust being deposited over the ocean’s surface or iron-rich minerals being carried to the ocean by glaciers or icebergs. 
   And there is another potential benefit beyond boosting the bottom of the food chain. When Mount Pinatubo erupted in 1991, it deposited about 40,000 tons of iron-rich dust into the world’s oceans. What happened as a result was remarkable: over the next few years, phytoplankton blooms increased substantially, causing planetary carbon dioxide levels to drop and oxygen levels to increase. It was estimated that over a billion tons of CO2 was removed from the atmosphere.
   There are now plans underway to do this on a large-scale, commercial basis. However, there is considerable uncertainty and disagreement as to whether it will do more harm than good on a large scale. Some scientists remain skeptical about whether the process would remove carbon dioxide for the long term and what the ecological impact will be. Further experimentation is needed and one thing is for certain: future policies and carbon-offset markets will emerge, and possibly without a sound scientific basis. Iron fertilization should be considered along with any other geoengineering solution. And if it feeds a few more whales in the process, all the better.

Sunday, October 7, 2012

A Strange Sight Over Moscow

On October 7th, 2009, a strange-looking formation was seen in the sky over Moscow. When it appeared, scores of supernatural enthusiasts speculated that it had been created be an alien spacecraft. Turns out, it was actually a hole-punch cloud. Because the center of the formation appears to be a falling streak of clouds, nepholologists call it a fallstreak hole. 
   A fallstreak hole is a large circular gap that can appear in cumulus clouds, usually at an elevation of six kilometers or more above the Earth. Such holes form when a cloud is made of both ice crystals and super-cooled water droplets that exist together in a delicate balance. When such a balance occurs, it only takes a slight disruption, such as a passing jet, to set off a chain reaction that transforms the super-cooled water droplets into ice which clings to existing ice particles. The quick build-up of ice falls from the cloud and dissipates the water, creating a void.
   Hole-punch clouds are rare, but when they do form, they’re large enough to be seen for many kilometers in every direction. Because they are so rare and have an unusual appearance, fallstreak holes are often mistaken for UFOs.
   Upon further investigation of the Moscow hole-punch cloud incident, it seems to have been inadvertently caused by the Russian Air Force—at the request of Yury Luzhkov, Moscow’s mayor—to test its cloud-seeding program. The idea was to fly over the approaching clouds and spray silver iodide into them. Moisture would quickly condense around the fine particles, creating snow much sooner than it would normally. 
   In theory, if the clouds shed enough precipitation before reaching the city, Moscow could avoid the usual heavy winter snowfalls for which they are so well known. Luzhkov said such efforts could save the city $4 million in snow-removal costs each year, and improve their quality of life during winter.
   But there was a problem: Mother Nature refused to cooperate. The pilots needed two weeks advance notice for maximum effectiveness, yet meteorologists had a hard enough time predicting snowfall two days in advance. So while Luzhkov blamed the hapless weathermen and promised to find a solution, Muscovites did not hold their breath. 

Monday, October 1, 2012

Bengal Tigers of the Sundarbans

The Sundarbans is a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site covering parts of Bangladesh and India. The region is densely covered by mangroves, and is the largest mangrove forest in the world. It is also one of the largest reserves for the Bengal tiger.
   The Sundarban forest lies in the expansive Bay of Bengal delta. Inland from the mangrove forest lies the seasonally flooded Sundarbans freshwater swamp. The Sundarbans is estimated to cover about 4,100 square kilometers and serves as a protective barrier against cyclone flooding. 
   A 2007 UNESCO report states that a likely 45-cm rise in sea level by the end of this century, along with other human-derived stresses, could lead to the destruction of 75% of the Sundarbans mangroves. 
A satellite image of the Sundarbans.
   The Sundarbans is intersected by a complex network of tidal waterways, mudflats and small islands of mangrove forests. Almost every part of the forest is accessible by boat. The fertile soil of the delta has been used for agriculture for centuries, with the forested regions dwindling to about one third the size that it originally measured some 200 years ago. What remains, along with the Sundarbans mangroves, is an important habitat for the endangered Bengal tiger. 
   Over the past century, the tiger population has fallen dramatically, and continues to decrease. Loss of habitat and poaching are the two most-serious threats to their survival.
   In 2006, the Indian government granted some of their most impoverished communities the right to own property in the forests, which brings them in conflict with the Bengal tiger. Tiger attacks in the Sundarbans kill from 50 to 250 people each year. Although precautions that were enacted in 2004 temporarily stalled the attacks, recently attacks have been on the rise. In 2007, Cyclone Sidr devastated the Bangladesh side of the swamp, depriving the tigers of their usual food sources and pushing them towards the more populated Indian side of the Sundarbans.
   Villagers tried wearing face masks on the back of their heads to confuse the tigers, which prefer to attack from behind. This worked for a while until the tigers figured it out, after which the attacks continued. Government workers wear strong padding on the back of the necks, similar to those worn by U.S. football players, to prevent the tigers from biting their spine. This is their favorite method of attack.
   Villagers in the area occasionally release livestock into the forest in order to provide an alternative food source for the tigers and discourage them from coming into the villages. The government subsidizes the project to encourage village participation.

If you enjoyed this article you might also want to read my article on the Siberian Tiger Project.