How Sea Snakes Survive Without Water to Drink

Earth is awfully wet: about 70 percent of the planet is covered by deep, blue expanses of water. But to ocean-faring sea snakes, their briny habitat is an oxymoron: Home is a vast aquatic desert.

Creatures like the sea snake were thought to live completely independent of fresh water, by quenching their thirsts through some type of saltwater adaptation like other marine animals. But now researchers have discovered that one species, the yellow-bellied sea snake, in fact relies on rainfalls for drinking water, and in between rains is able to make do in an extreme state of dehydration.

Scientists have recently started questioning whether marine vertebrates, such as the sea snake, truly live independently of fresh water. Several species of animals, including sea turtles, bony fishes, dolphins and whales developed specialized adaptations to thrive in saltwater. For example, birds and some marine reptiles have salt glands to excrete excess salts from the water they drink. 

It was commonly believed that sea snakes adapted to their environment in a similar fashion. But several studies published within the past few years have shown a link between fresh water availability and the distribution of sea snake populations. The only sources of fresh water in the open sea are narrow bands of freshwater lenses that are known to form on the surface of the ocean following heavy rainfalls. Since sea snake populations are often concentrated around these bands of freshwater, researchers believed they depend on the water for survival.

If this was true, it must mean that sea snakes can survive extreme dehydration. To see if this was indeed the case, researchers captured 500 yellow-bellied sea snakes on the Guanacaste coast off of Costa Rica. They wanted to test if the snakes would drink fresh water immediately following capture. If the snake was thirsty, it was a good sign that it was also dehydrated.

The researchers dried the snakes off, weighed them and measured them before giving them fresh water to drink. They found that snakes tended to drink more following periods of low rainfall, and the lighter they were (and thus the more dehydrated they were), the more they drank.

Their findings show that sea snakes live in a dehydrated state for several months at a time, due to the length of the dry season on the Guanacaste coast (December through May or June). The researchers published their results this week in the journal Proceedings of the Royal Society B.

The results show both the tenacity and fragility of yellow-bellied sea snakes, and perhaps other marine snakes. Dehydration at sea could be a unique challenge to marine vertebrates like the sea snake, and may explain their rapidly declining populations in some parts of the world.

Further study of these thirsty reptiles could help scientists determine how changing precipitation patterns in tropical oceans will impact these animals.

Photo credit: RobHamm/Shutterstock

View the original article here

Chemists work to desalinate the ocean for drinking water, one nanoliter at a time

View the original article here

Common Water

Sorry, I could not read the content fromt this page.

View the original article here

Science Podcast - Fracking and water quality, science software, flavor science, and more (17 May 2013)

Sorry, I could not read the content fromt this page.Sorry, I could not read the content fromt this page.

View the original article here

Picking apart photosynthesis: New insights could lead to better catalysts for water splitting

This illustration depicts a metal cluster prepared in the agapie group on a background of photosystem ii, the protein complex that performs photosynthesis in leaves. Credit: Emily Tsui

(Phys.org) —Chemists at the California Institute of Technology (Caltech) and the Lawrence Berkeley National Laboratory believe they can now explain one of the remaining mysteries of photosynthesis, the chemical process by which plants convert sunlight into usable energy and generate the oxygen that we breathe. The finding suggests a new way of approaching the design of catalysts that drive the water-splitting reactions of artificial photosynthesis.

"If we want to make systems that can do artificial photosynthesis, it's important that we understand how the system found in nature functions," says Theodor Agapie, an assistant professor of chemistry at Caltech and principal investigator on a paper in the journal Nature Chemistry that describes the new results.

One of the key pieces of biological machinery that enables photosynthesis is a conglomeration of proteins and pigments known as photosystem II. Within that system lies a small cluster of atoms, called the oxygen-evolving complex, where water molecules are split and molecular oxygen is made. Although this oxygen-producing process has been studied extensively, the role that various parts of the cluster play has remained unclear.

The oxygen-evolving complex performs a reaction that requires the transfer of electrons, making it an example of what is known as a redox, or oxidation-reduction, reaction. The cluster can be described as a "mixed-metal cluster" because in addition to oxygen, it includes two types of metals—one that is redox active, or capable of participating in the transfer of electrons (in this case, manganese), and one that is redox inactive (calcium).

"Since calcium is redox inactive, people have long wondered what role it might play in this cluster," Agapie says.

It has been difficult to solve that mystery in large part because the oxygen-evolving complex is just a cog in the much larger machine that is photosystem II; it is hard to study the smaller piece because there is so much going on with the whole. To get around this, Agapie's graduate student Emily Tsui prepared a series of compounds that are structurally related to the oxygen-evolving complex. She built upon an organic scaffold in a stepwise fashion, first adding three manganese centers and then attaching a fourth metal. By varying that fourth metal to be calcium and then different redox-inactive metals, such as strontium, sodium, yttrium, and zinc, Tsui was able to compare the effects of the metals on the chemical properties of the compound.

"When making mixed-metal clusters, researchers usually mix simple chemical precursors and hope the metals will self-assemble in desired structures," Tsui says. "That makes it hard to control the product. By preparing these clusters in a much more methodical way, we've been able to get just the right structures."

It turns out that the redox-inactive metals affect the way electrons are transferred in such systems. To make molecular oxygen, the manganese atoms must activate the oxygen atoms connected to the metals in the complex. In order to do that, the manganese atoms must first transfer away several electrons. Redox-inactive metals that tug more strongly on the electrons of the oxygen atoms make it more difficult for manganese to do this. But calcium does not draw electrons strongly toward itself. Therefore, it allows the manganese atoms to transfer away electrons and activate the oxygen atoms that go on to make molecular oxygen.

A number of the catalysts that are currently being developed to drive artificial photosynthesis are mixed-metal oxide catalysts. It has again been unclear what role the redox-inactive metals in these mixed catalysts play. The new findings suggest that the redox-inactive metals affect the way the electrons are transferred. "If you pick the right redox-inactive metal, you can tune the reduction potential to bring the reaction to the range where it is favorable," Agapie says. "That means we now have a more rational way of thinking about how to design these sorts of catalysts because we know how much the redox-inactive metal affects the redox chemistry."

The paper in Nature Chemistry is titled "Redox-inactive metals modulate the reduction potential in heterometallic manganese-oxido clusters."

Journal reference: Nature Chemistry

Provided by California Institute of Technology

View the original article here