Chemical water pollutants are generally atoms or molecules, which have been discharged into natural water bodies, usually by activities of humans. Common examples of such chemical water pollutants are mercury emanating from mining activity, certain nitrogen compounds used in agriculture, chlorinated organic molecules arising from sewage or water treatment plants or various acids which are the externalities of various manufacturing activities.

Physical water pollutants are either (a) much larger particles or (b) physical factors such as temperature change, both of which while not typically toxic, cause a variety of harmful effects. Read more

Sea ice is frozen seawater that floats on the ocean surface. Blanketing millions of square kilometers, sea ice forms and melts with the polar seasons, affecting both human activity and biological habitat. In the Arctic, some sea ice persists year after year, whereas almost all Southern Ocean or Antarctic sea ice is “seasonal ice,” meaning it melts away and reforms annually. While both Arctic and Antarctic ice are of vital importance to the marine mammals and birds for which they are habitats, sea ice in the Arctic appears to play a more crucial role in regulating climate.

Because they are composed of ice originating from glaciers, icebergs are not considered sea ice. Most of the icebergs infesting North Atlantic shipping lanes originate from Greenland glaciers. Read more

Dolphins use some algorithms of nonlinear math, scientists think. Supposedly, the smartest marine mammals do their calculations while hunting.

Researchers noticed that dolphins inject a jet of air bubbles into a shoal to make the fish crowd in one spot. However, these air bubbles might confuse the predators as well: dolphins use ultrasound sonars for orientation, but, as we know, air scatters sound waves. In order to move properly the mammals have to distinguish the sound reflected by the fish from the waves scattered by the bubbles. Read more

Titan, which is larger than Mercury, is the only world besides Earth known to have liquid on its surface. Its seas, made of liquid methane instead of water, have often led to speculation as to whether or not they could host life. In addition to its seas on its surface, scientists recently also discovered hints that Titan possesses an internal ocean, one of water and ammonia.

This artist’s illustration shows the likely interior structure of Saturn’s moon Titan.
The cool and sluggish interior failed to separate into completely differentiated layers of ice and rock. In addition to the hazy surface of Titan (yellow), the layers in the cutaway show an ice layer starting near the surface (light gray), an internal ocean (blue), another layer of ice (light gray) and the mix of rock and ice in the interior (dark gray). In the background are the Cassini spacecraft and Saturn, not to scale. Credit: NASA/JPL

Using radar to peer through Titan’s dense atmosphere, NASA’s Cassini spacecraft found that over time, a number of prominent surface features had shifted from their expected positions by up to 19 miles (30 kilometers), showing that the crust was moving and suggesting that it rested on liquid. Now Cassini’s gravity and radar observations of Titan have discovered more clues that it might have an underground sea. Read more

A crystal clear river is so clean that the 50ft deep riverbed can be seen from a bridge crossing over the water.

The 30km long Verzasca River in Switzerland is renowned all over the world for its clear turquoise waters.

Under the bridge: This stunning photo by Claudio Gazzaroli, 38, shows the arched Roman Bridge crossing over the Verzasca River in Switzerland from 50ft under water

But while pictures of the sparkling waters are often taken from the mountains surrounding the river or from bridges crossing over it, it’s much rarer to see photographs taken from the bottom of it. Read more