Straddling the heavily populated border between Rwanda and the Democratic Republic of Congo, Lake Kivu contains huge amounts of dissolved carbon dioxide and highly combustible methane gas.

Scientists believe the overall danger across the lake as a whole is small, but a pocket of gas in the comparatively shallow Gulf of Kabuno in the north-western corner of the lake may prove more problematic. Just 12 meters below the surface, an estimated three cubic kilometres of carbon dioxide is present, right atop a tectonic faultline. Scientists fear a major earthquake or a large lava flow from a nearby volcano could lead to a giant release of gas from the gulf.

Congo’s environment minister warned on Tuesday that this gas could explode any day, threatening the lives of tens of thousands.

“The risk of explosion is imminent,” environment minister Jose Endundo told Reuters in an interview. “It’s like a bottle of Coca-Cola or champagne. If there is too much pressure inside the bottle, it will explode. It’s the same phenomenon.”

In 1986, about 1,700 people were killed in Cameroon as 1,2 million tonnes of carbon dioxide trapped under Lake Nyos was released into the air.

“The risk is that this gas escapes and asphyxiates thousands of people. There is an urgent need to evacuate gas from the Gulf of Kabuno, which now holds 10 times the amount of carbon dioxide that Lake Nyos contained,” Endundo said.

“Anything is possible, if this cloud is pushed by the wind,” says Michel Halbwachs, a volcanologist and Lake Kivu expert with France’s Universite de Savoie. “We could have a very light scenario or we could have a very heavy scenario. (…) Entire neighbourhoods could be hit.“

The shores of the Gulf of Kabuno are home to several large villages, and roughly 20 km to the east is the city of Goma with a resident population of roughly 1 million.

The World Bank has set aside $3 million to fund a project to remove gas from the gulf, but this isn’t enough to complete the project and Congo is therefore currently looking for other sources of finance. Earlier this year, Congo and Rwanda agreed to a joint project to produce 200 megawatts of power from Lake Kivu’s methane reserves. Pumping out the carbon dioxide together with the methane reserves could help alleviate the risk of a disaster. Rwanda is already extracting small amounts of methane from the lake using a demonstration rig. By the end of last year, the rig was producing 2 megawatts of power.

Acesulfame K passes through the human body into wastewater, survives water treatment and accumulates in groundwater, Swiss researchers have found.

Acesulfame K turned out to be much more resilient towards treatment than saccharin, sucralose, and cyclamate – three other popular and commonly used artificial sweeteners.

The scientists tested tap water, urban groundwater, and both treated and untreated water samples from 10 different wastewater treatment plants. They also collected water samples from four rivers and eight lakes near Zurich and from a remote alpine lake.

In the untreated wastewaters, they could detect the presence of all four sweeteners (acesulfame K, saccharin, sucralose, and cyclamate), but in treated water 90% of saccharine and 99% of cyclamate were eliminated. Sucralose withstood treatment somewhat better, but the concentrations were still small. Surprisingly enough, acesulfame K proved much more resilient towards treatment and the equivalent of 10 milligrams per person per day could be detected in both untreated and treated waters.

Treated water often end up in lakes and rivers and no one knows whether acesulfame K has any impact on fish or the environment.

“These concentrations are astronomically high,” says Associate Professor Bruce Brownawell, an environmental chemist at Stony Brook University, New York “If I had to guess, this is the highest concentration of a compound that goes through sewage treatment plants without being degraded.”

The research team found no detectable amounts of artificial sweeteners in the remote alpine lake, but in the other rivers and lakes the amount of acesulfame K increase proportionally with nearby human population sizes. Acesulfame could also be detected in 65 of 100 groundwater samples and small amounts of the sweetener were also present in tap water. The levels detected are not considered detrimental to human health and were far too low to change the taste of the water.

The study has been published in the journal Environmental Science & Technology .

War on clams has been declared at Lake Tahoe, a large freshwater lake in the Sierra Nevada Mountains of the United States. Scuba divers have been enrolled in a 400,000 USD project aiming to completely rid the lake of all Asian clams. The anti-clam endeavour is scheduled to begin in mid-March and is a combined effort by the governments of Nevada and California.

The Asian clam (Corbicula fluminea) is native to Asia and parts of Africa where it inhabits streams, canals and lakes. In this part of the world it is a natural part of the ecosystems and is even known as the prosperity clam or good luck clam. The Asian clam was introduced to North America in the 1920s by Asian immigrants for whom it was an appreciated source of food. It would however take until 2001 before the first specimens were encountered in Lake Tahoe. Since the first finding, the clam has been collected from numerous locations Tahoe’s southeast shore and authorities now fear that it will pave the way for even more dangerous invasive species such as the Ukrainian Quagga mussel (Dreissena rostriformis bugensis) and the Russian Zebra mussel (Dreissena polymorpha).

”We’re concerned they could create a positive settlement situation for the quagga mussels,” says Steve Chilton, aquatic invasive species coordinator for the U.S. Fish and Wildlife Service. ”We’re basically looking at all avenues through which the quagga mussel could get into the lake and eliminate that risk factor as much as possible.”

Steps so far have primarily focused on mandatory boat inspections to ensure no mussels are attached to them when they launch into the lake, but scuba divers participating in the new anti-clam project will actually be removing Asian clams from Lake Tahoe’s southeast shore. Starting in mid-March, divers will place plastic sheets, so called bottom barriers, over selected clam beds in order to deprive the clams of oxygen and nutrients. Divers will also carry out ”diver-assisted suction”, e.g. manually vacuum clams off the bottom of Tahoe.

”This needs to be done. We have to get our hands around the Asian clam problem,” Tahoe Regional Planning Agency spokesman Dennis Oliver told the Reno Gazette-Journal. ”We need to find out what works and what works best. Once we know that, we can develop a program.”

Invasive mussel species are known to form huge populations in environments where they lack natural predators and can for instance clog water intakes, attach themselves to boats and docks, and litter sandy beaches.

North America is not the only continent with an Asian mussel problem; Corbicula fluminea has begun to spread throughout Europe as well. It was found in the Rhine as early in the 1980s and then gradually found its way into the Danube through the Rhine-Maine-Danube Canal. In 1998 the first specimens were found in the Elbe and the species is now also present in the rivers of Portugal.

Lake Victoria, the world’s second largest lake and the world’s largest tropical lake, has long been plighted by environmental problems caused by pollution and exotic species being introduced to the lake. On of the most well know of these problems was the introduction of Nile perch to the lake; a large predatory fish that all but wiped out the lakes wide variety of native, endemic species.

Moses Kabuusu, Member of Parliament for Kyamuswa country in Kalangala district, has now expressed concerns about another problem developing in the area. According to him the amount of fish in the lake has now become so low that crocodiles are increasingly looking at humans as food. The number of croc attacks on humans has indeed increased in Kalangala, but it is hard to tell whether this is due to less fish being present or if there are other reasons that have increased the number of attacks on humans.

Kabuusu warns people about spending time in the water due to the rampant problem of humans being eaten by crocodiles and adds that it is mostly people swimming in the lake and women getting water in the lake that are being hunted by crocodiles.

He has requested help by the Uganda Wild Authority.

Lake victoria beach.

The release of sediment and algae-boosting fertilizers into Lake Victoria can cause cichlid species to interbreed in the murky water, according to Ole Seehausen, evolutionary biologist at the University of Bern in Switzerland and the Swiss Federal Institute of Aquatic Science and Technology in Kastanienbaum.

In a recent article published in Nature, Seehausen and his colleagues are shedding some light on the question of how closely related species of cichlids living adjacent to each other in Lake Victoria manages to avoid interbreeding. According to Seehausen et al, species may develop and stay distinct because of how the members of each species see colours.

Seehausen and his research team have studied closely related species of Lake Victoria cichlids where the males are either blue or red. It has since long been known that females of these species prefer to mate with the male displaying the brightest colours, but the new research suggests that both sexes have evolved to preferentially see only red or blue. This means that if a brightly coloured red male swims by a blue-seeing female, she will not be able to appreciate his sexy brightness since see can not see the colour red.

“Reds and blues live in the exact same spot,” says Seehausen,. “Colour is very important in mate choice.”

In order to fully understand the role of vision in underwater evolution, we must be aware of how light acts when it penetrates the water. Blue colours shine much brighter than red ones in the shallows, while red pigmentation trumps blue as we proceed farther down. As you probably have guessed already, red cichlid species tend to be found near the surface in Lake Victoria, while the blue ones inhabit greater depths.

To learn more about what happens to cichlids in the transition between red and blue zones in the lake, Seehausen and his team studied species inhabiting the shores of five different islands. The cloudiness of the surrounding waters varies from island to island due to variations in sedimentation, giving the researchers a great opportunity to study the effects of varying water clearness.

In comparatively clear waters, the colour that appears brighter slowly and gradually changes from red to blue with depth. This makes each species stay within its own zone and prevents interbreeding. In more clouded waters, the change from red to blue occurs much more suddenly, causing a higher prevalence of interbreeding between closely related species of fish.

Further testing in laboratory aquariums showed that hybrid females, like the ones living in cloudy waters, did not favour red males over blue ones or the other way around. This distinguished them from non-hybrid females, since females belonging to a species with red-sensing eyes picked red males in the laboratory tanks while the blue-sensing females opted for blue beaus.

Seehausen is now worried that the unchecked release of sediment and algae-promoting fertilizers into Lake Victoria will cause more and more fish to interbreed, thereby greatly reducing the number of species in a lake famous for its astonishing biological diversity and degree of endemic species. “Species diversity in this lake has imploded in the last 30 years,” Seehausen says. “It is the largest human-witnessed mass extinction of vertebrates.“

You can read more in the article “Speciation through sensory drive in cichlid fish” by Seehausen et al. http://www.nature.com/nature/journal/v455/n7213/abs/nature07285.html