The primary research site for the 2011 Planetary Lake Lander field campaign is Laguna Negra, near the shore of which the PLL base camp is located. Laguna Negra (black lagoon) is so-named because it is so clear that at times its surface appears black.
But members of the PLL science team today began their exploration of a second nearby lake, Laguna Lo Encañado (rough translation: lagoon in a canyon). Unlike Laguna Negra, Laguna Lo Encañado is opaque, sea-green in color, and lies at the end of a long valley containing significant wetlands.
Until recently, Laguna Negra spilled over into Laguna Lo Encañado, which lies 200 meters lower in elevation. But the decrease in precipitation in the region and the shrinking of the Echaurren glacier, effects of rapid climate change, have caused the water level of Laguna Negra to drop several meters in only a few years.
Damaging UV radiation at 8500 feet above sea level, where Laguna Negra and Laguna Lo Encañado are situated, is much higher than at lower elevations. The difference between the two lakes, turbid Laguna Lo Encañado and transparent Laguna Negra, provides a valuable point of comparison for studying the strategies organisms employ to cope with this intense radiation.
The silt that washes into Laguna Lo Encañado absorbs UV radiation. Organisms living there don’t need to work as hard as do organisms in Laguna Negra to generate protective biological sunscreen compounds. Nor do they have to put as much energy into repairing DNA damage that exposure to UV radiation can cause.
Erich Fleming and Angela Detweiler, PLL team members based at the SETI Intitute and the NASA Ames Research Center (ARC) in Moffett Field, California, study the photosynthetic microbes that live in the two lakes. These organisms are capable of producing protective compounds to mitigate the effects of UV.
Ruben Sommaruga, a professor of limnology at the University of Innsbruck, in Austria, studies the organisms that live in alpine lakes, among them small, shrimp-like crustaceans known as copepods. Copepods obtain some of their UV-protective compounds by eating the microbes that live alongside them in the lakes. But when that doesn’t provide sufficient protection, they generate their own protection in the form of carotenoids, which turns them red. These same carotenoid compounds are found in carrots and are responsible for giving them their characteristic orange color.
Juvenile copepods – copepods go through many different stages before reaching adulthood – have not yet developed mouths, however, so they have no way to ingest protective compounds. In recent years scientists have learned that, at birth, juvenile copepods receive packages of protective compounds from their parents, to increase their chances of survival into adulthood.
Incidentally, all of us at PLL Base Camp are using the lake as the source of our drinking water. Which means we’re drinking a lot of copepods. We can see them, tiny little red dots floating around in our water bottles. To protect ourselves from UV, though, we still have to slather on sunscreen.
Quote of the day: “Now we have a system.”