The lake was like a mirror!
It is really windy in Patagonia, Bariloche no exception. So, when the wind drops it’s a chance to get out a sample on the big lake, Nahuel Huapi. So, that’s what we did yesterday, getting samples to check the levels of suspended ash in the water, measuring lake temperature profiles (6.7 C, and well mixed to bottom at 50m), and light penetration (probably 2-3 times less than “normal”, before the eruption). We also took a few zooplankton net tows and found a few lonely cyclopoid copepods but were a bit surprised to see a pretty thick collection of a filamentous diatom (Aulacoseira?), unusual for the lake apparently. Video HERE.
On Friday we went to the lakes to the northwest, closer to the Puyahue eruption and near the devastated town of Villa la Angostura. (full set of pictures at: LINK) The crew consisted of me, Monica, Esteban Balseiro, and postdoc Marcela Bastidas. The picture below is from Lake Espejo Grande, and shows the dock and “beach”. Obviously, a lot of pumice has accumulated here, on the downwind side. The turquoise color of the water is also a sign of the volcano – normally the lake is dark blue and super-transparent. Along with many other lakes, it now has the turquoise cloudiness like a lake receiving glacial flour. But the cloudiness is from the suspended ash. Despite a steady rain, we took pumice samples here and in an arm of Lake Nahuel Huapi, as well as water samples in a shallow lake called Lago Pire.
Pumice accumulated at the downwind end of Lago Espejo Grande, ~20 km from the Puyahue Volcano
Posted by Jim: Here’s a very fresh satellite image of the area around Bariloche, Argentina, where I will be on sabbatical leave starting 1 Sept. To the northwest you can see the plume from the eruption of the Puyehue volcano in Chile, which is still ongoing. The big blue lake is Lake Nahuel Huapi (Bariloche is on its shores, to the southeast). Most notable are the gray swirls and blotches. These are gigantic floating islands of pumice. Full picture is here.
Gray rafts of floating pumice in Lake Nahuel Huapi. The Puyahue volcano is at upper left.
The pumice was deposited during the initial eruption a month ago and it has been washing ashore ever since (see Esteban Balseiro’s video). Winter is descending in Bariloche now and we are planning a series of studies of the effects of the eruption on nutrient cycling and plankton communities in Nahuel Huapi and beyond. Now if they would just reopen the Bariloche airport!