Activities of November 3rd, 2006
By Nathalie Cabrol
Today we embarked on a high-altitude fishing trip...sort of. To be specific, high-altitude plankton netting. Since we are still waiting for the main equipment, which should arrive Monday, we decided to keep up with our schedule of scientific work at the lagunas. Fortunately, part of our equipment was sent directly to Bolivia and we had everything we needed: Plankton nets, boots, waders, sample bottlesÑand a plan.
Our goal was to sample copepods in Laguna Blanca. These tiny crustaceans, one millimeter or less in length locally, are extremely common in the world. However, we are not talking about common copepods here. Back in 2004, our team found a huge colony in the Licancabur summit lake at 5,916 meters. That alone makes it (to my knowledge) the highest colony reported so far. Obviously, with global warming and the formation of higher lakes in the Himalayas, it will not be long before we find them higher. But for now, we are focusing on those of the Licancabur region and they are fascinating.
Preliminary results of DNA sequencing for the Licancabur summit lake colony showed that the copepods were only 80% similar to other known copepod species, basically a different world. They are also as red as they can be. Underwater photographs clearly showed that their distribution in the water column followed very closely that of UV radiation (UVR) attenuation. On the surface of the summit lake, the total UVR is 216% that of sea level.
How did these copepods ended up in the summit lake? To what other organisms are they most closely related? Are their differences the results of adaptation to a unique environment, to isolation, or both? These are the questions that drove our "fishing" expedition at Laguna Blanca this morning. Laguna Blanca is located at the foot of Licancabur and we know from the presence of very pink flamingoes on the lake that there must be copepods in there. So, were the copepods of Laguna Blanca imported somehow to the summit lake and evolved there? Are they related? Did their eggs hitchhike on the backs of birds that we occasionally spotted in the crater during previous expeditions? The last eruption of Licancabur dates back 10,000 years. We do not know if there was only one lake or a series of lakes occupying the crater since then, alternately drying out and reappearing, but at most, evolution and adaptation had 10,000 years to work with. Now, how to demonstrate a potential link between copepods from Laguna Blanca and Licancabur (if any)? Go fishing and compare the DNA and morphology of the two colonies. Hence the boots, plankton nets, sunscreen, and sample bottles.
Next step: How do you find something that is really small in a very big lake? Either you waste a lot of time wandering around and do tentative sampling...or you get smart. Here, the concept of the food chain comes into action. We might not see the copepods but we definitely see the flamingoes feeding on them. Therefore, we took high positions on the lake shores by 9:30 am, when the thin layer of ice starts to melt and the flamingoes go grazing, and we watched where they were spending most of their time. After having ascertained the positions of a couple of potential good sites, we sneaked up on them with all the equipmentÉ They were not necessarily happy to share their sushi but we were certainly stunned to realize the incredible density of this colony of copepods. Each pass of the plankton nets brought myriads of them, from adults, to youngsters, females with eggs, and eggs.
This second day of science was extremely successful, following another very good day yesterday checking our UV plates. Tonight, we have achieved the first part of one of our most important science objectives. We have collected thousands of copepods from Laguna Blanca that will be shipped and distributed to 5 laboratories around the world in the coming days. The second part will be to obtain a comparable harvest from the summit lake of Licancabur to confirm our results of 2004 and to compare them with those from Laguna Blanca. Those samples will be sent to the same laboratories. We will finally know if /how the copepods of Laguna Blanca and those of the summit lake are related. About 1,500 meters in elevation separates them, and maybe thousands of years as well.
Differences were already obvious from simple observation. The adult copepods of Laguna Blanca are brownish, not red, except for the eggs and the young, which are very red). There are millions of them swimming at the surface of the lake whereas those of Licancabur were following closely UVR attenuation in the water column. None were observed above 50 cm depth. At Laguna Blanca, UVR is still 200% that of sea level. Is this slight difference ( 200%, as compared to 216% at 5,916 meters) enough to explain a difference in behavior? It cannot be related to season and reproduction since those of Licancabur were observed at the same time of the year in 2004. I am certain that these tiny creatures will have something interesting to teach us about UV adaptation.
The High Lakes 2006 team prepares to go "fishing" at Laguna Blanca.
Another spectacular sunrise at the refuge.
Flamingoes on Laguna Blanca point the way to the copepods.
The boots we used to go fishing, waiting for people to "suit up."
Rob, Clay and Matthieu bundle up. It was cold and windy the day we went fishing.
Nathalie and Macario drag one of the fishing nets along the surface of Laguna Blanca.
Nathalie and Macario again, with Edmond bring up the rear, holding the sample bottles. (But really, this is a nice picture of the mountains.)
Nathalie is excited because the fishing teams collected thousands of copepods and other wiggly things.
Nathalie pouring some of the collected organisms into a sample bottle held by Edmond. The purple gloves enable the team to avoid getting their hands sunburned while working in the water.
A close-up view of some of the copepods we collected. Photo by Matthieu Galvez.
Henry ties a plastic bag on his foot before putting on his second boot.