By Roy L Hales
We arrived at the Bavarian village of Iffeldorf the morning after the first snow, in late November, 2015. Dr. Uta Raeder, Co-Director of the Technical University of Munich (TUM) facility, greeted us in the parking lot. We huddled close, straining to catch her words before the wind, or traffic noises took, them away. She and her colleagues has been considering keeping us indoors. Instead they led us toward the boathouse, to see how they are monitoring how the climate is changing Germany’s lakes.
how climate is changing Germany’s lakes
Some of the blue-green algae and macrophytes (aquatic plants & higher algaes) in these lakes used to be typical of the Mediterranean.
A native macrophyte, found only in the warmest Bavarian lakes twenty years ago, is now common through-out Germany.
“These are indicators of warmer temperatures,” she said.
There were five of us, from print and web publications in Canada and the United States. Only four opted to venture out onto the lakes. I climbed into the first boat with Dr. Raeder, two of her colleagues and Danny Stephens from Germany Trade and Invest (GTAI). This was one of the stops on GTAI’s November 2015 press junket.
The string of twenty interconnected lakes has been here since the last Ice Age. They are ground fed, with water that does not freeze in the winter and remains cold throughout summer. Dr. Raeder said the lakes would not be as important if they emptied into a river.
Studying The Aquatic Macrophytes
They provide TUM with a natural laboratory, where the principal variables are depth of the groundwater inflows and the amount of pollution from the surrounding area. The university has been studying the aquatic macrophytes here since the 1970s.
“We use the macrophytes to identify the water quality, which is actually my main field of research. Normally waters dominated by macrophytes don’t have any problems with algae, because the macrophytes take all of the nutrigens from the water and there isn’t enough for the algae. If you have a shallow lake that has a lot of shade, or a huge inflow of nutrigens, then you have a lot of algae. No light can penetrate to the bottom of the lake and there are no macrophytes. It is one extreme or the other. Sometimes there is a switchover, depending on temperature etc, ” said Dr. Markus Hoffmann.
He added, “During the summer these lakes were covered by an aquatic algae mat. We had problems going through these mats with our boats because the algae got stuck in the motor every hundred meters. It was quite smelly and sometimes people got red hands from the toxigens the algae released. It was very unpleasant.”
“We want to have plants, not algae (in the lakes),” said Dr. Raeder.
Algae as a Carbon Sink
Some algae is good.
Sebastian Lenz, M.Sc., has been studying how the calcifying green algae Phacotus I operates as a CO2 sink. This would be difficult to apply on a large enough scale to combat climate change because “you need very special water quality to fix so much calcide inside the water column.” These conditions exist naturally at Iffeldorf.
“We have only been looking at the uppermost five meters, but now we are looking deeper inside the water. I am optimistic that our latest data will provide evidence of higher amounts of carbon dioxide,” he said.
The research team carries out experiments to see how different species will respond to increased temperatures and changes in precipitation patterns.
“If we know which kinds of plants would benefit and … which plants are dangerous, we can adapt our management methods,” said Dr Hoffman.
Black, Grey Or White
Half of the macrophyte species in Germany are invasive. Most of these arrived through agricultural imports, or people who dump the no longer wanted contents of their aquariums into local water systems.
Dr. Joachim Pander, from TUM’s river research facility at Freising, pointed out that invasive species of fish are also found in German waters. Carp are preying on native fish. Foreign crayfish are pushing out the local variety.
The team categorizes invasive species as black, grey or white, according to their impact on the local environment.
Remote Sensing Methods
Simon Baier, M.Sc., is on the team mapping the reeds and shore structure with remote sensing methods. Though they receive satellite images every three years, this is not frequent enough to help TUM keep track of an every changing landscape. So the team sometimes use UAVs equipped with hyper spectral and stereoscopic systems.
“They are a hot topic these days. Everyone is captured by this nice toy, sometimes called drones,” he said.
One of the advantages of green lidar imaging is that it penetrates water, enabling the researchers to see what is happening on the bottom of the lakes.
“We want to use this system to study the character of the reeds, and see if they are declining. Whether they are open reeds, or close dense reeds. We want to scan the lakes every two years and have accurate data, that is low cost and fast,” one of his associated added.