Mountain lakes are so hot right now

Mountain lakes are a popular alpine destination for camping, hiking and angling.  These waterbodies are also becoming ecosystems of interest for many climate researchers.  Just like in the arctic, alpine zones are disproportionately affected by climate change. Mountain ecosystems are warming at a substantially faster rate than lowland ones, and they’re giving us a glimpse of what kind of changes we might be in for – the canary in the coal mine for lakes.

Warming up

As alpine ecosystems warm up, things can change rapidly. As the air increases in temperature, so does the water temperature of lakes. Average annual snowpack declines and glaciers recede, leaving less cold water inflow. The combination of warming air and less seasonal cold water leads to ever-higher increases in water temperature. Warmer water can also stimulate primary productivity, and can lead to increased growth of large algae species, which are inedible to lake invertebrates.

Glacier recedence Adaekhutte

Photo comparison of the Gosaugletscher (Gosau glacier) in the Austrian Alps. The glacier has been receding rapidly, and has lost mass during most years since measurements began in 1954.

hintere gosausee

Photo of Hinterer Gosausee (Gosau Lake), Austria. Arrow shows the area of exposed lake bed that has resulted from decreasing annual snowpack and the receding Gosau Glacier.

As the glaciers recede, vegetation density increases, and timberline encroaches into higher altitudes. These changes in the land areas surrounding the lake can lead to substantial changes in water chemistry. For instance, in many northern temperate boreal and alpine lakes, the water is turning brown from increases in organic matter. This transition from alpine to vegetated conditions can lead to the loss of rare aquatic species, and shifts in invertebrate community structure.

Multiple stressors

While climate change on its own is already a concern for mountain lakes, the effects are often exacerbated by other stressors. Burning fossil fuels doesn’t just release greenhouse gasses – other chemicals hitch a ride on the flumes that rise out of the smoke stacks. Nitrous and Sulfur oxides (more commonly known as NOx and SOx) can be deposited by wind onto alpine landscapes and increase the acidity and nutrient levels of the water in mountain lakes. Toxic chemicals like mercury and persistent organic pollutants also get deposited and make their way into the aquatic food webs – and warmer waters could increase the rates at which organisms accumulate these toxins.

Mountain yellow-legged frog

The mountain yellow-legged frog, endemic to the Sierra Mountains of California, is threatened by climate change and the multiple other stressors affecting mountain ecosystems. Photo from the Center for Biological Diversity.

The rapid changes we’re seeing in mountain lakes, although informative for climate research, are a harbinger of what’s to come. Alpine ecosystems are under threat of losing species diversity, while those of us downstream (which is all of us) are under threat of losing our precious fresh water supply – 80% of which comes from the mountains.

Although the outlook for aquatic ecosystems under a changing climate is grim, every bit of action – whether it be from a change in lifestyle, political activism, and/or supporting climate change research – makes a difference. We hope our blog series on climate change has inspired you!

 

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