Underwater plants: Key indicators of lake health, not a sign of pollution

Contrary to popular belief, the presence of underwater plants, or macrophytes, is not a sign of poor water quality but rather a reliable indicator of a healthy aquatic ecosystem. Franziska Hübl from the Institute of Geodesy at TU Graz explains that macrophytes are vital bioindicators. "If something is wrong with the plants, much can fall out of balance," she stated.

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Macrophytes are an important bioindicator for a functioning ecosystem. If something is wrong with the plants, much can fall out of balance.

Hübl coordinated the FFG-funded project "Wamos," which investigates wave monitoring systems. The project's findings, due to be published in the fall, involved collaboration with various institutions, including the Carinthian Institute for Lake Research, FH Kärnten, and the water engineering institute at TU Graz.

Regular measurements at Lake Wörthersee in Austria revealed a concerning trend: a decline in underwater plant populations and a shift in species diversity. "The Wörthersee is a dream lake that is heavily used for tourism," Hübl noted, emphasizing the importance of its ecological health for tourism, recreation, water management, fisheries, habitat quality, climate regulation, and nutrient filtration.

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The vegetation periods of aquatic plants are getting longer with warmer temperatures. This is therefore advantageous for underwater plants, which are now even overwintering in part, meaning the plants should actually grow denser.

While warmer temperatures have extended growing seasons, potentially benefiting underwater plants, and fish like carp and bream can disturb the lakebed, researchers have largely ruled out factors such as pollutant input, water contamination, and climate change as the main drivers for the observed decline. The research team is now exploring other potential causes for the diminishing macrophyte populations.

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The Wörthersee is a dream lake that is heavily used for tourism.