The freshwater pearl mussel is one of Sweden's longest-living animals – some individuals can live up to 280 years. But it is also a so-called ecosystem engineer. By filtering water, slowing down water flow, and producing nutrient-rich feces, the mussels affect the entire watercourse's life. "They do so much more than you think," says Raviv Gal. "They may look a bit like stones and don't move much, but they have a significant impact on their surroundings."
Research with Unexpected Findings
In his dissertation, Raviv examined how mussels affect the decomposition of leaves, insect life, and fish behavior. The results were surprising:

• Slower decomposition of leaves – possibly because insects prefer to eat the mussels' feces rather than plant parts, or because the mussels protect the leaves from the flow.
• Less dominance of gnats – which benefits the diversity among bottom-dwelling animals.
• Better conditions for small trout, which find it easier to swim in fast flows in the presence of mussel populations.

"Mussels should probably become really popular among those who don't like gnats!" says Raviv, laughing.
Mussels in Decline, but the Nordic Region Has a Responsibility
The populations of freshwater pearl mussels have drastically decreased in Europe – up to 80 percent have disappeared in the last 90 years. Today, many of the remaining populations are found in Sweden and Norway.
"This makes us responsible," says Raviv. "We need to protect them, not just for the sake of the species, but also to preserve the entire ecosystem's function."
From Östergötland to Värmland, and from Land to Water
Raviv Gal was born in Israel but began his academic journey in Linköping. After a master's on endangered grasshoppers, he chose freshwater mussels – and now he will help with a new research project on damselflies.
"It feels incredible to have been able to contribute to the knowledge about these animals," says Raviv. "And the research doesn't end here!"