Raviv Gal does research that he hopes will contribute to healthier watercourses and increased biodiversity. Fewer blackflies, higher biodiversity, and slower decomposition – these are some of the unexpected effects that freshwater pearl mussels have on their surroundings in the stream. Raviv Gal recently defended his PhD in biology at Karlstad University.
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 faeces, mussels affect all life in the stream.
"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 big impact on their surroundings."
Research with Unexpected Findings
In his dissertation, Raviv examined how mussels affect the decomposition of leaves, insect life, and fish behaviour. The results were surprising:
- Slower decomposition of leaves – possibly because insects prefer to eat the mussels' faeces rather than leaf litter, or because the mussels protect the leaves from the flow.
- Less dominance of blackflies – which benefits the diversity of 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 blackflies!" says Raviv, laughing.
Mussels in Decline, but the Nordic Region Has a Responsibility
Freshwater pearl mussel populations 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 natural functioning of our rivers and streams."
From Östergötland to Värmland, and from Land to Water
Raviv Gal began his academic journey in Linköping. After a master's on endangered grasshoppers, he chose freshwater mussels – and he will now 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 I plan to keep working with invertebrates, one way or another!
