One of the main threats faced by these areas is the presence of introduced species that decimate the native ones and severely disrupt the balance of these ecosystems.
The biodiversity in high mountain lakes is greater than what we see at first glance. From tiny organisms like microscopic algae and small crustaceans that are part of the plankton, to plants, mollusks, worms, insects, and amphibians that live both at the bottom and along the shore of the pond and can be hard to spot due to their nocturnal habits.
In addition to those living in or near the water, alpine lakes are also crucial for other creatures that depend on them for food. This includes numerous birds and small mammals, such as bats or the desman (an insectivorous animal endemic to the Pyrenees).
All these forms of life typical of mountain lakes face significant challenges. One of the main ones is the presence of alien species, like fish, that humans have introduced into these isolated environments where they did not naturally occur. Fish prey on eggs, larvae, and small animals, harming native populations, disrupting the food web, and upsetting the balance in these valuable ecosystems.
Research projects like LIFE RESQUE ALPYR, coordinated by CEAB-CSIC, include efforts to eradicate them and restore native species and balance to high mountain lakes.
Ecological disruptions caused by invasive fish
For example, in a lake where trout has been introduced, there is significant disruption of the food network in the littoral zone (the fish eat the larger macroinvertebrates), leading to the disappearance of amphibians.
The negative effects increase when, in addition to trout, the lake also contains minnows (a small cyprinid also introduced in many Pyrenean lakes as live bait for trout fishing), as they also disrupt the pelagic food network in addition the area away from the shores.
If minnows proliferate greatly in the lake, they stir up the bottom sediments, fertilizing the water. As a result of the excessive availability of nutrients, too many microalgae grow, reducing oxygen levels in the water and its clarity.
Restoration of High Mountain Lakes
Restoring these alpine ecosystems involves eliminating introduced fish species. This is a laborious task done manually to avoid any negative impact. It can take between two to seven years.
The actions of the LIFE RESQUE ALPYR project include the eradication of fish in lakes, both in the Pyrenees and the Alps, to support the recovery of amphibian populations, semi-aquatic small mammals like the desman or the water shrew, some bat species, and the lacustrine habitat.
The methods have proven effective, as they were successfully tested in previous research projects like LIFE LIMNOPIRINEUS and LIFE BIOAQUAE.
The restoration task is considered complete when there is natural recolonization by native species, returning from nearby areas where they still existed. This recolonization has already occurred in lakes in the Pyrenees and Alps where the team coordinated by CEAB-CSIC has worked.
Additional information:
–LIFE RESQUE ALPYR PROJECT
L'entrada Invaders in high mountain lakes ha aparegut primer a CEAB.