Warm Waters Aid Northern Mollusk Invasion

Invasive freshwater mollusks, such as the Dreissena polymorpha, are expanding their range northward due to a combination of climate warming and artificially heated reservoirs. These heated industrial discharge waters create favorable conditions, acting as refuges where these thermophilic species can establish and reproduce, unlike less adapted species that cannot withstand lower temperatures.

The Dreissena mollusk, first found in the Arkhangelsk Region in 1897 after migrating from the Caspian Sea, now forms stable populations. While densities are lower than in southern regions, these mollusks still cause problems by fouling fishing nets, hydraulic structures, ships, and even submarines. Their ability to tolerate salinity up to 14 ppm allows them to colonize marine environments.

Researchers are exploring the possibility that genetic hybridization, possibly with species like Dreissena rostriformis, is contributing to the invasive species' success. These hybrid forms may possess genetic advantages that allow for greater adaptability to colder northern conditions and active reproduction. Studies are ongoing to understand the genetic makeup of populations thriving in warmer discharge waters.

Beyond direct warming, thermal pollution from industrial and energy facilities disrupts aquatic ecosystems. This pollution alters water chemistry, reduces oxygen solubility, and disrupts natural functioning, leading to shifts in aquatic organism composition. Thermophilic species like Dreissena benefit from these altered conditions, while thermosensitive species decline.