Scientists at the University of Cambridge replicated a 1964 River Thames survey and found that the depressed river mussels have completely disappeared.
Between 1964 and 2020 the study measured the change in size and number of all species of mussels.
Not only did native populations decline, but the mussels that were left were much smaller for their age.
In the freshwater environment, smills are important because of their ability to remove harmful organisms. They're exposed to a lot of water, and this makes them a good indicator of the health of the environment. A place for other aquatic species to live is provided by smelly shells.
There is a correlation betweenussels and the health of the river. Isobel Ollard is the first author of the report and is a PhD student in the University of Cambridge.
The survey didn't find any depressed river mussels, which raises concerns for the survival of this species.
There were new arrivals, including the non-native zebra mussel and the Asian clam, that were present in high numbers. The scientists think that the invaders hitched a ride on the boats and established themselves in the river.
The results are in a journal.
"This dramatic decline in native mussel populations is very worrying, and we're not sure what's driving it," said Professor David Aldridge, senior author of the report.
He said that the study provided an important warning signal about the world's freshwaters.
The decline in native mussel populations is thought to be the result of the Invasive species. There is more work that needs to be done. Changes in land use along the river could be one of the reasons for the change.
Many empty shells of the depressed river mussel, Pseudanodonta complanata, were found in the survey, which indicates that the species had been living at this site in the past. The depressed river mussel is in danger of extinction.
The population of duck mussels, Anodonta anatina, and the painter's mussel, Unio pictorum, decreased in 1964.
The scientists think the reduced growth rate may be related to the river returning to a more natural state. Increased regulation of sewage treatment has led to a decline in nitrate andphosphate levels in the river water. The food available to the mussels is limited by the growth of algae.
There are threats to smilng species around the world. The scientists say that regular population surveys of key species are necessary to track the health of rivers and guide their management.
Ollard contacted Christina Negus, who was a researcher at the University of Reading in the sixties, to make sure the survey was a replica of the original. The methods and equipment used by Negus were shared. The major contribution mussels make to the functioning of rivers continues to be cited extensively.
The data for "declines in freshwater mussel density, size and productivity in the River Thames over the past half century" was published in the University of Cambridge repository. There is a book titled "107863/CAM.80071."
Journal information: Journal of Animal Ecology
All Rights Reserved © 2024
