While 2020 has been the year of bad news, it seems that one crisis may have been averted at Smith Mountain Lake. A new study recently completed by Ferrum College reports that zebra mussels are unlikely to ever arrive.
Zebra mussels have been an ongoing concern at the lake for the past few years. The invasive organism has spread throughout the United States, as well as nearby lakes along the East Coast for the past 30 years.
The Smith Mountain Lake Association has focused on zebra mussels in recent years due to the damage they can do to bodies of water once they propagate into large numbers. They can hurt ecosystems, damage property, clog pipes and have sharp shells that can injure swimmers who walk on them.
Clay Britton, a Ferrum College professor and assisting scientist on Smith Mountain Lake’s water quality monitoring program, put the finishing touches on a study that was conducted between 2017 and 2019. Ferrum College students Kyle Hayley and Nick Blankenship originally worked on the study as a senior project through a grant from the Virginia Academy of Science.
“I just added to it and cleaned it up,” Britton said of the study.
The study tested calcium levels and lake temperature at multiple locations on the lake during several months throughout the year. Britton said temperature and calcium levels are key growth requirements for the invasive species.
According to the study, the temperature of the lake was 82 degrees or more during the summer months when tested. That temperature exceeds the upper limits that support zebra mussel survival at a time when zebra mussel spawning and larval development are highest.
“It looks like the water may be a little too warm for them,” Britton said of summer temperatures at the lake.
Those summer months also show a sharp reduction in calcium levels in the lake that is necessary in shell development for zebra mussels. The level of calcium in the lake drastically drop from May to August — the months when the mussels need it the most.
Calcium levels fell from a high of 22.5 parts per million in March to 7.73 ppm the following month during the time testing was done for the study. Levels hit a low of 4.36 ppm in August before jumping back to 22.3 ppm in October.
According to the study, calcium concentrations of between 12 to 19 ppm were seen as an optimal range for zebra mussel growth in North American populations. While the lake is at or above that minimum range for several months out of the year in the study, it is far below it during much of the summer.
The reason for the drop in calcium levels, according to the study, is due to photosynthesis of plant life in the lake that increases the pH that leads to a conversion of bicarbonate to carbonate. That conversion can also create a precipitation of calcium carbonate that tends to lower free calcium levels during the summer months.
While the results of the study are good news for lake residents, Britton warned that the study only looked at a few months between 2017 and 2019. “It is really just a snapshot,” he said.
Britton said lake residents and visitors still need to be aware of the dangers of zebra mussels. The lake is still habitable for the invasive species for several months out of the year. A small change in calcium levels or temperature during the summer months could make the lake habitable year-round.