When an alarming number of fish used for experiment and observation in the BGSU marine laboratory began dying last month, lab workers and biology professors were left wondering – what was killing their fish?

It wasn’t contaminated equipment, since no tools were shared from one tank to the next.

It wasn’t a different maintenance routine, since all tanks received the same treatment and care.

But Adam Smith, graduate coordinator for the marine lab, has a theory about what killed the fish in his lab.

It was something in the water.

“The municipal water source was the only common factor that came to mind,” Smith said.

In March, the lab staff noticed some tanks of fish were less healthy than others. In several tanks, fish showed symptoms of infections such as fin rot, which destroys tissue beginning at the edge of the fin, and dropsy, which causes swelling in fish organs and tissue.

Though not all tanks of fish became infected, according to Smith, the ones that did all experienced an “abnormally-high mortality rate.”

Smith, who studies communication in fish in his lab, said his was not the only lab which lost specimen.

Biology professor Sheryl Coombs said many fish in her lab, which studies fish physiology and functioning, succumbed to similar infections.

Coombs’ lab lost “a bunch” of research fish several weeks ago, but she said she found no evidence revealing whether the water source was the main or only cause.

But Smith said the lab should not rule out the possibility.

“The problem could have been something as simple as abnormally-high nutrient levels in the water source, which is what I personally expect,” he said.

These unusually high amounts of nutrients can occur when increased run-off gets into the water supply from heavy rains or melting snow, both common in the spring. Smith said if a saturation of those nutrients washes into the fish tanks, it can breed bacteria that can cause infections.

But according to Bill Ash, superintendent at Bowling Green’s Water Treatment Plant, there is nothing wrong with BG’s water supply and he isn’t sure why the marine lab would experience any adverse effects due to the water.

Ash said BG’s water currently meets all standards set by the Environmental Protection Agency and is perfectly safe for human use and consumption – though Smith said EPA standards aren’t always good enough to maintain fish in captivity.

But Ash said the only factor that may be potentially harmful to marine life might be a small amount of chlorine present in the water, which guards against bacteria and acts as a disinfectant.

But Ash said it’s unlikely the chlorine is what’s killing the fish.

“If the water is properly balanced for fish in terms of pH and chlorine, I don’t think it would be a problem at all,” he said.

Though Smith said he spoke with a representative from the water plant when he first detected the infections, Ash said he was unaware anyone from the University had come forth with the problem.

“If there are test results for this, I would like to see them,” he said. “Otherwise, I can’t really respond without seeing some results.”

But Smith said he doesn’t plan on pressing the issue, as most of the fishes’ symptoms have now cleared up and the infections were never a threat to humans.

“We are not interested in pointing fingers at the city,” he said. “We are only concerned with the well-being of our animals.”