Community members found a variety of dead fish in Ber Juan Lake in Rolla on Saturday, and Missouri Department of Conservation (MDC) agents said an algae die-off may have led to the localized fish kills after investigating the matter Sunday morning.
The MDC has an agreement with the city to manage the lake and conducted an investigation after two citizens reported seeing dead fish Saturday night to the staff of Rolla’s parks department. MDC agents walked the edge of the pond and saw numerous dead fish of various types and sizes, from 30-pound grass carp to five-pound bass – to this year’s ¼-inch fry, Rolla Parks and Recreation Director Floyd Jernigan said.
The agents then surveyed the lake temperatures and oxygen levels at different locations from their boat. From those readings, agents found oxygen was still being generated through the water from aerators installed by the city in 2016. Adult sunfish and numerous fry survived the event, likely due to the aerators, according to the MDC.
“This past week the pond was very pea soup green with planktonic algae that sits in the water column and this morning (Sunday) the pond is very clear to a little brown from the algae dying. The algae die-off possibly could have caused an acute overnight event Friday night, that caused fish to be trapped without oxygen and die, that wasn’t captured this morning,” according to MDC agents following their investigation on Sunday.
Another potential cause cited by agents was a small inflow of water from the city’s stormwater drainage system.
“Someone upstream in the neighborhood could have dumped something in the stormwater system that drains to the pond that was flushed in with Wednesday’s heavy 30-minute rain shower that caused this kill,” MDC agents noted. “Ber Juan pond being part of the city Storm Water Detention system can be its biggest downfall.”
Ber Juan Lake and Schuman Lake are part of the city’s stormwater detention effort and are a flood control component, Jernigan said. He added that staff of the city’s parks department did an initial cleanup of the area, and will continue their efforts, while the MDC will continue to monitor the pond, and test the water over the next several days.