An important natural habitat in Co Antrim could be lost if a privately owned reservoir is drained of too much water, it has been warned.
Kilwaughter Lake outside Larne dates back to 1810.
The lake is on private land and has multiple owners.
A report carried out on behalf of the Department for Infrastructure in 2019 found that the water level in the lake had to be reduced for public safety.
But Ryan Greer, who is property manager for one of the owners of the adjoining Kilwaughter Estate, said the potential environmental impact had not been properly considered.
He said the lake supports a huge variety of wildlife including seven different bat species, swans and a breeding pair of otters.
The lake is formerly part of the privately-owned estate which includes the now ruined 17th century Kilwaughter Castle.
Kilwaughter Estate still owns the fishing rights to the lake.
Mr Greer said an informal survey carried out by an experienced park ranger found that bats are using the lake as a swarming site and it is rare to find so many species in one place.
Kilwaughter Minerals Limited, which owns one bank of the lake, said it has a legal obligation to reduce the water level.
But Mr Greer said an environmental survey should first be carried out to assess the impact of any changes to the water level on wildlife.
He said nesting season "was the worst time" to alter the reservoir.
"No actual survey has been done as far as we know and we have asked," he said.
"That is our prime concern because the lake is the focal point for the ecosystem.
"I absolutely respect the needs of public safety but can a solution not be found that satisfies public safety and wildlife requirements? Why does drainage have to be an option? Can the lake not be repaired?
Mr Greer said he had highlighted his concerns with the Department for Infrastructure several months ago.
A spokesman for the Department for Infrastructure said: "Kilwaughter Lake is a controlled reservoir".
"A reservoir engineer has recommended that the water level is reduced."
The Department of Agriculture, which includes the Northern Ireland Environment Agency (NIEA), was contacted for a comment but has not responded.
A spokesperson for Kilwaughter Minerals Limited said it owns one bank of the lake which is "part of an isolated parcel of land with no connection to any business operations".
"Following a survey of the pond commissioned by the Department for Infrastructure... all owners were informed that the water level must be lowered in the interests of safety and to avoid flooding where a breach could endanger lives in a community," he said.
"It is our legal obligation to follow the Department’s recommendations, which are enforceable by law.
"As such the level of pond will be reduced in small increments leaving the reservoir safe with circa 10,000 cubic meters of water.
"Kilwaughter Minerals Limited works closely with our local community and has regularly engaged with all relevant stakeholders."
