benthic barrier
n.— «Where the watermilfoil is too dense for that approach (scientists have found as many as 300 stems per square meter), divers fasten huge sheets of plastic, called benthic barriers, to the lake bottom to blot out the sun.…“We have two locations we have been working with the benthic mats where we’ll return, and we’ll add four more locations.”» —“Battling a Nasty Green Invader From the Deep” by Lisa W. Foderaro in Schroon, New York New York Times June 12, 2007. (source: Double-Tongued Dictionary)