Experts say this year has been the worst for a phenomenon that is turning Long Island?s waters brown and killing creatures that live in them. As they continue to search for a cause, those who depend on the bays for their livelihoods are left to deal with the consequences.

?Brown tide,? the growth of dark, dense, deadly algae on Long Island?s south shore has been killing shellfish since 1985.

Peconic Baykeeper Kevin McAllister says the epidemic can have a snowballing effect on the environment. Less light is getting through the water, which hurts the growth of vital plant life below, explains McAllister. As the algae bloom dies off, McAllister says, oxygen is suppressed, which ends up killing crabs and fish.

McAllister says the brown tide stretched from the Shinnecock Bay all the way to Freeport this season, crossing the Suffolk County line for the first time.

Some researchers say the over-harvesting of clams may be a factor that led to the current condition. Others say it may be caused by lawn fertilizer runoff.

"Once it gains a foothold, there's not a lot that can stop it except for very high summer temperatures,? Marine biologist Chris Gobler says.