John Neukam has been catching crabs in pots near the Middle River for decades. But this year, the crabs have been dying in the water, suffocated by a bright green algae bloom that is choking off oxygen and worrying watermen and recreational boaters.
"You crab all week, you get a bushel and a half in your live box, and they die," said Neukam, after checking his pots yesterday morning. "I've been here all my life - 64 years - and we've only had this one other time, when fertilizer from a farm seeped into the cove."
People who live in subdivisions off the coves and creeks in the Middle River area have been scared to eat the fish they catch, worried about letting their children and dogs swim in the water, and in some cases unable to get their boats out from their docks, which have been socked in by the thick, carpet-like algae.
The state Department of Natural Resources says the algae is not toxic, but it is alarming. When the algae dies, the decomposition sucks the oxygen out of the water, killing crabs and fish. The algae also blocks sunlight from the beneficial bay grasses, which provide a refuge for shellfish and crabs.
The area that has seen the algae explosion is home to striped bass, white and yellow perch, catfish, Atlantic needlefish, chain pickerel and other species.
"This is an important area for commercial harvest of eels and catfish," said Mike Naylor, a DNR biologist who was checking out the bloom in the Baltimore County waterways yesterday. "We don't want a fish kill."
But there is little the state can do to fight the stringy, filamentous algae, which clumps together like knots of tangled green hair.
In smaller amounts, algae is a natural part of the ecosystem, but it is cropping up in huge patches throughout the Chesapeake Bay, a reminder of the impact people and development can have on the estuary and the fragile nature of the small coves and fingers that branch off of it. Such blooms are commonly caused by excess nutrients, including nitrogen and phosphorus, which come from such things as fertilizer and auto exhaust. The pollutants run off the land into the water.
"We have a lot of people in these watersheds and very little forest cover left," Naylor said. "So our waters have more nutrients than they should, and they're warmer than they should be, so these things combine to allow algae to thrive."
The type of algae causing havoc off the Middle River is multicellular, different from the floating single-celled algae that is more common throughout the bay.
