Thousands of fish in tributaries of the Patapsco and Magothy rivers have been killed over the past week by lack of oxygen, caused in part by drought, say state environment officials.
Such widespread oxygen depletion has not been seen in more than a decade, said Charles A. Poukish, a specialist with the Maryland Department of the Environment. He is investigating the most recent fish kills in the Baltimore metropolitan area.
"We periodically see these types of things in some areas of the [Chesapeake] Bay every summer," Poukish said. "Typically, it happens on a smaller scale, but this year it has happened all at once. We don't expect the situation to improve until we have a major change in the weather."
Affected tributaries along the Patapsco River include: the Inner Harbor, Bear Creek, Marley Creek, Colgate Creek, Curtis Bay, Furnace Creek, Stony Creek and Bodkin Creek. The Magothy River's affected waterways are: Cattail Creek, Cockey Creek and Deep Creek.
"We have thousands of fish dead and dying in these areas," Poukish said. "It is a major fish kill."
He said it is difficult to estimate the number of dead fish in this type of fish kill because the larger fish sink to the bottom before floating to the surface.
Eel, yellow and white perch, chain pickerel, largemouth bass, menhaden and catfish have been lost.
Chelsea Beach resident Bob Wright called environmental officials after spotting dead fish in Cockey Creek last weekend. He noticed a few dead fish Friday evening. On Saturday, Wright said, fish were swimming in circles before "going belly-up." By Sunday, he estimated seeing as many as 300 dead fish in the creek.
"My first thought was I bought this place on the water after retiring, and a month later I wake up to find dead fish all over," said Wright, a former Navy officer. "I was discouraged, to say the least. I guess `appalled' would be a better word."
The statewide drought, which has bedeviled area farmers and gardeners this summer, is also creating problems for aquatic life in the Chesapeake Bay tributaries.
Poukish theorizes that the dry, hot conditions have led to a consolidation of nutrients found in bay waters, such as nitrogen and phosphorus. In turn, the high concentration of nutrients helped create larger algae blooms. The decomposition of these blooms, fueled by the warmer temperatures, has left dangerously low levels of dissolved oxygen in the waters.
Poukish said that oxygen levels in affected waters are at 1 part per million. Anything below 2 is lethal to most breathing organisms, he said.
"It's all a function of dissolved oxygen, algae crashes, excess nutrient loads and various dynamic systems in the bay itself," Poukish said.
Poukish said the drought has caused evaporation of surface waters and its replacement with saltier, toxic water from the bottom. This has promoted the death and decomposition of algae and has further used up oxygen.
"We need some rain to move that water mass out and make it less condensed with nutrients," he said.
Poukish and other members of the state's Fish Kill and Ecological Assessments Section have been investigating affected tributaries of the Patapsco and Magothy rivers since Thursday. The strong "rotten egg" odor they found at several sites indicates sulfides, which form in the absence of oxygen, he said.
One incident that occurred near the Coast Guard station in Curtis Bay involved about 30 dead bluegill, white and yellow perch. At a site in Colgate Creek, investigators found 100 dead fish.
On Saturday, environment officials began an investigation of Eli Cove, at the headwaters of Stony Creek, after a resident spotted numerous brown bullhead catfish struggling near the surface.
Other factors besides the drought may have played a role in the fish kills, Poukish said.
"Quite possibly, the overcast skies may have reduced photosynthesis, and thereby reduced the oxygenation ability of the algae that's left," he said. (Photosynthesis is the process by which green plants turn sunlight into food and produce oxygen as a byproduct.)
Melody Paschetag, a hydrologist with the National Weather Service, said that Maryland is in a drought warning and that recent rains won't have a long-term effect.
"When we're 10 inches below for the year, we need quite a bit of rain to make a dent in the drought," Paschetag said.
Pub Date: 6/29/99