BALTIMORE, MD (July 28, 2010) – The Maryland Department of the Environment (MDE) investigated a fish kill on the Severn River on July 26, 2010. MDE staff estimate the total number of dead fish is a thousand or more, consisting mainly of small fish of several species, including Bay Anchovy, Atlantic Menhaden, Atlantic Needlefish, and White Perch. A heavy algae bloom was present.
Examination of the water sample collected on July 26, 2010, from the Severn River at the Sunrise Beach community revealed an algae bloom of the dinoflagellate Gyrodinium uncatenum. This species does not produce a toxin, but because of its large size can cause a high biological oxygen demand when the bloom dies, resulting in oxygen depletion. The cause of the fish kill was low dissolved oxygen induced by the large bloom of non-toxic algae.
There is no human health concern for this species of algae. MDE advises residents not to swim with dead fish and to use caution when handling them, due to possible bacterial contamination associated with decomposition of the dead fish.
While algae blooms are affected by natural conditions such as hot temperatures and heavy rains, they are also a symptom of an impaired Chesapeake Bay and waterways and a reminder of the importance of reducing nitrogen pollution from all sources: stormwater runoff, septic systems, agriculture, air emissions, and wastewater.