Seasonal Variations of Acetylcholinesterase Activity Levels in Mummichogs in Three Tributaries of the Chesapeake Bay

Organophosphates and carbamates, typically used as pesticides, as well as heavy metals and some detergents are known to cause neurological effects on aquatic organisms upon exposure by inhibiting the activity of acetylcholinesterase (AChE) in nerve cells leading to decreased muscle control and possibly death. Organophosphates and carbamates break down quickly in the environment making them difficult and costly to measure directly. AChE inhibition in aquatic organisms can be used to indirectly measure exposure to anticholinesterase pollutants. We conducted an ecosystem assessment of three Chesapeake Bay watersheds with divergent land use characteristics (agricultural, developed, mixed) and collected mummichogs (Fundulus heteroclitus) during the spring, summer, and fall 2007-2009 (n=972) to assess the effects of anticholinesterase compounds. A microplate assay was developed to determine if any inhibition of AChE activity occurred in brain tissue due to exposure to pollutants in the aquatic environment. Preliminary results suggest a seasonal variability with summer showing greatest inhibition of AChE activity.  Additional analysis will explore site specificity and the possible correlation between activity levels and water quality data.