BIOINDICATORS OF ENVIRONMENTAL CHANGE IN THE CHESAPEAKE BAY

Particularly sensitive to changes in water quality, benthic foraminifera are useful bioindiactors of environmental change in aquatic systems. Certain key indicator species are highly responsive to alterations in environmental conditions, e.g., changes in dissolved oxygen (DO), salinity, and nutrient levels. Previous studies suggest that anthropogenic perturbations that alter run-off, sedimentation rates, and water chemistry, have caused environmental changes on decadal and millennial scales within the Chesapeake Bay.

A detailed study of a 2 meter piston core (reflecting approximately 200 years of sediment record) acquired from north of Annapolis, Maryland, reveals distinct faunal changes in benthic foraminifera. Elphidium selseyense and Elphidium clavatum generally inhabit well-oxygenated waters with low rates of sedimentation. Apparent in the upper portion of the core is a rapid transformation from a community dominated by Elphidium sp. to one dominated instead by Ammobaculites sp., which predominately flourish in waters with low to hypoxic levels of DO with higher rates of sedimentation. The decrease in Elphidium sp. and subsequent increase in Ammobaculites sp. is consistent with the interpretation of increased sedimentation rates and/or decline in oxygen levels. Concurrently at this point in the core is a rise in the relative abundance of Ammonia sp., Like Ammobaculites sp., Ammonia sp. also inhabits waters with higher sedimentation rates and low levels of DO. These changes in faunal composition are therefore strongly indicative of altered conditions of water quality over the last 200 years.

Evidence of faunal change carries important implications for management efforts for the Chesapeake Bay - assessing pre-perturbation faunal conditions is imperative for the synthesis of effective measures of preservation and conservation.