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J. Aaron Hipp - Ecological Modeling Lab

University of California - Irvine

Temporal and Spatial Analysis of Water Clarity in Subestuaries of the Chesapeake Bay

Water clarity is a salient measure of water quality for scientist and non-scientist, alike. Clear water allows deeper penetration of sunlight, therefore increasing photosynthetic processes and decreasing hypoxia. Links between water clarity and eutrophication, total suspended sediments (TSS), point source and non-point source pollution have been well established. Similarly, perceived bathing and recreation risks among civilians were found to be closely correlated with water clarity and color.

Of import to the Chesapeake Bay study area is the correlation between water clarity and submerged aquatic vegetation (SAV). SAV offers critical habitat throughout various life stages of both finfish and shellfish, as well as provides an essential component to sediment stabilization and a balanced aquatic ecosystem. Subestuaries of the Chesapeake Bay have experienced dramatic declines, due primarily to decreases in water clarity, in SAV population over the past 50-80 years. Potential explanations mirror those of decreased water clarity - eutrophication, TSS, and point and non-point pollution.

Eutrophication, a dramatic increase in aquatic organic material due to the diffusion of nutrients, is at the nucleus of the decrease in SAV and water clarity. Point source and non-point source runoff of phosphorus (P) and nitrogen (N), from various land uses, exacerbate eutrophication and lead to an abnormal increase in phytoplankton. These algal blooms can block sunlight from penetrating the water surface and cause anoxic conditions as the algae die and settle in the benthos.

The restoration of SAV is a critical component of the 2000 Chesapeake Bay Agreement, a document committing various states and parties to improving and protecting the water quality and natural habitats of the bay.

The overall goal of my research was to establish and understand how local watershed characteristics interact with subestuary characteristics to affect water clarity. I used Secchi depth data across 21 years and 59 subestuaries to analyze temporal and spatial variability in local watershed characteristics and responses. The first research procedure will be to establish any correlations between water clarity and precipitation. We will analyze temporal variability in weather and responses for individual subestuaries and the Chesapeake Bay.

Water clarity and quality correlate with many anthropogenic and ecological processes throughout the Chesapeake Bay. Through temporal and spatial analysis, I began to shed light on the correlations between Secchi depth, a simple measure of water clarity and therefore quality, and precipitation, land use, subwatershed metrics, and estuary properties. This research attempted to identify spatial and temporal variability among subwatersheds and subestuaries. The study of shallow and coastal ecosystems provides an in-depth look at the essential habitat of SAV. SAV has greatly decreased over several decades and with it populations of native finfish and shellfish have also decreased. By correlating Secchi depth (water clarity) to processes and parameters across 59 unique subestuaries we are better able to understand each parameter's individual and collective affect. This information can now be extrapolated across the entire Chesapeake Bay - leading to better design restoration efforts and policy decisions.

Funding provided by the Smithsonian Women's Committee