CHANGES IN DISTRIBUTION OF SEAGRASSES IN THE CHESAPEAKE BAY: A GIS ANALYSIS OVER FOUR DECADES

Abstract

The distribution of seagrasses in the Chesapeake Bay estuary are changing spatially and temporally. Changes in seagrass distribution occurring in the Chesapeake Bay along with sedimentation, nutrient inputs, and human population growth in the watershed were mapped, analyzed, and reviewed in this study. These impacts continue to threaten and hinder seagrass growth with increased nutrients and sedimentation from farms, developments, and drainage systems across the watershed. Macroalgae, epiphytes, and non-native grasses have begun to dominate as primary producers, however, these organisms cannot sustain the same habitats and services provided and maintained by seagrass meadows. While some seagrass beds have shown decreases in abundance, even complete decimation, other areas have shown an increase in distribution due to restoration efforts and stricter nutrient limitations. Due to the size of the Chesapeake Bay watershed, which includes six states and the District of Columbia, not all nutrient limitations are equal nor are all jurisdictions involved adhering to the limitations set forth by the U.S. EPA. While there are other mitigating factors, human population growth and increased activities have been shown to be the primary impact driving seagrass decline. More humans equal more runoff, nutrient and sediment inputs, increased impermeable surfaces, which increases turbidity, harmful algal blooms, and dead zones, depleting necessary light and oxygen to the water columns surrounding seagrass meadows.