You can help protect the Magothy from your own backyard. Consider limiting fertilizer application, scooping pet waste, installing a rain garden and minimizing impervious surfaces. For helpful tips on these and other practices see:
From Your Backyard to Our Bay, Anne Arundel County
Being Bay-Wise: Landscaping Tips for a River-Friendly Backyard
10 Things Marylanders Can Do Today to Reclaim the Bay, Maryland Department of the Environment
Rainscaping Chesapeake Ecology Center