And improving their health is critical not only because of their historically important economic value. The animals also filter phytoplankton and other organic matter, a process which clarifies bay water and reduces oxygen depletion. American shad landings have also declined, as have river herring stocks. Overfishing, blockage of spawning areas, degradation of water quality and habitat loss have all played a part. Eggs and larvae of tese species require dissolved oxygen levels higher than that often present in much of the bay.
Adults also require better water quality during upstream spawning migrations.
As with animals, plants would gain from better conditions in the bay. Submerged aquatic vegetation increases sediment stability, lessens turbidity and affects nutrient cycling. SAV in the bay and most of its tributaries is generally increasing. This covers only a few of the many interactions between water quality and bay tributaries' living resources. The species above are only a few that would benefit from nutrient reductions.