* Water quality may be affected by anthropogenic factors, as well as natural events such as excessively wet years, and storm.
* Land use changes are primary factors causing water quality and habitat degradation in the bay’s watershed.
* Too much sediment usually shows degraded habitat, water clarity is impacted, and it also increases toxic material, and pathogens.
* Nutrients in the Chesapeake Bay continue to degrade water quality, which is mostly derived from agricultural land use. (Agricultural fertilizer and manure sources have shown to have contributed 34% of nitrogen and 45% phosphorus within the Chesapeake Bay. (other sources include industrial wastewater)
* Harmful algal bloom (HAB) producing dinoflagelletes have resulted in “red tides” that generally occur annually (summer, and early fall) in the lower York River.
* The study showed contamination within the water such as mercury and PCB from agricultural use
* Sediments in the York River recorded levels of PCB ranging from 1-5 ppb with more elevated levels (25 ppb) being observed in some contributing tidal creeks.
* In contrast to mercury where atmospheric deposition is a primary pathway, PCBs are generally released into the environment from runoff processes occurring at hazardous waste sites.
* Almost 20 percent of the York River’s assessed shellfish waters have been classified as impaired.
* At low concentrations phytoplankton and cyano-bacteria usually are no threat to humans or environmental health,
* However in certain conditions when there are high concentrations they can accumulate enough toxins to affect water quality, oxygen dynamics, and the food web of estuaries.
* Results show depletion of oxygen (hypoxia) is a reoccurring condition in the Chesapeake Bay