Hypoxia (Dead Zone)
Less oxygen dissolved in the water is often referred to as a “dead zone” because most marine life either dies, or, if they are mobile such as fish, leave the area. Habitats that would normally be teeming with life become, essentially, biological deserts. The Chesapeake Bay suffers from summer bouts of hypoxia caused when excess nitrogen and phosphorus, chiefly from fertilizer runoff and sewage plants, feed “blooms” of microscopic algae too numerous to be eaten by other creatures. The algae die and decompose in a process that hogs oxygen.
Over half of the U.S. estuaries now experience natural or human-induced hypoxic conditions at some time each year and evidence suggests that the frequency and duration of hypoxic events have increased over the last few decades.
Scientists expect the Chesapeake Bay to see an above-average dead zone this summer, due to the excess nitrogen that flowed into the Bay from the Potomac and Susquehanna rivers this spring. More here… and here…
Harmful Algae Blooms
Harmful algae blooms (HAB) are associated with and symptomatic of dead zone conditions. If you have observed a patch of water that is colored red or mahogany you should contact Virginia’s toll-free HAB hotline at (888) 238-6154 in order to help track and quantify the problem.
HABs can be toxic to aquatic life such as fish, oysters and crabs, and they block sunlight from reaching bay grasses growing at the bottom of the creeks and inlets. “Red Tides” can also cause skin irritation or other sickness to people who come into contact with them. Your pets are not immune: it might be a good idea to keep your dogs on the dock.