Dead Zones: When Livable Waters Can’t Breathe
In one of our all-time spooky boat trips, we motored with scientists out of Louisiana into the Gulf of Mexico aboard a 57-foot trawler packed with scuba tanks and strange gear. The mission: Measure the size of the Dead Zone, the huge expanse of water rendered all but lifeless from farm fertilizers flowing down the Mississippi River from Midwestern farm fields.
Twenty-five or so miles from shore, researchers dropped monitors overboard and fixed their gazes on computer screens. Before long, they jumped in the water. They returned to tell of an ocean floor that looked like the moon, layered with white bacteria and nothing living. Even the worms lay dead.
Meters on deck showed less than two parts-per-million oxygen, the level at which water is declared hypoxic: lacking enough oxygen to support fish, shrimp or anything that breathes. The size of this toxic mess proved startling: roughly 6,000 square miles, bigger than New Jersey.
Bored or maybe bummed at the underwater devastation, we grabbed a fishing pole with an empty hook and stuck on a shrimp left over from lunch. Suddenly, something yanked ferociously on the line.
Holy mackerel! Had we hooked a scientist?
No, it was a fish, a sheepshead, which grow big (seven or eight pounds) offshore. But how could this be, in the Dead Zone?
We learned the reason, and it was one of the lessons pertinent for us a decade later amid predictions by the Chesapeake Bay Program of the worst oxygen-low dead zones this decade in the Bay.
Nitrogen-laden fertilizers pour into the Bay and its tributaries from farm fields, poultry farms, outmoded sewage treatment plants and from lawns overfertilized in hopeful ignorance (see this week’s Bay Gardener).
When the water warms, phytoplankton dine on the nitrogen, with a second course of phosphorus from all those fertilizers, creating algae blooms that suck away oxygen.
So how did we catch that fish? Rather than being one huge blob, the hypoxic water runs in layers, much like a parfait from the ice cream shop, that shift beneath the surface at various depths. We were fortunate to hang our bait in an area with oxygen, where our sheepshead (which became dinner) swam or drifted.
Our situation is different and better than that in the Gulf of Mexico. First, Chesapeake Bay is smaller, so it is possible to legislate solutions and make them stick.
Second, we’re well ahead of others in public awareness as well as in our connection to the waters that our fertilizers imperil.
Knowledge and connection create an environment where we can publicize and analyze our problem, which in turn can build the political will to do something about the problem.
That’s what we’ll be hoping when we’re out on the Bay, anyway, while blaming others when we can’t catch a fish.
(Learn more about dead zones from hypoxia expert and columnist Tom Horton, one of the authors scheduled to speak along with U.S. Rep. Wayne Gilchrest in Free Food for Thought, Bay Weekly’s Forum on Living Waters, June 1, at Historic London Town and Gardens in Edgewater, from 7-9pm. See our ad in this issue or call Bay Weekly at 410-867-0304 to rsvp.)