2. Hypoxia & Nutrient Loading

Nutrients are usually limited

• This limits the amount of plant growth• In oceans, the limiting nutrient is usually

Nitrogen (N)

• Where does N come from?• Is it limiting in estuaries? Why?

Eutrophication

• Too much of a good thing!• Over fertilized plants (mostly plankton) in water

cause an increase “aging” of the estuary• How?• Excess Nutrients=Increased phytoplankton growthdeathsinkdecomposition

Problem

• During decomposition, dissolved Oxygen is used up during the death that comes after eutrophication, there’s way too much O2 leaving the system-what happens when oxygen is lacking?

Result

• Extremely low O2 dissolved in the water.

• What is this known as. . . . ?

HYPOXIA!!!!

When is hypoxia a problem?

• March & August. . . Why?• During these months, more than usual, the

thermocline prevents mixing of warm, less dense surface water with cooler, denser bottom water

• The result. . . . Not enough O2

Solutions to Hypoxia• Improve STP’s (each one treats > 40 million gallons/day!)

Treatments: 1º – filtering & settling to remove solids2º – biologically remove organic nutrients,

required by law, grow bacteria to help decompose organics3º - advanced; chemically removes inorganic

nutrients, very costly

Solutions to Hypoxia cont.2) Reduce runoff

To reduce chemicals getting into wetlands or out to estuaries, some companies put down

-Sheets/tarps-Haybales-Terracing

Solutions to Hypoxia cont.

3) Reduce fertilizers on lawns/crops– Think about what times of

year fertilizers are usually applied!

Solutions to Hypoxia cont.4) Reduce phosphates & other

nutrients in products we use (i.e. soaps, which we did)

Mmmm. . .

so fun to swim in this!