Dissolved Oxygen The Good Gas Photosynthesis Your

Dissolved Oxygen The Good Gas

Photosynthesis: Your one-stop shop for all of your oxygen needs! Solar energy + 6 CO 2 + 6 H 2 O → C 6 H 12 O 6 + 6 O 2 Happy Rays of Sunshine Carbon Dioxide (from air) Oxygen Carbohydrate (plant material) (to air) Water (from ground)

Aquatic plants and phytoplankton (single cell floating plants) release oxygen into the water as a product of photosynthesis Happy Rays of Sunshine CO 2

Phytoplankton (single cell plants) – are the base of the aquatic food web and provide most of the aquatic oxygen.

Submerged aquatic plants can provide shelter for young fish as well as house an abundant food supply.

Oxygen: A Soluble Gas H 2 O O 2 O 2 H 2 O O 2 H O H 2 O 2 H 2 O

Habitat Classification Based on DO Concentration > 2 mg/L Normoxic 0. 2 – 2 mg/L Hypoxic 0 – 0. 2 mg/L Anoxic Most fish need oxygen levels > 2. 0 mg/L

Respiration: How we, the animals, use oxygen (and plants too!) C 6 H 12 O 6 + 6 O 2 → 6 CO 2 + 6 H 2 O + energy (in form of ATP) Carbohydrate + Oxygen Carbon Dioxide + Water + Energy Oxygen in CO 2 and H 2 O out Energy out n te i ra Previous Meal Car hyd bo

CO 2: A Soluble Gas Too! CO 2 O CO 2 2 H 2 O O 2 CO 2 O 2 H O H 2 O 2 H 2 O CO 2 H 2 O

Biological Production and Consumption of Oxygen Heat Energy Solar Energy CO 2 Respiration Photosynthesis C 6 H 12 O 6 O 2 Biomass (g/m 2/yr) Chemical Energy (ATP)

Daily Aquatic Oxygen Cycle Sunshine Moonshine Dissolved Oxygen Moonshine Midnight Sunrise Noon Sunset Midnight

Day Night Photosynthesis ∞ ∞ Respiration

Low Respiration High Respiration Photosynthesis ∞ ∞ Respiration

High Photosynthesis Low Photosynthesis ∞ ∞

CO 2+H 2 O H 2 CO 3 H++HCO 3 - 2 H++CO 3 - An increase in CO 2 causes an increase in H+ Sunshine Moonshine p. H Level Moonshine p. H Midnight Sunrise Noon Sunset Midnight

Decomposition – Not good for DO • Decomposer organisms (mainly bacteria) consume oxygen – Sometimes consume oxygen faster than plants can produce it, even during the middle of the day! • A sudden increase in organic matter (think leaf litter) can create a spike in decomposition activity – especially if it is hot – Hurricanes not only add organic matter to our waterways, but also stir up the sediment. – Can cause fish kills!!

Abiotic Factors That Affect DO Concentration • Temperature • Wind • Water Clarity • Cloud Cover • Current Velocity (Flow)

Temperature • The warmer water is, the less DO it can hold 100% Saturation Lavel – Think about opening a coke bottle after it sat a few hours on the dash of your car in August. 100% DO Saturation 20 18 16 14 12 10 8 6 4 2 0 0 5 10 15 20 25 30 35 Temperature (C) • Excess DO evaporates into the atmosphere!

Oxygen Can Diffuse Out of or Into the Water Column Atmosphere Oxygen diffuses out of water column Oxygen diffuses into water column Oxygen > 100% Saturation Oxygen < 100% Saturation Water Column

Wind Stirs in atmospheric oxygen

Current Velocity • The faster water flows, the more atmospheric oxygen is mixed into the water.

Water Clarity Amount of Sunlight Reaching Plants The muddier the water is, the less light reaches the plants!

Cloud Cover • Clouds decrease the amount of sunlight reaching aquatic plants, thus oxygen production is reduced.