Dissolved Oxygen The Good Gas

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

CO 2 O2O2 Aquatic plants and phytoplankton (single cell floating plants) release oxygen into the water as a product of photosynthesis

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 H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O O2O2 H2OH2O H2OH2O H2OH2O O2O2 O2O2 O2O2 O2O2 O2O2 H2OH2O O2O2 H2OH2O

Hypoxic Anoxic Normoxic Habitat Classification Based on DO Concentration 0 – 0.2 mg/L 0.2 – 2 mg/L > 2 mg/L 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 + 6O 2 → 6CO 2 + 6H 2 O + energy (in form of ATP) Carbohydrate + Oxygen  Carbon Dioxide + Water + Energy Oxygen in CO 2 and H 2 O out Previous Meal Carbohydrate in Energy out

CO 2 : A Soluble Gas Too! H2OH2O H2OH2O H2OH2O H2OH2O O2O2 H2OH2O H2OH2O H2OH2O O2O2 O2O2 O2O2 O2O2 O2O2 H2OH2O O2O2 H2OH2O CO 2

C 6 H 12 O 6 Solar Energy Heat Energy Biomass (g/m 2 /yr) O2O2 Chemical Energy (ATP) Photosynthesis Respiration Biological Production and Consumption of Oxygen

Daily Aquatic Oxygen Cycle SunriseNoonSunsetMidnight Dissolved Oxygen SunshineMoonshine

∞ Day ∞ Night Photosynthesis Respiration

∞ Photosynthesis Respiration ∞ Low Respiration High Respiration

∞∞ High Photosynthesis Low Photosynthesis

SunriseNoonSunsetMidnight CO 2 +H 2 O  H 2 CO 3  H + +HCO 3 -  2H + +CO 3 - An increase in CO 2 causes an increase in H +  pH SunshineMoonshine pH Level

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 Water Clarity Current Velocity (Flow) Wind Cloud Cover

Temperature The warmer water is, the less DO it can hold –Think about opening a coke bottle after it sat a few hours on the dash of your car in August. Excess DO evaporates into the atmosphere! 100% DO Saturation Temperature (C) 100% Saturation Lavel

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