AP Lab #12 Dissolved Oxygen & Aquatic Primary Productivity part I

In an aquatic environment, O2 must be in a solution in a free state before it is available for use by heterotrophic organisms…

In the atmosphere … O2 is abundant In an aquatic environment, O2 must be in a solution in a free state before it is available for use by heterotrophic organisms… The concentration of O2, and its distribution in an aquatic environment (the pond, ocean etc.), are directly dependent on factors that greatly affected by biological processes! In the atmosphere … O2 is abundant

In an aquatic environment O2 is NOT as abundant as in a terrestrial… Terrestrial = 200 mL O2/ 1 L air Aquatic = 10 mL O2/ 1 L water WHY??? In an aquatic environment O2 is NOT as abundant as in a terrestrial…

Terrestrial = 200 mL O2/ 1 L air Aquatic = 10 mL O2/ 1 L water O2 distribution in water depends on: currents, winds, tides etc. mixing it up ! O2 diffuses 300,000 X’s faster in air than water

O2 distribution in water also depends on: pH, Terrestrial = 200 mL O2/ 1 L air Aquatic = 10 mL O2/ 1 L water O2 distribution in water also depends on: pH,

O2 distribution in water also depends on: salinity, Terrestrial = 200 mL O2/ 1 L air Aquatic = 10 mL O2/ 1 L water O2 distribution in water also depends on: salinity,

O2 distribution in water also depends on: elevation Terrestrial = 200 mL O2/ 1 L air Aquatic = 10 mL O2/ 1 L water O2 distribution in water also depends on: elevation

O2 distribution in water also depends on: temperature Terrestrial = 200 mL O2/ 1 L air Aquatic = 10 mL O2/ 1 L water O2 distribution in water also depends on: temperature

HIGHER O2 (DO) CONCENTRATION (ppm) at: “Help - I am suffocating!!!” neutral pH low elevation low salinity low temperature

Terrestrial = 200 mL O2/ 1 L air Aquatic = 10 mL O2/ 1 L water O2 distribution in water also depends on: partial pressure of O2 in the air above the water !

LESS O2 IN WATER AT HIGHER ELEVATIONS THAN AT LOWER ELEVATIONS

You could think about the amount of O2 in the air @ these locations…

Terrestrial = 200 mL O2/ 1 L air Aquatic = 10 mL O2/ 1 L water O2 distribution in water also depends on: amount (rate) of photosynthesis & respiration

photosynthesis increases the D.O. (ppm) ! respiration decreases the D.O.(ppm) …

Indicator of health of lake ! measuring D.O. is a determiner as to whether the biological activities requiring O2 are occurring (respiration) Indicator of health of lake !

Which environment has the greater concentration of dissolved oxygen: Explain. or a clear pond? a heavy algal mat?

Clear water holds more dissolved oxygen than water with a heavy algal mat. Although photosynthesis in the algal mat will produce a great deal of oxygen, the decay of so much organic matter will result in a net depletion of oxygen due to DECOMPOSERS.

??? SAY WHAT????

DECOMPOSERS w/ be in a large amount BECAUSE THE ALGAE WILL EVENTUALLY DIE... The decomposers w/ come on the scene and will USE THE OXYGEN, thus decreasing the amount of DO

Just HOW do you measure D.O.? Winkler method

Just HOW do you measure D.O.? via. titration

WINKLER METHOD to determine D.O. 1. Add alkaline iodide & manganous sulfate to a water sample. Manganous hydroxide will be produced. This will be acidified, & will spontaneously be converted to a manganese compound by the O2 in the water sample

WINKLER METHOD to determine D.O. 2. Add alkaline potassium iodide azide (KOH) to the water sample. Iodine will be released -> H2O will turn yellow **The quantity of free iodine is equivalent to the amount of D.O. in the water.**

WINKLER METHOD to determine D.O. 3. A starch indicator is then added… to determine amount of iodine via. titration H2O will turn purple You remember, titration is adding a substance of known concentration to a solution containing a substance of unknown concentration… until a specific reactions completed and a color change occurs.

WINKLER METHOD to determine D.O. 4. The amount of D.O. can then be determined by titrating a portion of the sample with sodium thiosulfate until a colorless endpoint is reached.

AP Lab #12 Dissolved Oxygen & Aquatic Primary Productivity part I

MEASURING D.O. In order to measure how much oxygen water can hold (the saturation) you will also need to be able to read a nomograph:

the percent oxygen saturation for a water sample at 10oC that has 7mg O2/L is 45% saturation nomograph

the percent oxygen saturation for a water sample at 25oC that has 7mg O2/L is 65% saturation nomograph

Goggles and gloves MUST be worn Day 1 temp. effect 4 degrees C 25 degrees C 30 degrees C Goggles and gloves MUST be worn

AP Lab #12 Dissolved Oxygen & Aquatic Primary Productivity Day 2

Day 2 we will compare D.O. values in water samples exposed to differing amounts of light

Primary Productivity the rate @ which biomass is produced & stored (by autotrophs) via. photosynthesis in an ecosystem

Primary Productivity amount of organic compound formed from photosynthesis amount of organic compound used by respiration - Aquatic P.P.

Net Primary Production Primary Productivity amount of organic compound formed from photosynthesis - amount of organic compound used by respiration Net Primary Production

Primary Productivity can be measured by: *rate of CO2 utilization *rate of sugar formation (glucose produced) *rate of O2 production in the light

Primary Productivity can be measured by: can calculate the amount of carbon that has been “bound” in organic compounds over a time via. RATE OF O2 PRODUCTION

You will monitor the effect of varying light levels on D. O You will monitor the effect of varying light levels on D.O. in an algae-rich water culture

Just HOW do you measure primary productivity? Light-Dark bottle O2 method

Light-Dark bottle O2method to determine primary productivity 1. Measure D.O. concentration in an initial sample CONTROL TO COMPARE 2. Measure D.O. concentration in a dark sample JUST CELL RESPIRATION 3. Measure D.O. concentration in a light sample PHOTOSYNTHESIS & CELL RESPIRATION

Light-Dark bottle O2method to determine primary productivity RESPIRATION -> initial sample - dark sample GROSS PRIMARY PRODUCTION -> light sample + amount used in dark sample NET PRIMARY PRODUCTION -> light sample - dark sample

Day 2 primary productivity

Day 2 primary productivity

Day 2 primary productivity 3. Each bottle will have the % light it will receive..

Day 2 primary productivity 3. Each bottle will have the % light it will receive..

Day 2 primary productivity 3. Each bottle will have the % light it will receive..

Day 2 primary productivity

Respiration Net Productivity L - I = Net Productivity I - D = Respiration L - D = Gross Productivity note: dark is a negative number L DO (mL O2 / L) Net Productivity I Gross Productivity Respiration I = Initial Bottle L = Light Bottle D = Dark Bottle D Incubation Time (hours) 24

(light - initial) + (initial - dark) = gross productivity net productivity + respiration = gross productivity (light - initial) + (initial - dark) = gross productivity (light) + (- dark) = gross productivity light - dark = gross productivity you subtract to get gross b/c:

this number will be negative

this number will be negative

How do lakes age?

OLIGOTROPHIC

OLIGOTROPHIC Very little nutrients (nitrogen & phosphorus Deep Clear Very little algae Colder Highly oxygenated

A oligotrophic lake Oligotrophic lakes are very low in nutrients, so few algae grow and the water is very clear. Oligotrophic lakes are biologically less productive lakes (they have the lowest level of biological productivity), and support very few plants and fish.

MESOTROPHIC Medium amount of nutrients (nitrogen & phosphorus) Clear Algal blooms in late summer on top~ D.O. higher on top Warm on top /Colder on bottom Higher decomposition rate on bottom~ D.O. lower on bottom

EUTROPHIC High amount of nutrients (nitrogen & phosphorus) Shallow/ Murkey Algal blooms b/c of nutrients / high fish Higher decomposition rate on bottom~ D.O. lower all over

EUTROPHICATION a natural process that occurs in an aging lake or pond as that body of water gradually builds up its concentration of plant nutrients.

EUTROPHICATION Cultural or artificial eutrophication occurs when human activity introduces increased amounts of these nutrients, which speed up plant growth and eventually choke the lake of all of its animal life.

A eutrophic lake

A eutrophic lake is shallow with high nutrient content. The phytoplankton are very productive and the waters are often murky. Ecologist use the term to describe relatively productive habitats and communities having good nutrient supply and to separate them from unproductive oligotrophic ones, characterized by a nutrient deficiency.

A eutrophic lake

A oligotrophic lake

SPRING TURNOVER