• Subjects– Energy Flow and Chemical Cycles– Photosynthesis and Respiration– Plant Processes

• Standards

Next Generation Biology Environmental

Modeling how photosynthesis transforms light into chemical energy

Ecosystem dynamics between single-cell and multi-cellar organisms

Connectedness between terrestrial and aquatic chemical cycles

Look respiration utilizes oxygen to release chemical energy

Assess the flow of energy through an ecosystem and how humans can modify natural balances

Eutrophication

Eutrophication

The oversupply of nutrients to an ecosystem and subsequent effects on primary production

What is eutrophication?

What is a nutrient? What are some examples?

A substance that provides nourishment essential for growth and maintenance of life. Some examples are Phosphate (PO4

3-), Nitrate/Nitrite (NO3-/NO2

-), or Ammonia (NH4+)

phosphorous

oxygen

oxygen

oxygen

nitrogennitrogen nitrogen

hydrogen

Phosphate Nitrate Nitrite Ammonia

Why are these nutrients important to biology

How do you make DNA?

What is a cell wall?

What is needed to make protein?

Phospholipid

What controls nutrient flux into marine systems?

• Weathering of rock• Biological recycling• Direct usage of

organic compounds• Conversion of organic

to inorganic in anoxic systems

• Anthropogenic input• Fertilizers• Runoff• What other human

activities contribute?

Consequences of EutrophicationMany unpredictable results

• Algal Blooms• Net loss of oxygen

and dead zones• Fish kills

Oxygen %Photosynthesis

Dep

th

Dead Zone

Min Max

CO2 + H2O + light O2 + CH2O

O2 + CH2O CO2 + H2O + Energy

Photosynthesis fuels respiration

Surface

Bottom

What type of primary producers do nutrients stimulate?

• Cyanobacteria– 0.5-1 μM to 40 μM– Single celled or chain forming

• Diatoms– 2 μM to 500 μM– Single celled or chain forming– Silica frustules (skeletons)– Variety of colors (green, yellow,

brown)• Based on their photosynthetic

pigments

• Dinoflagellates– 5 μM to 2,000 μM– Again variety of colors due to

pigments– Typically have a flagella

Synechococcus Microcystis

Thalassiarsira Diatom Morphologies

These Consequences have major impacts on marine food webs

Why?

The nutrient input off-sets the balance between microbial energy the oxygen budget.

After oxygen is used up, larger organisms (fish and inverts) die or move away leaving behind microbes that thrive in low oxygen environments

Activity Questions

• Will terrestrial fertilizer (miracle-gro) stimulate aquatic primary producers?

• Will there be a difference in species composition between marine and freshwater species stimulated by nutrients in the fertilizer?

• Is there a direct correlation to the amount of nutrients added to the amount of primary producers grown?

Activity Outline• Experiment

– Get 6 bottles per group (3 fresh/3 marine)– Add 500mL of either lake or marine water to

each bottle– There will be 3 treatments per experiment

• Control (no fertilizer added)• 0.5mL liquid fertilizer• 1.0mL liquid fertilizer

– Label and Add desired fertilizer to each bottle then mix

– Place near window

• Microscope Check– Take ~1mL from the experiments already set up

and place on slide and cover with another slide– Examine under under a microscope and record

differences between treatments

Follow-up questions1. What were the differences between the fresh and saltwater experiments (e.g., color of

phytoplankton, species composition)?2. Predict what the effect would be if you kept adding fertilizer to the bottles? Would

primary productivity continue to increase in proportion to how much fertilizer is added?3. Would you expect either N or P to be the main limiting nutrient in saltwater? In

freshwater? Why? 4. Is there a difference between the chemicals used in terrestrial fertilizers and the

chemicals required for aquatic primary production?5. What other chemical(s) could limit primary production?6. How does an increase in primary production lead to oxygen loss in some aquatic

systems?7. Are some oceanographic regions especially susceptible to oxygen loss due to

eutrophication? Where are these regions? Why are they susceptible? The northern Gulf of Mexico at the mouth of the Mississippi River is a good example here. This habitat/ecosystem could be discussed in the context of eutrophication, oxygen loss, and effects on ecosystems and economic activities (e.g., fisheries).

8. At the regional scale, have there been any reports of fish kills near you that can be linked to eutrophication?

9. How could the runoff of excess fertilizer from farmlands be reduced or eliminated?