Phosphorus and Nitrogen

1. Phosphorus and Nitrogen

2. Phosphorus How is P used in organisms? • Biomolecules • ADP and ATP • nucleic acids • phospholipids (cell membranes) • apatite (bones and tooth enamel)   

3. Forms of Phosphorus • Phosphorus in aquatic systems is usually categorized how we measure it. • Dissolved P = Any P that goes through a 0.45um filter • PO43- polyphosphates • Dissolved organic phosphates • Particulate P = Any P that is retained on the filter in algae, zooplankton, detritus, attached to sediment particles. • Total P = Dissolved P + Particulate P • Reactive P = P that reacts with molybdenum to form a blue color. • The most commonly measured forms of P are Total Phosphorus (TP) and Dissolved Reactive Phosphorus (DRP)

4. Limiting nutrients • Theoretically, phosphorus is usually the most limiting nutrient in freshwater systems as determined by Liebig’s Law of the Minimum and Ecological stoichiometry

5. Liebig’ Law Growth is limited by the nutrient that is in shortest supply. P C Fe N

6. Limiting nutrients • Ecological stoichiometry • Ratios of elements in plankton and other organisms • Important in addition to Liebig’s law

7. Stoichiometry gives the “recipe” for phytoplankton Cake Example 2 1/4 cups sifted cake flour2 teaspoons baking powder1/2 teaspoon salt1/2 pound Butter 2 cups sugar4 large egg yolks2 teaspoons vanilla1 cup sour cream4 large egg whites

8. Recipe for phytoplankton is the Redfield Ratio • In the 1950sAlfred Redfield found in the deep ocean an average phytoplankton composition (by number of atoms) of   C       H      O      N     P    S Fe 106    263    110   16    1     0.7 0.01 Note that C, H, O, and N are required in greater proportion than P. Why then are these NOT the generally nutrient limiting?

9. C       H      O      N    P     S Fe 106    263   110   16    1     0.7 0.01 • In freshwater systems P is usually limiting because the amount of P available to primary producers is much less than the amount requiredrelative to the other elements. • P makes up only ~1% of organic matter which implies that if nothing else is limiting, then increasing P can theoretically generate >100X the weight of added P in algae

10. The Burglar Baker • Suppose you were a baker and wanted to sabotage a rival baker by stealing supplies from his storehouse. You can carry 50 lbs. of any ingredient with you. • What do you steal in order to prevent him from making the most cakes? 2 1/4 cups sifted cake flour2 teaspoons baking powder1/2 teaspoon salt1/2 pound Butter 2 cups sugar4 large egg yolks2 teaspoons vanilla1 cup sour cream4 large egg whites

11. 2 1/4 cups sifted cake flour2 teaspoons baking powder1/2 teaspoon salt1/2 pound Butter 2 cups sugar4 large egg yolks2 teaspoons vanilla1 cup sour cream4 large egg whites i.e. If you have plenty of everything else, then with only ½ teaspoon of salt, you can bake a cake.

12. Phosphorus and Lake Classification The productivity of a lake is often determined by its P loading and its volume (mean depth)

14. Sources of Phosphorus • Weathering of calcium phosphate minerals, especially apatite [Ca5(PO4)3OH] from sediments of ancient oceans. There are no important gaseous sources of P. • Anthropogenic P is now often much greater than natural inputs of P in many watersheds • Sewage, agriculture, etc.

15. Sources of Phosphorus • Increased production of algae due to increased Anthropogenic P input is cultural eutrophication • Anthropogenic P may come from • point sources (think of a pipe) • nonpoint sources (diffuse, like agriculture runoff)

16. Point and Nonpoint sources thinkquest.org

17. External vs. Internal P Loading • “Loading” refers to input of a nutrient per unit time • Usually calculated for rivers as concentration x flow • External loading refers to sources outside the lake (as in previous slide) • If all external sources of P were removed, a lake would continue to grow algae for many years. This is because P is recycled within the lake. This recycling is termed Internal Loading

18. Lake sediments can trap P under oxic conditions or release P under anoxic conditions Oxygen profile of sediments in oxic conditions Diffusion Barrier P diffusion

19. Internal P Loading • P may be recycled in the food web several times • Phytoplankton are extemely efficient at absorbing any P that is released by excretion or decomposition • Eventually P will be lost from lake either by outflow or by sedimentation to the lake bottom. • P is bound in lake sediments under oxic conditions, but may be regenerated from sediments under anoxic conditions (iron and microbes play an important role) lakes.chebucto.org/DATA/PARAMETERS/TP/popup.html

20. Internal P Loading • Deep lakes with oxic hypolimnia and long WRT may retain 70-90% of incoming P in the sediments • Lakes with Anoxic hypolimnia retain only half as much P as lakes with oxic hypolimnia • Therefore external loading may result in a positive feedback loop that amplifies eutrophication. lakes.chebucto.org/DATA/PARAMETERS/TP/popup.html

21. external P loading phytoplankton  regeneration of P from sediments  decomposition  hypoxia Positive Feedback Loop

22. Bioturbation With Mayflies Without Mayflies J. Chaffin Physical re-suspension by organisms living in oxic sediments may also increase the regeneration of Phosphorus from sediments into the overlying water

23. Phosphorus Remediation • Eutrophication can be ugly: high algal biomass (sometimes toxic), hypoxia, fish kills, foul smells • One answer is to reduce P loading by • Removing P from waste water (tertiary treatment) • Diverting waste water (see Lake Washington) • Using natural or constructed wetlands to trap P • Using buffer strips to trap agricultural runoff • Using pumps to aerate the hypolimnion

24. Wastewater Treatment Addition of alum to precipitate P www.defra.gov.uk

25. Buffer Strips www.epa.gov/owow/nps/Section319III/OH.htm NRCS

26. Hypolimnion Aeration content.cdlib.org/xtf/data

27. The importance of the Maumee River watershed in phosphorus loading to Lake Erie http://web2.uwindsor.ca/lemn/LEMN2010.htm

29. D. Dolan, LEMN conf. 2010

30. A look at P in the Maumee River(from P. Richards and D. Baker, NCWQR) Study completed in 1995 showed almost all trends improving, now they are getting worse.

31. Both river flow and DRP concentration have increased, therefore much greater DRP loading

32. The Maumee River watershed is causing a high degree of stress to Lake Erie J. Kelly, LEMN Conf. 2010

34. Where is the dissolved P coming from?Investigation by the Ohio Phosphorus Task Force • Agriculture • Conservation Tillage • Reduces soil erosion, but… • Fertilizer remains near the soil surface and is more easily washed into tributaries

35. Stratification of P in soils

36. Conservation Tillage may have unintentional side effects

37. Where is the dissolved P coming from?Investigation by the Ohio Phosphorus Task Force • Agriculture • Conservation Tillage • Fertilizer is not incorporated into the soil and is more easily washed into tributaries • Fall application of fertilizers • Continuation of old P-building practice • CAFOS (concentrated animal feeding operations) • Produce large amounts of animal waste with poor waste treatment practices • Municipalities • Combined sewer overflows (CSOs) • Addition of P to water supply as anti-corrosive • See Ohio Lake Erie Phosphorus Task Force Final Report http://www.epa.state.oh.us/portals/35/lakeerie/ptaskforce/Task_Force_Final_Report_April_2010.pdf

38. The Microcystis-Anabaena bloom of 2009 was the largest in recent years in our sampling region • …until 2011 2011

39. Phosphorus loading is important, but what about Nitrogen? Nitrogen loading and concentration drop during the summer, leading to Nitrogen-limited conditions. Phosphorus remains high throughout the growing season.