Mississippi River Water Quality: Policy, Landscapes and Hypoxia

Transcription

1 Mississippi River Water Quality: Policy, Landscapes and Hypoxia Dennis Keeney Distinguished Lecture R. Eugene Turner Dept. Oceanography and Coastal Studies Louisiana State University 12 November 2009 Leopold Center for Sustainable Agriculture

2 Dr. Dennis Keeney You can prove almost anything on the internet: is this young Dennis? In front of the pack? Watching for hazards coming up from behind? Colleague?

3 Hypoxia and Water Quality Landscapes and Policy Future Iowa

4 Our watershed * 0.6% 58% 18% 21% [w & w 2.4%] 500 km

5 ,600 sq km 6,800 sq mi ,600 sq km 6,414 sq mi ,200 sq km 7,032 sq mi

6 Data source: N.N. Rabalais, Louisiana Universities Marine Consortium, R.E. Turner, Louisiana State University Funded by: NOAA, Center for Sponsored Coastal Ocean Research

7 Seasonal oxygen concentration off the Louisiana coast Bottom layer oxygen hypoxic Justic, Rabalais, Wiseman and Turner

8 How does the bottom layer become hypoxic?

9 Upper Water Column Pycnocline Cross-shelf Contours Transect C Stations 1-9 July 12, 1995 Density Oxygen Warm+fresh Cold+salty <2 mg/l Km from coast D e p t h Salinity (psu) and Temperature o C Oxygen Temp Salinity Oxygen (mg/l)

10 A Global Epidemic Díaz & Rosenberg more of concern The distribution matches the global human footprint in developed countries and is increasing in developing countries.

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12 Fisheries: densities of bottom-feeding fish (croaker) and shrimp Years without hypoxia 20 m 80 m Croaker croaker Years with hypoxia Shrimp shrimp 20 m 80 m Croaker croaker 95% 75% 50% 25% Shrimp shrimp Fig. By K. Craig, Duke

13 Is this a natural phenomena?

14 It s not climate change (yet?) Mississippi River Vicksburg Variable discharge, but no long-term trend ( ) Coherence within basin

15 A mostly N limited system N load higher? Algal production higher? Oxygen concentration lower? Sedimentary record? Models?

16 Water quality changes in the Mississippi River at New Orleans Turner, R. E., N. Qureshi, N. N. Rabalais, Q. Dortch, D. Justic', R. Shaw and J. Cope Fluctuating silicate:nitrate ratios and coastal plankton food webs. Proc. National Academy of Sciences (USA) 95:

17 Diatoms... Biologically-bound Silica (BSi) Diatoms to Zooplankton to fish

18 Diatoms in the sediments (%BSi) and N loading in the Mississippi River

19 Oxygen south of Grande Isle, LA Turner, R. E., N. N. Rabalais, E. M. Swenson, M. Kasprzak, and T. Romaire Summer Hypoxia, Northern Gulf of Mexico: 1978 to Marine Environmental Research (LOOP Data, 59: Turner et al. 2005)

20 Benthic Foraminifera = indicator organisms Oxygen tolerant Oxygen intolerant the A / E index

21 Predicting Hypoxia in summer (nitrate flux in the spring) None before then drought Turner et al., Marine Pollution Bulletin

22 Hypoxia per unit nitrate: rising (with burps) Turner, R. E., N. N. Rabalais and D. Justic Gulf of Mexico hypoxia: Alternate states and a legacy. Environmental Science and Technology 42:

23 Yes, increased N loading led to: 1) more phytoplankton production, and 2) lower oxygen, and,. easy to model using only N

24 Important Factors for Hypoxia Unimportant (or Minimal) Factors for Hypoxia Stratification Currents Winds, waves Nutrient-enhanced primary production High flux of surface carbon to the seabed Oxygen consumption exceeds oxygen resupply Directly proportional to N load Sediment carbon legacy Deep-water oxygen minimum layer Allochthonous river carbon Ground water Wetland erosion Estuarine nutrients Mississippi River deltaic levees Reduced suspended sediments Upwelled nutrients Climate (not as yet)

25 Alternative System States coastal waters and coastal wetlands

26 Water quality changes in the Mississippi River at New Orleans 1:1 atomic ratio Turner, R. E., N. Qureshi, N. N. Rabalais, Q. Dortch, D. Justic', R. Shaw and J. Cope Fluctuating silicate:nitrate ratios and coastal plankton food webs. Proc. National Academy of Sciences (USA) 95:

27 (Photo: Q. Dortch) (Officer and Ryther 1980 Mar. Ecol. Progr. Ser. 3, 83-91) Officer and Ryther s Hypothesis and Redfield ratios O Si:Din > 1:1 diatoms as prey zooplankton as predators desirable fish community Si:Din<1:1 flagellated algae, incl. harmful algal blooms zooplankton reduced undesirable or reduced fish stocks Dinoflagellates

28 The Baltic

29 Po River delta Northern Adriatic: P and N limited (Blooms are in red)

30 Harmful algae in Louisiana coastal waters Psuedonitzchia sp. Parsons et al Limnol Oceanogr. 47:

31 QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. Downstream: Louisiana Wetlands

32 Consistency in various systems: Changes following nutrient additions to freshwater and saltwater marsh soils* Organic soil accumulation Soil decomposition Root biomass Soil strength Elevation change same or lower faster lower lower same or lower

33 Consequences: Fewer roots and rhizomes Less organic matter Weaker soils And when a storm comes: Lift Off!

34 Landscape influences Land use drives water quality worldwide and also in this watershed Key variables: cropping patterns, fertilizer use, tributary size, drainage

35 Land Under Drainage

36 N Losses under different land uses (kg km -2 yr -1 ) Ground level before 1950 Tillage and Cropping treatment Continuous bluegrass (native cover) 11 Corn, wheat, clover-rotation 485 Continuous corn 1,213 Plowed 4 inches (fallowed) 2,172 early 2000s 3,850 From: Turner and Rabalais, BioScience 2003; Miller et al. ES&T 2006 N

37 Before After

38 Landscape influences: early 1900s and now Nitrate And cropland Broussard and Turner 2009, FEE 7:

39 Land use and nitrate runoff Crumpton et al. 2006, Iowa

40 Percent of County Area in Cropland Percent of County Area in Corn Broussard and Turner 2009, FEE

41 QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture.

42 200 years of landwater couplings o From Turner and Rabalais, BioScience, in press o

43 Impairments from nutrients are significant, but are not the only stressor U.S. E.P.A Wadeable streams assessment. A collaborative survey of the nation s streams. Office of Research and Development, Office of Water. Washington, D.C. EPA 841-B

44 Hypoxia and Water Quality Landscapes and Policy Future Iowa

45 Land Use: Cropland Diversity Lower Crop Diversity Lower Landscape Diversity Fewer Farms Bigger Farms Farris et al., Iowa DNR

46 Small and Large Farm comparisons Large farms compared to Small farms are: Area 4.2 X larger $ Production per area 1.9 X greater Payments per farm 18.3 X greater Payments per acre 4.3 X larger Payments per $ value 2.3 X larger

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48 Choices - what is missing from these pictures? Are land-use activities degrading the global environment in ways that ultimately undermine ecosystem services, human welfare, and the long-term sustainability of human societies? (Foley et al. 2005) Will agriculture move more towards an industrial model that is more and more like a factory, which will ultimately fail society, or might we put more culture in agriculture and improve the nation s food security and social welfare?

49 Choices Multi-functional landscapes: examples from Minnesota using existing resources Sediment Nitrogen Phosphorus Greenhouse gas Soil organic carbon Lethal fish effects Production costs N fertilizer use Farm payments Net farm income Scenario % change A B C D Boody et al BioScience 55: 27

50 Some Implications The relationships between current agricultural practices and their associated water quality impacts can be quantitatively measured on a sub-basin scale Crop type and cropland diversity will play a major role when managing high quality waters A WATERSHED PROBLEM REQUIRES A WATERSHED PLAN!!! Addressing these coupled issues will require inventive agricultural systems and unprecedented political and social collaboration 5,000+ km 2 experimental eco-socio-political units* *Jordan et al Sustainable development of the agricultural bio-economy. Science 316:

51 IOWA As Iowa goes, so goes the watershed

52 A land in transition and changes How to keep working lands working Communities Climate change Trade National policies, e.g., water quality, subsidy size and distribution Biomass conversion, etc

53 If you are working only on problems that can solved in your lifetime, then maybe you aren t thinking big enough! Wes Jackson

54 Who here is, or will become: The Leader The Lookout The Colleague

55 Thank you

56 This presentation is the property of the presenter who has obligations to the co-authors and others who may have given permission to use proprietary graphics; this presentation is not to be copied or used by anyone else; it shall not be copied, reproduced or distributed for another s use, and it shall not be presented in another venue without the expressed written approval of the presenter.