1. Hypoxia in the Gulf of Mexico Nancy N. Rabalais Louisiana Universities Marine Consortium nrabalais@lumcon.edu

2. Distribution and dynamics of hypoxia What are the proximal causes? What are the ultimate causes? What has changed over time? What are the consequences? What are the solutions?

3. LUMCON Louisiana Universities Marine Consortium

4. R/V ACADIANA R/V PELICAN

6. -94.0-93.5-93.0-92.5-92.0-91.5-91.0-90.5-90.0-89.5 28.5 29.0 29.5 30.0 A'1 A'2 A'3 A'4 A'5 A'6 A1 A2 A3 A4 A5 A6 A7 A8 A9 B2 B4 B6 B8 B9 B10 C1 C3 C4 C5 C6B C6A C8 C9 C8A C9A C10 D'0 D'1 D'2 D'3 D'4 D'5 D'6 D1 D1N D2 D2A D3 D4 D5 D6 D7 E1 E2 E2A E3 E4 E5 E6 F1 F2 F3 F4 F5 F6 F7 G1 G2 G3 G4 G5 G6 H1 H2 H3 H4 H5 H6 H7 I1 I2 I3 I4 I5 I6 I7 J1 J2 J3 J4 J5 J6 J7 K1 K2 K3 K4 K5 K6 K7 M1 M2 M3 M4 M5 P1 P2 P3 P4 P5 R1 R2 R3 R5 Calcasieu Marsh I. Atchafalaya R. Pt. au Fer Mississippi R. Terrebonne & Timbalier Bays Barataria Bay Southwest Pass C7 Louisiana Texas Sabine SHELFWIDE SURVEY, MID-SUMMER F0 F1 F2 C9 C8 C7 C6 C6B C5 C4 C3 C1 F3 F4 F5 F6 THE DATA SOURCES 7.5 m 19 m 12 m MONTHLY TRANSECTS INSTRUMENT MOORING SHELFWIDE SURVEY, MID-SUMMER F0 F1 F2 C9 C8 C7 C6 C6B C5 C4 C3 C1 F3 F4 F5 F6 F0 F1 F2 C9 C8 C7 C6 C6B C5 C4 C3 C1 F3 F4 F5 F6 THE DATA SOURCES 7.5 m 19 m 12 m 7.5 m 19 m 12 m 7.5 m 19 m 12 m 7.5 m 19 m 12 m MONTHLY TRANSECTS

7. (Source: N. Rabalais, LUMCON)

8. (Rabalais et al., 2002)

9. Estimated Size of Bottom-Water Hypoxia in Mid-Summer (Modified from Rabalais et al. 2002) Area (km 2 )

10. TRANSECT C (Source: B. Cole, LUMCON)

11. (Rabalais et al., 2002)

12. OFFSHORE OIL PLATFORM SITE OF INSTRUMENT MOORING C/T/DO 7.5 m 19 m 12 m C/T X X ADCP

13. ST53 #3 Station C6B Sampling design C/T/DO 7.5 m 19 m 12 m C/T X X ADCP

14. (Source: N. Rabalais, LUMCON)

15. Linked Land/Ocean Ecosystem

17. (CENR, 2000)

18. 0510 20 25 30 35 D.O. Sal. and Temp. 9/18/92 11:56 0 5 10 15 20 0 05105 20 25 30 35 2025 30 35 Depth (m) D.O. Sal. and Temp. 5/26/92 11:02 8/12/92 11:03 Temp. C Sal. ‰ D.O.mg/L C6B 05 10 25 30 35 D.O.

19. Nitrogen, phosphorus (and silica) are essential for the growth of phytoplankton. Most often, however, problems with an overabundance of nutrients in marine systems are the result of excess nitrogen rather than phosphorus. (Lohrenz et al., 1997)

20. (Rabalais et al., 2002)

21. Surface Chlorophyll a (  g/l) Longitude (W) (Rabalais et al., 2002)

22. http://www.mvn.usace.army.mil/eng/edhd/tar.gif

23. (Source: D. Justić, LSU)

24. A Coupled Biological/Physical Model of Oxygen Concentration (Justic et al. 2002)

25. (Scavia et al., 2003)

26. Comparisons: Both Models Indicate Little Hypoxia Prior to Early 1970s 1955196019651970197519801985199019952000 Bottom Years Scavia et al. 2003 Justic et al. 2002

27. 93.5 29.0 29.5 30.0 92.591.590.589.5 29.0  75%  25%  50%  25% Sabine L. Atchafalaya R. Terrebonne Bay transect F transect C Mississippi R L. Calcasieu Frequency of Hypoxia 1985 – 2002 Bottom Water < 2 mg/L Modified from Rabalais et al. (2001) Is it Water (Physics)? or Nutrients (Biology)?

28. There are clear signals that humans have altered the global cycles of nitrogen and phosphorus over large regions and increased the mobility and availability of these nutrients to marine ecosystems.

29. N Fixation: Fertilizer & Legumes & Fossil Fuels (Galloway et al. 2002)

30. Greater input of growth limiting nutrient Higher concentration of that nutrient in the water Increased phytoplankton production and algal blooms Increased sedimentation of organic matter Oxygen deficiency below the halocline; hydrogen sulfide formation Elimination of benthic animals below the halocline More filamentous green algae Less brown algae and eelgrass Fewer regions of suitable habitat for feeding and reproduction More zooplankton More benthic animals on bottoms above the halocline More fish above the halocline Less fish below the halocline Less light penetration (Source: N. Rabalais, LUMCON)

31. (Goolsby et al., 1999) 58% crop 21% range 18% wooded 2.4% water/wetlands 0.6% urban

32. Riverine N and P tripled and doubled Spring nitrate peak now present Changes closely related to N and P fertilizer applications in watershed Offshore nutrient compositions shifted Water quality changes in nutrients, primarily, less in flow or delivery of flow Nutrient concentrations and loads changed dramatically in the last half of the 20 th century

33. Nitrogen Source Distribution (Goolsby et al., 1999)

36. (© F. Viola, 1991) Increasing Productivity Worsening Hypoxia Consistent with Increase in Riverine N Load Hypoxia Has NOT Always Been Present

37. O 2 > 2 mg/l The “Dead Zone” is ……. ….. not completely “dead.” N. Rabalais (© F. Viola, 1991)

38. Effects of Hypoxia on Fisheries Resources (Rabalais et al., 2001) Direct mortality Altered migration Reduction in suitable habitat Increased susceptibility to predation Changes in food resources Susceptibility of early life stages (© F. Viola, 1991) K. St. Pé

39. ( © F. Viola) Stressed Benthos Bacterial Mats (© F. Viola, 1991) D. Harper

40. ROV, Remotely Operated Vehicle (© F. Viola, 1991)

41. (Downing et al., 1999) O 2 at 14 m > 2 mg/L Bottom O 2 at 20 m = 0.05 mg/L (© F. Viola, 1991)

42. ( Downing et al., 1999)

43. ? Production and Fishery Yield SE North Sea N Gulf of Mexico Adriatic Sea Great Lakes Kattegat Baltic Sea Seto Inland Sea Yellow Sea NW Black Sea Chesapeake Bay OligotrophicMesotrophicEutrophic(Dystrophic?) Nutrient Loading Oligo-Meso-Eu- Dys-trophic Benthos Demersal fish Zooplanktivorous fish Other zooplankton feeders (e.g., jellyfish) SeasonalPermanent bottom hypoxia (Modified from Caddy, 1993)

44. 1,100 miles from Des Moines, Iowa Overwhelming source of nutrients Can the situation be reversed, is there a solution?

45. Average Dissolved Oxygen Response Composite Results for 1985, 1988, 1990 Percent Change Relative to Base Percent Load Reduction (Vic Bierman, Limno-Tech, Inc.)

46. (Zaitsev, 1992) Development of Hypoxia NW Shelf Black Sea

47. Fertilizer N and P Trends NW Shelf Black Sea (Mee, 2001) N and P Loads Corresponded to Fertilizer Use

48. (Mee, 2001)

49. (Source: D. Scavia, NOAA)

50. Gulf Action Plan: GOALS  Coastal. By 2015, reduce hypoxia below 5,000 km 2.  Basin. Restore and protect the waters of Basin States and Tribes.  Communities. Improve social and economic conditions in the Basin. - Aim to achieve a 30% reduction in N discharge to the Gulf, 5-yr running average - Voluntary actions, incentives, education

51. 198519861987198819891990199119921993199419951996199719981999200020012002 goal 0 5000 10000 15000 20000 25000 (modified from Rabalais et al. 2002) Areal Extent of Hypoxic Zone 1985 - 2002 Area (km 2 ) 2015 Goal for 5-yr running average <5,000 1985-1992 average 1993-2002 average 5-yr running average no data

52. Two key ways to reduce loads: Decrease N loss from land Increase Denitrification

53. Agricultural Non-Point Sources Tertiary treatment 20 (point sources) (point sources) (Mitsch et al. Doering et al.) Nitrogen Reduction (1000 MT/yr) Farm N management 1,400 - 1,900 Alt. crop systems 500

54. Nitrogen Reduction (1,000 MT/yr) Wetlands 300Wetlands 300 Riparian Buffers 300Riparian Buffers 300 Coastal Diversion 50Coastal Diversion 50 Increasing Denitrification (Mitsch et al.)

55. Potential N Reduction (1000 mt N/yr) (Data Source: Mitsch et al. 1999, 2001; CENR 2000) 300 (12%) 300 (12%) 500 (19%) 50 (2%) 900 (35%) 20 (1%) 500 (19%)

56. (From Bricker et al., 1999)

57. A National Problem 44 (From Bricker et al., 1999) = High Eutrophic Conditions Over 60% of U.S. estuaries show high eutrophic conditions (Bricker et al., 1999) Nutrient pollution is largest U.S. coastal pollution problem (NRC, 2000)

58. Global Distribution of Documented Oxygen Depletion n = 146 (Diaz and Nestlerode, 2003)

59. Hypoxia, Then & Now 44 (Diaz and Rosenberg, 1995) 50 (Science, 1998) 57 (Diaz and Rosenberg, 2000) 114 (Diaz, 2001) 146 (Diaz and Nestlerode, 2003)

60. 2025-2034 2090-2099 Hadley Canadian Projected Changes in Average Annual Runoff for Basins Draining to Coastal Regions

61. What do you predict with regard to distribution and severity of hypoxia, in the Gulf and elsewhere, with? warming climate doubled CO2 atmospheric concentration changes in freshwater inflow frequency and severity of storms? How will fishery resources change?