The emerging issue of hypoxia in Canadian coastal waters

1. The emerging issue of hypoxia in Canadian coastal waters DFO national science workshop Mont-Joli, Québec, Canada November 21, 2006 Denis Gilbert Ocean and Environmental Science Branch Maurice-Lamontagne Institute Department of Fisheries and Oceans (DFO) Mont-Joli, Québec, Canada

2. Talk outline • Eastern Canada: St. Lawrence Estuary, Emerald Basin, Bedford Basin • Western Canada: Strait of Georgia, station Papa, Oregon events give forewarning for Vancouver Island • Global synthesis: 14 papers planned by SCOR Working group 128 on coastal hypoxia Denis Gilbert, IML, 2006-11-21

3. Regions considered in this talk Station Papa Strait of Georgia St. Lawrence Estuary Bedford Basin Oregon coast Emerald Basin Denis Gilbert, IML, 2006-11-21

4. Water properties on the27.25 kg/m3density surface T S O2 O2 sat. Gilbert et al. (2005, L&O, 50: 1654-1666)

5. Temperature and oxygen in LSLE (300 m+) Gilbert et al. (2005, L&O, 50: 1654-1666)

6. Water mass mixing: NACW – LCW 1980-2003 53% LCW, 47% NACW 1931-1935 72% LCW, 28% NACW Gilbert et al. (2005, L&O, 50: 1654-1666)

7. Near-bottom oxygen measured during the 2004-2005 stock assessment surveys Gilbert et al. (2006, Naturaliste Canadien)

8. Near-bottom oxygen in 2004-2005:Interpretation for cod Color coding 21% saturation = LC_50 28% saturation = LC_05 28% < O2 < 70% reduced growth O2 > 70% : optimal growth Plante et al (1998, J. Fish Biology, 53: 1342–1356) Chabot et Dutil (1999, J. Fish Biology, 55: 472–491)

9. Oxygen levels selected by various species Gilbert et al. (2006, Naturaliste Canadien)

10. Northwest Atlantic water masses Mode 1 Mode 2 Pershing et al. 2001, Oceanography, 14: 76-82

11. T-S-O2-nutrients timeseries at 150m depth in Emerald Basin Drinkwater et al 2002 NAFO SCR 02/42 Denis Gilbert, IML, 2006-11-21

12. Bedford Basin monitoring station Bill Li, BIO

13. Bedford Basin monitoring station (continued) Bill Li, BIO

14. Straits of Juan de Fuca and Georgia Diane Masson & Patrick Cummins, IOS

15. The Strait of Georgia Deep, central Basin Latitude Longitude Diane Masson & Patrick Cummins, IOS

16. Temperature and oxygen trends - Strait of Georgia Temperature trend (°C/year) Diane Masson & Patrick Cummins, IOS

17. Decreased solubility due to warmer water only accounts for 25% of oxygen decrease (i.e. saturation is decreasing !) Diane Masson & Patrick Cummins, IOS

18. Coupled atmosphere-ocean-ice & biogeochemistry model suggest … • Oxygen levels will decline in the intermediate and deep ocean • Oxygen decline reflects changes due to solubility, ocean dynamics and ocean biology • An expansion of low oxygen regions like the eastern equatorial Pacific (≈20% increase) • We need better global observations to monitor oxygen changes Richard Matear, CSIRO, Australia

19. Observed Pacific oceanoxygendistribution Modelled Matear and Hirst 2003, GBC

20. Ice-ocean-atmosphere coupled model with biogeochemistry predicts a 20% increase in global volume of hypoxic waters Matear and Hirst (2003, GBC)

21. Station Papa At Ocean Station Papa, oxygen has been declining steadily since 1994. As oxygen is consumed through the remineralization of detrital materials, nitrate and CO2 are produced. The interior of the ocean is currently nutrient rich but oxygen depleted. This trend is linked with widespread changes being observed in the North Pacific. Frank Whitney, IOS

22. Dead zones off Oregon Coast in July and August: 2002, 2004 and 2005 Grantham et al. (2004, Nature, 429:749-754)

23. Argo floats with oxygen sensors Denis Gilbert, IML, 2006-11-21

24. Argo profilingfloat 4900637 Near Vancouver Island Latitude: 46.431 °N Longitude: 128.25 °W

25. Papers proposed by SCOR WG 128 on hypoxia • Global coverage of hypoxic zones (Nancy Rabalais, USA) • Oxygen trends over past 100 years (Denis Gilbert, Canada) • Historical record from sediments (Andy Gooday, U.K.) • Upwelling-dominated systems (Pedro Monteiro, South Africa) • Systems with high anthropogenic N & P inputs (unknown author) • Recovery following remediation efforts (Michael Kemp, USA) • Benthic-pelagic coupling (Jack Middelburg, Netherlands) Denis Gilbert, IML, 2006-11-21

26. Papers proposed by SCOR WG 128 on hypoxia (continued) • Greenhouse gas emission – N20 & CH4 (Wajih Naqvi, India) • Impacts of global warming (Richard Matear, Australia) • Effects on nekton and plankton (Werner Ekau, Germany) • Microbial communities (Osvaldo Ulloa, Chile) • Knowledge gaps and future research (unknown lead author) • Designing hypoxia observing systems (unknown lead author) • Overall summary of all papers (Jing Zhang, China) Denis Gilbert, IML, 2006-11-21

27. SUMMARY (1/2) • St. Lawrence Estuary, Emerald Basin and Strait of Georgia oxygen levels are influenced by interannual variations in water properties over the upper continental slope. • Bedford Basin undergoes short periods of hypoxia followed by quick recovery during episodic bottom water renewal events. Denis Gilbert, IML, 2006-11-21

28. SUMMARY (2/2) • Enhanced upper ocean stratification may be responsible for reduced winter ventilation at station Papa. We may witness episodes of more severe hypoxia off Vancouver Island within the next decade. • Coastal hypoxia is an issue of growing concern around the world. Other countries (Denmark, Sweden, U.S.) are considering and/or implementing mitigation measures to restore key ecosystem functions and services. Denis Gilbert, IML, 2006-11-21