RISE R iver- I nfluences on S helf E cosystems – The Columbia River Plume Program

1. RISE River-Influences on Shelf Ecosystems – The Columbia River Plume Program David A. Jay Department of Environmental and Biomolecular Systems OGI School of Science and Engineering Oregon Health and Science University With thanks to the RISE Team

2. Project Title – Collaborative Research: Productivity, Biogeochemical Transformations and Cross-margin Transport in an Eastern Boundary Buoyant Plume Region Target area – the Columbia River (CR) plume in a shelf setting extending from mid-Oregon to mid-Washington Left: SeaWiFS 26 June 2000, Chl, mg m-3 Note high Chl off WA Right: CZ Color Scanner,from 24 May 1982 Note large plume area

3. Why the Columbia River (CR) Plume? • CR is a typical large, productive plume that impacts the global carbon budget through enhanced cross-margin transport • Average flows is 7,000 m3s-1 • Range in 2,000 to 25,000 m3s-1 • It is small enough to be tractable (barely!) • CR has little excess N, so plume physical effects on biogeochemical processes can be isolated • Low-N CR can be contrasted with more-often studied plumes from eutrophic rivers like the Mississippi • CR plume entrainment, modification and transport of dissolved/particulate material significant • Poses flow and fisheries management issues that require new science and are typical of large rivers

4. The Hypotheses – 1961 data, from Anderson, 1972

5. H1,the “Plume Hypothesis”: During upwelling the growth rate of phytoplankton within the plume exceeds that in nearby areas outside the plume being fueled by the same upwelling nitrate. Questions -- • Do plume stability and turbidity affect phytoplankton growth rates and/or species composition? • Does iron in the plume (either water column or sediment-derived) alter growth rates? • Do grazer species and grazing rates in the plume differ from those outside the plume? • Does the plume spatially concentrate either phytoplankton or zooplankton? If so, how and where? • Does the presence of an offshore plume front inhibit plankton growth rates on the Oregon shelf?

6. H2, the “Transport Hypothesis”: The plume enhances cross-margin transport of plankton and nutrients. Questions -- • Do entrained upwelling nutrients increase the plankton standing stock in the plume? • How, where and when are plankton entrained into and transported by the plume? • Does the carbon export per unit distance along coast exceed that in regions without a plume? • What is the composition of matter preferentially exported by the plume?

7. H3, the “Iron Hypothesis”: Plume-specific nutrients (Fe and Si) alter and enhance productivity on nearby shelves. Questions -- • Is shelf primary productivity off WA greater than that off OR for the same applied alongshore wind stress? • Is this due to enhanced Fe availability off WA, either from the water column or from the sediments? • Does diatom size differ between the two shelves? • Do grazers, pathways and 2nd productivity depend on Fe?

8. Some Important Processes –

9. Fe Biogeochemistry in the Plume Area -- • Dissolved Fe (dFe), SiO4 supplied to plume by CR in spring, Particulate Fe supplied to shelf in winter (which is more vital?) • Plume Fe, SiO4 combine with upwelled N and P, enhance Chl Observationsand conceptual model for role of dFe:

10. CR Plume Biophysical Processes (Concepts) – • WA productivity generally higher, winter or spring Fe input?? • Plume moves south and offshore during upwelling • Fe from river, BBL and from plume mixing • Vertical mixing crucial to availability of nutrients to plume

11. Plume Mixing and Fronts – • Plume is highly mobile, with winds • Pulsed, tidal outflow • Shear induced mixing occurs at fronts and in interior due to winds, internal tides and plume motion • Internal tidal currents >barotropic tides • Internal tides variable,because of plume motion and?? • N mixed into plume crucial to productivity

12. How do we Address the Hypotheses?

13. Sampling Program 2004 to 2006 – • 2-3 week cruises in June 2004 -2006 (high-flow), August 2005 (low-flow); additional BPA/NMFS cruises • Three biophysical mooring with ADCP, CT, nutrients • Two vessels: • most biogeochemistry on R/V Wecoma • ADCP, Triaxus surveys, water properties, turbulent mixing, some biology on R/V Pt Sur • COAST, OR and WA ECOHAB and BPA/NMFS also have moorings • 1-km and 4-km coastal radars + COAST • Aircraft salinity sensing (2004) with BPA/NMFS

14. PI Roles:

15. Questions Addressed by Collaborating Projects – • CR flow and plume are strongly affected by climate – • How do secular change, ENSO and Pacific Decadal Oscillation affect plume productivity and juvenile salmonids? (GLOBEC and NMFS/BPA) • CR is a huge Fe source (NMFS/BPA projects) – • How has river management affected coastal production via nutrient and micronutrient supply? • Can some negative effects of water, Fe loss be reversed? • CR flow and fisheries management are internationally influential (NMFS/BPA projects) – • How does plume affect juvenile salmon and other fish resources? • How has flow management altered plume? • How are flow/salmon management constrained by climate change? • Toxic algal blooms off central OR and N. WA – • How are these affected by upwelling, Fe, grazing? (ORHAB, ECOHAB) • Plume fronts: What is their time-space distribution? (NESDIS)

16. Broader Impacts – • RISE will help understand plumes on eastern boundary currents worldwide • Expands the suite of issues addressed by Co-OP • Important international implications for flow and salmon management • Regional importance for groundfish, crab management • Education: 6 undergrads, 8 grad students and 2 postdocs • Outreach program: will involve 4 high school teachers in summer research, 2 years each

17. RISE Summary – • The interdisciplinary RISE team includes 12 PIs • We are at the beginning of an exciting program, with many challenges ahead • RISE will apply new ideas, technologies and models to a difficult set of problems – the physics and biogeochemistry of buoyant plumes • RISE will interact strongly with other programs in the region. This will greatly increase the impacts of our work

18. Hydrologic Change and the CR Plume -- • CR spring flow is down >40% due to flow regulation, irrigation • SPM supply is down ~50% • Plume volume is much smaller, 1961 vs. 1999 as example: • June 1961 and 1999 natural flows both very high (>20,000 m3 s-1) • Actual 1999 flow was ~ 11,000 m3 s-1, 1961 was ~20,000 m3 s-1 • 1999 plume covered only ~65% of area covered in 1961, • fronts were weaker, smaller in area June 1961 Plume June 1999 Plume

19. Possible Historical Changes in dFe Input -- • Assumes that dFe geo-chemistry is unaltered • Uses simple USGS models of 1990s data • CR is a Mississippi-sized source of dFe • Modern dFe input is mostly in winter • Historic dFe input was mostly in spring • Interaction of dFe with floodplain and estuary have changed greatly 1997 Beaver Fe transport, Hindcast from US GS model, 95% confidence limits shaded 1880 Beaver Fe transport, Hindcast from US GS model, 95% confidence limits shaded

20. Changes in N and Si Inputs -- • Eutrophication is NOT aCR issue • N, POM inputs to river have increased, but: • Reservoirs increase T & residence time, decrease turbidity • Fluvial production up ~4x • Changes in flow have increased estuary residence time and use of N • Annual export of N to plume may have decreased • Biggest decrease in N supply in spring, because there was historically little production in cold, turbid, high-flow river • Si input likely not changed very much – always in excess • Zero salinity river water no longer injected into plume Chl data from Larry Small, OSU