Nitrogen sources and sinks in Bah

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Influence of Yaqui Valley Agricultural Activities
on Marine Ecosystem Processes in the Gulf of
California Evidence from Remote Sensing
J. Michael Beman Pamela A. Matson School of
Earth Sciences, Stanford University
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Outline

• Introduction
• Remote Sensing Statistical Analyses
• Explanations Implications
• Conclusions Future Directions

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50 km
The Yaqui Valley-Gulf of California
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The Yaqui Valley

• Extremely Nitrogen-rich system
• 60 x 106 kg N applied per crop cycle
• Large N losses to the atmosphere, groundwater,
  and surface waters of the Valley (Harrison and
  Matson, 2003 Matson et al. 1998, Panek et al.
  2000 Riley and Matson, 2000 Riley et al. 2001)
• Dissolved N losses are determined by highly
  regular irrigation/fertilization events

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The Gulf of California

• Dynamic Marine Region
• Diverse sixth-richest center of marine endemism
  worldwide (Roberts et al., 2002)
• Productive classically understood as a highly
  productive marine region (Zeitzschel, 1969)
• High priority for conservation proposed marine
  reserve network (Sala et al., 2002)
• Complex circulation patterns result of shallow
  sills, deep basins and strong tides (9 m in
  northern Gulf)
• Nutrient-rich waters at depth deep inflow from
  the Pacific (Bray and Robles, 1991)
• Upwelling zones northerly winds in winter drive
  upwelling along the west coast of mainland
  Mexico, including the Yaqui coast

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• What happens at the intersection of an intensive
  agricultural area, the Yaqui Valley, and a
  dynamic marine region, the Gulf of California?
• Can N losses from terrestrial agricultural
  systems affect marine ecosystem processes?

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• What happens at the intersection of an intensive
  agricultural area, the Yaqui Valley, and a
  dynamic marine region, the Gulf of California?
• Can N losses from terrestrial agricultural
  systems affect marine ecosystem processes?
• In coastal systems Yes
• (Cloern 2001 NRC 2000 many others)
• In the open ocean No
• (Falkowski et al. 2000)
• In the coastal ocean Rarely
• (Turner and Rabalais, 1994 Naqvi et al. 2000)
• However, it has become increasingly apparent
  that the effects of excess nutrients in coastal
  systems are not minor and localized, but have
  large-scale implications and are spreading
  rapidly (Rabalais, 2002)

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• Can N losses from terrestrial agricultural
  systems affect marine ecosystem processes?
• Nutrient inputsupwelled or terrestrialwill
  increase phytoplankton biomass (chlorophyll a)
  visibly in ocean color imagery
• Corresponding sea surface temperature (SST)
  signal associated with upwelling-derived
  nutrients No SST signal associated with
  terrestrial inputs
• Multi-Sensor Remote Sensing approach
• SeaWiFS - 1 km HRPT data, processed to L2 chl a
  data using OC 4v4 algorithm
• AVHRR - JPL PO DAAC 9 km Pathfinder SST
• Statistical analyses

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Remote Sensing Analysis
Cross-Gulf Transect
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Distance along transect (km)
1998
2001
2002
2000
1999
100 mg/m3
10 mg/m3
1 mg/m3
0.1 mg/m3
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Distance along transect (km)
1998
2001
2002
2000
1999
35 C
25 C
15 C
5 C
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100 mg/m3
10 mg/m3
1 mg/m3
0.1 mg/m3
35 C
25 C
15 C
5 C
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Patterns in Imagery

1. Large seasonal cycles in chl a and SST
2. Periods of elevated biomass (blooms) superimposed
   on seasonal chl a signal
3. Blooms can extend across the entire Gulf
4. In some cases blooms are related to colder water,
   indicative of upwelling
5. Close correspondence between fertilization/irrigat
   ion events and blooms is also clearly evident

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Statistical Analysis
Cross-Tóbari Transect
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Log chlorophyll a (mg/m3)
Sea Surface Temperature (C)
1998
2001
2002
2000
1999
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Log chlorophyll a (mg/m3)
Windspeed (m/s)
1998
2001
2002
2000
1999
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Statistical Analysis

• Linear Regression
• Y ß0 ß1X1 ß2X2 ßkXk
• Generalized Linear Models (GLM)
• Y g(b0 b1X1 b2X2 bkXk) error
• -or-
• f(µY) b0 b1X1 b2X2 bkXk
• Y-µY residual signal

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Chlorophyll a (mg/m3)
Chlorophyll Residual GLM CHL b0 b1(SST)
b2(SST_at_WIND) link function log residual
Pearson b0 3.295095 0.052812 b1 -0.059943
0.003502 b2 0.001236 0.000651
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Explanations for ocean color patterns

• Direct Effects
• Supply of N from Yaqui
• Supply of other nutrients (Fe,P)
• Indirect multiplier effects/Interactions
• Processing changes concentration/form of N
• Interaction between Yaqui inputs upwelling
• N deficit in upwelled waters P supplied in
  excess deficit satisfied by Yaqui inputs
• Other
• Sediment plumes
• Extremely consistent upwelling

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Implications for Marine Reserves
1998-2002 - SeaWiFS chlorophyll
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Implications for Marine Reserves
Lobos
Tóbari
Figure from Sala et al. (2002) A General Model
for Designing Networks of Marine Reserves,
Science 2981991-1993
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Conclusions

• Can N losses from a terrestrial agricultural
  system affect marine ecosystem processes in the
  Gulf of California?
• Yes Increasing evidence from remote sensing
  demonstrates that agricultural activities in the
  Yaqui Valley influenceor interact withmarine
  ecosystem processes in the Gulf

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Conclusions

• Terrestrial-marine linkages could have important
  implications for marine conservation in the Gulf,
  and may be more common than previously thought
  (e.g., Florida Keys, Channel Islands)
• Multi-sensor remote sensing combined with
  statistical modeling is a powerful tool for
  studying these linkages, and could be applied to
  similar systems around the world

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Future work

• Remote Sensing and Other Data
• 2002-2003 MODIS SST chlorophyll near-daily
  coverage, better spatial/radiometric resolution
• Improved wind data (direction max speed)
• Statistics
• Spectral analysis neural nets model
• Model SST wind as smooth functions (splines)
• Include irrigation events in GLMs
• f(µY) b0 b1(SST) b2(WIND)
  bk(0,0,1,0,etc.)
• Biogeochemical processes at different spatial
  scales..

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Future work
Biophysical Processes
NTR/DNF/Annamox/N2O Production Eutrophication
Carbon Cycle (Biomass, PP) Secondary effects
(O2, Reserves)
Lobos
System
Tóbari
Yaqui Coastal Area
Gulf of California
Remote Sensing
ALI/Landsat Hyperion
MODIS 250 m
MODIS 500 m
MODIS 1 km products, SeaWiFS
Spatial Scale
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Future work

• NSF Integrated Carbon Cycle Program (ICCR)
• Do biogeochemical transformations impact the
  transport of C into the Gulf?
• What determines the C content composition of
  plumes extending from the estuaries into the
  Gulf?
• What is the eventual fate of C associated with
  the plumes?

Lobos
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Future work
Biophysical Processes
NTR/DNF/Annamox/N2O Production Eutrophication
Carbon Cycle (Biomass, PP) Secondary effects
(O2, Reserves)
Lobos
System
Tóbari
Yaqui Coastal Area
Gulf of California
Remote Sensing
ALI/Landsat Hyperion
MODIS 250 m
MODIS 500 m
MODIS 1 km products, SeaWiFS
Spatial Scale
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Tóbari Biogeochemistry
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Tóbari Biogeochemistry Chl a (mg/m3)
8
6
4
2
0
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Tóbari Biogeochemistry NO3- (µM)
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40
30
20
10
0
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Tóbari Biogeochemistry NH4 (µM)
125
100
75
50
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Future work

• What is the fate of N entering Tóbari How is N
  transformed via microbial processes? How much N
  is lost from the system?
• What are the processes responsible for the N
  conundrum (low NO3-/high NH4) in Tóbari?
• Inhibition or limitation of nitrification?
• Rapid denitrification?
• Upwelled NO3-, or entirely Yaqui-derived?
• Upwelled NH4, or entirely Yaqui-derived?
• Active annamox or somehow inhibited/limited?
• Can we link biogeochemical data to
  remotely-sensed data? Are there relationships
  between the spectral and biogeochemical
  properties of water masses?

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Policy Implications

• Gulf of California
• What role do agricultural influences play in the
  sustainability of the Gulf as a whole? Are they
  irrelevant in the context of other changes?
• How do we manage linked terrestrial-marine
  systems such as the Gulf?
• Tóbari
• How vulnerable is Tóbari? Is there potential for
  conservation or remediation of its resources?
• How economically and culturally vulnerable are
  its fishing communities?
• Are there educational opportunities we can become
  involved with (Don Chayo and Manuel)?

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Acknowledgements

• Remote sensing support Kevin Arrigo, Rochelle
  Labiosa, Gert van Dijken, Ocean Biogeochemistry
  Lab, Department of Geophysics
• Irrigation and meteorological data Ivan
  Ortiz-Monasterio and CIMMYT
• Field work Esther Cruz Colin, Juan Antonio
  Delgado, Ivan Ortiz-Monasterio
• Shrimp, cerveza and boat time Manuel Nieblas
  Lopez and the pescadores of Bahía del Tóbari
• The David and Lucile Packard Foundation
• National Science Foundation Graduate Research
  Fellowship Program

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1/15/03
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1/19/03 1/20/03
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Lobos
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In situ SeaBASS SeaWiFS OC 4v4 Chlor_MODIS Chlor_a_2 (SeaWiFS analog) Chlor_a_3 (Clark Semi-Analytical) GSFC MODIS (msl12)
In situ SeaBASS
SeaWiFS OC 4v4
Chlor_MODIS
Chlor_a_2 (SeaWiFS analog)
Chlor_a_3 (Clark Semi-Analytical)
GSFC MODIS (msl12)
Lobos