Xinping HuWei-Jun CaiWei Jun Cai

Department of Marine Sciences, University of Georgia

Nancy N. RabalaisLouisiana Universities Marine ConsortiumLouisiana Universities Marine Consortium

http://www.gulfhypoxia.net/

http://www.gulfhypoxia.net/

Question:Q

Did the DWH oil spill contribute to O22consumption in shelf waters of the northern

Gulf of Mexico in the summer of 2010?

The area of Gulf hypoxia was not significantly larger than the 5-yr average

S (H i Al T i lStorm events (Hurricane Alex, Tropical Depression Bonnie)

(2010 Gulf Hypoxia Press release, http://www.gulfhypoxia.net)

nGOM 20 50m shelf bottom waternGOM 20 50m shelf bottom water

200

250

200

250

200

250

200

250

200

250 nGOM 20-50m shelf bottom water

200

250

200

250 nGOM 20-50m shelf bottom waterol

kg-1

)

150

ol k

g-1)

150

ol k

g-1)

150

ol k

g-1)

150

ol k

g-1)

150

ol k

g-1)

150

ol k

g-1)

150

U (

mo

50

100June 2006

U (

mo

50

100June 2006Sept 2006U

(m

o

50

100June 2006Sept 2006U

(m

o

50

100June 2006Sept 2006U

(m

o

50

100June 2006Sept 2006U

(m

o

50

100June 2006Sept 2006U

(m

o

50

100June 2006Sept 2006

AO

0

50

AO

0

50

AO

0

50 May 2007

AO

0

50 May 2007Aug 2007A

O

0

50 May 2007Aug 2007Jul 2009

AO

0

50 May 2007Aug 2007Jul 2009Jul 2011

AO

0

50 May 2007Aug 2007Jul 2009Jul 2011

2000 2100 2200 2300-50

2000 2100 2200 2300-50

2000 2100 2200 2300-50

2000 2100 2200 2300-50

2000 2100 2200 2300-50

2000 2100 2200 2300-50

2000 2100 2200 2300-50

Jul 2010

DIC (mol/kg)DIC (mol/kg)DIC (mol/kg)DIC (mol/kg)DIC (mol/kg)DIC (mol/kg)DIC (mol/kg)

2006-2011 sampling stations (20-50 m)

nGOM 20 50m shelf bottom waternGOM 20 50m shelf bottom water

200

250 nGOM 20-50m shelf bottom waternGOM 20-50m shelf bottom waterol

kg-1

)

150oil leak effect

U (

mo

50

100June 2006Sept 2006

AO

0

50 May 2007Aug 2007Jul 2009Jul 2011

2000 2100 2200 2300-50

Jul 2010

DIC (mol/kg)

Bottom water in the hypoxic zone comes from lateral movement of offshore water

D i h d l f h i h i During the development of hypoxia, there is no exchange between the atmosphere and the bottom water (i e no overturning)the bottom water (i.e., no overturning)

Typical remineralization of marine-produced organic matter (with Redfield composition)

(CH O) (NH ) (H PO ) 138O 106CO 16HNO H PO4(CH2O)106(NH3)16(H3PO4)+138O2 106CO2 + 16HNO3 + H3PO4

O2 consumption : CO2 productionO2 consumption : CO2 production138 : 106

ratio = 1.3

Remineralization of alkane (CnH2n+2) and alkene(C H ) j f l(CnH2n) – major components of petroleumCnH2n+2+(3n+1)/2O2 nCO2 + (n+1)H2OCnH2n+3n/2O2 nCO2 + nH2On 2n / 2 2 2

O2 consumption : CO2 production(3n+1)/2 : n = 1.5~2 (alkane)3n/2 : n = 1.5 (alkene)

22.5

CO2 methane (CH4)

0.51

1.52

onsu

mpt

ion/

prod

uctio

n

alkene (CnH2n)

00 5 10 15

O2

c

n

hydrocarbonslope = 1 5 2 0With the same amount of

AO

U

slope = 1.5-2.0With the same amount of oxygen consumption, DIC production from remineralization of h d b ll algal material

slope = 1.3hydrocarbon is smaller!

DIC

200

250GOMECC

200

250GOMECC

200

250GOMECCJul 2011200

250GOMECCJul 2011Jul 2010200

250GOMECCJul 2011Jul 2010

ol k

g-1)

150

ol k

g-1)

150slope = 1 26ol

kg-1

)

150

ol k

g-1)

150

Jul 2010

ol k

g-1)

150

Jul 2010

2.01.5

U (

mo

50

100

U (

mo

50

100slope = 1.26

U (

mo

50

100

U (

mo

50

100

U (

mo

50

100

AO

0

50

AO

0

50

AO

0

50

AO

0

50

AO

0

50

2000 2100 2200 2300-50

2000 2100 2200 2300-50

2000 2050 2100 2150 2200 2250 2300 2350-50

2000 2050 2100 2150 2200 2250 2300 2350-50

2000 2050 2100 2150 2200 2250 2300 2350-50

DIC (mol/kg)DIC (mol/kg)DIC (mol/kg)DIC (mol/kg)DIC (mol kg-1)

All bottom waters at d h h 20

0.5

deeper than the 20 m isobath (Sal:34.4-36.3)

(‰)

-0.5

0.0 13CDIC = 13COM+a/DICRemineralizing OM is likely marine origin( i ll 22 0‰)

13C

DIC

-1 5

-1.0

13COM = -(22.1±0.5)‰

(typically ~-22.0‰)

-28~-30‰ (terrestrial OC)

1/DIC0.42 0.43 0.44 0.45 0.46

-2.0

1.5 OM ( )r2 = 0.99

-28~-30‰ (terrestrial OC)-40~-60‰ (petroleum OC)

1/DIC

Hydrocarbon remineralization did occur in the nGOM shelf waters following the DWH eventg

Reaction stoichiometry is a useful tool to examine the effect of oil spill on the ocean waters, especially when multi-year data are compareddata are compared

Currently, there was no indication of petroleum hydrocarbon remineralization in the 20-50 m depth band in July 2011,

i d i i f f i iprimary driving force for oxygen consumption remains remineralization of algal material (δ13COM = -22‰)

Water column data do not necessarily reflect potential impact Water column data do not necessarily reflect potential impact of oil contamination/remineralization in coastal/shelf sediments, and shallower depth (<20 m).

1. High precision instruments in characterizing i i b (DIC lk li iseawater inorganic carbon system (DIC, alkalinity,

pH)

2. Underway pCO2 for survey of sea surface CO2partial pressure

3. Microelectrochemical sensors for sediment studies

Wei-Jen Huang, Yongchen Wang, GuirongHan, Baoshan Chen, Qian Li (UGA)

Mandy Joye (UGA) Steve Lohrenz, Kjell Gunderson, and Alan

Shiller (USM) Mike Murrell, John Lehrter, Jim Hagy (EPA

G lf E l Di i i )Gulf Ecology Division) Steve DiMarco (TAMU) Lora Pride and Windy Morrison (LUMCON) Chris Langdon (RSMAS) Rik Wanninkhof, Tsung-Hung Peng

(AOML/NOAA) Jay Brandes (SkIO) OSV Bold (EPA), R/V Cape Hatteras, R/V

P li d R/V R BPelican, and R/V Ron Brown Gulf of Mexico and US East Coast Carbon

(GOMECC) Project

3500) 3000

3500(

mol

kg-1

2500

DIC

(

2000

Time4/1/10 8/1/10 12/1/10 4/1/11 8/1/11

1500

Timehttp://nwis.waterdata.usgs.gov/usa/nwis/qwdata