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Kevin&D.&Kroeger1,&Neil&Ganju1,&John&W.&Pohlman1,&Serena& Moseman<Val>erra2,&Jianwu&Tang3,&Christopher&Weidman4,& Adrian&Green1,&Sandra&Baldwin1,&T.W.&Brooks1,&Michael& Casso1&

1USGS,&Woods&Hole&Coastal&&&Marine&Science&Ctr,&MA,&USA& 2University&of&Rhode&Island,&Kingston,&RI,&USA& 3The&Ecosystems&Center,&Woods&Hole,&MA,&USA& 4Waquoit&Bay&Na>onal&Estuarine&Research&Reserve,&

Falmouth,&MA,&USA&&

Blue&Carbon&in&Coastal&Wetlands:&Considera>on&of& Lateral&and&Ver>cal&Carbon&and&Greenhouse&Gas& Fluxes&

In&>dal&wetland&carbon&and&GHG&budgets&we&also&need&to& consider&the&lateral&fluxes:&C&fluxes&may&be&large…&

Modified&from&Cai&2011&

(E) (F) (G) (H) (A) (B) (C) (D)

Maria%Tzortziou,%Patrick%J%Neale,%J%Patrick%Megonigal%%

Megonigal&&&Neubauer&

Net&ecosystem&C&balance&(NECB)&& &NECB&=&NEP&–&RCH4&–&FL.& &NEP:&net&ecosystem&produc>on,&closed&transparent&chamber& & &RCH4:&CH4&flux&measured&simultaneously&with&NEP;&FL:&net&lateral&flux&&

Photo&provided&by&Jim&Rassman& (WBNERR)& The&most&intensive&work&has& been&at&the&Sage&Lot&Pond& site.& & WBNERR&staff&installed&a& boardwalk,&bridges&and&other& infrastructure.& & The&site&is&their&Salt&Marsh& Observatory,&and&there&is& con>nuous&monitoring&of& many&parameters.& & Lateral&flux&measurements& are&made&at&the&mouth&of& this&creek.& Sage%Lot%Pond:%Lowest%N%site% Water&flux&(u&x&A),&m3/s:& <High<frequency& measurements&to&reduce&error& <Maximum&channel&coverage& <Consistent&procedure& & & Concentra>on&(c),&g/m3:& <Sufficient&ver>cal/lateral& sampling&& <Look&for&proxy&parameters& that&we&can&measure& con>nuously& & & & Total&flux&(u&x&A&x&c),&g/s& & Analytes:&CO2,&DIC,&DOC,&CH4,& POC,&N2O,&N,&P&

Conceptual&approach&to&lateral&flux&measurements&

R² = 0.92197

1.0 1.5 2.0 2.5 3.0 3.5 0.1 0.2 0.3 0.4 0.5

DOC (ppm) FDOM (Voltage)

April& June& July& P&<&0.05&

• FDOM&and&DOC&have&strong&

posi>ve&correla>on&

• FDOM/DOC&vary&seasonally&

Is&FDOM&a&good&proxy&for&DOC?&

0& 0.1& 0.2& 0.3& 0.4& 0.5& 14.8 15 15.2 15.4 15.6 15.8 16 18th 16:51:01 19th 16:51:01 20th 16:51:01 21st 17:25:01 22nd 17:25:01 23rd 17:25:01

Date and Time Pressure%(psia)%%

July%

FDOM%(Voltage)%

Pressure& FDOM& Salinity&

0
 5
 10
 15
 20
 25
 30
 35
 40
 26
 27
 28
 29
 30
 Methane
(ppm)
 Salinity
 Salinity
 Methane
 7.3
 7.4
 7.5
 7.6
 7.7
 7.8
 7.9
 8
 8.1
 0
 200
 400
 600
 800
 1000
 1200
 1400
 1600
 1800
 12:00
 14:24
 16:48
 19:12
 21:36
 0:00
 2:24
 pH
 Carbon
dioxide
(ppm)
 Carbon
dioxide
 pH


April&9,&2012—Full&>dal&cycle&with&gas&measurements&

Flood& Ebb&

0
 200
 400
 600
 800
 1000
 1200
 1400
 1600
 1800
 CO2
(ppm)
 0
 200
 400
 600
 800
 1000
 1200
 1400
 1600
 1800
 7.3
 7.4
 7.5
 7.6
 7.7
 7.8
 7.9
 8
 8.1
 Carbon
dioxide
(ppm)
 pH
 0
 200
 400
 600
 800
 1000
 1200
 CDOM
(counts)
 0
 5
 10
 15
 20
 25
 30
 35
 40
 0
 200
 400
 600
 800
 1000
 1200
 1400
 1600
 1800
 Methane
(ppm)
 CO2
(ppm)
 0
 5
 10
 15
 20
 25
 30
 35
 40
 26
 26.5
 27
 27.5
 28
 28.5
 29
 29.5
 Methane
(ppm)
 Salinity


Flood& Ebb&

Water&flux&(m3/s)& Methane&(nM)& Methane&flux&(µmol/s)&

0
 5
 10
 15
 20
 25
 30
 35
 40
 26
 27
 28
 29
 30
 Methane
(ppm)
 Salinity
 Salinity
 Methane
 7.3
 7.4
 7.5
 7.6
 7.7
 7.8
 7.9
 8
 8.1
 0
 200
 400
 600
 800
 1000
 1200
 1400
 1600
 1800
 12:00
 14:24
 16:48
 19:12
 21:36
 0:00
 2:24
 pH
 Carbon
dioxide
(ppm)
 Carbon
dioxide
 pH


Flood& Ebb&

Interpreta>ons&and&Comments&on& Methods&

• Measurements&and&understanding&of&lateral&fluxes&are&cri>cal&to&

calcula>ons&of&carbon&budgets,&and&to&interpreta>ons&of&C&sequestra>on& and&GHG&flux&rates.&

• Saline&wetland&porewater&may&be&the&major&source&for&CO2,&DIC&and&DOC,&

with&flux&rates&influenced&by&>dal&amplitude.&

• Reduced&salinity&(groundwater<influenced)&porewater&is&likely&the&major&

source&for&high&CH4&concentra>ons&at&low&>de.&&

• High&sensi>vity&of&flux&calcula>ons&to&small&differences&in&concentra>on&at&

>mes&of&major&water&flux&is&a&cri>cal&feature&and&limita>on:&Insufficient& frequency&of&measurements&or&insufficient&accuracy&could&contribute&to& the&lack&of&consensus&in&the&literature&about&the&role&of&coastal&wetlands& as&exporters&or&importers&of&carbon.&

• Con>nuous&data&appears&to&be&necessary,&given&the&high&degree&of&

variability&on&daily&>mescales&and&sensi>vity&of&calcula>ons&to&small& differences&in&concentra>on&between&flood&and&ebb&>de,&and&to&temporal& varia>ons&in&the&water&budget.&