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Blue&Carbon&in&Coastal&Wetlands:&Considera>on&of& Lateral&and&Ver>cal&Carbon&and&Greenhouse&Gas& Fluxes& Kevin&D.&Kroeger 1 ,&Neil&Ganju 1 ,&John&W.&Pohlman 1 ,&Serena& Moseman<Val>erra 2 ,&Jianwu&Tang 3 ,&Christopher&Weidman 4 ,& Adrian&Green 1 ,&Sandra&Baldwin 1 ,&T.W.&Brooks 1 ,&Michael& Casso 1& 1 USGS,&Woods&Hole&Coastal&&&Marine&Science&Ctr,&MA,&USA& 2 University&of&Rhode&Island,&Kingston,&RI,&USA& 3 The&Ecosystems&Center,&Woods&Hole,&MA,&USA& 4 Waquoit&Bay&Na>onal&Estuarine&Research&Reserve,& Falmouth,&MA,&USA& & In&>dal&wetland&carbon&and&GHG&budgets&we&also&need&to& consider&the&lateral&fluxes:&C&fluxes&may&be&large…& Modified&from&Cai&2011&

Maria%Tzortziou,%Patrick%J%Neale,%J%Patrick%Megonigal%% (A) (B) (C) (D) (E) (F) (G) (H) Net&ecosystem&C&balance&(NECB)&& &NECB&=&NEP&–&RCH 4 &–&FL.& &NEP:&net&ecosystem&produc>on,&closed&transparent&chamber& & &RCH 4 :&CH 4 &flux&measured&simultaneously&with&NEP;&FL:&net&lateral&flux&& Megonigal&&&Neubauer&

Sage%Lot%Pond:%Lowest%N%site% 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.& Photo&provided&by&Jim&Rassman& (WBNERR)& Conceptual&approach&to&lateral&flux&measurements& Water&flux&(u&x&A),&m 3 /s:& <High<frequency& measurements&to&reduce&error& <Maximum&channel&coverage& <Consistent&procedure& & & Concentra>on&(c),&g/m 3:& <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:&CO 2 ,&DIC,&DOC,&CH 4 ,& POC,&N 2 O,&N,&P&

Is&FDOM&a&good&proxy&for&DOC?& 3.5 • FDOM&and&DOC&have&strong& posi>ve&correla>on& 3.0 • FDOM/DOC&vary&seasonally& DOC (ppm) 2.5 2.0 R ² = 0.92197 1.5 P&<&0.05& 1.0 0 0.1 0.2 0.3 0.4 0.5 FDOM (Voltage) June& April& July&

July% 0.5& 16 15.8 0.4& Pressure%(psia)%% FDOM%(Voltage)% 15.6 0.3& 15.4 0.2& 15.2 0.1& 15 14.8 0& 18th 19th 20th 21st 22nd 23rd 16:51:01 16:51:01 16:51:01 17:25:01 17:25:01 17:25:01 Date and Time Pressure& FDOM& Salinity& April&9,&2012—Full&>dal&cycle&with&gas&measurements& 40
 30
 Salinity
 Methane
 35
 30
 29
 Methane
(ppm)
 25
 Salinity
 20
 28
 15
 10
 27
 5
 0
 26
 1800
 8.1
 Carbon
dioxide
 1600
 8
 pH
 1400
 Carbon
dioxide
(ppm)
 7.9
 1200
 7.8
 1000
 pH
 7.7
 800
 7.6
 600
 7.5
 400
 7.4
 200
 0
 7.3
 12:00
 14:24
 16:48
 19:12
 21:36
 0:00
 2:24
 Flood& Ebb&

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


Water&flux&(m 3 /s)& Methane&(nM)& Methane&flux&(µmol/s)& Flood& Ebb& 40
 30
 Salinity
 Methane
 35
 30
 29
 Methane
(ppm)
 25
 Salinity
 20
 28
 15
 10
 27
 5
 0
 26
 1800
 8.1
 Carbon
dioxide
 1600
 8
 pH
 1400
 Carbon
dioxide
(ppm)
 7.9
 1200
 7.8
 1000
 pH
 7.7
 800
 7.6
 600
 7.5
 400
 7.4
 200
 0
 7.3
 12:00
 14:24
 16:48
 19:12
 21:36
 0:00
 2:24
 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&CO 2 ,&DIC&and&DOC,& with&flux&rates&influenced&by&>dal&amplitude.& • Reduced&salinity&(groundwater<influenced)&porewater&is&likely&the&major& source&for&high&CH 4 &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.&