DIC/

DOC

conc

entr

atio

n

[DOC]

[DIC]

Low baseflowDeep flow paths

Intermediate---- high baseflow

Storm flowShallow flow paths

DOC quantity and quality can be influenced by warming/salinity at baseflow.

Streamflow Based Conceptual Framework for Urban Carbon Transport

DOM lability

Dissolved Organic M

atter Quality

RecalcitrantLabile

Streamflow

Labile organic matter from sewage leaks and storm drains can contribute to DOM pool.

Leaf-free seasonPeak growing season: increased ET

Resp

iratio

n

Prim

ary

Prod

uctio

n

shaded headwatersnon-shaded river

-4

-2

0

2

1 10 100

NE

P g

C m

2 d

ay

Paint Branch

-4

-2

0

2

1 10 100

Discharge ft3s

1

NE

P g

C m

2 d

ay

Season

Spring

Summer

Fall

Winter

Sligo Creek

-4

-2

0

2

10 100 1000

NE

P g

C m

2 d

ay

Northeast Branch

Export and metabolism of carbon in urban watersheds: Climate implications Rose M. Smith1, Sujay S. Kaushal1

1University of Maryland College Park

Motivation Urbanization and climate change influence riverine carbon

fluxes to estuaries by altering the hydrologic regime, water

temperature, and anthropogenic sources of organic matter.

Carbon cycling has implications for freshwater food webs,

estuarine ecosystems, and greenhouse gas emissions,

however little is known about how land use and climatic

factors influence carbon processing and transport in rivers.

Objectives 1) Quantify rates of carbon transport and metabolism

in four urban watersheds which vary in catchment size

2) Develop a conceptual framework for understanding

shifts in carbon export, quality, and metabolism

across flow conditions in developed watersheds

Methods - Dissolved C Export: 3 years of biweekly sampling +

USGS LOADEST model

- Metabolism: Baysean Metabolic model (BaMM) used

to estimate GPP and ER based on diurnal DO and

temperature over 2 years

- Organic Matter Quality: Lability metrics quantified

based on spectrofluorometric excitation-emission

measurements.

- CO2 concentrations: Measured DIC and pH biweekly

and determined the proportion of dissolved CO2 using

CO2SYS model of the inorganic carbon system.

Acknowledgements:

National Science Foundation, Maryland Sea Grant Fellowship Program,

Maryland Water Resources Research Center, University of Maryland

Graduate Summer Research Fellowship; ESSIC/Geology Travel Grant

Conclusions - Annual DOC export from highly developed

streams was comparable to forested streams

in similar regions and DOM quality resembles

soil/leave despite reduced forest cover.

- Light availability may limit GPP more than

nutrients.

- CO2 concentrations are on par with DOC, and

streams were net sources of CO2 throughout

the year.

- Greenhouse gas implications of C and N

loading in urban areas warrant further study

DEPARTMENT OF GEOLOGY

1. Dissolved Carbon form and quality varies with flow : DOC was flushed and DIC was diluted with

increasing flow. Dissolved organic matter (DOM) character became less labile at high flows.

4. Net Ecosystem

Productivity across

flow conditions.

NEP (net ecosystem

productivity, GPP-ER)

was greatest at medium

flows for all sites.

Periods of positive NEP

were greater in the

open-channel site

compared to smaller

streams with seasonal

shading from riparian

trees.

-5.0

-2.5

0.0

2.5

Dec-2011 Apr-2012 Aug-2012 Dec-2012 Apr-2013 Aug-2013 Dec-2013 Apr-2014 Aug-2014

gC

m2 d

ay

GPP

ER

NEP

Stream Metabolism: Northeast Branch Anacostia

atmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentrationatmospheric concentration

1000

2000

3000

4000

5000

6000

NERP PBCP SLIGOStream

pC

O2

atm Site

NERP

PBCP

SLIGO

Carbon Dioxide

Sampling sites in the Anacostia Watershed

Results

2. Daily stream metabolism and seasonal variations: Streams

were generally heterotrophic (ER>GPP) with limited periods of net-

production (GPP>ER) during spring. Data shown from one site

(Northeast Branch).

3. Carbon Dioxide:

concentrations of CO2 was

super-saturated compared to

the atmosphere on all dates.

Paint Branch

Northeast

Branch

Northwest

Branch

Sligo Creek

Conceptual Framework

5. Conceptual Framework highlighting the

influence of flow on carbon cycle parameters in

urban streams. As DOC fluxes increase, DOM

quality becomes less labile. Anthropogenic

influences such as warming, salinization, sewage,

and stormwater may influence DOC fluxes and

DOM quality. In-stream GPP and ER rates

peaked during moderate flow conditions and

reduced during low-flow due to seasonal shading

from riparian trees which coincides with high

evapotranspiration.

0

4

8

12

16

10 1000

DO

C m

g/L

Dissolved Organic Carbon

5

10

15

20

25

10 1000Discharge (cfs)

DIC

mg/

L

Dissolved Inorganic Carbon

0.6

0.7

0.8

10 1000

BIX

Site

NERP

NWHV

PBCP

SLIGO

BIX: Freshness Index

Shaded headwaters Non-shaded River