LBA-ECO CD06 Carbon Sources and Respiration Rates in Rivers in Amazonas and Acre: 2005-2006

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LBA-ECO CD-06 Carbon Cycling in Rivers in Amazonas and Acre, Brazil: 2005-2006
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Revision date: September 13, 2012

Summary:

This data set provides measured and calculated variables describing the carbon pools in river waters, CO2 respired from the water and total amount of CO2 evaded, dissolved oxygen isotopes (delta 18O-O2), and concentration of bacterial cells in river water.

Samples were collected from 10 white-water rivers, two clear-water streams (one each in Amazonas and Acre), and two black-water rivers in Amazonas from July to September 2005, which coincided with a severe drought in the western and southern regions of the Amazon Basin (Zeng et al. 2008). Eight of these sites were resampled during August through September 2006 of the following year (no drought).

There is one comma-delimited data file with this data set.

Figure 1. Map of study sites within the Amazon River Basin. Major tributaries are in grey. The circled sites are located in the state of Acre, whereas the others are in the state of Amazonas (Ellis et al., 2012).

Data Citation:

Cite this data set as follows:

Ellis, E.E, J.E. Richey, A.K. Aufdenkampe, A.V. Krusche, P.D. Quay, C. Salimon and H. Brandao da Cunha. 2012. LBA-ECO CD06 Carbon Sources and Respiration Rates in Rivers in Amazonas and Acre: 2005-2006. Data set. Available on-line [http://daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. http://dx.doi.org/10.3334/ORNLDAAC/1125

Implementation of the LBA Data and Publication Policy by Data Users:

The LBA Data and Publication Policy [http://daac.ornl.gov/LBA/lba_data_policy.html] is in effect for a period of five (5) years from the date of archiving and should be followed by data users who have obtained LBA data sets from the ORNL DAAC. Users who download LBA data in the five years after data have been archived must contact the investigators who collected the data, per provisions 6 and 7 in the Policy.

This data set was archived in September of 2012. Users who download the data between September 2012 and August 2017 must comply with the LBA Data and Publication Policy.

Data users should use the Investigator contact information in this document to communicate with the data provider. Alternatively, the LBA website [http://lba.inpa.gov.br/lba/] in Brazil will have current contact information.

Data users should use the Data Set Citation and other applicable references provided in this document to acknowledge use of the data.

1. Data Set Overview:

Project: LBA (Large-Scale Biosphere-Atmosphere Experiment in the Amazon)

Activity: LBA-ECO

LBA Science Component: Carbon Dynamics

Team ID: CD-06 (Richey / Victoria)

The investigators were Richey, Jeffrey E.; Victoria, Reynaldo Luiz; Souza, Reginaldo; Aalto, Rolf Erhart; Abdo, Mara Silvia Aguiar; Alin, Simone Rebecca; Aufdenkampe, Anthony K.; Ballester, Maria Victoria Ramos; Barbosa, Roosevelt Passos; Bernardes, Marcelo Correa; Bezerra de Barros Lima, Roberta ; Bolson, Marcos Alexandre; Bolson, Marcos Alexandre; Bonelle, Nilton; Brito, David Silva; Cabianchi, Giovana; Cogo, Michelle Cristine; da Silva, Luis Vilmar Souza; Dalmagro, Higo Jose; de Oliveira, Carolina Barisson Marques; Deus, Fabiano Alves de ; Devol, Allan H.; do Nascimento, Clive Reis; Ellis, Erin Elizabeth; Ferro, Jaderson Coradi; Filho, Walter Jorge do Nascimento; Frickmann, Fernando Cruz ; Gamero Guandique, Manuel Enrique; Gomes, Beatriz M.; Gomes, Viviane; Gouveia Neto, Sergio Candido; Hanada, Lais de Carvalho; Holtgrieve, Gordon William; Kelly Batalha Silva, Roberta ; Krusche, Alex ; Kurzatkowski, Dariusz ; Lacerda, Francisco A. Siebra; Leite, Nei Logsdon, Miles Grant; Macedo, Gelson de; Marcondes, Renata; Marilheuza, Campos Paro; McGeoch, Lauren; Melo, Emanuele Gurgel de Freitas; Mendes, Francisco de Assis; Moreira, Marcelo Zacharias; Munhoz, Kelli; Neu, Vania; Ometto, Jean Pierre; Pimentel, Tania Pena; Priante Filho, Nicolau Rabelo, Claudenir Silva; Rasera, Maria de Fatima Fernandes Lamy; Remington, Sonya Marie; Rodda, Sarah; Ruiz Mateus, Neuza Maria; Salimon, Cleber; Santiago, Alailson Venceslau; Santos, Arnoldo Marcilio dos; Silva, Cleoni Virginio da; Silva, Jonismar; Silva, Simao Correa da; Sousa, Eliete; Souzapetro, Petronio Lopes de; Toledo, Andre Marcondes Andrade; Tumang, Cristiane Azevedo; Umetsu, Cristiane Akemi Victoria, Daniel de Castro and Xavier, Farley de Oliveira. You may contact Ellis, Erin Elizabeth (ellise@u.washington.edu).

LBA Data Set Inventory ID: CD06_Carbon_respiration

2. Data Characteristics:

Data are presented in one ASCII comma separated file:

CD06_River_respiration_survey.csv

Column	Heading	Unit/format	Description
1	Site Name		Name of the river of stream sampled
2	Sampling Year	YYYY	Year in which samples were collected
3	Date	YYYYMMDD	Date on which samples were collected
4	Latitude	decimal degrees	Geographic coordinates for the sampling site reported in degrees latitude
5	Longitude	decimal degrees	Geographic coordinates for the sampling site reported in degrees longitude
6	Area_watershed	km2	Area of the watershed for the river sampled reported in square kilometers
7	Hydrograph_stage		Hydrograph stage indicating if the river level was falling, at a minimum, rising or at a maximum
8	Water_type		Water type: clear, black or white
9	Depth	m	Sampling depth reported in meters
10	DO	umol/L	Dissolved oxygen concentration reported in micromoles of oxygen per liter of water (umol/L)
11	pCO2	Pa	Partial pressure of CO2 gas in water reported in pascals
12	DIC	umol/L	Dissolved inorganic carbon concentration reported in micromoles of C per liter of water (umol/L)
13	delta_13C _DIC	per mil	delta 13C of the dissolved inorganic carbon component reported in per mil relative to the PDB standard
14	ph		ph of the river water
15	Temp	degrees C	Temperature of the river water at the time of sampling reported in degrees Celcius
16	Respiration	umol CO2/m2/s	Depth integrated respiration rate. Flux of CO2 reported in micromoles of CO2 per square meter per second (umol CO2/m2/s)
17	SE_Respiration	umol CO2/m2/s	Standard error of the calculated respiration flux (N=3) reported in micromoles of CO2 per square meter per second (umol CO2/m2/s)
18	Evasion_CO2	umol CO2/m2/s	Evasion flux of CO2 reported in micromoles of CO2 per square meter per second (umol CO2/m2/s)
19	SE_Evasion	umol CO2/m2/s	Standard error of the calculated evasion flux of CO2. Error was propagated using Monte Carlo boot strapping procedures. Reported in micromoles of CO2 per square meter per second (umol CO2/m2/s)
20	Resp/Evas	percent	Percent of CO2 evasion flux attributed to respiration calculated as respiration/ evasion *100. Reported in percent
21	SE_R/E	percent	Standard error of the calculated fraction of evasion represented by respiration
22	WC_Respir_Rate	umol O2/L/h	Water-column respiration rate reported in micromoles of oxygen per liter per hour (umol O2/L/h)
23	O2_Sat		The concentration of oxygen measured in the river water relative to the concentration that would be expected if the water-column was 100% saturated with oxygen at that temperature. Data are reported as proportions with values ranging from 0 to 1, to convert the value to percent multiply the current value by 100
24	delta_18O_DO	per mil	delta 18O of the dissolved oxygen in the river water reported in per mil relative to the SMOW (standard mean ocean water) standard
25	TSS	mg/L	Concentration of total (CSS + FSS) suspended sediment reported in milligrams per liter (mg/L)
26	CSS	mg/L	Concentration of coarse suspended sediment (63 micrograms) reported in milligrams per liter (mg/L)
27	FSS	mg/L	Concentration of fine suspended sediment (between 0.7 micrograms and 63 micrograms) reported in milligrams per liter (mg/L)
28	TOC	mg C/L	Concentration of total organic carbon reported in milligrams C per liter (mg C/L)
29	CPOC	mg C/L	Concentration of coarse particulate organic carbon reported in milligrams C per liter (mg C/L)
30	FPOC	mg CL	Concentration of fine particulate organic carbon reported in milligrams C per liter (mg C/L)
31	DOC	mg C/L	Concentration of dissolved organic carbon reported in milligrams C per liter (mg C/L)
32	DOC_high_MW	mg C/L	Concentration of high molecular weight dissolved organic carbon defined as greater than 100 kDa in size and reported in milligrams C per liter (mg C/L)
33	DOC_med_MW	mg C/L	Concentration of medium molecular weight dissolved organic carbon defined as less than 100 kDa but greater than 5 kDa in size and reported in milligrams C per liter (mg C/L)
34	DOC_low_MW	mg C/L	Concentration of low molecular weight dissolved organic carbon defined as less than 5 kDa in size and reported in milligrams per liter (mg/L)
35	C:N_CPOC	per mil	The atomic carbon to nitrogen ratio of the coarse particulate organic carbon reported in milliliters
36	C:N_FPOC	per mil	The atomic carbon to nitrogen ratio of the fine particulate organic carbon reported in milliliters
37	delta_13C_CPOC	per mil	delta 13C of the dissolved coarse particulate organic carbon component reported in per mil relative to the PDB standard.
38	delta_13C_FPOC	per mil	delta 13C of the dissolved fine particulate organic carbon component reported in per mil relative to the PDB standard
39	delta_13C_DOC	per mil	delta 13C of the dissolved organic carbon component reported in per mil relative to the PDB standard
40	delta_13C_CO2resp	per mil	delta 13C of the carbon dioxide resulting from respiration reported in per mil relative to the PDB standard
41	Conc_bacteria	cells/ml	Concentration of bacterial cells reported in number of cells per milliliter of water (cells/ml)

missing data are represented by -9999

Column

Heading

Unit/format

Description

Site Name

Name of the river of stream sampled

Sampling Year

YYYY

Year in which samples were collected

Date

YYYYMMDD

Date on which samples were collected

Latitude

decimal degrees

Geographic coordinates for the sampling site reported in degrees latitude

Longitude

decimal degrees

Geographic coordinates for the sampling site reported in degrees longitude

Area_watershed

km2

Area of the watershed for the river sampled reported in square kilometers

Hydrograph_stage

Hydrograph stage indicating if the river level was falling, at a minimum, rising or at a maximum

Water_type

Water type: clear, black or white

Depth

Sampling depth reported in meters

umol/L

Dissolved oxygen concentration reported in micromoles of oxygen per liter of water (umol/L)

pCO2

Partial pressure of CO2 gas in water reported in pascals

DIC

umol/L

Dissolved inorganic carbon concentration reported in micromoles of C per liter of water (umol/L)

delta_13C _DIC

per mil

delta 13C of the dissolved inorganic carbon component reported in per mil relative to the PDB standard

ph of the river water

Temp

degrees C

Temperature of the river water at the time of sampling reported in degrees Celcius

Respiration

umol CO2/m2/s

Depth integrated respiration rate. Flux of CO2 reported in micromoles of CO2 per square meter per second (umol CO2/m2/s)

SE_Respiration

umol CO2/m2/s

Standard error of the calculated respiration flux (N=3) reported in micromoles of CO2 per square meter per second (umol CO2/m2/s)

Evasion_CO2

umol CO2/m2/s

Evasion flux of CO2 reported in micromoles of CO2 per square meter per second (umol CO2/m2/s)

SE_Evasion

umol CO2/m2/s

Standard error of the calculated evasion flux of CO2. Error was propagated using Monte Carlo boot strapping procedures. Reported in micromoles of CO2 per square meter per second (umol CO2/m2/s)

Resp/Evas

percent

Percent of CO2 evasion flux attributed to respiration calculated as respiration/ evasion *100. Reported in percent

SE_R/E

percent

Standard error of the calculated fraction of evasion represented by respiration

WC_Respir_Rate

umol O2/L/h

Water-column respiration rate reported in micromoles of oxygen per liter per hour (umol O2/L/h)

O2_Sat

The concentration of oxygen measured in the river water relative to the concentration that would be expected if the water-column was 100% saturated with oxygen at that temperature. Data are reported as proportions with values ranging from 0 to 1, to convert the value to percent multiply the current value by 100

delta_18O_DO

per mil

delta 18O of the dissolved oxygen in the river water reported in per mil relative to the SMOW (standard mean ocean water) standard

TSS

mg/L

Concentration of total (CSS + FSS) suspended sediment reported in milligrams per liter (mg/L)

CSS

mg/L

Concentration of coarse suspended sediment (63 micrograms) reported in milligrams per liter (mg/L)

FSS

mg/L

Concentration of fine suspended sediment (between 0.7 micrograms and 63 micrograms) reported in milligrams per liter (mg/L)

TOC

mg C/L

Concentration of total organic carbon reported in milligrams C per liter (mg C/L)

CPOC

mg C/L

Concentration of coarse particulate organic carbon reported in milligrams C per liter (mg C/L)

FPOC

mg CL

Concentration of fine particulate organic carbon reported in milligrams C per liter (mg C/L)

DOC

mg C/L

Concentration of dissolved organic carbon reported in milligrams C per liter (mg C/L)

DOC_high_MW

mg C/L

Concentration of high molecular weight dissolved organic carbon defined as greater than 100 kDa in size and reported in milligrams C per liter (mg C/L)

DOC_med_MW

mg C/L

Concentration of medium molecular weight dissolved organic carbon defined as less than 100 kDa but greater than 5 kDa in size and reported in milligrams C per liter (mg C/L)

DOC_low_MW

mg C/L

Concentration of low molecular weight dissolved organic carbon defined as less than 5 kDa in size and reported in milligrams per liter (mg/L)

C:N_CPOC

per mil

The atomic carbon to nitrogen ratio of the coarse particulate organic carbon reported in milliliters

C:N_FPOC

per mil

The atomic carbon to nitrogen ratio of the fine particulate organic carbon reported in milliliters

delta_13C_CPOC

per mil

delta 13C of the dissolved coarse particulate organic carbon component reported in per mil relative to the PDB standard.

delta_13C_FPOC

per mil

delta 13C of the dissolved fine particulate organic carbon component reported in per mil relative to the PDB standard

delta_13C_DOC

per mil

delta 13C of the dissolved organic carbon component reported in per mil relative to the PDB standard

delta_13C_CO2resp

per mil

delta 13C of the carbon dioxide resulting from respiration reported in per mil relative to the PDB standard

Conc_bacteria

cells/ml

Concentration of bacterial cells reported in number of cells per milliliter of water (cells/ml)

missing data are represented by -9999

Example data records

Site Name,SamplingYear,Date,Latitude,Longitude,Area_watershed,Hydrograph_stage,Water_type,Depth,DO,
pCO2,DIC,delta_13C _DIC,ph,Temp,Respiration,SE_Respiration,Evasion_CO2, SE_Evasion,Resp/Evas,SE_R/E,
WC_Respir_Rate,DO_Sat,delta_18O_DO,TSS,CSS,FSS,TOC,CPOC,FPOC,DOC,DOC_high_MW,DOC_med_MW,
DOC_low_MW, C:N_CPOC,C:N_FPOC,delta_13C_CPOC,delta_13C_FPOC,delta_13C_DOC,delta_13C_CO2resp,Conc_bacteria

Campina,2006,20060817,-2.589,-60.033,10,falling,black,0.3,102.6,
1308,344.7,-26.6,4,25.1,-9999,-9999,-9999,-9999,-9999,-9999,
-9999,-9999,-9999,4,3.1,0.9,32.8,1.3,0.18,31.3,3.6,21.1,
6.6,29.6,23.6,-29,-29.2,-9999,-9999,-9999
Barro_Branco,2005,20050716,-2.93,-59.974,10,falling,clear,0.4,186.9,
970,327.4,-22.4,4.6,25.6,0.014,0.007,12.41,-9999,0.11,0.05,
0.13,0.76,25.7,0.5,0.5,-9999,3.4,0.17,0.08,3.2,-9999,-9999,
2.2,23.8,10.7,-29.9,-28.2,-9999,-9999,-9999
Barro_Branco,2006,20060829,-2.93,-59.974,10,falling,clear,0.4,196.1,
731,279.9,-24.3,4.7,25.8,-9999,-9999,-9999,-9999,-9999,-9999,
0.03,0.83,25.2,0.3,0.1,0.2,2.4,0.03,0.07,2.2,0.1,1.3,
0.9,23.5,16,-29.7,-27,-29.8,-9999,164355
...
Negro,2005,20050802,-3.062,-60.285,716770,falling,black,34,101.3,
659,208.5,-25.2,5.1,29.2,1,0.4,12.7,0.8,8,3,
0.11,0.55,27,0.4,0,0.4,9.6,0,0.56,9,2.9,3,
3.1,11.6,11.7,-31.5,-29.6,-9999,-9999,-9999
Negro,2006,20060811,-3.062,-60.285,716770,falling,black,34,93.7,
491,222.8,-25.6,4.8,29.1,0.8,0.4,4.3,0.5,20,10,
0.08,0.51,27.3,6.6,1.4,5.1,7.6,0.06,0.35,7.2,1.3,4.1,
1.9,18.9,11.1,-29.8,-28.9,-29.7,-30.1,2137375
...
Catuaba,2005,20050830,-10.073,-67.614,10,Low,clear,0.5,207.7,
201,121,-16.9,6.2,23.5,0,0.008,2.87,-9999,1,0,
0.17,0.88,24.7,4.2,0.2,4,2.1,0.01,0.5,1.6,0.8,0.2,
0.5,18,11.4,-30,-28.6,-9999,-9999,-9999
Catuaba,2006,20060925,-10.073,-67.614,10,Low,clear,0.5,217.9,
163,108.5,-20.2,5.1,24,-9999,-9999,-9999,-9999,-9999,-9999,
0.36,0.86,25.3,9.3,0.3,9,2.6,0.03,1.05,1.5,0.8,0,
0.7,20.7,9.9,-29.5,-29.1,-28.7,-28.3,2208262
Humaita,2005,20050826,-9.751,-67.672,10,Low,white,0.3,156.5,
281,104.9,-17.1,5.6,27.9,0.1,0.03,1.13,-9999,6,2,
0.76,0.62,27,4.6,0.6,4,4.2,0.05,0.48,3.7,1.1,-9999,
-9999,18.4,8.5,-29.7,-27.4,-9999,-9999,-9999

Site boundaries: (All latitude and longitude given in decimal degrees)

Site (Region)	Westernmost Longitude	Easternmost Longitude	Northernmost Latitude	Southernmost Latitude	Geodetic Datum
Amazon Basin (Amazon Basin)	-72.7	-58.746	-2.589	-10.073	World Geodetic System, 1984 (WGS-84)

Site (Region)

Westernmost Longitude

Easternmost Longitude

Northernmost Latitude

Southernmost Latitude

Geodetic Datum

Amazon Basin (Amazon Basin)

-72.7

-58.746

-2.589

-10.073

World Geodetic System, 1984 (WGS-84)

Time period

The data set covers the period 2005/07/16 - 2006/09/25
Temporal Resolution: Data were collected in two campaigns: one July through September 2005 and the second August through September 2006

Platform/Sensor/Parameters measured include:

FIELD INVESTIGATION / ANALYSIS / RESPIRATION
LABORATORY / MASS SPECTROMETER / CARBON
LABORATORY / MASS SPECTROMETER / NITROGEN
FIELD INVESTIGATION / ANALYSIS / CARBON DIOXIDE
LABORATORY / MASS SPECTROMETER / DISSOLVED SOLIDS
LABORATORY / MASS SPECTROMETER / ISOTOPES
FIELD INVESTIGATION / ANALYSIS / DISSOLVED GASES
LABORATORY / FLUORESCENCE MICROSCOPY / BIOMASS

3. Data Application and Derivation:

The purpose of this work was to understand the factors that control the range of water-column respiration rates observed in rivers and streams across the Amazon Basin. Accordingly, the investigators sampled rivers with a range of water chemistry types and respiration rates to determine how in situ concentrations of various parameters affected respiration rates. They then performed a series of statistical analyses, including partial correlation, step-wise backward multiple linear regression, and standard linear regression. To be considered a candidate for the multiple linear regression, input variables were excluded if they were highly correlated with each other (i.e. had a value of r that exceeded 0.7), or if there was more than one missing datum per variable.

Much of the details on the derivitization of the data is reported in the methods section below and users are encouraged to view Ellis et al., (2012), for full details. Many parameters were processed minimally post field collection.

4. Quality Assessment:

We list the precision below for the following variables analyzed in this study:

delta 13C: 0.3 per mil
pH: 0.1 pH unit.
DIC concentration: 1 percent of DIC value.
Respiration rate: 0.01 umol O2 L-1 hr-1
delta 18O of dissolved O2: 0.2 per mil

All measures of organic carbon concentration

(DOC, DOC > 100 kDa, DOC between 5-100
kDa, DOC < 5 kda) FPOC, CPOC)= 0.1 mg L-1

All measures of suspended sediment concentration

(TSS,FSS, CSS) = 0.1 mg L-1

Bacterial concentration:

x 10^6 cells mL-1

5. Data Acquisition Materials and Methods:

Study area:

Samples were collected during 2005 and 2006 in the Brazilian states of Acre and Amazonas, which are located in southwestern and central Amazonia. Locations were chosen to represent a range of water types and conditions found in these regions. Due to the predominance of white-water Rivers in both Amazonas and Acre and the logistical challenges of reaching a variety of river types in this large region, investigators sampled 10 white-water rivers of varying sizes. They also sampled two clear-water streams (one each in Amazonas and Acre), and two black-water rivers in Amazonas. Watershed areas ranged from less than 10 km2 to 2,910,510 km2, which were calculated as in Mayorga et al. (2005). Not all sites were in the same stage of the hydrograph at the time of sampling. All rivers in Acre were in the low water stage, whereas rivers draining Amazonas were in the falling-water stage. Investigators collected samples from 14 sites from July to September 2005, which coincided with a severe drought in the western and southern regions of the Amazon Basin (Zeng et al. 2008). Eight of these sites were resampled during August through September 2006 of the following year (no drought).

Sample collection:

Water samples were collected from the thalweg of rivers using a submersible pump placed at six-tenths of the total river depth.
Field probes (Thermo Orion 290 A+ pH meter, a Chek Mite CD-30 conductivity meter, and a 55 YSI dissolved oxygen probe) were immersed in a continuously overflowing graduated cylinder for ph, conductivity, and dissolved oxygen concentration determinations.
Samples from small streams were collected directly below the water surface to minimize disturbance.

Analysis methods:

PCO2 was analyzed via headspace equilibration following the methods of Cole et al. (1994) and modified as in Alin et al. (2010).
- PCO2 samples were either measured immediately using infra-red gas analysis via a Li-Cor LI-820 (Alin et al. 2010) or stored in glass bottles until analysis with a Shimadzu gas chromatograph (GC-17A equipped with flame ionization and electron capture detectors and a methanizer).

Bulk size fractions of coarse particulate organic carbon (CPOC [greater than 63 um], FPOC [0.7 to 63 um], and DOC [less than 0.7 um]) were filtered in the field, whereas size fractionation of DOC was processed in the laboratory.
Coarse suspended sediment (CSS) concentrations were measured by first passing a known volume of river water through a 63-um sieve, and then later drying and weighing the sieved material. CSS concentrations were multiplied by percent by weight C to determine CPOC concentrations.
The material collected from a plankton net was preserved with HgCl2 for later analyses of weight percentages (percent by weight) of C, N, and delta 13Cof CPOC.
Sieved river water was homogenized with a churn splitter (Wilde and Radtke 2003) and then filtered, providing the fine suspended sediment concentration (FSS) by mass difference (Aufdenkampe et al. 2001).
Sieved water was also passed through precombusted glass fiber filters (GF/F), which were then analyzed for d13C, percent by weight of C and N, and FPOC concentrations.
The filtrate of the GF/F filter (defined as DOC) was stored in precombusted glass vial and immediately preserved with HgCl2 pending no further analysis. Centrifuge ultrafiltration was used to size-fractionate DOC into the following categories:
- high molecular weight (HMW; greater than 100 kDa)
- medium molecular weight (MMW; between 5 and 100 kDa)
- low molecular weight (LMW; less than 5 kDa) DOC, using a method modified from Burdige and Gardner (1998).

Water was filtered through two GF/F filters in the field, placed on ice in the dark, transported back to the laboratory, and refrigerated until analyzed (within 48 h). Fifteen milliliters of sample were then centrifuged for 40 min.

Filtrate was analyzed according to the following:
- To calculate the percentage of DOC that was less than size X, we used the following equation (see Ellis et al., 2012).
  %DOC< x = DOC_FV_F/ DOC₁V₁ x 100
- To determine the concentration of DOC (less than 5 kDa or less than 100 kDa) the unfiltered DOC concentration was multiplied by the percentage of DOC in the given size category.
- The concentration of the size fractions of DOC was obtained by subtracting the appropriate value(s) from the original DOC concentration.
- DOC concentrations were measured after acidification and sparging with high-temperature combustion using a Shimadzu TOC500A carbon analyzer (2005 samples) and a Shimadzu TOC-V CPH carbon and nitrogen analyzer (2006 samples).
- Those samples with high DIC concentrations were acidified and sparged for an additional 20 min to ensure DIC removal.

Carbon isotopic analyses and C:N ratios

Stable isotopes (13:12C) of carbon were measured in both the inorganic and organic size fractions to aid in partitioning among end-member sources. Results are given in delta notation with units of per mil, and were normalized relative to Vienna Peedee Belemnite.

After drying coarse and fine materials in a 60 degree C oven, the samples were analyzed for delta 13C and C:N ratios using a Finnigan Delta Plus mass spectrometer coupled to a Fissions EA 1110 CHN analyzer with a precision of 0.3 per mil for the mass spectrometer.
For 2005 samples, the C:N ratio was obtained directly from a model 440 CHN analyzer made by Exeter Analytical.
The delta 13C of DOC was analyzed using an automated method in which DIC was sparged from the sample after adding phosphoric acid, followed by sodium persulfate oxidation of DOC to CO2. The CO2 gas was carried to an infra-red gas analyzer and then to a PDZ Europa-Hydra 20-20 isotope ratio mass spectrometer. Only the 2006 samples were analyzed.
DIC field collections and isotopic measurements (delta 13C of DIC) were conducted as in Quay et al. (1992), with a precision of 0.03 per mil for the 2006 samples. DIC concentrations were calculated from pH and PCO2 for the 2005 samples. We used temperature-dependent equilibrium constant values (K1, K2, and KH) as reported in Clark and Fritz (1997).
To estimate the delta 13C of phytoplankton, we used an isotopic fractionation factor of 12 to 17 per mil between the delta 13C of H2CO3 (calculated from the delta 13C of DIC [as in Mayorga 2004, using the equilibrium fractionation factors from Zhang et al., 1995]) and phytoplankton. This fractionation factor is derived from the relationship between H2CO3 and POM (predominantly phytoplankton) in the surface ocean (Goericke and Fry 1994).

Calculation of CO2 gas evasion flux

Most of the gas evasion rates were also published in Alin et al. (2010) and were determined using a floating chamber equipped with a fan. However, not all sites were analyzed by Alin et al. (2010). Thus, for these sites, the gas evasion flux (in µmol/(m2*s)) was determined by using the difference between the pCO2 measurements of the atmosphere and the water (as described in detail in Ellis et al. (2012)) using the following equation:

F= kCO2 * gamma* (PCO2_atm- PCO2_s)

where:

F is the outgassing flux of CO2 in (µmol m-2 s-1)
kCO2 is the temperature-dependent gas exchange coefficient for CO2 (m d-1)
gamma is CO2 solubility (µmolm-3*uPa-1;Weiss 1974)
PCO2_atm and PCO2_s are the partial pressures of CO2 in the atmosphere and solution, respectively.

kCO2 was determined as a function of wind speed (Alin et al. 2010). A value of k600, the gas transfer velocity for freshwater at 20°C, was selected for each wind speed based on the relationship between k600 and u10 values presented in Alin et al. (2010).

Monte Carlo error-propagation techniques were used to determine the error of our calculated gas evasion flux.

In situ respiration rates

Respiration rates were calculated at all sites by measuring the consumption of oxygen over a 24-h period.

Five initial and final replicate samples were incubated in 60-mL acid-washed Biological Oxygen Demand bottles in the dark in river water held at ambient temperatures.
Bottles were agitated twice daily by gently inverting them several times to reduce aggregate formation.
Oxygen concentrations were measured by Winkler Titrations (Wetzel and Likens 1991) using a Hach titrator. Dissolved oxygen consumption was determined as the rate of change between the initial and final replicates over the incubation period.

Calculation of the depth-integrated respiration rate

The depth-integrated respiration rate for a given site was calculated from the respiration rate (i.e. measurements of oxygen consumption (in umols L-1 h-1). This rate was converted to CO2 production by using a respiratory coefficient of 1. It was then multiplied by the depth of the river to yield a depth-integrated respiration rate in terms of umols CO2 m-2 s-1. The error was determined using Monte Carlo error propagation techniques.

Bacterial abundance measurements

Bacterial abundance measurements were made by epifluorescence microscopy using 4,6-diamidino-2-phenylindole(DAPI) optical filters in 2006.

Forty-milliliter samples were collected, preserved with formaldehyde to a final concentration of 2%, and analyzed within 2 to 4 months of collection.
A surfactant (0.5% solution of Triton X-100 in distilled water) was added drop-wise to particle-rich samples, which were then sonicated for 10 min.
Next, the sample solution was stained with Acridine Orange for 3 min.
Samples were then filtered using 0.22 µm black polycarbonate-membrane filters, and stained with DAPI for 10 min. Because these samples had high sediment concentrations, this dual-stain technique was necessary to illuminate the bacterial cells against the particle-rich background for counting purposes (Schmidt et al. 1998).
Between 250 mL and 5 mL of sample were used, such that 200 cells were counted in 20 fields.

Measurements of delta 18O-O2 and delta 18O-H2O

Stable isotopes of oxygen dissolved in water delta 18O-O2) were measured to assess the origin of O2 (Holtgrieve et al. 2010).

Samples were analyzed within 3 months using a Finnigan Delta XL continuous-flow mass spectrometer (Thermo Electron Corp).
Masses 32, 34, and 40 (16O : 16O, 18O : 16O, and 40Ar) were simultaneously measured (Barth et al., 2004; Holtgrieve et al., 2010).
Water isotopes (delta 18O-H2O), which came from a separate sample of river water, were analyzed on a Micromass Isoprime mass spectrometer.
Results are given relative to Standard Mean Ocean Water in delta notation with units of per mil.

6. Data Access:

This data is available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Data Archive Center:

Contact for Data Center Access Information:
E-mail: uso@daac.ornl.gov
Telephone: +1 (865) 241-3952

7. References:

Alin, S.R., M.F.F.L. Rasera, C.I. Salimon, J.E. Richey, G.W. Holtgrieve, A.V. Krusche and A. Snidvongs. 2010. Physical controls on carbon dioxide transfer velocity and flux in low-gradient river systems and implications for regional carbon budgets. J. Geophys. Res.-Biogeosci. 116: GO1009, doi:10.1029/2010JG001398

A.K., J.I. Hedges, J.E. Richey, A.V. Krusche and C.A. Llerena. 2001. Sorptive fractionation of dissolved organic nitrogen and amino acids onto fine sediments within the Amazon Basin. Limnol. Oceanogr. 46: 1921-1935, doi:10.4319/lo.2001.46.8.1921

Barth, J.A., C.A. Tait, and M. Bolshaw. 2004. Automated analyses of 18O/16O ratios in dissolved oxygen from 12-mL water samples. Limnol. Oceanogr.: Methods 2: 35-41, doi:10.4319/lom.2004.2.35

Burdige, D.J., and K.G. Gardner. 1998. Molecular weight distribution of dissolved organic carbon in marine sediment pore waters. Mar. Chem. 62: 45-64, doi:10.1016/S0304-4203(98)00035-8

Clark., and P. Fritz. 1997. Environmental isotopes in hydrogeology. Lewis.

Cole, J.J., N.F. Caraco, G.W. Kling, and T.K. Kratz. 1994. Carbon dioxide super saturation in the surface waters of lakes. Science 265: 1568-1570, doi:10.1126/science.265.5178.1568

Goericke, R., and B. Fry. 1994. Variations of marine plankton d13C with latitude, temperature, and dissolved CO2 in the world ocean. Glob. Biogeochem. Cycles 8: 85-90, doi:10.1029/93GB03272

Holtgrieve, G.W., D.E. Schindler, T.A. Branch and Z. Teresa Amar. 2010. Simultaneous quantification of aquatic ecosystem metabolism and re-aeration using a Bayesian statistical model of oxygen dynamics. Limnol. Oceanogr. 53:1047-1063, doi:10.4319/lo.2010.55.3.1047

Mayorga, E. 2004. Isotopic constraints on sources and cycling of riverine dissolved inorganic carbon in the Amazon Basin. Ph.D. thesis. Univ. of Washington

Mayorga, E., M.G. Logsdon, M.V. Ballester and J.E. Richey. 2005. Estimating cell-to-cell land surface drainage paths from digital channel networks, with an application to the Amazon basin. J. Hydrol. 315: 167-182, doi:10.1016/j.jhydrol.2005.03.023

Quay, P.D., D.O. Wilbur, J.E.Richey, J.I. Hedges, A.H. Devol and R. Victoria. 1992. Carbon cycling in the Amazon River: Implications from the 13C compositions of particles and solutes. Limnol.Oceanogr. 37: 857-871, doi:10.4319/lo.1992.37.4.0857

Schmidt, J.L., J.W. Deming, P.A. Jumars and R.G. Keil. 1998. Constancy of bacterial abundance in surficial marine sediments. Limnol. Oceanogr. 43: 976-982, doi:10.4319/lo.1998.43.5.0976

Sioli, H. 1984. The Amazon: Limnology and landscape ecology of a mighty tropical river and its basin. Kluwer Academic

Wetzel, R.G., AND G.E. Likens. 1991. Limnological analyses, 2nd ed. Springer-Verlag.

Wilde F.D. and D.B. Radtke. 2003. National field manual for the collection of water-quality data, U.S. Geological Survey.

Zeng, N., J.-H. Yoon, J.A. Marengo, A. Subramaniam, C.A. Nobre, A. Mariotti and J.D. Neelin. 2008. Causes and impacts of the 2005 Amazon drought. Environ. Res. Lett. 3:014002. doi:10.1088/1748-9326/3/1/014002

Zhang, J., P.D. Quay and D.O. Wilbur. 1995. Carbon isotope fractionation during gas-water exchange and dissolution of CO2. Geochim. Cosmochim. Acta 59: 107-114, doi:10.1016/0016-7037(95)91550-D

Related Publications

Ellis, E.E., J.E. Richey, A.K. Aufdenkampe, P.D. Quay, A.V. Krusche, C. Salimon, and H.B. da Cunha. 2012. Factors controlling aquatic respiration and its role in fueling CO2 gas evasion in rivers of the central and southwestern Amazon Basin. Limnol. Oceangr. 57(2), 2012, 527-540. doi: 10.4319/lo.2012.57.2.0527

Summary:

Data Citation:

Implementation of the LBA Data and Publication Policy by Data Users:

Table of Contents:

1. Data Set Overview:

2. Data Characteristics:

3. Data Application and Derivation:

4. Quality Assessment:

5. Data Acquisition Materials and Methods:

6. Data Access:

Data Archive Center:

7. References: