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Title: Regional Groundwater and Storms Are Hydrologic Controls on the Quality and Export of Dissolved Organic Matter in Two Tropical Rainforest Streams, Costa Rica

Abstract

A paired-watershed approach was used to compare the quality and fluxes of dissolved organic matter (DOM) during stormflow and baseflow in two lowland tropical rainforest streams located in northeastern Costa Rica. The Arboleda stream received regional groundwater (RGW) flow, whereas the Taconazo stream did not. DOM quality was assessed with absorbance and fluorescence and stable carbon isotope (δ 13C-DOC) values. RGW DOM lacked detectable fluorescence and had specific ultraviolet absorption (SUVA 254) and absorbance slope ratio (S R) values consistent with low aromaticity and low molecular weight material, respectively. We attributed these properties to microbial degradation and sorption of humic DOM to mineral surfaces during transport through bedrock. SUVA 254 values were lower and SR values were higher in the Arboleda stream during baseflow compared to the Taconazo stream, presumably due to dilution by RGW. However, no significant difference in SUVA 254 or SR occurred between the streams during stormflow. SUVA254 was negatively correlated to δ13C-DOC (r 2 = 0.61, P < 0.001), demonstrating a strong linkage between stream DOM characteristics and the relative amounts of RGW flow and local watershed runoff containing soil and throughfall C sources. Mean DOC export from the Taconazo stream during the study period wasmore » 2.62 ± 0.39 g C m -2 year -1-2 year -1, one of the highest exports reported and demonstrating a substantial impact of old RGW from outside the watershed boundary can have on surface water carbon cycling.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [1];  [3]; ORCiD logo [3];  [1]
  1. North Carolina State Univ., Raleigh, NC (United States)
  2. North Carolina State Univ., Raleigh, NC (United States); Stroud Water Research Center, Avondale, PA (United States)
  3. Florida Intl Univ., Miami, FL (United States)
Publication Date:
Research Org.:
North Carolina State Univ., Raleigh, NC (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1537329
Alternate Identifier(s):
OSTI ID: 1425504
Grant/Contract Number:  
SC0006703
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Biogeosciences
Additional Journal Information:
Journal Volume: 123; Journal Issue: 3; Journal ID: ISSN 2169-8953
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Environmental Sciences & Ecology; Geology

Citation Formats

Osburn, Christopher L., Oviedo-Vargas, Diana, Barnett, Emily, Dierick, Diego, Oberbauer, Steven F., and Genereux, David P. Regional Groundwater and Storms Are Hydrologic Controls on the Quality and Export of Dissolved Organic Matter in Two Tropical Rainforest Streams, Costa Rica. United States: N. p., 2018. Web. doi:10.1002/2017jg003960.
Osburn, Christopher L., Oviedo-Vargas, Diana, Barnett, Emily, Dierick, Diego, Oberbauer, Steven F., & Genereux, David P. Regional Groundwater and Storms Are Hydrologic Controls on the Quality and Export of Dissolved Organic Matter in Two Tropical Rainforest Streams, Costa Rica. United States. doi:10.1002/2017jg003960.
Osburn, Christopher L., Oviedo-Vargas, Diana, Barnett, Emily, Dierick, Diego, Oberbauer, Steven F., and Genereux, David P. Wed . "Regional Groundwater and Storms Are Hydrologic Controls on the Quality and Export of Dissolved Organic Matter in Two Tropical Rainforest Streams, Costa Rica". United States. doi:10.1002/2017jg003960. https://www.osti.gov/servlets/purl/1537329.
@article{osti_1537329,
title = {Regional Groundwater and Storms Are Hydrologic Controls on the Quality and Export of Dissolved Organic Matter in Two Tropical Rainforest Streams, Costa Rica},
author = {Osburn, Christopher L. and Oviedo-Vargas, Diana and Barnett, Emily and Dierick, Diego and Oberbauer, Steven F. and Genereux, David P.},
abstractNote = {A paired-watershed approach was used to compare the quality and fluxes of dissolved organic matter (DOM) during stormflow and baseflow in two lowland tropical rainforest streams located in northeastern Costa Rica. The Arboleda stream received regional groundwater (RGW) flow, whereas the Taconazo stream did not. DOM quality was assessed with absorbance and fluorescence and stable carbon isotope (δ13C-DOC) values. RGW DOM lacked detectable fluorescence and had specific ultraviolet absorption (SUVA254) and absorbance slope ratio (SR) values consistent with low aromaticity and low molecular weight material, respectively. We attributed these properties to microbial degradation and sorption of humic DOM to mineral surfaces during transport through bedrock. SUVA254 values were lower and SR values were higher in the Arboleda stream during baseflow compared to the Taconazo stream, presumably due to dilution by RGW. However, no significant difference in SUVA254 or SR occurred between the streams during stormflow. SUVA254 was negatively correlated to δ13C-DOC (r2 = 0.61, P < 0.001), demonstrating a strong linkage between stream DOM characteristics and the relative amounts of RGW flow and local watershed runoff containing soil and throughfall C sources. Mean DOC export from the Taconazo stream during the study period was 2.62 ± 0.39 g C m-2 year-1-2 year-1, one of the highest exports reported and demonstrating a substantial impact of old RGW from outside the watershed boundary can have on surface water carbon cycling.},
doi = {10.1002/2017jg003960},
journal = {Journal of Geophysical Research. Biogeosciences},
number = 3,
volume = 123,
place = {United States},
year = {2018},
month = {2}
}

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