Title: Enhanced Aquatic Respiration Associated With Mixing of Clearwater Tributary and Turbid Amazon River Waters

Abstract

When water bodies with unique biogeochemical constituents mix together there is potential for diverse responses by aquatic microbial communities and associated ecosystem functions. Here we evaluate bulk respiration rates under varying mixtures of turbid Amazon River water and two lowland tributaries—the Tapajós and Xingu rivers—based on O2 drawdown in dark rotating incubation chambers. Preliminary experiments containing 50% Tapajós River and 50% Amazon River water were performed during falling water. More detailed experiments containing 5%, 17%, 33%, and 50% tributary water were performed for both the Tapajós and Xingu rivers at 3 different rotation velocities (0, 0.22, and 0.66 m s-1) during the falling water period. Respiration rates were higher in the mixtures compared to both river endmembers in most experiments. For both the Xingu and Tapajós rivers a 17% mixture yielded maximal respiration rates that were 1.6 to 2.8 times faster than each tributary, respectively. The 50% mixtures, on the other hand, only yielded 1.4 to 1.9 times amplified respiration rates for the Tapajós and Xingu rivers, respectively, and in one case was respiration was 2.8 times lower in the 50% mixture compared to the tributary. We hypothesize that these enhanced respiration rates are driven, in part, by microbial primingmore » effects that have been previously identified on a molecular level for these rivers. The results of this study suggest that there may be a “sweet spot” for priming effects to occur in terms of the relative abundance of “priming” and “primed” substrates.« less

Authors:

Ward, Nicholas D. ^[1]; Sawakuchi, Henrique O. ^[2]; Richey, Jeffrey E. ^[3]; Keil, Richard G. ^[3]; Bianchi, Thomas S. ^[4]

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+ Show Author Affiliations

1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Univ. of Washington, Seattle, WA (United States); Univ. of Florida, Gainesville, FL (United States)
2. Univ. of Washington, Seattle, WA (United States); Univ. de São Paulo, Piracicaba (Brazil); Umeå Univ., Umeå (Sweden)
3. Univ. of Washington, Seattle, WA (United States)
4. Univ. of Florida, Gainesville, FL (United States)

Publication Date:

2019-05-08

Research Org.:

Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1530887

Alternate Identifier(s):

OSTI ID: 1530746

Report Number(s):

PNNL-SA-140620
Journal ID: ISSN 2296-6463

Grant/Contract Number:  

AC0576RL01830; AC05-76RL01830

Resource Type:

Accepted Manuscript

Journal Name:

Frontiers in Earth Science

Additional Journal Information:

Journal Volume: 7; Journal ID: ISSN 2296-6463

Publisher:

Frontiers Research Foundation

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; respiration; aquatic; priming; carbon; mixing; Amazon, aquatic, bacteria, biogeochemistry, carbon cycling, continuum, decomposition, ecosystem, ecotone, global change, gradients, interface, metabolism, microbes, microbial, organic matter, oxygen, priming, respiration, river, terrestial aquatic interface