Influence of plankton metabolism and mixing depth on CO 2 dynamics in an Amazon floodplain lake.

Autor: Amaral JHF; Coordenação de Dinâmica Ambiental, Laboratório de Ecossistemas Aquáticos, Instituto Nacional de Pesquisas da Amazônia, Manaus, Amazonas, Brazil; Programa de Pós-graduação em Ecologia, Instituto Nacional de Pesquisas da Amazônia, Manaus, Amazonas, Brazil. Electronic address: jh.amaral@gmail.com., Borges AV; Chemical Oceanography Unit, University of Liège, Liège, Belgium. Electronic address: alberto.borges@ulg.ac.be., Melack JM; Bren School of Environmental Science and Management, University of California, Santa Barbara, CA, USA. Electronic address: john.melack@lifesci.ucsb.edu., Sarmento H; Universidade Federal de São Carlos, Departamento de Hidrobiologia, Laboratory of Microbial Processes and Biodiversity, São Carlos, São Paulo, Brazil., Barbosa PM; Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil., Kasper D; Coordenação de Dinâmica Ambiental, Laboratório de Ecossistemas Aquáticos, Instituto Nacional de Pesquisas da Amazônia, Manaus, Amazonas, Brazil; Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil., de Melo ML; Universidade Federal de São Carlos, Departamento de Hidrobiologia, Laboratory of Microbial Processes and Biodiversity, São Carlos, São Paulo, Brazil., De Fex-Wolf D; Coordenação de Dinâmica Ambiental, Laboratório de Ecossistemas Aquáticos, Instituto Nacional de Pesquisas da Amazônia, Manaus, Amazonas, Brazil., da Silva JS; Coordenação de Dinâmica Ambiental, Laboratório de Ecossistemas Aquáticos, Instituto Nacional de Pesquisas da Amazônia, Manaus, Amazonas, Brazil., Forsberg BR; Coordenação de Dinâmica Ambiental, Laboratório de Ecossistemas Aquáticos, Instituto Nacional de Pesquisas da Amazônia, Manaus, Amazonas, Brazil.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2018 Jul 15; Vol. 630, pp. 1381-1393. Date of Electronic Publication: 2018 Mar 07.
DOI: 10.1016/j.scitotenv.2018.02.331
Abstrakt: We investigated plankton metabolism and its influence on carbon dioxide (CO 2 ) dynamics in a central Amazon floodplain lake (Janauacá, 3°23' S, 60°18' W) from September 2015 to May 2016, including a period with exceptional drought. We made diel measurements of CO 2 emissions to the atmosphere with floating chambers and depth profiles of temperature and CO 2 partial pressure (pCO 2 ) at two sites with differing wind exposure and proximity to vegetated habitats. Dissolved oxygen (DO) concentrations were monitored continuously during day and night in clear and dark chambers with autonomous optical sensors to evaluate plankton metabolism. Overnight community respiration (CR), and gross primary production (GPP) rates were higher in clear chambers and positively correlated with chlorophyll-a (Chl-a). CO 2 air-water fluxes varied over 24-h periods with changes in thermal structure and metabolism. Most net daily CO 2 fluxes during low water and mid-rising water at the wind exposed site were into the lake as a result of high rates of photosynthesis. All other measurements indicated net daily release to the atmosphere. Average GPP rates (6.8gCm -2 d -1 ) were high compared with other studies in Amazon floodplain lakes. The growth of herbaceous plants on exposed sediment during an exceptional drought led to large carbon inputs when these areas were flooded, enhancing CR, pCO 2 , and CO 2 fluxes. During the period when the submerged herbaceous vegetation decayed phytoplankton abundance increased and photosynthetic uptake of CO 2 occurred. While planktonic metabolism was often autotrophic (GPP:CR>1), CO 2 out-gassing occurred during most periods investigated indicating other inputs of carbon such as sediments or soils and wetland plants.
(Copyright © 2018 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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