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.
Chemical Oceanography Unit, University of Liège, Liège, Belgium.
Sci Total Environ. 2018 Jul 15;630:1381-1393. doi: 10.1016/j.scitotenv.2018.02.331. Epub 2018 Mar 7.
We investigated plankton metabolism and its influence on carbon dioxide (CO) 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 emissions to the atmosphere with floating chambers and depth profiles of temperature and CO partial pressure (pCO) 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 air-water fluxes varied over 24-h periods with changes in thermal structure and metabolism. Most net daily CO 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 (6.8gCmd) 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, and CO fluxes. During the period when the submerged herbaceous vegetation decayed phytoplankton abundance increased and photosynthetic uptake of CO occurred. While planktonic metabolism was often autotrophic (GPP:CR>1), CO out-gassing occurred during most periods investigated indicating other inputs of carbon such as sediments or soils and wetland plants.
我们调查了浮游生物代谢及其对二氧化碳（CO）动态的影响，研究地点位于亚马孙河中游泛滥平原湖泊（Janauacá，3°23'S，60°18'W），研究时间为 2015 年 9 月至 2016 年 5 月，其中包括一段异常干旱的时期。我们使用漂浮室进行了昼夜 CO 排放到大气中的测量，并在两个具有不同风暴露和靠近植被栖息地的地点进行了温度和 CO 分压（pCO）的深度剖面测量。在清澈和黑暗的室中，使用自主光学传感器连续监测溶解氧（DO）浓度，以评估浮游生物代谢。夜间群落呼吸（CR）和总初级生产力（GPP）速率在清澈的室中较高，并与叶绿素-a（Chl-a）呈正相关。CO 气-水通量随热结构和代谢的变化在 24 小时内变化。在风暴露的地点，在低水位和中水位上升期间，由于光合作用速率高，大部分净日 CO 通量都进入湖中。其他所有测量都表明，净日通量都释放到大气中。与亚马孙河泛滥平原湖泊的其他研究相比，平均 GPP 速率（6.8gCmd）较高。在异常干旱期间，暴露的沉积物上草本植物的生长导致这些地区被淹没时大量的碳输入，从而增强了 CR、pCO 和 CO 通量。在淹没的草本植物腐烂期间，浮游植物的丰度增加，发生了 CO 的光合作用吸收。虽然浮游生物代谢通常是自养的（GPP:CR>1），但在大多数研究期间都发生了 CO 排放，表明其他碳输入，如沉积物或土壤和湿地植物。
