Methane production by microphytobenthos and its contribution to the benthic methane flux from the coastal zone of the Baltic Sea

微型底栖植物产生甲烷及其对波罗的海沿岸地区底栖甲烷通量的贡献

• 批准号: 498237456
• 负责人: Professor Dr. Ulf Karsten
• 金额: --
• 依托单位: Leibniz-Institut für Ostseeforschung Warnemünde (IOW)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/498237456?language=en
• 关键词: Methane; production; microphytobenthos; its; contribution

Increasing natural emissions of the greenhouse gas methane (CH4) substantially impact the Earth climate. In this context, near-shore waters play a key role because water column CH4 concentrations in these areas are much higher when compared with the open waters. However, little is known about CH4 emitters in shallow coastal zones or their contribution to the atmospheric CH4 flux. Moreover, a series of recent studies indicate that microbial CH4 production is not limited to strictly anoxic conditions and might be widespread in the oxic water column. This oxic CH4 production places the CH4 source close to the water surface, thereby intensifying fluxes to the atmosphere. Based on these recent investigations and a proposed linkage between primary production and CH4 formation, we hypothesize that microphytobenthos (MPB) communities, as major primary producer in many coastal systems, play a significant role in shallow-water CH4 dynamics. To explore MPB-associated CH4 production, we will investigate the potential of this CH4 source, by conducting incubation experiments and determining the rates of both primary production and CH4 production by abundant benthic diatom species. The use of a novel cavity ring-down spectroscopy-based semi-continuous method in closed incubation experiments will enable sensitive measurements of CH4 production in high temporal resolution over day/night cycles. The experiments will be undertaken under controlled temperature and light conditions and will use axenic/xenic clonal cultures of selected MPB diatoms to identify the main effectors and those species with the highest CH4 production rates. Experiments using 13C-labeled precursor substrates will be performed to identify and characterize MPB-associated CH4 production pathways. Previous studies of oxic CH4 production were mostly mechanistic laboratory studies that used culture samples; whether the measured CH4 production rates were representative of those in natural systems was not determined. To overcome these limitations in our study, the incubation experiments with clonal cultures will be accompanied by natural MPB communities sampled from the shallow waters at Askö island (Swedish Baltic Sea) and from the inner coastal waters of the Darss-Zingst Bodden Chain (German Baltic Sea), thus covering different sediment types, hydrodynamic conditions, and MPB communities. To align benthic CH4 fluxes from MPB communities with overall benthic and sea-to-air fluxes of CH4, we will determine CH4 fluxes between the sediment, water column, and atmosphere in both study areas.

温室气体甲烷（CH4）自然排放的增加对地球气候产生了重大影响。在这种情况下，近岸水域起着关键作用，因为这些地区的水柱CH4浓度比开阔水域高得多。然而，对于浅海带的CH4排放者及其对大气CH4通量的贡献知之甚少。此外，最近的一系列研究表明，微生物CH4的产生不仅限于严格的缺氧条件，而且可能广泛存在于含氧水柱中。这种氧化CH4的产生使CH4源靠近水面，从而加强了向大气的通量。基于这些最新的研究和初步提出的初级生产与CH4形成之间的联系，我们假设微底栖植物群落（MPB）作为许多沿海系统的主要初级生产者，在浅水CH4动态中起着重要作用。为了探索mpb相关的CH4产生，我们将通过进行孵育实验并确定丰富的底栖硅藻物种的初级生产和CH4生产速率，来研究这种CH4来源的潜力。在封闭孵育实验中使用一种新的基于腔衰荡光谱的半连续方法，将能够以高时间分辨率在昼夜周期中对CH4的产生进行敏感测量。实验将在受控的温度和光照条件下进行，并将使用选定的MPB硅藻的无菌/异种克隆培养来确定主要的效应物和那些具有最高CH4产率的物种。实验将使用13c标记的前体底物来鉴定和表征mpb相关的CH4生产途径。以前对氧化甲烷生成的研究大多是使用培养样品的机械实验室研究；测定的CH4产率是否代表自然系统的产率尚未确定。为了克服研究中的这些局限性，克隆培养的孵育实验将在Askö岛（瑞典波罗的海）浅水和Darss-Zingst博登链（德国波罗的海）内沿海水域取样的天然MPB群落中进行，从而涵盖不同的沉积物类型，水动力条件和MPB群落。为了将MPB群落的底栖生物CH4通量与总体底栖生物和海洋-空气CH4通量结合起来，我们将测定两个研究区沉积物、水柱和大气之间的CH4通量。