Controls on zooplankton methane production in the central Baltic Sea
Controls on zooplankton methane production in the central Baltic Sea
复制标题
DOI：
10.5194/bg-16-1-2019
复制
发表时间：
2018-08
期刊：
影响因子：
4.9
通讯作者：
Beate Stawiarski;S. Otto;V. Thiel;U. Gräwe;N. Loick‐Wilde;A. Wittenborn;S. Schloemer;Janine Wäge;G. Rehder;M. Labrenz;N. Wasmund;O. Schmale
中科院分区：
文献类型：
--
作者：
Beate Stawiarski;S. Otto;V. Thiel;U. Gräwe;N. Loick‐Wilde;A. Wittenborn;S. Schloemer;Janine Wäge;G. Rehder;M. Labrenz;N. Wasmund;O. Schmale
抽象的。最近在有毒的地表水中发现了几种产甲烷途径，但它们与自然环境的相关性仍不清楚。我们的研究考察了夏季期间在波罗的海中部反复出现在温跃层之下的独特的甲烷(CH4)浓缩。与该地区前人的研究一致，我们发现哥特兰盆地西部和东部甲烷分布的差异，表明后者在温跃层以下原位产生甲烷(浓度为14.1±6.1nM，δ13C CH4−62.9‰)。通过使用高分辨率的波罗的海水文模型，我们表明，温跃层以下的甲烷可以通过上升流事件向海面输送，从而有助于海-气界面的甲烷通量。为了量化与浮游动物相关的甲烷产生率，我们开发了一条海上甲烷溶出-氧化线，以测定摄食14C标记浮游植物的桡足类动物的甲烷释放率。结果表明：(1)甲烷产生量随桡足类数量的增加而增加；(2)与长角毛足虫孵化的甲烷产生率(12 5±4 9fmol甲烷桡足类−1 d−1)高于与Acartia spp.孵化的产甲烷速率。(84±19fmolCH4，−1d−1)是浮游动物群落的优势种，(3)甲烷只在红藻上产生。饮食，而不是蓝藻饮食。此外，桡足类特有的甲烷产生速率随着孵化时间的延长而增加。后者的发现表明，水生微生物的产甲烷底物是通过在取食、排便或从粪便颗粒扩散过程中的细胞破坏而释放的。在野外，特别高的甲烷浓度与显示高丰度的DMSP/DMSO的Dinophyceae的站点相吻合。从富含浮游植物和桡足类动物的样品中提取的脂类生物标志物表明，Dinophyceae是以长角毛虫为主的浮游动物群落的主要食物来源，支持波罗的海中部桡足类动物放牧、DMSP/DMSO释放和次温跃层甲烷积累之间的联系。
Abstract. Several methanogenic pathways in oxic surface waters were recently discovered, but their relevance in the natural environment is still unknown. Our study examines distinct methane (CH4) enrichments that repeatedly occur below the thermocline during the summer months in the central Baltic Sea. In agreement with previous studies in this region, we discovered differences in the methane distributions between the western and eastern Gotland Basin, pointing to in situ methane production below the thermocline in the latter (concentration of CH4 14.1±6.1 nM, δ13C CH4 −62.9 ‰). Through the use of a high-resolution hydrographic model of the Baltic Sea, we showed that methane below the thermocline can be transported by upwelling events towards the sea surface, thus contributing to the methane flux at the sea–air interface. To quantify zooplankton-associated methane production rates, we developed a sea-going methane stripping-oxidation line to determine methane release rates from copepods grazing on 14C-labelled phytoplankton. We found that (1) methane production increased with the number of copepods, (2) higher methane production rates were measured in incubations with Temora longicornis (125±49 fmol methane copepod−1 d−1) than in incubations with Acartia spp. (84±19 fmol CH4 copepod−1 d−1) dominated zooplankton communities, and (3) methane was only produced on a Rhodomonas sp. diet, and not on a cyanobacteria diet. Furthermore, copepod-specific methane production rates increased with incubation time. The latter finding suggests that methanogenic substrates for water-dwelling microbes are released by cell disruption during feeding, defecation, or diffusion from fecal pellets. In the field, particularly high methane concentrations coincided with stations showing a high abundance of DMSP/DMSO-rich Dinophyceae. Lipid biomarkers extracted from phytoplankton- and copepod-rich samples revealed that Dinophyceae are a major food source of the T. longicornis dominated zooplankton community, supporting the proposed link between copepod grazing, DMSP/DMSO release, and the build-up of subthermocline methane enrichments in the central Baltic Sea.