The greenhouse gases methane (CH₄) and carbon dioxide (CO₂) are end products of microbial anaerobic degradation of organic matter (OM) in lake sediments. Although previous research has shown that phytoplankton lipid content influences sediment methanogenesis, current understanding on how OM quality affects methanogenesis is still limited. Such information is needed to more accurately assess how lake greenhouse gas emissions may change in response to anthropogenic activities. We cultured 11 phytoplankton species from five classes and studied how taxonomic identity, C : N ratio, lipid content, and fatty acid composition of phytoplankton biomass affects the CH₄ and net CO₂ production in anaerobic lake sediments with an incubation experiment that lasted > 100 d. The carbon-normalized potential CH₄ (0.09–0.23 μmol mg C⁻¹ d⁻¹) and net CO₂ (0.09–0.28 μmol mg C⁻¹ d⁻¹) production rates were not related to phytoplankton taxonomic affiliation (e.g., class, species), C : N ratio, or fatty acid composition of algal biomass. Methane or net CO₂ production potentials did not increase with higher lipid content (10–30%); however, total fatty acid content had a weak correlation with CH₄ production potential. In contrast to previous research, our results suggest that lipid content is of minor importance in determining methanogenesis rates from the biomass of multispecies phytoplankton communities settling on sediments. The decrease in CO₂ concentration and the correlation between stable carbon isotope signatures of CH₄ and molar ratio of CH₄ and CO₂ at the end of the experiment may indicate that importance of hydrogenotrophic methanogenesis, which uses CO₂ when other substrates become limiting, increased during the long incubation.

中文翻译：

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脂质含量和生物分类对湖泊沉积物中浮游植物生物量甲烷和二氧化碳产生的影响

温室气体甲烷（CH ₄）和二氧化碳（CO ₂）是湖泊沉积物中微生物厌氧降解有机物（OM）的最终产物。尽管先前的研究表明浮游植物的脂质含量会影响沉积物的甲烷生成，但目前对OM质量如何影响甲烷生成的理解仍然有限。需要这些信息来更准确地评估湖泊温室气体排放如何响应人为活动而改变。我们培养了五类11种浮游植物，研究了浮游生物生物量的生物分类同一性，C：N比，脂质含量和脂肪酸组成如何影响CH ₄和净CO _2。持续> 100 d的孵化实验生产厌氧湖沉积物。碳-归一化电势CH ₄（0.09-0.23  μ摩尔毫克Ç ^-1 d ^-1）和二氧化碳净₂（0.09-0.28  μ摩尔毫克Ç ^-1 d ^-1）的生产速率是不相关的浮游植物分类从属关系（例如，类别，种类），C：N比或藻类生物质的脂肪酸组成。较高的脂质含量（10％至30％）不会产生甲烷或净CO _2的生产潜力。但是，总脂肪酸含量与CH _4的相关性较弱生产潜力。与以前的研究相比，我们的研究结果表明，脂质含量在决定沉积物上的多种浮游植物群落生物量的产甲烷率中的重要性不大。实验结束时，CO ₂浓度的降低以及CH _4的稳定碳同位素特征与CH ₄和CO _2的摩尔比之间的相关性可能表明氢营养甲烷化的重要性，当其他底物变得有限时，会利用CO ₂，在长时间的孵化中增加。