Center for Ecological Research, Kyoto University, Otsu, Shiga, Japan.
School of Marine Resources and Environment, Tokyo University of Marine Science and Technology, Tokyo, Japan.
Geobiology. 2023 Sep;21(5):671-685. doi: 10.1111/gbi.12569. Epub 2023 Jul 11.
In freshwater systems, contributions of chemosynthetic products by sulfur-oxidizing bacteria in sediments as nutritional resources in benthic food webs remain unclear, even though chemosynthetic products might be an important nutritional resource for benthic food webs in deep-sea hydrothermal vents and shallow marine systems. To study geochemical aspects of this trophic pathway, we sampled sediment cores and benthic animals at two sites (90 and 50 m water depths) in the largest freshwater (mesotrophic) lake in Japan: Lake Biwa. Stable carbon, nitrogen, and sulfur isotopes of the sediments and animals were measured to elucidate the sulfur nutritional resources for the benthic food web precisely by calculating the contributions of the incorporation of sulfide-derived sulfur to the biomass and of the biogeochemical sulfur cycle supporting the sulfur nutritional resource. The recovered sediment cores showed increases in S-depleted sulfide at 5 cm sediment depth and showed low sulfide concentration with high δ S in deeper layers, suggesting an association of microbial activities with sulfate reduction and sulfide oxidation in the sediments. The sulfur-oxidizing bacteria may contribute to benthic animal biomass. Calculations based on the biomass, sulfur content, and contribution to sulfide-derived sulfur of each animal comprising the benthic food web revealed that 58%-67% of the total biomass sulfur in the benthic food web of Lake Biwa is occupied by sulfide-derived sulfur. Such a large contribution implies that the chemosynthetic products of sulfur-oxidizing bacteria are important nutritional resources supporting benthic food webs in the lake ecosystems, at least in terms of sulfur. The results present a new trophic pathway for sulfur that has been overlooked in lake ecosystems with low-sulfate concentrations.
在淡水系统中，沉积物中硫氧化细菌产生的化学生物产作为底栖食物网的营养资源的贡献仍不清楚，尽管化学生物产可能是深海热液喷口和浅海系统中底栖食物网的重要营养资源。为了研究这种营养途径的地球化学方面，我们在日本最大的淡水（中营养）湖中两个地点（90 和 50 米水深）采集了沉积物岩芯和底栖动物。测量沉积物和动物的稳定碳、氮和硫同位素，以通过计算生物量中硫化物衍生硫的掺入和支持硫营养资源的生物地球化学硫循环的贡献，精确阐明底栖食物网的硫营养资源的硫营养资源。回收的沉积物岩芯显示在 5 厘米沉积物深度处 S 耗尽的硫化物增加，并且在较深的层中显示出低硫化物浓度和高 δ S，表明微生物活动与硫酸盐还原和沉积物中的硫化物氧化有关。硫氧化细菌可能为底栖动物生物量做出贡献。基于组成底栖食物网的每个动物的生物量、硫含量和对硫化物衍生硫的贡献的计算表明，硫氧化细菌产生的化学生物产占比底栖食物网中总生物量硫的 58%-67%。如此大的贡献意味着硫氧化细菌的化学生物产是支持湖泊生态系统底栖食物网的重要营养资源，至少在硫方面是如此。这些结果提出了一个新的硫营养途径，该途径在硫酸盐浓度低的湖泊生态系统中被忽视了。
