俄罗斯勘察加半岛热泉的地球化学和微生物学

Geochemistry and Microbiology of Hot Springs in Kamchatka, Russia

勘察加半岛位于欧洲板块、北美板块和太平洋板块交汇的过渡带上,是世界火山活动最活跃的地区之一。其众多的热液系统不断的向地表释放地热气体和流体。以N2和CO2为主的地热气体也经常含有高浓度的H2,CH4和H2S。大气水和熔岩水构成了勘察加热泉水的主要源,水体温度从20℃到>90℃不等。水化学性质变化同样显著,pH范围从3.1到9.8。热泉水溶解盐以氯化钠为主,同时包括K+,H3BO3,H4SiO4,Ca2+和SO42-等其他多种溶解组分。此区域也有以直链烷烃为主的石油形成。从勘察加的热泉系统中已分离出至少24种嗜热微生物。尽管其中大多数是异养微生物,但根据其生存环境的特点,自养微生物在热泉系统中可能同样很多。这些微生物对碳、硫和铁在热液系统中的生物地球化学循环有着非常重要的作用。目前,非培养的方法和生物定量的手段已用来研究勘察加热泉中微生物生态及其所具有的生物地球化学功能。

Kamchatka is one of the most active regions of volcanism in the world because it is located in the transitional zone where the Eurasian plate, North American plate and Pacific plates meet. As a result, Kamchatka has numerous hydrothermal systems, which constantly release geothermal gases and fluids out to the earth surface. Geothermal gases such as N_2 and CO_2 may prevail in the outflows but H_2, CH_4 and H_2S occur frequently. Hot spring waters in Kamchatka may have multiple origins including meteoric and magmatic water. The temperature of these hot springs ranges from ~20 ℃ to greater than 90 ℃. Water chemistry also varies dramatically with pH ranging from 3.1 to 9.8. Hydrothermal fluids are sodium chloride water dominant and may contain various dissolved constituents including K +, H_3BO_3, H_4SiO_4, Ca 2+, and SO_4 2-. Volcanic ore-formation prevails in the high thermal activity regions in Kamchatka and precipitates may be dominated by silica crusts, sulfur and Hg-Sb-As-FeS deposits. Oils are also generated in the region and dominated by n-alkanes.More than 24 novel thermophilic microorganisms have been isolated from hot springs in Kamchatka. Most of these isolates are heterotrophs; however, autotrophs may be equally abundant depending on the spring conditions. Collectively, these organisms may play important roles in biogeochemical cycling of carbon, sulfur and iron in the hydrothermal system. Culture-independent approaches and quantitative methods are now employed to enhance our understanding of the ecology and biogeochemical functions of microorganisms in Kamchatka hot springs.