Evidence for active microbial nitrogen transformations in sea ice (Gulf of Bothnia, Baltic Sea) in midwinter
Evidence for active microbial nitrogen transformations in sea ice (Gulf of Bothnia, Baltic Sea) in midwinter
复制标题
仲冬海冰（波的尼亚湾、波罗的海）微生物氮转化活跃的证据
作者：
H. Kaartokallio
摘要1998年2月，对波罗的海波的尼亚湾冰芯、盐水和下垫水样品中的营养盐浓度、叶绿素a、细菌生物量和浮游生物的相对活性进行了研究。检查海冰是典型的波罗的海;冰散装盐度从0.1到1.6 psu不等，并在底层水盐度为4.2至4.7 psu。在2- 3个月大的海冰（厚度0.4-0.6 m）中，海冰群落处于冬季阶段，叶绿素a浓度一般低于1 mg m−3，异养生物占生物组合的7-20%。在一个月大的冰层（厚度0.2-0.25米）中，冰泉已经开始出现水华，叶绿素a浓度高达5.6 mg m−3。相对于低盐度，在冰柱中发现了高浓度的NH+4、NO−2、PO 3 +4和SiOH 4。结果表明，冰季期间，冰上部积累了大气营养盐负荷，冰上部10-20 cm的营养盐主要来源于大气。控制海冰营养状态的最重要的生物过程是营养再生、营养吸收和氮转化。营养物质的再生是特别活跃的中间部分的50至60厘米厚的冰和随后的营养物质的积累可能会增强冰泉水华。亚硝酸盐积累和反硝化活性位于与营养物再生相同的冰层中，这与观察到的含氮营养物浓度之间的显着相关性一起表明波罗的海海冰内层发生了活跃的氮转化。
Abstract Nutrient concentrations, chlorophyll-a, bacterial biomass and relative activity of denitrifying organisms were investigated from ice-core, brine and underlying water samples in February 1998 in the Gulf of Bothnia, Baltic Sea. Examined sea ice was typical for the Baltic Sea; ice bulk salinity varied from 0.1 to 1.6 psu, and in underlying water salinity was from 4.2 to 4.7 psu. In 2- to 3-months-old sea ice (thickness 0.4–0.6 m), sea-ice communities were at the winter stage; chl-a concentrations were generally below 1 mg m−3 and heterotrophic organisms composed 7–20% of organism assemblage. In 1-month-old ice (thickness 0.2–0.25 m), an ice spring bloom was already developing and chl-a concentrations were up to 5.6 mg m−3. In relation to low salinity, high concentrations of NH+4, NO−2, PO3+4 and SiOH4 were found in the ice column. The results suggest that the upper part of ice accumulates atmospheric nutrient load during the ice season, and nutrients in the upper 10–20 cm of ice are mainly of atmospheric origin. The most important biological processes controlling the sea-ice nutrient status are nutrient regeneration, nutrient uptake and nitrogen transformations. Nutrient regeneration is specially active in the middle parts of the 50- to 60-cm-thick ice and subsequent accumulation of nutrients probably enhances the ice spring bloom. Nitrite accumulation and denitrifying activity were located in the same ice layers with nutrient regeneration, which together with the observed significant correlation between the concentrations of nitrogenous nutrients points to active nitrogen transformations occurring in the interior layers of sea ice in the Baltic Sea.