Copepod carcasses as microbial hot spots for pelagic denitrification
Copepod carcasses as microbial hot spots for pelagic denitrification
复制标题
DOI：
10.1002/lno.10149
复制
发表时间：
2015-11-01
影响因子：
4.5
通讯作者：
Gissel Nielsen, Torkel
中科院分区：
文献类型：
--
作者：
Glud, Ronnie N.;Grossart, Hans-Peter;Gissel Nielsen, Torkel
桡足类暴露于高非捕食性死亡率和他们的尸体分解作为微生物的微生物活动加强。因此，下沉的尸体可以代表缺氧微环境，在其他有氧水柱中维持厌氧微生物途径。使用非侵入性的O-2成像，我们的文件，尸体的哲水蚤finmarchicus缺氧内部，即使在完全空气饱和的环境O-2水平。缺氧的程度逐渐扩大，随着环境O-2水平的降低。同时进行的微生物采样显示，在所有调查的胴体样品中亚硝酸盐还原酶基因（nirS）的表达，从而记录了胴体中微生物脱氮的潜力。nirS基因偶尔在活桡足类中表达，但不像在尸体中那样一致。在（15）NO3-修正的海水中孵化下沉的尸体证明了反硝化作用，其中平均34%+/- 17%（n=28）是由硝化作用维持的。然而，活性是高度可变的，并强烈依赖于周围的O-2水平。尽管反硝化作用即使在空气饱和度（302 mol L-1）下也存在，但在环境温度为7 ℃、空气饱和度为20%（55 mol O-2 L-1）时，平均胴体比活度增加了几个数量级，接近1 nmol d（-1）。沉尸C.因此，finmarchicus代表热点的中上层反硝化作用，但数量的重要性，作为一个汇的生物可利用的氮是强烈依赖于周围的O-2水平。胴体相关的反硝化作用的重要性可能是非常显着的O-2耗尽的环境中，如氧气最低区（OMZ）。
Copepods are exposed to a high non-predatory mortality and their decomposing carcasses act as microniches with intensified microbial activity. Sinking carcasses could thereby represent anoxic microenvironment sustaining anaerobic microbial pathways in otherwise oxic water columns. Using non-invasive O-2 imaging, we document that carcasses of Calanus finmarchicus had an anoxic interior even at fully air-saturated ambient O-2 level. The extent of anoxia gradually expanded with decreasing ambient O-2 levels. Concurrent microbial sampling showed the expression of nitrite reductase genes (nirS) in all investigated carcass samples and thereby documented the potential for microbial denitrification in carcasses. The nirS gene was occasionally expressed in live copepods, but not as consistently as in carcasses. Incubations of sinking carcasses in (15)NO3-amended seawater demonstrated denitrification, of which on average 34%+/- 17% (n=28) was sustained by nitrification. However, the activity was highly variable and was strongly dependent on the ambient O-2 levels. While denitrification was present even at air-saturation (302 mol L-1), the average carcass specific activity increased several orders of magnitude to approximate to 1 nmol d(-1) at 20% air-saturation (55 mol O-2 L-1) at an ambient temperature of 7 degrees C. Sinking carcasses of C. finmarchicus therefore represent hotspots of pelagic denitrification, but the quantitative importance as a sink for bioavailable nitrogen is strongly dependent on the ambient O-2 level. The importance of carcass associated denitrification could be highly significant in O-2 depleted environments such as Oxygen Minimum Zones (OMZ).