另一个二氧化碳问题——海水酸化正在威胁全球海洋,但对威胁进行量化困难 ...

另一个二氧化碳问题——海水酸化正在威胁全球海洋,但对威胁进行量化困难重重

2010-07-03 14:44:50 阅读13 评论0 字号:

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原文日期: 2010-07-02

2010年7月1日/奥勒松,斯匹茨卑尔根


IN THE waters of Kongsfjord, an inlet on the coast of Spitsbergen, sit nine contraptions that bring nothing to mind as much as monster condoms. Each is a transparent sheath of plastic 17-metres long, mostly underwater, held in place by a floating collar. The seawater sealed within them is being mixed with different levels of carbon dioxide to see what will happen to the ecology of the Arctic waters.

孔斯峡湾(Kongsfjord)是挪威海岸的一片小小水域入口,这里布置着9个怎么看都像是特大号避孕套的新奇玩意。每个都是17米长的塑胶套子,大部分淹没于水下,由一个浮动的环状装置固定住。这些套子内部被密封的海水中混入了不同浓度的二氧化碳,(人们希望)探究这样一种装置会对北冰洋的生态带来何种影响。



As carbon dioxide levels go up, pH levels come down. Acidity depends on the presence of hydrogen ions (the H in pH) and more hydrogen ions mean, counterintuitively, a lower pH. Expose the surface of the ocean to an atmosphere with ever more carbon dioxide, and the gas and waters will produce carbonic acid, lowering pH on a planetary scale. The declining pH does not actually make the waters acidic (they started off mildly alkaline). But it makes them more acidic, just as turning up the light makes a dark room brighter.

当二氧化碳浓度上升,PH值相应下降。酸度取决于氢离子浓度,浓度越高则PH值越低。海洋表面与二氧化碳浓度日益上升的大气接触,将会形成碳酸,从而在全球规模上降低PH值。这并不是说下降的PH值使海水变酸了(因为海水通常是略呈碱性的),而是说让海水“更酸”了,这就像在一个昏暗的屋子里打开灯使它更亮一些一样。


Ocean acidification has further chemical implications: more hydrogen ions mean more bicarbonate ions, and fewer carbonate ions. Carbonate is what corals, the shells of shellfish and the outer layers of many photosynthesising plankton and other microbes are made of. If the level of carbonate ions falls too low the shells can dissolve or might never be made at all. There is evidence that the amount of carbonate in the shells of foraminifera, micro-plankton that are crucial to ocean ecology, has recently dropped by as much as a third.

1-----海洋酸化在化学上还有更深的意义:越多的氢离子意味着越多的重碳酸根离子,以及(相应的)更少的碳酸根离子。而碳酸盐是珊瑚、贝类外壳和许多行光合作用的浮游生物和其他微生物外壳的组成物质。如果碳酸根离子浓度降低超过一定限度,那么贝壳将开始溶解,甚至根本据不会形成。已经有证据显示一类对于海洋生态极为重要的微生物——有孔虫外壳的碳酸盐含量最近已经下降了三分之一。


Since becoming a topic of widespread worry about five years ago, the changing pH of the oceans has been added to the litany of environmental woes. Richard Feely, a researcher at the Pacific Marine Environmental Laboratory in Seattle, provided a gift to headline writers when he dubbed acidification “global warming’s evil twin”. Nowadays Dr Feely prefers to call it “the other carbon-dioxide problem”.

自从约5年前成为广为传播的忧虑话题之一之后,环境问题的冗长清单上又多了一项海洋PH值的变化问题。来自西雅图太平洋海洋环境实验室(Pacific Marine Environmental Laboratory)的研究者理查德·菲利(Richard Feely)为媒体界提供了一个礼物,他将海洋酸化现象戏称为“全球变暖的罪恶孪生兄弟”。但现在他更愿意称之为“另一个二氧化碳问题”。


But for all this concern, how bad the change in pH will be for oceans is not yet clear. Indeed, such are the complexities of studying ocean life that the true risk may become apparent only in retrospect.

但尽管如此,关于到底PH值变化会对海洋有多大影响的问题依然尚未明晰。确实是这样,研究海洋生物的复杂困难就在于只有在你事后回过头去看的时候才能清晰看到真正的危险。


There is no doubt that a pH drop is under way. For example, as the atmospheric carbon-dioxide level in Hawaii goes up, the pH at a mid-ocean mooring about 450km to the north-west goes down (see chart). But the decline is a lot bumpier than the rise: the pH difference from one year to the next is frequently greater than the change in average pH levels over 20 years.

无容置疑,PH值的下降正在进行当中。举例而言,夏威夷附近大气的二氧化碳浓度不断上升,位于其西北大约450公里处的PH浮动装置测量数据出现下降。(见图表)但这种下降趋势相比上升具有很大的波动性——年际变化常常大于过去20年数据的PH平均值变化幅度。



This is because the atmosphere does not have an iron grip on the carbon-dioxide level in surface waters. Increased photosynthesis will use up carbon dioxide; increased respiration produces more of it. Water coming up from below will often have a lower pH than the surface water, because at depth there is no photosynthesis but plenty of respiration. In many places, natural variations in pH will be larger than long-term changes in its mean.

这是因为大气二氧化碳含量在近水面附近并非一成不变。增强的光合作用将减少二氧化碳浓度,而增强的呼吸作用则其相反作用。从深处上涌的海水常常具有较之表层海水更高的PH值,因为在海洋深处没有光合作用,只有呼吸作用。在很多地方,PH值的自然差异将大于长期的PH值变化趋势平均值。


This is not to say that such changes have no effect. If peak acidities rather than long-term averages are what matters most, natural variability could make things worse. But it does suggest that the effects will be far from uniform.

这并非是说这种变化没有影响。如果真正造成影响的是酸度的峰值有多高,而非长期的酸度平均值,那么自然的差异将可能使事情变得更糟。但这也确实告诉我们:(海洋酸化对于我们的)影响将不会是各地一样的。


So, too, does research on how organisms respond to lower pH. Iris Hendriks of the Mediterranean Institute for Advanced Studies recently analysed data from a wide sample of research into how individual organisms respond to increased carbon dioxide in their seawater. She found that the range of responses was wide, with some seeming to prefer the lowered pH. She also found that the effects to be expected in the 21st century were on average comparatively modest.

在这些困难也同样体现在对于有机体如何应对PH值降低的研究上。来自地中海高等研究所(Mediterranean Institute for Advanced Studies)的爱丽丝·亨德里克斯(Iris Hendriks)新近分析了大量有关生物个体如何应对水体中升高的二氧化碳含量的研究数据。她发现这种应对反应是多种多样的,甚至有部分生物似乎很喜欢降低后的PH值。她同时还发现21世纪我们将要面对的影响后果将不会非常严重。


Some researchers feel the way her study lumps things together plays down the more damaging effects. Even if that is so, there is a fair chance that the literature surveyed was biased the other way. Data showing a deleterious effect might well be more likely to be written up and published than data showing nothing much.

一些研究者认为她将各种事物堆砌在一起的研究方法会造成对更严重危害的低估。但即便这一说法成立,我们仍然可以说这些被调查的论文充满偏见。显示有害结果的数据较之显示无害结果的数据更可能引起重视并得到出版。


If some creatures can tolerate lower pHs and others cannot, you might expect things to average out: the tolerant and adaptable prosper, the more pernickety perish. For the “primary producers” in the ocean—the mostly single-celled creatures that photosynthesise—this will probably be the case. But changes in the relative prevalence of different photosynthesisers could still matter. The ecology of the oceans is all about who eats what, and small changes in the population of certain creatures near the bottom of the web could have large effects on larger ones that eat them. Some creatures may be double-whammied by having less of what they like to eat and by the pH itself, amplifying the disruption. And adaptation is not without costs: dealing with lower pH may divert a creature’s resources from other ends.

如果一部分生物能够容忍更低的PH值而另一部分不能,那么你可能会倾向得出某种均衡:那些能够适应的物种繁荣昌盛,那些不能适应的物种则随之灭绝。对于海洋中的“初级生产者”——大部分进行光合作用的单细胞生物而言,这也许就是即将发生的事。但不同光合作用生物之间的比例仍然将构成问题。海洋生态系统其实就是谁吃谁的问题。食物网底端的微小变化可能将对吃它们的较大生物构成影响。有些生物可能将面临祸不单行的境地——既要面对PH值下降本身的威胁,还要应付食物减少的问题,这让问题火上浇油。另外,适应并非是没有代价的:适应PH值降低可能意味着应付其他方面的改变。


This is where the condoms—or mesocosms, as their scientific caretakers would prefer it—come in. They are part of the European Project on Ocean Acidification (EPOCA), an initiative employing over 100 researchers, more than 30 currently in the Arctic. EPOCA is the most thorough investigation so far attempted of the effect of pH changes at the level of a whole ecology.

这就是那些避孕套——或者按照照看它们的科学家的话来说“中型实验生态系”(mesocosm)——的作用。这是欧洲海洋酸化研究项目(EPOCA)的一部分,这一计划雇佣了超过100名科研人员,其中超过30人目前正在北极地区。EPOCA是迄今最详尽的对于PH值变化对于整个生态系统影响进行的研究。


By looking at which creatures flourish in their mesocosms, Ulf Riebesell of the Leibniz Institute for Marine Studies in Kiel and his colleagues hope to see changes as they take place by keeping an eye on the water chemistry and nutrient levels. Dr Riebesell is particularly interested in the ecosystem role of pteropods, also called sea butterflies. These elegant micro-molluscs are a vital food for some fish. In the first year of their life, pink salmon eat more pteropods than anything else.

通过观察哪些生物会在“中型实验生态系”中繁荣昌盛,来自德国基尔莱布尼茨海洋研究所(Leibniz Institute for Marine Studies )的伍尔夫·里贝赛尔(Ulf Riebesell)和他的同事们将严密关注水体化学成分以及营养物质水平以期看到变化。里贝赛尔博士尤其感兴趣的是一类叫做“翼足类”,也叫“海蝴蝶”的生物在生态系统中的作用。这些优雅的微型软体动物是某些鱼类的重要食物。在孵化后的{dy}年内,粉色鲑鱼的主食就是这种翼足类动物。


If reshaping food webs marginalises the pteropods, the salmon will have to adapt or die. But though the mesocosms may shed light on the fate of the pteropods, the outlook for the salmon will remain conjectural. Though EPOCA is ambitious, and expensive, the mesocosms are too small to contain fish, and the experiments far too short to show what sort of adaptation might be possible over many years, and what its costs might be.

如果食物链的重塑造成翼足类的数量减少,那么鲑鱼将不得不适应,或者灭绝。但虽然“中型实验生态系”可以让我们看到翼足类的命运,但鲑鱼的命运仍然只是我们的猜测。尽管EPOCA是雄心勃勃而代价昂贵的,“中型实验生态系”仍然太小,根本无法容得下鱼类,而实验为期也太短,无法知晓多年后可能发生何种适应现象,以及这种适应的代价是什么。


This is one of the reasons why the fate of coral reefs may be more easily assessed than open-water ecosystems. The thing that provides structure in open-water ecosystems is the food-web, which is hard to observe and malleable. In reefs, the structure is big lumps of calcium carbonate on which things grow and around which they graze and hunt. Studies of Australia’s Great Barrier Reef show that levels of calcification are down, though it is not yet possible to say changes in chemistry are a reason for this. Current research comparing chemical data taken in the 1960s and 1970s with the situation today may clarify things.

这就是为什么珊瑚礁的命运较之开放水域生态系统的命运更加容易被人认识的原因之一。开放水域的结构体现在其食物链之中,然而食物链难以进行观察,且其本身是充满弹性的。对于珊瑚礁而言,结构就是大块的碳酸钙礁石,一切都发生在礁石之上或周围。对于澳洲大堡礁的研究发现钙化率在下降,尽管尚无证据显示这和水体化学成分变化有关。目前进行的研究和20世纪60到70年代采集的水体化学数据进行对比之后事情可能就会清楚了。


But singling out the role of acidification will be hard. Ocean ecosystems are beset by changes in nutrient levels due to run off near the coasts and by overfishing, which plays havoc with food webs nearly everywhere. And the effects of global warming need to be included, too. Surface waters are expected to form more stable layers as the oceans warm, which will affect the availability of nutrients and, it is increasingly feared, of oxygen. Some, including Dr Riebesell, suspect that these physical and chemical effects of warming may prove a greater driver of productivity change in the ocean than altered pH. Wherever you look, there is always another other problem.

但是单独分离出酸化的作用将是非常困难的。海洋生态系统遭受由于海岸带侵蚀造成的水体营养成分变化,还有过度捕捞,这在全球各地引发食物链的灾难性后果。全球变暖的影响也必须考虑在内。随着水温上升,海洋表层水体将变得更加稳定,这将阻碍营养物质的获取,并且更让人担忧的是,阻碍氧气的获取。一些人,包括里贝赛尔博士,认为这样的物理和化学后果对生产率造成的影响将超过PH值变化产生的影响。不管你考虑哪一方面,总有另一个问题存在。

 

2----古代海洋把不流动的CO2喷向天空

标题:
来源:
原文作者: Wendy Zukerman
原文日期: 2010-06-05

在上个冰期末,二氧化碳含量增长了近50%。但是这些二氧化碳从哪里来?这个长期的气候谜题仍未被解决。


Climate scientists have suspected - but never been able to prove - that the CO2 was the result of a huge belch of gas from the oceans. They predicted that the ice age had slowed ocean circulation, trapping CO2 deep within it, and that warmer temperatures reversed this process.

气候学家猜测——但仍未被证明——二氧化碳是来自海洋的大规模气体喷发的结果。他们预测兵器减慢了大洋环流,把二氧化碳留在其中,而高温反转了这个过程。


Signs of stagnant CO2-rich water have now been discovered 3700 metres beneath the Southern Ocean's seabed, between Antarctica and South Africa.

富含二氧化碳的不流动水迹象已经被发现,在南极洲和南非中间的南冰洋海床以下3700米。


Stewart Fallon of the Australian National University in Canberra and his colleagues collected samples from drill cores of the marine crust of tiny marine fossils called foraminifera. Different species of these lived at the surface and the bottom of the ocean. The chemical composition of their shells is dependent on the water they form in and how much CO2 it contains.

堪培拉澳大利亚国立大学的Stewart Fallon和他的同事收集海洋地壳中的名为有孔虫的海洋生物化石。这种生物的不同种类生活在海洋的表面或底部。它们贝壳的化学成分取决于它们吸收的水以及其中含多少二氧化碳。


The team found that species of foraminifera living on the sea floor around the time of the ice age contained more carbon than those that floated at the surface (). They also found this discrepancy disappeared around 19,000 years ago, which is also when the ice sheets began to melt.

这个团队发现冰期中生活在海底的有空虫种类所含二氧化碳比那些浮游在表面的种类多)。他们还发现这种差异消失在19,000年之前,同时也是冰原开始融化的时间。


The findings could help predict how ocean circulation will affect atmospheric CO2 levels in future, says Will Howard of the University of Tasmania, Australia.

澳大利亚塔斯马尼亚大学的Will Howard说这个发现在将来可以帮助预测大洋环流如何影响二氧化碳浓度。

3------标题:
来源:
原文作者: Steve Connor,
原文日期: 2010-05-20

作者:史蒂夫康纳,科学编辑

2010年5月20日


珊瑚礁对海水温度升高及由此导致的海水酸性增加很敏感

对过去20年来所采集到的海洋温度数据xxx的研究表明,世界海洋正在变暖,升温是实实在在的而且幅度还很大。

测量海洋的温度并非易事,但做这项{zx1}研究的科学家们认为,现在有无可辩驳的证据表明,海洋几百米的上层正在变暖,温度的上升与人为的气候变化是一致的。

研究结果很重要,因为与有较大变化倾向的陆地温度测量相比,海水温度被认为是全球变暖更加可靠和令人信服的信号。这是由于天气的波动性影响和城市的蔓延,都市的“热岛”效应可以人为地增加当地地表温度。

参与这项研究的科学家们研究了浮选设备测量采集的海洋上层700米的温度记录。他们得出的结论是,海洋上层在所研究的1993年到2008年这段时期显著变暖,而且比政府间气候变化委员会(IPCC)前一个报告中所用的升温估计速度还略快。

由西雅图美国国家海洋大气管理局约翰莱曼领导的研究小组,发现尽管某些数据有不确定性,研究期间收集到的温度数据表明海洋上层“平稳变暖”。

海洋温升是件大事,因为海洋是巨大的“全球热量储存和碳汇”- 储存热量的能力约为大气的1000倍。水越热吸收燃烧化石燃料产生所排到大气中的多余二氧化碳能力就越弱,随着海水变暖,海洋也不断扩张,导致海平面上升。温度测量采集所使用的设备原是由军方开发来估算水下声纳信号速度的。

这些投弃式深温计(XBTs)最近被更先进的雅高(Argos)仪器所替代,随着其自动下沉与上浮采集海洋不同深度的温度。


使用两种不同类型的仪器来测量同一物理现象,及对早期XBT设备准确性的怀疑,使人们对海洋上层温度记录的可靠性质疑。这使得莱曼博士和他的研究组做了这次重新评估,研究结果发表在《自然》杂志上。

科罗拉多博尔德美国国家大气研究中心的凯文崔伯斯说:“尽管观测数据本身存在相当的不确定性,他们从得到的数据发现,全球海洋上层平稳变暖”。

自2003年以来温度上升出现了略微回落,科学家说他们无法解释海洋暖化明显变缓的现象,因为海平面不断上升,而有证据表明,这一定是由海洋热膨胀以及基于陆地的冰原和冰川融化两者引起的。

崔伯斯博士说:“加热并没有停止。并非温度已停止上升,只是上升的速度没有以前快。目前我们对此无法解释。可能是由于海洋温度数据存在潜在更深入的问题或是对数据的处理有问题”。

南安普敦国家海洋学中心的彼得查纳表示,总体情况是明确的- 海洋正在升温。他说:“我确信这一点。一切都与此结论相符。从统计数据看,升温幅度显著,而近几年的温度回落并不显著。这项研究xx了对详情喋喋不休的质疑。它表明气候变暖是真实的


 

 

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