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本帖{zh1}由 lilywizardry 于 2010-7-6 19:22 编辑
Ocean acidification
海洋酸化
The other carbon-dioxide problem
Acidification threatens the world’s oceans, but quantifying the risks is hard
另一个二氧化碳难题
酸化问题正威胁全球海洋，但评估其危害却很困难
Jul 1st 2010 | NY ALESUND, SPITSBERGEN
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.
在位于斯匹次卑尔根岛（译注：是挪威的斯瓦尔巴群岛中{zd0}的一个岛）孔斯峡湾的水域中，立着九个让人一看见就会联想到巨型安全套的装置。每一个都是17米长的透明塑料套状物，大部分没在水下，由一个浮圈进行固定。用不同浓度的二氧化碳与密封在套状物中的海水进行反应，以期预测对北冰洋水域生态的影响。
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.
随着二氧化碳浓度的提高，PH值会下降。酸碱度由氢离子浓度（pH中的H）决定，其浓度越高，相反则PH值越低。要是海洋的表面与含更高二氧化碳的大气层接触，那么水和气会产生更多的碳酸，在全球范围内降低PH值。但PH值的降低并不会使海水真的变成酸性（海水原属弱碱性）。而会使其向酸性发展，就像在一间黑屋里慢慢扭开灯，会使房间逐渐变亮一样。
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.
海洋的酸化还有更深的化学含义：氢离子越多，重碳酸根离子就越多，碳酸根离子则越少。碳酸盐是珊瑚、贝类的壳和很多光合作用浮游生物以及其它微生物的外壳的组成成分。如果碳酸根离子浓度降得太低，这些外壳就会溶解或根本无法形成。有孔虫类是对海洋生态至关重要的微型浮游生物，有证据表明，其外壳中碳酸盐的含量近年来有降低，最多的达三分之一。
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”.
从大概5年前大家都开始谈论这个问题以来，海洋PH值的变化已被当做一系列环境灾难中新的一项。理查德?菲力是西雅图太平洋海洋环境实验室的研究员，当他把酸化问题称为“全球变暖的双胞胎恶魔”时，就给编写头版新闻的提供了一份大礼。现在菲力博士则更愿意称之为“另一个二氧化碳难题”。
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.
但其实是，我们还不清楚PH值的变化对海洋的危害究竟有多大。海洋生态的研究是如此复杂，也许其真正的危害只有在今后回顾时才能明了。
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.
毫无疑问PH 值的下降已经在发生。例如在夏威夷，大气中二氧化碳浓度在升高，其西北方向约450公里处海洋监测点的PH值在下降（见图表）。但其下降曲线的振幅却比上升曲线的振幅的大得多：PH值的年际变化常常要比20年平均PH值的变化要大。
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.
这是因为大气没有从海洋表层水体获取二氧化碳浓度的能力。光合作用的增加会消耗二氧化碳，呼吸作用的增加则产生二氧化碳。深层海水的二氧化碳浓度要比在浅层的要低，因为在深层没有光合作用而呼吸作用却很强。很多地方PH值的自然变化要比长期平均值的变化还大。
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.
不是说这些变化不会造成影响。如果是酸碱度的峰值而不是长期平均值的影响{zd0}，自然的变化可能会使情况更糟。但这也说明了各种影响之间的差异很大。
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.
同样，对不同生物应对PH值下降的研究结果也是各式各样。地中海高级研究院的爱丽丝?亨德里克斯对大量的研究数据进行了分析，了解单个生物体对提高了二氧化碳浓度的海水是如何响应的。她发现这些响应有很大的区别，有些似乎更适合于低PH值环境。她还认为在21世纪酸化问题的影响相对而言并不大。
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.
有些研究人员认为她把研究数据混在一起进行分析的方法忽视了更严重的危害影响。即便是这样，其它的研究项目也同样有可能偏向另一极端。相比而言，那些表明有危害影响的数据更可能被夸大论述并得到发表。
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.
如果有些生物能承受低PH值而有些却不能，你可能就会认为事情无关紧要：能承受和适应的就会兴旺，不能适应的则消亡。对海洋中的“初级生产者”--进行光合作用的单细胞生物而言，情况可能会是如此。但是，各类进行光合作用的生物之间谁占优势的变化依然重要。海洋生态就是研究谁吃谁的问题，靠近食物链底层某些生物数量的小变化，可能对以其为食的上层生物造成大的影响。可能因遭受到缺少食物和PH值变化的双重打击，有些生物会加速灭亡。即使能适应的也要付出代价：为了应付低PH值，生物可能不得不搭上原来用于其它用途的资源。
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.
这就是为什么要设立那些看来像安全套似的装置--科研人员称之为围隔生态系统。这是欧洲海洋酸化研究项目（EPOCA）的一部分，该项目聘请了100多位研究人员，其中30多人目前在北极地带。对PH值变化所造成的全球生态影响，欧洲海洋酸化研究项目做了迄今为止最彻底的调查。
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.
要观察哪些生物在围隔生态系统内繁殖更快，德国基尔市莱布尼茨海洋研究所的优福?里贝塞和他的同事们要监测水的化学和营养成分浓度，以期发现这些变化。里贝塞博士特别感兴趣的是生态系统中翼足类的作用，它也被称作海底蝴蝶。这些优雅的小软体动物是某些鱼类的重要食物。这也是细鳞大马哈鱼在出生后一年内吃得最多的东西。
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.
如果食物链的改变使得翼足类生物减少，大马哈鱼就得去适应，否则就会消亡。尽管围隔生态系统的试验也许揭示出了翼足类生物的命运，大马哈鱼的未来仍然是难以预测。虽然欧洲海洋酸化研究项目是雄心勃勃，不吝经费，围隔生态系统还是太小，不能放鱼实验，试验期也太短暂，不能推论许多年以后会产生哪些适应性，以及要付出怎样的代价。
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可能比海洋水域的生态系统更容易预测的原因之一。为海洋生态系统提供架构的的食物链，是难以监测和不断变化的。珊瑚礁的结构是大量成块的碳酸钙，微生物附于其上进行生长和捕获食物。尽管还不知道海水化学成分的变化是否是原因之一，对澳大利亚大堡礁的研究显示，珊瑚礁钙化的速度在下降。目前已有研究试图把60-70年代的监测数据和现状的进行比较，以期找清原因。
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.
但是要划分出酸化的作用是很困难的。海洋生态环境还受到流入海洋的地表径流带来的营养物浓度变化的影响，及几乎在各处都造成食物链大破坏的过度捕捞的影响。全球变暖当然也是影响之一。随着海洋升温，表层水体更易形成稳定层，就会影响到营养物的获得，而且更令人担忧的是会影响对氧的吸收。包括里贝塞博士在内的一些人猜测，相比PH值的变化而言，全球升温引起的物理和化学变化对海洋生物的变化起了更大的推动作用。不管你怎样去看，都已经存在着那“另一个难题”。 |
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