Official 36 Passage 2


Early Ideas about Deep-sea Biology


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  • In 1841 Edward Forbes was offered the chance to serve as naturalist aboard HMS Beacon, an English Royal Navy ship assigned to survey the Aegean Sea. For a year and a half the Beacon crisscrossed the Aegean waters. During that time Forbes was able to drag his small, triangular dredge-a tool with a leather net for capturing creatures along the sea bottom-at a hundred locations, at depths ranging from 6 to 1,380 feet. He collected hundreds of different species of animals, and he saw that they were distributed in eight different depth zones, each containing its own distinct assemblage of animal life, the way zones of elevation on the side of a mountain are populated by distinct sets of plants.

    Forbes also thought he saw, as he later told the British Association, that "the number of species and individuals diminishes as we descend, pointing to a zero in the distribution of animal life as yet unvisited. This zero, Forbes casually speculated-he simply extended a line on his graph of animal number versus depth-probably began at a depth of 1,800 feet. Below that was the final zone in Forbes's scheme, zone nine, a zone that covered most of the ocean floor and thus most of the solid surface of Earth: Forbes called this the azoic zone, where no animal, to say nothing of plants, could survive.

    Forbes's azoic zone was entirely plausible at the time, and it was certainly far from the strangest idea that was then entertained about the deep sea. In the first decade of the nineteenth century, a French naturalist named François Péron had sailed around the world measuring the temperature of the ocean. He found that the deeper the water, the colder it got, and he concluded that the seafloor was covered with a thick layer of ice. Péron ignored the fact that water expands when it freezes and that ice therefore floats. A more popular belief at the time was that water at great depth would be compressed to such a density that nothing could sink through it. This ignored the fact that water is all but incompressible. But even the more sensible naturalists of the day were guilty of a similar misconception. They imagined the deep sea as being filled with an unmoving and undisturbable pool of cold, dense water. In reality the deep is always being refreshed by cold water sinking from above.

    The central implication of all these misconceptions was that nothing could live in the abyss (deep), just as Forbes's observations seemed to indicate. But Forbes erred in two ways. One was the particular study site he happened to use as a springboard for his sweeping postulate of a lifeless abyss. Although the Aegean had been the birthplace of marine biology, its depths are now known to be exceptionally lacking in animal diversity. Moreover, through no fault of his own, Forbes was not particularly successful at sampling such life as did exist at the bottom of the Aegean. It was his dredge that was inadequate. Its opening was so small and the holes in the net so large that the dredge inevitably missed animals. Many of those it did catch must have poured out of its open mouth when Forbes reeled it in. His azoic zone, then, was a plausible but wild extrapolation from pioneering but feeble data.

    As it turned out, the existence of the azoic zone had been disproved even before Forbes suggested it, and the theory continued to be contradicted regularly throughout its long and influential life. Searching for the Northwest Passage from the Atlantic to the Pacific in 1818, Sir John Ross had lowered his "deep-sea clam"-a sort of bivalved sediment scoop-into the waters of Baffin Bay(an inlet between the Atlantic and Arctic oceans), which he determined to be more than a thousand fathoms deep in some places. Modern soundings indicate he overestimated his depths by several hundred fathoms, but in any case Ross's clam dove several times deeper than Forbes's dredge. It brought back mud laced with worms, and starfish that had entangled themselves in the line at depths well below the supposed boundary of the azoic zone.

  • 在1841年,Edward Forbes得到了一个作为自然学家随船考察的机会,这艘船叫做HMS Beacon,是一艘意在探索爱琴海的英国皇家海军船只。 一年半的时间里,Beacon号详细考察了爱琴海。 就是在这个时期内,Forbes通过拖拽一种三角形的名为dregdge的工具探究了上百处地点。这种工具有一个皮革制成的网,可以从海底捕获生物。它的作业范围可以从6英尺深入到1380英尺。 他收集了上百种不同的海洋生物,并且观察到他们分布在八个不同深度的空间里。每一个空间都拥有自己独特的生物集合,就类似于不同高度的山上分布着明显是不同类型的植被一样。

    Forbes后来告诉英国相关组织,他同样认为“越往海底潜,生物的种类和数量越少,这就暗示在我们还未探索过的海域,有一个空间是没有生物分布的”。 这个没有生物存在的空间,Forbes在他绘制的生物数量和深度示意图上划了条线,随意地推测这个区域的深度大约是从1800英尺向下。 在这条线之下是Forbes图上的最后一个区域,第九区,这个区域涵盖了大部分的海床也就是大多数的地球固态表面:Forbes把这个区域称为无生命区,动物和植物都不能在这个区域生存。

    Forbes的无生命区在当时看来是完全可信的。它和当时关于深海的最奇怪的理论大相径庭。 在十九世纪开头的十年间,一个叫做Francois的法国自然学家环游世界,并且测量了海水的温度。 他发现海水越深就越冷,这样他得出结论说海床被厚厚的冰层覆盖着。 Peron忽视了水结冰以后密度会变低,冰会浮在水面上。 当时更流行的观点是海洋最深处的海水会被极度压缩,以至于没有生物可以潜入这一层。 这个理论忽视了水是几乎不能压缩的这个事实。 但是即使是当时更加理智的自然学家也会作出类似的误解。 他们想象深海是一池不能运动的、波澜不惊的紧实冷水。 但实际上,这个深度的海水是经常被上面流下来的冷水更新的。

    这些错误理论的中心观点是没有生物可以在深海中生存,就像Forbes的观察结论所说明的一样。 但是Forbes在两点上弄错了。 第一点是他用以得出无人区存在这个普遍结论的研究地点选择有误。 即使爱琴海是海洋生物学的起源地,它的深度范围里的生物种类是特别有限的。 第二点是,尽管Frobes本身并没有错,但是他在爱琴海深海取样的过程是不成功的。 原因是他使用的工具dregdge并不足以成功取样。 这个工具的直径太小了,网上的洞又太大了,导致这个工具不可避免地会漏掉一些海底生物。 它可能的确能捕捉到一些生物,但是当Frobes开始拉起它时,很多动物就从洞里漏出去了。 所以他的无生物区的理论看上去是貌似可信的,而且推动了对海底生物的研究,但实际上是站不住脚的。

    就像事实所说明的那样,无生物区的存在在Forbes提出其存在之前就已经被否定了。在Frobes理论漫长而具有影响力的一生中,它被多次反对过。 John Ross爵士在1818年探索从大西洋到太平洋的西北航道中,把他的测量工具deep-sea clam——一种双壳沉淀的勺子——深入到巴芬湾(大西洋和北冰洋的入口)里,深度超过了一千英寻。 现代测量水深的工具显示他高估了几百英寻的深度,但是即便如此,Ross的工具下潜的深度也比Frobes的深。 这个工具带上来含有虫子的海泥,还捞上来缠在工具上的海星。它们被打捞上来的深度已经在无生物区的划分界线之下了。
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    原文定位:It was his dredge that was inadequate. Its opening was so small and the holes in the net so large that the dredge inevitably missed animals.





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