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Manipulating the chemosynthetic and photosynthetic support of river food webs

操纵河流食物网的化学合成和光合作用支持

基本信息

批准号：
NE/H02235X/1
负责人：
Jon Grey
金额：
$ 57.65万
依托单位：
Queen Mary University of London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2011
资助国家：
英国
起止时间：
2011 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FH02235X%2F1
关键词：
Manipulating chemosynthetic photosynthetic support river

项目摘要

We are probably all familiar with the basic principle that life on earth is reliant on primary production i.e. photosynthetic plants driven by energy from the sun. There was a great deal of interest in 1977 when images of bizarre 6ft tubeworms and giant clams came up from the depths of the Pacific to reveal significant production, indeed whole communities reliant upon chemical energy (chemosynthesis). Few, if any, would suspect that such chemosynthetic life may be significant in the classic chalk rivers of southern England. However, a fortuitous finding, as part of a wider NERC LOCAR project into the ecological significance of river water and groundwater exchange, suggests that this is the case. We measured the stable carbon isotope values of common aquatic invertebrates (small crustacea and insects) and their putative food sources in one of our focal model systems (the River Lambourn) because we can use stable isotopes to trace energy sources and fluxes through food webs. Whereas the values for small shrimps and blackfly larvae reflected that of the dominant photosynthetic production, the cased larvae of the common caddisflies were distinctly different. Remarkably, such isotope values characterise an input of methane-derived carbon and our calculations suggest that the caddisflies were receiving a 20-25 % chemosynthetic carbon 'subsidy'. Freshwater may comprise only 3% of the Earth's total water, and rivers a vanishingly small percentage of that, yet it is this tiny percentage with which we think we are most familiar, and upon which we rely in our everyday lives. Our earlier research suggests we do not know as much about the processes in rivers as we first thought; a completely novel source of carbon, in effect, fuelling life in the river. Of course, methane is a powerful greenhouse gas and the more we know about how it is produced and cycled in the environment, the better. These first findings prompted us to examine the relative proportion of chemosynthetic to photosynthetic production under simple conditions in the laboratory and we showed that chemosynthesis was indeed a significant source of energy; around 6% but with the potential to be higher under natural conditions. What we need to do now is to scale up these simple measurements in the laboratory to realistic field-trials in which we can manipulate both the amount of methane and sunlight. Then we can map the stable isotope 'patterns' we see in the insects directly onto the processes which we hypothesised were the drivers of that pattern and close this knowledge gap. At the River Laboratory of the Freshwater Biological Association, there are a number of stream channels which we can use as the basis for our experimentation, although we will need to modify those to our specific requirements. The channels are fed with water from the R Frome which we have previously found to have the highest summer concentration of methane, ideal for our experiments. In a series of experiments, we will manipulate methane concentration, sunlight and animal numbers, while measuring concurrent photosynthetic and chemosynthetic production. If we can demonstrate that the whole food web, including the plants, are ultimately affected by methane cycling, then our first calculations of the importance of methane subsidy (20-25%) are underestimates, and chemosynthetic production is even more important to the life in these rivers. In summary, we will combine the traditional river ecology expertise of Hildrew and Woodward, with the stable isotope expertise of Grey, and gas and nutrient cycling expertise of Trimmer in a new collaboration to re-appraise how productivity in our rivers is governed.

我们可能都熟悉地球上的生命依赖于初级生产的基本原理，即由太阳能驱动的光合植物。1977年，当奇异的6英尺长的管虫和巨大的蛤蜊的图像从太平洋深处出现时，人们产生了极大的兴趣，揭示了巨大的生产，实际上整个社区都依赖于化学能（化学合成）。几乎没有人会怀疑这种化学合成生命在英格兰南部的典型白垩河流中可能是重要的。然而，一个偶然的发现，作为一个更广泛的NERC LOCAR项目的一部分，河流水和地下水交换的生态意义，表明情况确实如此。我们测量了常见的水生无脊椎动物（小甲壳动物和昆虫）的稳定碳同位素值和他们的假定的食物来源在我们的焦点模型系统之一（兰伯恩河），因为我们可以使用稳定同位素跟踪能源和通量通过食物网。而小虾和黑蝇幼虫的值反映了占主导地位的光合生产，普通石蛾的案件的幼虫是明显不同的。值得注意的是，这样的同位素值是甲烷衍生碳的输入，我们的计算表明，石蛾接受了20- 25%的化学合成碳“补贴”。淡水可能只占地球总水量的3%，河流在其中所占的比例微乎其微，但我们认为我们最熟悉的就是这一小部分，我们在日常生活中依赖于它。我们早期的研究表明，我们对河流中的过程并不像我们最初认为的那样了解;实际上，这是一种全新的碳源，为河流中的生命提供燃料。当然，甲烷是一种强大的温室气体，我们越了解它是如何产生和在环境中循环的，就越好。这些初步发现促使我们在实验室简单条件下检查化学合成与光合产物的相对比例，我们表明化学合成确实是一种重要的能量来源;约为6%，但在自然条件下可能更高。我们现在需要做的是将这些简单的实验室测量扩大到现实的实地试验，在实地试验中，我们可以操纵甲烷和阳光的数量。然后，我们可以将我们在昆虫中看到的稳定同位素“模式”直接映射到我们假设是该模式的驱动程序的过程中，并缩小这一知识差距。在淡水生物协会的河流实验室，有一些河流通道，我们可以使用它们作为我们实验的基础，尽管我们需要根据我们的具体要求进行修改。这些通道的水来自R弗罗姆，我们以前发现那里夏季甲烷浓度最高，非常适合我们的实验。在一系列实验中，我们将操纵甲烷浓度、阳光和动物数量，同时测量光合作用和化学合成的产量。如果我们能证明整个食物网，包括植物，最终都受到甲烷循环的影响，那么我们对甲烷补贴重要性的初步计算（20-25%）被低估了，而化学合成生产对这些河流中的生命更为重要。总之，我们将联合收割机结合传统的河流生态学专业知识的希尔德鲁和伍德沃德，与稳定同位素专业知识的灰色，气体和营养循环专业知识的特里默在一个新的合作，以重新评估生产力在我们的河流是如何管理。