Dominance of autochthonous autotrophic carbon in food webs of heterotrophic rivers
Dominance of autochthonous autotrophic carbon in food webs of heterotrophic rivers
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DOI：
10.1034/j.1600-0706.2002.960315.x
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发表时间：
2002-03-01
期刊：
影响因子：
3.4
通讯作者：
Delong, AD
中科院分区：
文献类型：
--
作者：
Thorp, JH;Delong, AD
本文解决了河流异养悖论，“如果生态系统作为一个整体是异养的，河流食物网中的动物生物量如何主要由本地自养生产提供燃料？”经过审查，来自热带、温带和北极河流的稳定同位素数据提供了与修订后的河流生产力模型（RPM）一致的证据：“在大多数河流的中高营养水平（大于或等于第4级），支持总体后生动物生产和物种多样性的主要年度能量来源是通过食藻和分解者途径进入食物网的原生初级生产”。修正后的RPM与异养悖论并不冲突，因为：(a)分解者（微生物环）食物途径处理大部分运输的、外来的和本地的碳，并且在某些情况下与藻类呼吸一起，是河流异养状态的主要原因（P/R < 1）；但是(b)中高营养水平的生物量生产主要由藻类-食草动物（浮游植物和底栖微藻）途径支持，该途径与分解者途径的联系很弱。藻类-食草动物途径支持大多数后生动物生物量的原因是，外来碳大多是顽固性的，而来自原生初级生产的碳虽然数量少得多，但通常更不稳定（更容易吸收），每单位质量含有更多的能量，并且通常是后生动物的首选。
This paper addresses the river heterotrophy paradox, "How can animal biomass within riverine food webs be fueled primarily by autochthonous autotrophic production if the ecosystem as a whole is heterotrophic?". Reviewed, stable isotope data from tropical, temperate, and arctic rivers provide evidence consistent with the revised riverine productivity model (RPM): "The primary, annual energy source supporting overall metazoan production and species diversity in mid- to higher-trophic levels of most rivers (greater than or equal to4th order) is autochthonous primary production entering food webs via algal-grazer and decomposer pathways". The revised RPM does not conflict with the heterotrophy paradox because: (a) the decomposer (microbial loop) food pathway processes most of the transported, allochthonous and autochthonous carbon and, with algal respiration in some cases, is primarily responsible for a river's heterotrophic state (P/R < 1); but (b) biomass production of mid- to higher-trophic levels is principally supported by an algal-grazer (phytoplankton and benthic microalgae) pathway that is only weakly linked to the decomposer pathway. The reason the algal-grazer pathway supports the majority of metazoan biomass is that allochthonous carbon is mostly recalcitrant, whereas carbon from autochthonous primary production, though much less plentiful, is commonly more labile (easier to assimilate), contains more energy per unit mass, and is typically preferred by metazoa.