Resource limitation of autotrophs and heterotrophs in boreal forest headwater streams

IF 1.7 4区 环境科学与生态学 Q3 ECOLOGY Freshwater Science Pub Date : 2022-08-16 DOI:10.1086/722256
Sophie Alden Weaver, Jeremy B. Jones
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引用次数: 1

Abstract

Autotrophic and heterotrophic microbes in stream biofilms dominate biogeochemical cycling and rely on nutrient and energy resources for growth and productivity. In the boreal forest, variation in these resources can originate from permafrost distribution and controls competition for nutrients between stream autotrophs and heterotrophs. We investigated which resources control nutrient uptake and metabolism in headwater stream biofilms of subarctic Alaska, USA, and how resource availability affects competition for inorganic nutrients. We hypothesized that the competitive outcome between autotrophs and heterotrophs for inorganic nutrients would be dependent on availability of organic C, or inorganic nutrients (N and P). To test our hypotheses, we measured resource limitation at the patch and reach scales along a permafrost gradient in interior Alaska. At the patch scale, nutrient diffusing substrata revealed that, secondary to light, N and P were colimiting to autotrophic growth, whereas C was primarily limiting to heterotrophic respiration. In the presence of labile C, heterotrophs exhibited a larger response to nutrient enrichment and outcompeted autotrophs for inorganic nutrients. At the reach scale, light availability had the largest influence on nutrient uptake, but inorganic nutrients were also important. The positive response to increased nutrient and C availability at the patch scale suggests that the predicted increase in exports into fluvial networks with permafrost degradation will alter biofilm structure and function. Ultimately, biofilm communities will shift to more heterotroph-dominated patches if heterotrophs outcompete autotrophs for inorganic nutrients. As permafrost thaws and nutrients and organic C mobilize into streams, nutrient uptake dynamics and competition within biofilms will be altered, affecting nutrient use and export.
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北方森林源头溪流中自养生物和异养生物的资源限制
溪流生物膜中的自养和异养微生物主导着生物地球化学循环,并依赖营养和能源资源来生长和生产力。在北方森林中,这些资源的变化可能源于永久冻土的分布,并控制着溪流自养生物和异养生物之间对营养物质的竞争。我们研究了哪些资源控制着美国阿拉斯加亚北极地区源头溪流生物膜中的养分吸收和代谢,以及资源可用性如何影响对无机养分的竞争。我们假设自养生物和异养生物对无机营养素的竞争结果将取决于有机C或无机营养素(N和P)的可用性。为了验证我们的假设,我们测量了阿拉斯加内陆永久冻土梯度上的斑块和河段的资源限制。在斑块尺度上,营养扩散基质显示,N和P对自养生长的抑制作用仅次于光,而C主要限制异养呼吸。在不稳定C存在的情况下,异养生物对养分富集表现出更大的反应,而对无机养分的反应则优于自养生物。在覆盖范围内,光照有效性对养分吸收的影响最大,但无机养分也很重要。在斑块规模上,对养分和碳有效性增加的积极反应表明,随着永久冻土退化,预计向河流网络的出口将增加,这将改变生物膜的结构和功能。最终,如果异养生物在无机营养方面的竞争力超过自养生物,生物膜群落将转变为更以异养生物为主的斑块。随着永久冻土融化,营养物质和有机碳进入溪流,生物膜内的营养物质吸收动态和竞争将发生变化,影响营养物质的使用和出口。
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来源期刊
Freshwater Science
Freshwater Science ECOLOGY-MARINE & FRESHWATER BIOLOGY
CiteScore
4.10
自引率
0.00%
发文量
49
审稿时长
6-12 weeks
期刊介绍: Freshwater Science (FWS) publishes articles that advance understanding and environmental stewardship of all types of inland aquatic ecosystems (lakes, rivers, streams, reservoirs, subterranean, and estuaries) and ecosystems at the interface between aquatic and terrestrial habitats (wetlands, riparian areas, and floodplains). The journal regularly features papers on a wide range of topics, including physical, chemical, and biological properties of lentic and lotic habitats; ecosystem processes; structure and dynamics of populations, communities, and ecosystems; ecology, systematics, and genetics of freshwater organisms, from bacteria to vertebrates; linkages between freshwater and other ecosystems and between freshwater ecology and other aquatic sciences; bioassessment, conservation, and restoration; environmental management; and new or novel methods for basic or applied research.
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