Spatial heterogeneity and biological productivity in a large river ecosystem

大型河流生态系统的空间异质性和生物生产力

• 批准号: 227578-2007
• 负责人: Frenette, JeanJacques
• 金额: $ 1.05万
• 依托单位: Université du Québec à Trois-Rivières
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2009
• 资助国家: 加拿大
• 起止时间: 2009-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=425186
• 关键词: Spatial; heterogeneity; biological; productivity; large

The long-term objective of my research program is to model interactions between physical and chemical factors and lower food web processes in the St. Lawrence River (SLR). Identifying the primary sources of carbon supporting food webs is a fundamental step towards understanding the structure and function of aquatic ecosystems. Some studies have argued for a dominant role of terrestrial carbon and heterotrophy in river food webs while others have stressed the greater importance of in situ photosynthetic sources. In either case, the transported matter in the river is transformed by light or bacterial activity which affects its bioavailability and flow to downstream consumers. This study aims at understanding how the transfer of matter (e.g. nutrients, phytoplankton) and organisms between habitats (connectivity) is controlling food availability and biodiversity, important for determining carbon sources supporting food webs and productivity in large river ecosystems. Lac St. Pierre (LSP) is the largest fluvial lake (~400 km2) of the SLR and is well recognized for its high productivity. However, there is a large gap in knowledge about the fate of matter leaving LSP into the fluvial estuary, which connects to the estuarine transition zone (ETZ). The ETZ is light-limiting for photosynthesis and marks where freshwater meets saltwater. It is recognized for its very high productivity, and as a large nursery area for several fish species. I hypothesize that much of the productivity in the ETZ is dependent on transported material from the fluvial estuary, which in turn receives high dissolved organic matter and nutrients from LSP. I recently established that LSP can contribute significantly to downstream productivity through large populations of ice-algae drifting during the ice-break period in spring. This finding opens a totally new perspective for understanding aquatic productivity in large rivers. This NSERC program on the SLR ecosystem integrates: 1) ETZ as a key habitat of large rivers, acting as a gateway to the sea through the exchanges of carbon and sediments; and 2) winter biological activities in north-temperate rivers, in which river ice biota may substantially contribute to annual primary productivity and carbon transfer along the food web.

我的研究计划的长期目标是模拟圣劳伦斯河 (SLR) 物理和化学因素与下游食物网过程之间的相互作用。确定支持食物网的碳的主要来源是了解水生生态系统结构和功能的基本步骤。一些研究认为陆地碳和异养在河流食物网中起主导作用，而另一些研究则强调原位光合来源的重要性。在任何一种情况下，河流中运输的物质都会被光或细菌活动所转化，从而影响其生物利用度和流向下游消费者。本研究旨在了解栖息地之间物质（例如营养物、浮游植物）和生物体的转移（连通性）如何控制食物供应和生物多样性，这对于确定支持大型河流生态系统食物网和生产力的碳源非常重要。圣皮埃尔湖 (LSP) 是 SLR 最大的河流湖（约 400 平方公里），以其高生产力而闻名。然而，对于离开 LSP 进入与河口过渡区 (ETZ) 连接的河流河口的物质的命运，人们的了解还存在很大差距。 ETZ 对光合作用进行光限制，并标志着淡水与咸水的交汇处。它以其极高的生产力而闻名，并且是多种鱼类的大型育苗区。我假设经济特区的大部分生产力依赖于来自河流河口的运输物质，而河流河口又从 LSP 接收高溶解有机物和营养物质。我最近发现，LSP 可以通过春季破冰期间大量冰藻的漂流，对下游生产力做出重大贡献。这一发现为理解大河流的水生生产力开辟了全新的视角。 NSERC 关于 SLR 生态系统的计划整合了：1）ETZ 作为大河流的关键栖息地，通过碳和沉积物的交换充当通往海洋的门户； 2）北温带河流的冬季生物活动，其中河流冰生物群可能对年度初级生产力和食物网沿线的碳转移做出重大贡献。