Importance of ecological boundaries in aquatic ecosystem processes

水生生态系统过程中生态边界的重要性

• 批准号: 6216-2009
• 负责人: Planas, Dolores
• 金额: $ 2.11万
• 依托单位: Université du Québec à Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2011
• 资助国家: 加拿大
• 起止时间: 2011-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=474081
• 关键词: Importance; ecological; boundaries; aquatic; ecosystem

During recent past decades, harmful algal blooms have increased world wide in aquatic ecosystems, and not only in eutrophic ecosystems. In continental waters these blooms are mainly due to potentially toxic blue-green algae (cyanobacteria). The relationship between blue-green blooms and lake fertilisation by nutrients, particularly phosphorus (P), is known since the early 70s. The question today is why the blooms also occur in lakes with low nutrient concentrations in their surface waters. In some of these lakes external P-loading has been decreased in the last 20-30 years, in others external anthropogenic sources are unknown. In these low surface nutrient lakes the occurrence and intensity of the blooms varies between years. Recently, the increase of noxious blue-greens has been attributed to global warming, and the author of this hypothesis advocates for more detailed studies of climate change and population dynamics of bloom-forming blue-greens. In our 5-yr study we wish to verify some of the mechanisms related to climate that could control algal community structure and blue-green blooms in small lakes. In particular, we want to measure the importance of wind-induced physical forcing at the bottom of lakes (benthic boundary layer) in the fluxes of nutrients and organisms from littoral and deep habitats to the water column (pelagic habitats); and between physically constrained adjacent areas (e.g. thermocline in stratified lakes). Our hypotheses are that: i) it is the P-accumulated in the sediments that allows the growth of the bottom resting stages of algae in lakes with low external P loads and, ii) the intensity of the physical forcing of nutrients and organisms through boundaries links the different habitats (from the bottom to the water column and through the water column) and creates a positive or negative feedback in algae recruitment. Our study constitutes a novel approach to explaining the inter-annual variability in algae community structure in stratified lakes and may explain cyanobacteria blooms. Our understanding of the importance of the physical forcing on ecological processes in stratified small lakes should produce better tools for noxious bloom management and control.

近几十年来，全球水生生态系统中的有害藻类大量繁殖，而不仅仅是富营养化生态系统。在大陆水域，这些水华主要是由潜在有毒的蓝绿藻（蓝细菌）造成的。自 20 世纪 70 年代初以来，人们就知道蓝绿色水华与养分（尤其是磷 (P)）对湖泊施肥之间的关系。今天的问题是，为什么水华也会发生在地表水中养分浓度较低的湖泊中。在过去 20-30 年中，其中一些湖泊的外部磷负荷有所减少，而在其他湖泊中，外部人为来源未知。 在这些低表层养分的湖泊中，水华的发生和强度因年份而异。最近，有毒蓝绿藻的增加被归因于全球变暖，该假设的作者主张对气候变化和开花蓝绿藻的种群动态进行更详细的研究。在我们为期五年的研究中，我们希望验证一些与气候相关的机制，这些机制可以控制小湖泊中的藻类群落结构和蓝绿色水华。特别是，我们想要测量湖底（底栖边界层）风引起的物理强迫对于从沿海和深层生境到水柱（远洋生境）的营养物和生物体通量的重要性；以及物理限制的相邻区域之间（例如分层湖泊中的温跃层）。我们的假设是：i）沉积物中积累的磷允许外部磷负荷较低的湖泊中藻类底部静止阶段的生长，ii）营养物和生物体通过边界的物理强迫强度将不同的栖息地（从底部到水柱并通过水柱）联系起来，并在藻类补充中产生正反馈或负反馈。我们的研究提出了一种新方法来解释分层湖泊中藻类群落结构的年际变化，并可能解释蓝藻水华。我们对物理强迫对分层小湖泊生态过程的重要性的理解应该为有毒水华管理和控制提供更好的工具。