Ecological Drivers of Freshwater Macroalgal Blooms across Trophic Gradients

淡水巨藻在营养梯度上大量繁殖的生态驱动因素

• 批准号: RGPIN-2018-05443
• 负责人: Kirkwood, Andrea
• 金额: $ 2.04万
• 依托单位: University of Ontario Institute of Technology
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=682287
• 关键词: Ecological; Drivers; Freshwater; Macroalgal; Blooms

The incidence of freshwater algal blooms has been increasing across North America, including regions with no historical record of bloom occurrence. This is a disconcerting trend when considering the negative social and economic impacts of algal blooms. Eutrophication and climate change have been implicated as major drivers of microalgal (i.e., phytoplankton) blooms. In contrast, macroalgal (i.e., visible mat-forming algae) blooms are not consistently explained by nutrients, nor is much known about the role of climate change. Morphologically diverse species of macroalgae bloom across a range of habitats and nutrient conditions (i.e., trophic states), even in systems where nutrients are low. This “nutrient-biomass” paradox may be explained by the shared characteristics of freshwater macroalgae: (1) a colony-matrix; and (2) a benthic or near-bed habitat. One possible driver of macroalgal blooms across trophic gradients involves the microbial community that lives on/within the colony-matrix (i.e., the “epibiome”), which may facilitate or supplement growth when external nutrients are variable or low. Another possible ecological driver is nutrient bioavailability in the benthic zone, whereby blooming species can exploit alternative forms of nutrients (e.g., dissolved organic phosphorus) compared to competing organisms. A likely over-arching driver of macroalgal blooms is climate change, which can either directly or indirectly influence bloom development irrespective of trophic state. As such, there are three main research objectives for this proposed program of study: (1) Determine how climate change directly/indirectly influences macroalgal blooms; (2) Assess the role of organic nutrient supply in macroalgal bloom development; and (3) Evaluate the role of the epibiome in facilitating growth in bloom-forming macroalgae. Three diverse, but representative macroalgal species (Didymosphenia geminata, Nitellopsis obtusa and Cladophora glomerata) with documented nuisance growth in systems representing a broad trophic gradient will be the main study taxa. Overall, this proposed research program will offer new insight on causes of nuisance macroalgal growth, including similarities and differences across taxa and ecosystems. It is anticipated that this information will prove useful to water managers from various levels of government seeking to control nuisance macroalgae outbreaks in their jurisdictions.

北美淡水藻华的发生率一直在增加，包括没有历史记录的地区。考虑到藻华对社会和经济的负面影响，这是一个令人不安的趋势。富营养化和气候变化已被认为是微藻（即浮游植物）大量繁殖的主要驱动因素。相比之下，大藻（即可见的形成席地的藻类）的大量繁殖并不能一致地用营养物质来解释，对气候变化的作用也知之甚少。形态多样的巨藻物种在一系列栖息地和营养条件（即营养状态）中大量繁殖，即使在营养含量低的系统中也是如此。这种“营养-生物量”悖论可以用淡水巨藻的共同特征来解释：(1)集落基质；(2)底栖动物或近床栖息地。大藻华跨越营养梯度的一个可能驱动因素涉及生活在菌落基质上/内部的微生物群落（即“表观群落”），当外部营养变化或低时，它们可能促进或补充生长。另一个可能的生态驱动因素是底栖区营养物质的生物可利用性，与竞争生物相比，开花物种可以利用其他形式的营养物质（例如溶解的有机磷）。气候变化可能是大型藻华的首要驱动因素，无论营养状态如何，气候变化都可以直接或间接影响藻华的发展。因此，这个拟议的研究项目有三个主要的研究目标：(1)确定气候变化如何直接/间接影响大藻华；(2)评价有机养分供给在大藻华发育中的作用；(3)评价表观群落对大藻华生长的促进作用。三种不同但具有代表性的巨藻物种（双藻、黑藻和Cladophora glomerata）在具有广泛营养梯度的系统中有记录的滋扰生长将是主要的研究分类群。总的来说，这个拟议的研究计划将提供新的见解，对令人讨厌的大型藻类生长的原因，包括类群和生态系统的异同。预计这些信息将对各级政府设法控制其管辖范围内有害大型藻类爆发的水管理人员有用。