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Fisheries management influences phytoplankton biomass of Amazonian floodplain lakes
Journal of Applied Ecology ( IF 5.7 ) Pub Date : 2020-09-14 , DOI: 10.1111/1365-2664.13763
João Vitor Campos‐Silva 1, 2, 3, 4 , Carlos A. Peres 4, 5, 6 , João Henrique Fernandes Amaral 7 , Hugo Sarmento 8 , Bruce Forsberg 9 , Carlos Roberto Fonseca 1
Affiliation  

  1. Tropical floodplains secure the protein supply of millions of people, but only sound management can ensure the long‐term continuity of such ecosystem services. Overfishing is a widespread threat to multitrophic systems, but how it affects ecosystem functioning is poorly understood, particularly in tropical freshwater food webs. Models based on temperate lakes frequently assume that primary producers are mostly bottom‐up controlled by nutrient and light limitations, with negligible effects of top‐down forces. Yet this assumption remains untested in complex tropical freshwater systems experiencing marked spatiotemporal variation.
  2. We use consolidated community‐based fisheries management practices and spatial zoning to test the relative importance of bottom‐up versus top‐down drivers of phytoplankton biomass, controlling for the influence of local to landscape heterogeneity. Our study focuses on 58 large Amazonian floodplain lakes under different management regimes that resulted in a gradient of apex‐predator abundance. These lakes, distributed along ~600 km of a major tributary of the Amazon River, varied widely in size, structure, landscape context, and hydrological seasonality.
  3. Using generalised linear models, we show that community‐based fisheries management, which controls the density of apex predators, is the strongest predictor of phytoplankton biomass during the dry season, when lakes become discrete landscape units. Water transparency also emerges as an important bottom‐up factor, but phosphorus, nitrogen and several lake and landscape metrics had minor or no effects on phytoplankton biomass. During the wet‐season food pulse, when lakes become connected to adjacent water bodies and homogenise the landscape, only lake depth explained phytoplankton biomass.
  4. Synthesis and applications. Tropical freshwaters fisheries typically assume that fish biomass is controlled by bottom‐up mechanisms, so that overexploitation of large predators would not affect overall ecosystem productivity. Our results, however, show that top‐down forces are important drivers of primary productivity in tropical lakes, above and beyond the effects of bottom‐up factors. This helps us to understand the enormous success of community‐based ‘fishing agreements’ in the Amazon. Multiple stakeholders should embrace socio‐ecological management practices that shape both bottom‐up and top‐down forces to ensure biodiversity protection, sustainable fisheries yields and food security for local communities and regional economies.


中文翻译:

渔业管理对亚马逊河漫滩湖浮游植物生物量的影响

  1. 热带洪泛区确保了数百万人的蛋白质供应,但只有合理的管理才能确保此类生态系统服务的长期连续性。过度捕捞是对多营养系统的普遍威胁,但人们对它如何影响生态系统功能的了解很少,特别是在热带淡水食物网中。基于温带湖泊的模型经常假设初级生产者大多是自下而上地受养分和光的限制,而自上而下的作用则微不足道。然而,这种假设在经历明显的时空变化的复杂热带淡水系统中仍然未经检验。
  2. 我们使用基于社区的综合渔业管理实践和空间分区来测试浮游植物生物量的自下而上与自上而下驱动力的相对重要性,并控制本地对景观异质性的影响。我们的研究集中在58种大型亚马逊河漫滩上,这些湖泊在不同的管理制度下导致了尖锐捕食者数量的梯度。这些湖泊分布在亚马逊河主要支流的约600公里处,其大小,结构,景观背景和水文季节性变化很大。
  3. 使用广义线性模型,我们表明,控制湖泊基层捕食者密度的社区渔业管理,在旱季中湖泊成为离散的景观单位时,是浮游植物生物量最强的预测指标。水的透明性也是一个重要的自下而上因素,但是磷,氮以及一些湖泊和景观指标对浮游植物的生物量影响很小或没有影响。在潮湿季节的食物脉动期间,当湖泊与相邻水体相连并使景观均匀化时,只有湖泊深度解释了浮游植物的生物量。
  4. 综合与应用。热带淡水渔业通常假设鱼类生物量受自下而上的机制控制,因此大型捕食者的过度开发不会影响整个生态系统的生产力。然而,我们的结果表明,自上而下的作用力是自下而上因素的影响之外,是热带湖泊初级生产力的重要驱动力。这有助于我们了解亚马逊社区基于社区的“捕鱼协议”的巨大成功。多个利益相关者应采用能够形成自下而上和自上而下的力量的社会生态管理实践,以确保为当地社区和区域经济提供生物多样性保护,可持续渔业产量和粮食安全。
更新日期:2020-09-14
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