Effects of habitat complexity on community structure and predator avoidance behaviour of littoral zooplankton in temperate versus subtropical shallow lakes
Effects of habitat complexity on community structure and predator avoidance behaviour of littoral zooplankton in temperate versus subtropical shallow lakes
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DOI：
10.1111/j.1365-2427.2007.01748.x
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发表时间：
2007-06-01
影响因子：
2.7
通讯作者：
Jeppesen, Erik
中科院分区：
文献类型：
--
作者：
Meerhoff, Mariana;Iglesias, Carlos;Jeppesen, Erik
1. 结构复杂性可以稳定捕食者-猎物的相互作用，并通过为猎物提供避难所来影响营养级联的结果。在深湖中，脆弱的浮游动物垂直移动以躲避鱼类的捕食。相比之下，在温带浅湖中，水下植物通常为大型浮游动物提供了一个躲避鱼类捕食的避难所，这对整个生态系统产生了影响。为了测试大型植物在温带和亚热带湖泊中作为浮游动物庇护的程度，我们在乌拉圭（南纬30度-35度）和丹麦（北纬55度-57度）的五对浅湖的沿岸地区引入了人工植物床。我们使用了不同建筑的植物（淹没的和自由漂浮的），沿着浑浊度的梯度，湖泊配对。研究发现，不同气候带沿海地区浮游动物群落结构（属级分类丰富度、组成和密度）存在显著差异。温带湖泊中存在较多的大体类群（通常包括水蚤），而亚热带湖泊中存在较多的小体类群。在温带湖泊中，底栖/与植物相关的枝海动物的属数和密度也更高。温带湖泊的甲壳类动物密度均高于温带湖泊（约为温带湖泊的5.5倍）。鱼类和虾类（古虾属）对亚热带湖泊植物床浮游动物的捕食压力似乎更大，而远洋无脊椎动物潮虾类（Chaoborus sp.）略多于温带湖泊。相比之下，温带湖泊中与植物相关的大型掠食性无脊椎动物的数量是亚热带湖泊的8倍。人工淹没植物比自由漂浮植物有更多的枝状纲动物，这在亚热带湖泊中尤其避免。温带湖泊浮游动物总体密度和个体类群的水平迁移模式频繁出现，而亚热带湖泊则没有。与此相反，在亚热带，无论水的浑浊度如何，浮游动物整体和大多数个体分类群的垂直迁移模式都占主导地位。较高的鱼类捕食率可能决定了亚热带湖泊枝海洋群落的总体结构和动态。我们的研究结果支持这样的假设，即水平迁移在亚热带地区比在温带湖泊中更不普遍，并且在亚热带地区没有捕食者回避行为有效地抵消捕食压力。水生植物作为浮游动物的避难所，对水透明度的积极影响，在温暖的湖泊中可能通常很弱或很少。
1. Structural complexity may stabilise predator-prey interactions and affect the outcome of trophic cascades by providing prey refuges. In deep lakes, vulnerable zooplankton move vertically to avoid fish predation. In contrast, submerged plants often provide a diel refuge against fish predation for large-bodied zooplankton in shallow temperate lakes, with consequences for the whole ecosystem.2. To test the extent to which macrophytes serve as refuges for zooplankton in temperate and subtropical lakes, we introduced artificial plant beds into the littoral area of five pairs of shallow lakes in Uruguay (30 degrees-35 degrees S) and Denmark (55 degrees-57 degrees N). We used plants of different architecture (submerged and free-floating) along a gradient of turbidity over which the lakes were paired.3. We found remarkable differences in the structure (taxon-richness at the genus level, composition and density) of the zooplankton communities in the littoral area between climate zones. Richer communities of larger-bodied taxa (frequently including Daphnia spp.) occurred in the temperate lakes, whereas small-bodied taxa characterised the subtropical lakes. More genera and a higher density of benthic/plant-associated cladocerans also occurred in the temperate lakes. The density of all crustaceans, except calanoid copepods, was significantly higher in the temperate lakes (c. 5.5-fold higher).4. Fish and shrimps (genus Palaemonetes) seemed to exert a stronger predation pressure on zooplankton in the plant beds in the subtropical lakes, while the pelagic invertebrate Chaoborus sp. was slightly more abundant than in the temperate lakes. In contrast, plant-associated predatory macroinvertebrates were eight times more abundant in the temperate than in the subtropical lakes.5. The artificial submerged plants hosted significantly more cladocerans than the free-floating plants, which were particularly avoided in the subtropical lakes. Patterns indicating diel horizontal migration were frequently observed for both overall zooplankton density and individual taxa in the temperate, but not the subtropical, lakes. In contrast, patterns of diel vertical migration prevailed for both the overall zooplankton and for most individual taxa in the subtropics, irrespective of water turbidity.6. Higher fish predation probably shapes the general structure and dynamics of cladoceran communities in the subtropical lakes. Our results support the hypothesis that horizontal migration is less prevalent in the subtropics than in temperate lakes, and that no predator-avoidance behaviour effectively counteracts predation pressure in the subtropics. Positive effects of aquatic plants on water transparency, via their acting as a refuge for zooplankton, may be generally weak or rare in warm lakes.