Control of periphyton standing crop in an Atlantic Forest stream: the relative roles of nutrients, grazers and predators
Control of periphyton standing crop in an Atlantic Forest stream: the relative roles of nutrients, grazers and predators
复制标题
大西洋森林溪流中附生植物的控制：营养物质、食草动物和捕食者的相对作用
DOI：
10.1111/fwb.12441
复制
发表时间：
2014
影响因子：
2.7
通讯作者：
E. Zandonà
中科院分区：
文献类型：
--
作者：
C. Lourenço‐Amorim;Vinicius Neres‐Lima;T. Moulton;Cristiano Yuji Sasada;Priscila Oliveira‐Cunha;E. Zandonà
总结1。水生藻类是为食物链提供能量的重要来源。浮游藻生物量可以由自下而上和自上而下的力量控制，但很少有研究同时调查这些影响，特别是在热带溪流中，浮游藻可以是一个非常重要的碳源。在此，我们研究了巴西沿海热带河流中营养物质的自下而上效应和食草动物和捕食者的自上而下效应。我们采用营养扩散基质来测试营养限制，并将其放置在不同强度的电封闭室内，以防止消费者进入通电区域。采用单氮富(N)、单磷富(P)、氮+磷（NP）和不添加养分的对照(C)四种基质。电封闭有三种处理方式：高电流排除捕食者（奥氏沼虾）和食草动物（贝氏蜉蝣），低电流只排除虾，以及不通电的控制处理，允许虾和蜉蝣进入。3. 河流中的限制营养物是氮。我们的研究结果显示了更大程度的自下而上效应，与食草动物或捕食者相比，周围植物藻类对营养添加的反应更强烈。自上而下的控制没有那么强，但周围藻对食草动物的反应是消极的，特别是在没有捕食者的情况下。这表明虾直接或间接地抑制了蜉蝣的放牧活动。在没有食草动物的情况下，周围生长藻类对营养物的反应更强。因此，直接或间接通过营养级联的自上而下效应可以抑制对氮添加的响应，从而降低资源限制的程度。
SUMMARY 1. Periphytic algae are an important source of energy fuelling stream food webs. Periphytic algal biomass can be controlled by bottom-up and top-down forces, but there are few studies that have investigated these effects simultaneously, especially in tropical streams, where periphyton can be a very important carbon source. Here, we investigated the bottom-up effects of nutrients and the top-down effects of grazers and predators in a coastal tropical stream in Brazil. 2. We employed nutrient-diffusing substrata to test for nutrient limitation, placed inside electric exclosures of different intensities, which prevented consumers from entering the electrified area. We used four types of substrata: one enriched with nitrogen alone (N), one with phosphorus alone (P), one with nitrogen + phosphorus (NP) and one control with no nutrients added (C). The electric exclosure had three treatments: high electricity that excluded both predators (Macrobrachium olfersi shrimps) and grazers (Baetidae mayflies), low electricity that excluded only shrimps, and a control treatment with no electricity where both shrimps and mayflies were allowed to enter. 3. The limiting nutrient in the stream was nitrogen. Our results showed a greater magnitude of bottom-up effects, with periphytic algae responding more strongly to nutrient addition than to grazers or predators. Top-down control was not as strong, but periphytic algae responded negatively to grazers, especially in the absence of predators. This suggests that shrimps, either directly or indirectly, inhibit mayfly grazing activity. The response of periphytic algae to nutrients was stronger in the absence of grazers. Thus, top-down effects, both directly and indirectly through a trophic cascade, can dampen the response to nitrogen addition, diminishing the degree of resource limitation.