Effects of nutrients and light on periphyton biomass and nitrogen uptake in Mediterranean streams with contrasting land uses
Effects of nutrients and light on periphyton biomass and nitrogen uptake in Mediterranean streams with contrasting land uses
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DOI：
10.1111/j.1365-2427.2007.01742.x
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发表时间：
2007-05
影响因子：
2.7
通讯作者：
D. Schiller;E. Martí;J. Riera;F. Sabater
中科院分区：
文献类型：
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作者：
D. Schiller;E. Martí;J. Riera;F. Sabater
总结1。利用营养物扩散基质（NDS）来确定营养物和光作为受不同人类影响的地中海河流周围植物生物量和氮(N)吸收的潜在限制因子的相对重要性。研究的营养物质为磷(P)和氮(N)，并进一步区分了周边植物群落对N（即NO3-N和NH4-N）的响应。为了研究光照和养分对周围植物生物量的影响，比较了开放和封闭林冠下NDS的叶绿素a累积速率。短期添加NO3-15N后，通过NDS的15N变化来测定养分有效性对周围植物吸收的影响。2. 结果表明，光照是影响研究水体藻类生物量的主要因素。开放林冠的藻类生物量总体上高于封闭林冠。NDS试验模拟的养分有效性在两种光照条件下都没有增加藻类生物量。3. 在对照处理（即环境浓度）中，随河流氮有效性的增加，周围植物NO3-N吸收率增加，C: N摩尔比下降。在N修正的NDS中，人为增加环境氮浓度会改变NO3-N的吸收速率。生长在富氮基质上的浮游植物组合似乎优先吸收来自基质的扩散氮，而不是来自水柱的氮。这种响应因流而异，并取决于环境氮的可用性。4. 两种速效氮源对不同基质的周生植物生物量影响不显著。尽管如此，我们发现两种氮源对水柱吸收氮的影响存在差异。NH4-N似乎是NDS上外围植物生长的首选氮源。5. 研究结果表明，尽管水管理人员很少考虑到河岸带对光照有效性的影响，但在控制人类活动引起的富营养化效应方面，它可能比营养物质更重要。最后，我们的研究结果证实，在检查人类改变的河流中的N保留时，不仅要考虑浓度的增加，而且要考虑化学计量失衡。
Summary 1. Nutrient diffusing substrata (NDS) were used to determine the relative importance of nutrients and light as potential limiting factors of periphyton biomass and nitrogen (N) uptake in Mediterranean streams subjected to different human impacts. The nutrients examined were phosphorus (P) and N, and we also further differentiated between the response of periphyton communities to N species (i.e. NO3-N and NH4-N). To examine the effect of light and nutrients on periphyton biomass, chlorophyll a accrual rates on NDS located at open and closed canopy sites were compared. The effect of nutrient availability on periphyton uptake was measured by 15N changes on the NDS after NO3-15N short-term nutrient additions. 2. Results show that light was the main factor affecting algal biomass in the study streams. Algal biomass was in general higher at open than at closed canopy sites. Nutrient availability, as simulated with the NDS experiments, did not enhance algal biomass accrual in either of the 2 light conditions. 3. In the control treatments (i.e. ambient concentrations), periphyton NO3-N uptake rates increased and C : N molar ratios decreased consistently with increases in N availability across streams. NO3-N uptake rates were altered when ambient N concentrations were increased artificially in the N amended NDS. Periphyton assemblages growing on N enriched substrata seemed to preferentially take up N diffusing from the substratum rather than N from the water column. This response differed among streams, and depended on ambient N availability. 4. Periphyton biomass was not significantly different between substrata exposed to the two forms of available N sources. Nonetheless, we found differences in the effects of both N sources on the uptake of N from the water column. NH4-N seemed to be the preferred source of N for periphyton growing on NDS. 5. Results suggest that the effect of riparian zones on light availability, although seldom considered by water managers, may be more important than nutrients in controlling eutrophication effects derived from human activities. Finally, our results confirm that not only increases in concentration, but also stoichiometric imbalances should be considered when examining N retention in human altered streams.