In situ nutrient assays of periphyton growth in a lowland Costa Rican stream
In situ nutrient assays of periphyton growth in a lowland Costa Rican stream
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哥斯达黎加低地溪流中附生生物生长的原位营养分析
作者：
C. Pringle;Pia Paaby;P. Vaux;C. Goldman
AbstractNutrient限制初级生产力的实验评估使用原位生物测定技术在Quebrada萨尔托，三级热带流排水的北方山麓中央山脉在哥斯达黎加。生物测定采用富含营养物质的人工基质，这些营养物质通过琼脂-砂基质缓慢扩散（Pringle & Bowers，1984）。多元比较的回归系数，描述叶绿素a的积累通过时间不同的营养处理，揭示了积极的微量营养素的影响（S）。营养素处理组合（Fe、B、Mn、Zn、Co、Mo、EDTA），添加和不添加硝酸盐和磷酸盐，与所有其他处理相比，表现出显著更大的叶绿素a积累（P < 0.05），支持在基质定殖14天后超过对照的3倍。主要营养元素（N或P）都没有产生显着的刺激，虽然N处理显示出超过50%的叶绿素a比对照后14天。同样，硅，EDTA，和Si + N + P处理没有表现出叶绿素a响应曲线，显着不同于对照。在实验期间，Salto中的平均NH 4-N和（NO2 + NO3）-N浓度分别为2.0 µM（28.6 µg · l−1）和7.2 µM（100.2 µg · l −1）。高浓度的PO 4-P（
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2019 - 06 - 22 00：00：00（
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= 3.0 µM; 94.0 µg · l−1），因此氮磷摩尔比较低
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= 4.7）。尽管潜在的N限制在系统中，N和P似乎是在增长饱和水平。这可能是由于微量营养素的限制和/或光的限制，在密集的阴影上游部分的流的附生生物生长。
AbstractNutrient limitation of primary production was experimentally assessed using an in situ bioassay technique in the Quebrada Salto, a third-order tropical stream draining the northern foothills of the Cordillera Central in Costa Rica. Bioassays employed artificial substrata enriched with nutrients that slowly diffuse through an agar-sand matrix (Pringle & Bowers, 1984). Multiple comparisons of regression coefficients, describing chlorophyll-a accrual through time for different nutrient treatments, revealed positive micronutrient effect(s). Micronutrient treatment combinations (Fe, B, Mn, Zn, Co, Mo, EDTA), supplemented with and without nitrate and phosphate, exhibited significantly greater chlorophyll-a accrual over all other treatments (P < 0.05), supporting over three times that of the control after 14-d of substratum colonization. Neither of the major nutrients (N or P) produced a significant stimulation, although the N treatment displayed ≃50% more chlorophyll-a than the control after 14-d. Similarly, Si, EDTA, and Si + N + P treatments did not exhibit chlorophyll-a response curves that were significantly different from the control. During the experiment, mean NH4-N and (NO2 + NO3)-N concentrations in the Salto were 2.0 µM (28.6 µg · l−1) and 7.2 µM (100.2 µg · l −1), respectively. High concentrations of PO4-P (
$$ar X$$
= 2.0 µM; 60.9 µg · l−1) and TP (
$$ar X$$
= 3.0 µM; 94.0 µg · l−1) were also found, and consequently low molar N:P ratios
$$ar X$$
= 4.7). Despite the potential for N limitation in the system, both N and P appear to be at growth saturating levels. This may be due to micronutrient limitation and/or light limitation of periphyton growth in densely shaded upstream portions of the stream.