Department of Biology, Idaho State University, Pocatello, Idaho, USA.
Environ Monit Assess. 1984 Mar;4(1):67-79. doi: 10.1007/BF01047622.
We conducted a series ofin situ experimental nutrient additions in two Idaho streams: Deep Creek, a desert stream located in Southeastern Idaho, and Big Wood River, situated in a mountainous region of Central Idaho. In both streams, a homogeneous reach was partitioned into almost identical channels. This allowed us to vary nutrient levels and measure algal response in experiments uncomplicated by differences in other factors.Ammonium nitrate was added to the treatment channels in Deep Creek. After nine days,Cladophora glomerata still predominated in both the control and treatment channels and algal biomass was not statistically different between the two. In the Big Wood River experiment significant differences in chlorophylla concentrations were not detected among three treatments of differing nitrogen enrichment and the control for both natural and artificial substrates. Also chlorophylla levels were not correlated with nitrogen concentrations, and the composition of algal communities remained similar among all treatments.We conclude that macronutrient enrichment of streams does not necessarily result in an increase in algal density or a change in algal community structure so long as other factors, which may limit the use of nutrients by algae, remain unaltered. Our results suggest that light, current velocity, and macroinvertebrate grazing may account for the failure of the periphyton to respond toin situ additions of nitrogen (and phosphorus) in our study streams.
深溪，位于爱达荷州东南部的一条沙漠溪流，和比格伍德河，位于爱达荷州中部的山区。在这两条溪流中，一个均匀的河段被分隔成几乎相同的通道。这使我们能够在不受其他因素差异影响的实验中改变营养水平并测量藻类的反应。深溪的处理通道中添加了硝酸铵。九天后，在对照和处理通道中，胶须藻仍然占优势，藻类生物量在两者之间没有统计学差异。在比格伍德河实验中，不同氮富集处理与对照之间在叶绿素 a 浓度方面没有显著差异，无论是天然还是人工基质。此外，叶绿素 a 水平与氮浓度无关，并且所有处理中藻类群落的组成仍然相似。我们得出结论，只要可能限制藻类利用营养物质的其他因素保持不变，溪流中的大量营养物质富集不一定会导致藻类密度增加或藻类群落结构发生变化。我们的结果表明，光、流速和大型无脊椎动物摄食可能是我们研究溪流中附着生物对原位添加氮（和磷）没有反应的原因。
