Data for: Dark matters – contrasting responses of stream biofilm to browning and loss of riparian shading

Concentrations of terrestrial-derived dissolved organic carbon (DOC) in freshwater ecosystems have increased consistently, causing freshwater browning. The mechanisms behind browning are complex, but in forestry-intensive regions browning is accelerated by land drainage. Forestry actions in streamside riparian forests alter canopy shading, which together with browning is expected to exert a complex and largely unpredictable control over key ecosystem functions. We conducted a stream mesocosm experiment with three levels of browning (ambient vs. moderate vs. high, with 2.7 and 5.5-fold increase, respectively, in absorbance) crossed with two levels of riparian shading (70% light reduction vs. open canopy) to explore the individual and combined effects of browning and loss of shading on the quantity (algal biomass) and nutritional quality (polyunsaturated fatty acid and sterol content) of the periphytic biofilm. We also conducted a field survey of differently colored (4.7 to 26.2 mg DOC L-...

淡水生态系统中陆源溶解有机碳（terrestrial-derived dissolved organic carbon, DOC）的浓度持续升高，引发了淡水褐变现象。褐变的发生机制较为复杂，而在林业密集区域，土地排水会加速这一褐变进程。溪流沿岸河岸林的林业经营活动会改变冠层遮阴状况，该变化与褐变效应共同作用，预计会对关键生态系统功能产生复杂且难以预测的调控作用。本研究开展了一组溪流中宇宙（stream mesocosm）实验，设置三个褐变水平（自然背景组、中度组与高度组，其中中度组与高度组的吸光度分别较自然背景组提升2.7倍与5.5倍），并与两种河岸遮阴处理进行交叉搭配（70%光照削减与冠层开放），以探究褐变与遮阴丧失对周丛生物膜（periphytic biofilm）的数量指标（藻类生物量）及营养品质（多不饱和脂肪酸与甾醇含量）的单独与联合效应。本研究同时针对水色各异（4.7至26.2 mg DOC L-...）的溪流开展了野外调查。