Fine transported organic matter collected from mainstem Big Creek, Middle Fork Salmon River, Idaho, USA (2010-2011).

We sampled transported organic matter in Big Creek mainstem monthly from December 2010 to March 2011. During each month, transported organic matter was collected during 3 time periods (morning, mid-day, and night) for a 24 h period to encompass diel variability. Each month, fine (<1 mm, >= 53 µm) transported organic matter (FTOM) was collected from the thalweg for 1 - 4 h. Fine transported organic matter (FTOM) was collected mechanically by pumping river water through a hose attached to a fencepost. The intake was surrounded by a 1-mm mesh and was positioned in the thalweg at c. 0.6 total depth. The water was then pumped to the shore and into 53-µm mesh net. At the end of each sampling period, FTOM nets were removed and rinsed with filtered river water. FTOM was sub-sampled (20 - 50 mL), filtered onto pre-combusted (400 °C for 30 min) and pre-weighed glass-fiber filters (0.7 mm), and frozen immediately. FTOM samples were analyzed for chl-a concentrations and not for AFDM. FTOM filtered sub-samples were used to quantify chl-a concentrations. Based on standard methods (APHA, 1998, Davis et al. 2013), filters were analyzed for chlorophyll-a (chl-a, measure of algal pigments and index of living primary producers). Filters were extracted in methanol for c. 12 h, analyzed for chl-a with a spectrophotometer and corrected for phaeophytin.

本研究于2010年12月至2011年3月期间，每月对大溪主河道中的输运有机质（transported organic matter）进行采样。每月均开展24小时采样以覆盖昼夜变化，采样时段分为清晨、正午与夜间三个阶段。每月均从河道深槽（thalweg）处采集粒径介于53 μm至1 mm之间的细粒输运有机质（fine transported organic matter, FTOM），采样时长为1至4小时。细粒输运有机质（FTOM）通过机械抽水方式采集：将连接于栅栏柱的软管伸入河水进行抽水。采样入口处包裹1 mm孔径筛网，置于河道深槽内约为总水深0.6倍的位置。随后河水被抽送至岸边并注入53 μm孔径的滤网中。每个采样时段结束后，取下FTOM滤网并用过滤后的河水进行冲洗。将FTOM进行20至50 mL的分样，随后过滤至预先经400℃灼烧30分钟并预称重的玻璃纤维滤膜（0.7 mm）上，并立即冷冻保存。FTOM样品仅用于分析叶绿素a（chl-a）浓度，不开展灰分干重（AFDM）检测。分样过滤后的FTOM用于定量检测chl-a浓度。依据标准方法（APHA, 1998; Davis等, 2013），对滤膜进行叶绿素a（chl-a，藻类色素的表征指标与活体初级生产者的丰度指数）分析。将滤膜置于甲醇中萃取约12小时，随后使用分光光度计检测chl-a浓度，并针对脱镁叶绿素进行校正。