WAMSI Node 1.1.3 - Perth soft sediment studies

Twenty-nine sites have been surveyed: 13 in Marmion Marine Park (one near the sewage outfall and the remaining forming transects across a depth gradient with 4 inner, 4 mid and 4 outer), 6 in Cockburn Sound (5 forming a transect along an anthropogenic stress gradient at the northern end and 1 at the southern end), 2 localities between these regions at City Beach and Hall Bank, 1 within the Swan River and 7 at Jurien Bay to the north. At each site, physical factors of bottom water temperature, depth, water column light attenuation and the structure of sediment such as presence of ripples, depth of anaerobic sand and compactness were recorded. In addition, a water column integrated sample was collected and chlorophyll a quantified. Five transects of 5x1m were established at each site, ten 30mm diameter cores to 50mm depth and three 150mm diameter cores to 100mm depth were randomly collected within the transect, and all macrofauna collected using a small rake to search the sediment. Macrofauna were identified, counted and weighed. The small cores were sectioned into 0-2cm and 2-5cm depths and the size fractions from all 10 relating to 1 transect pooled and subsampled: one was analysed for organic carbon and nitrogen and a second for benthic microalgae biomass as chlorophyll a. One of the large cores was dry sieved through a set of 15 sieves from 0.063 to 8.0 mm pore size to determine proportions of grain size. One of the remaining cores was washed through 9 sieves from 8.0 to 0.5mm and biomass of infauna of each size class determined and daily secondary production calculated.

本研究共调查了29个采样位点：其中13个位于马米恩海洋公园（Marmion Marine Park），含1个临近排污口的位点，其余12个沿深度梯度布设样带，分为近岸、中程、远岸各4个；6个位于科克本湾（Cockburn Sound），其中5个沿北端人为胁迫梯度设置样带，剩余1个位于南端；两区域之间的两处位点为城市海滩（City Beach）与霍尔岸（Hall Bank）；1个位于天鹅河（Swan River）境内；另有7个位于北部的朱里恩湾（Jurien Bay）。每个位点均记录了多项物理环境参数：底层水温、水深、水柱光衰减率，以及沉积物结构特征，包括波纹发育状况、厌氧砂层厚度与沉积物紧实度。此外，采集水柱整合样品并对叶绿素a（chlorophyll a）含量进行定量检测。每个位点设置5条5×1m的样带，在样带内随机采集10根直径30mm、深度50mm的沉积物柱样，以及3根直径150mm、深度100mm的沉积物柱样；同时使用小型耙具挖掘沉积物，采集所有大型底栖动物（macrofauna）。随后对大型底栖动物完成分类鉴定、计数与称重。将小型柱样按0~2cm和2~5cm两个深度层级进行分层，将对应同一条样带的10根小型柱样的同深度组分混合后分样：一份用于有机碳与总氮含量分析，另一份以叶绿素a为指标测定底栖微藻生物量。选取一根大型柱样，通过孔径0.063~8.0mm的15级筛网开展干筛分析，以测定沉积物粒度组成比例。剩余大型柱样中的一根经孔径8.0~0.5mm的9级筛网冲洗筛分，测定各粒径级的底内动物（infauna）生物量，并计算其日次级生产力。