Mesozooplankton Size-Fractionated Dry Weight, cruise PTS03, July 2016

Mesozooplankton samples were taken during the summer of 2016 between July 24-30 aboard R/V Point Sur using a mininess (BIONESS) tow system. Samples were taken from three nets, corresponding to three depth intervals (e.g. bottom, midwater, surface). Nets had 202 micrometer mesh size. Samples were transferred into a bucket immediately after retrieval and carbonated water was added to the sample to stop or avoid further 'net feeding' or regurgitation from individual zooplankton. Typically, each net sample was split in two aliquots using a Folsom Splitter aboard the ship. The 1/2 aliquot separated from the original sample was then split further in two subsamples: one was used to measure mesozooplankton dry weight and the other was processed for gut fluorescence. When samples were too thick, the initial sample was split into smaller aliquots (clearly indicated in the dataset). The corresponding aliquot was then size fractionated into five classes using sieves with meshes measuring: 0.212, 0.5, 1, 2, and 4.75 mm. Filtered seawater was used during sample split and size fractionation. Next, each size fraction was filtered onto pre-weighted nitex circles (2.5 mm diameter) with a 0.202 mesh size. Nitex circles were individually put in labeled plastic petri dishes and stored stacked inside sealed plastic bags to avoid moisture from getting in touch with the nitex before using them. After fractionation, each sample was poured onto a nitex circle using a filtering system aboard the ship, rinsed with DI water, transferred to its pre-labeled petri dish and frozen immediately after filtering. At the lab, the samples were dried up in an oven at 60 degrees Celsius over a period of 48 hours and weighted immediately after taking each sample out of the oven. The difference between the weight of the filter minus the weight after drying the sample constituted the mesozooplankton dry weight. These data will be used in combination with other mesozooplankton net data to study zooplankton processes in the river-dominated northern Gulf of Mexico.

2016年夏季7月24日至30日，研究人员搭乘“Point Sur”号科考船（R/V Point Sur），使用微型拖网（mininess/BIONESS）系统采集中型浮游动物（mesozooplankton）样本。本次采样共设置三张网具，分别对应底层、中层水体与表层三个深度水层，网孔孔径均为202微米。样本采集后立即转移至桶内，加入碳酸水以终止或防止浮游个体进一步发生网内摄食或吐食反流。通常情况下，每份网采样本会通过船上的福尔萨姆分样器（Folsom Splitter）分为两份子样本；其中一份原始子样本会再次拆分，分别用于测定中型浮游动物干重与开展肠道荧光检测。若样本量过大，则先将原始样本拆分为更小的子样本（数据集内已明确标注此类情况）。随后，对对应子样本使用孔径分别为0.212、0.5、1、2及4.75毫米的筛网进行粒径分级，共划分为5个粒径等级，分样与粒径分级过程均采用过滤海水作为介质。将每个粒径分级的样本过滤至预先称重的孔径为0.202毫米、直径2.5毫米的尼替克斯（Nitex）滤膜圆片上，每张滤膜圆片单独放入标注有信息的塑料培养皿中，堆叠存放于密封塑料袋内，以防在使用前受潮。在船上利用过滤装置将每份分级后的样本转移至尼替克斯滤膜圆片上，并用去离子水（DI water）冲洗，随后转移至预先标注的培养皿中，过滤完成后立即冷冻保存。返回实验室后，将样本置于60摄氏度的烘箱中烘干48小时，取出后立即称重；滤膜初始重量与样本烘干后的重量差值，即为中型浮游动物的干重。本数据集将与其他中型浮游动物网采数据结合使用，以研究以河流输入为主的墨西哥湾北部海域的浮游动物生态过程。