Community analysis of planktonic protozoa following exposure to dispersant only and physically and chemically dispersed crude oil with environmental data

This study involved a 7 day land-based mesocosm experiment within 120 gallon tanks placed in a temperature controlled water bath. The mesocosm set up is located at UTMSI, Port Aransas, Texas. Natural seawater was pumped from the shipping channel into each tank during an incoming tide to obtain natural plankton communities. Each tank had a gentle aeration system installed to provide mixing and ensure oxygenation levels remain consistent. The experiment was carried out between December 7th and 14th, 2016 during which three treatments were tested alongside a control. All treatments plus the control were tested in triplicate tanks. These treatments consisted of crude oil only at 10ppm, chemically dispersed crude oil at 10ppm (dispersant to oil ratio of 1:20) and dispersant only at the same concentration used in the 10ppm dispersed oil treatment (5µg/L). Samples were collected every 24hrs to analyze protozoan community alterations. Both live and preserved samples were analyzed via microscopy methods and Flow imaging cytometry. This allowed the examination of daily survival, mortality and potential recovery rates of protozoan species within conditions which best reflect ambient environmental conditions.本研究开展了一项为期7天的陆上中型实验生态系（mesocosm）实验，实验装置为置于控温水浴槽内的120加仑实验槽。该中型实验生态系装置设于德克萨斯州阿兰瑟斯港的UTMSI。实验于涨潮时段从通航水道抽取天然海水注入各实验槽，以获取天然浮游生物群落。每个实验槽均配备温和曝气系统，用于实现水体混合并维持溶解氧水平稳定。本实验于2016年12月7日至14日开展，共设置1组对照组与3组处理组，所有对照组及处理组均设置3个重复实验槽。3组处理组分别为：仅添加10ppm原油的实验组、10ppm化学分散原油实验组（分散剂与原油质量比为1:20），以及仅添加与10ppm分散原油处理组同等浓度（5μg/L）分散剂的实验组。每24小时采集一次样本，用于分析原生动物群落的动态变化。采用显微镜法与流式成像细胞计数法（Flow imaging cytometry）对活体样本与固定保存样本均开展检测分析。该实验设计可在最贴近自然环境的条件下，对原生动物物种的每日存活、死亡及潜在恢复速率进行检测评估。