Superoxide dismutase measurements as a complement to tackle the responses of Cnemidocarpa verrucosa sp. A to sedimentation due to rapid climate change

Rapid regional warming causes glacial retreat and melting of ice caps along the West Antarctic Peninsula, in consequence, sediment discharge into marine coastal areas reduces food availability and impairs respiratory performance of benthic filter-feeders. Here we analyzed the response of a highly abundant Antarctic ascidian Cnemidocarpa verrucosa sp. A to experimental changes in sedimentation rates through enzymatic measurements: Caspase and Superoxide Dismutase. Experimental work was carried out at Dallmann laboratory, Carlini Station in Potter Cove (58°40'W; 62°14'S), South Shetland Islands, Antarctica; during the summer campaign 2015/2016. Animals were collected by SCUBA diving at 20-30 m water depth (58°39'37,86W; 62°14'6, 153S), placed in containers with seawater from the sampling site, and immediately transferred to the experimental facilities of the laboratory. Specimens were placed in a 100 L container after cleaning their tunics from large epibionts. Both species were kept in an open flow system with unfiltered natural seawater (0 ± 1 °C) directly pumped from the cove for ten days, to allow for recovery from sampling and acclimation to the experimental system. Thereafter, specimens (n=10) with similar body sizes (approximately 10cm high) were selected, and 1-2 individuals were placed randomly in six aquaria (8 L), with individual closed circulation systems (EHEIM universal 300 Water Pump (300l/h)) and a venturi to assure constant aeration inside the aquaria. The six aquaria were placed in a 90 L running seawater bath (open system) for the incubation experiments in order to keep constant temperature (1.76 ± 0.37 °C). Treatment was applied to three aquaria which consisted in applying a single pulse of 200 mg L-1 of sediment per experimental aquarium. The experiment was stopped when turbidity was no longer observed in the water (36 h after exposure). The control treatments were maintained in seawater without sediment addition. Sediment used for the treatment was obtained using a grab sampler at 20 m depth in Potter Cove, from the surface bottom sediments of the inner cove (around 15 m depth, close to the mouth of the major creek), dried at 70 °C and sieved through a 50 μm mesh, following the protocol of Torre et al. (2012). After exposure, animals were dissected on ice, branchial basket, mantle, and gut were separated and frozen at -80ºC. […]

快速的区域性增温导致西南极半岛的冰川退缩和冰盖融化，因此，沉积物排放至海洋海岸区域，降低了食物的可获取性，并损害了底栖滤食者的呼吸功能。在本研究中，我们对一种高度丰富的南极海鞘（Cnemidocarpa verrucosa sp. A）对沉积速率实验性改变的响应进行了分析：通过酶活性测量，包括半胱氨酸蛋白酶和超氧化物歧化酶。实验工作于2015/2016年夏季在南设得兰群岛波特尔湾的卡尔尼尼站Dallmann实验室进行；动物样本通过潜水收集于20-30米水深（58°39'37.86W；62°14'6.153S），置于装有采样点海水的容器中，并立即转移至实验室的实验设施。在清除大型附着生物后，标本被放置于100升容器中。两种物种在开放式流动系统中保持，使用未过滤的自然海水（0 ± 1 °C），直接从海湾泵送，持续十日，以使动物从采样中恢复并适应实验系统。此后，选取了身体大小相似（约10厘米高）的标本（n=10），并将1-2个个体随机放置于六个水族箱（8升）中，每个水族箱配备独立循环系统（EHEIM通用300升每小时水泵）和文丘里管，以确保水族箱内氧气供应的稳定性。六个水族箱被放置于90升流动海水浴（开放式系统）中，进行孵化实验，以维持恒定的温度（1.76 ± 0.37 °C）。实验组的水族箱中施加了200毫克/升的单一脉冲沉积物处理。实验在水中不再观察到浑浊度（暴露后36小时）时停止。对照组则维持在海水中，不添加沉积物。用于处理的沉积物采用抓斗式采样器在波特尔湾20米深度采集，从内湾的表层底泥（约15米深度，靠近主要溪流的河口）中获取，于70°C下干燥，并通过50微米网筛，遵循Torre等（2012）的方案。暴露后，动物在冰上解剖，分离鳃篮、外套膜和肠道，并冷冻于-80°C。