Inorganic ion concentrations in bodyfluids of marine invertebrates exposed to low salinity in the laboratory@en

Laboratory experiments were conducted in the climate chambers at GEOMAR Helmholtz Centre for Ocean Research Kiel in the time between March and November 2018. Experiments were designed to study the effect of long-term (1 month) exposure to low salinity in osmoconforming invertebrates. The study organisms (Asterias rubens, Mytilus edulis, Littorina littorea, Diadumene lineata, Strongylocentrotus droebachiensis and Psammechinus milliaris) were collected in Kiel Fjord, Eckernförder Bight or the Kattegat from spring to autumn 2018. Organisms were acclimated to climate chamber conditions for 1 week (under habitat salinity, 14˚C, constant aeration) and then subjected to salinity acclimation for 1-2 weeks until the final salinity treatment level was reached. Then different salinity treatments were maintained for 4 weeks. Water physiochemistry (temperature, salinity, pH, nitrite, nitrate, phosphate) was recorded frequently. After the experiment, samples were taken from seawater and body fluids to measure total osmolality (mosmol/kg) with an osmomat and inorganic ions (mmol/l). No body fluid samples were taken from Diadumene lineata as organisms were too small and volumes too low. Anions were measured with a novel protocol via ion chromatography, cations were measured via flame photometry.本实验于2018年3月至11月间，在基尔亥姆霍兹海洋研究中心（GEOMAR Helmholtz Centre for Ocean Research Kiel）的人工气候舱内开展。实验旨在探究渗透压顺应型无脊椎动物长期（1个月）暴露于低盐环境的效应。本实验所用生物包括多棘海盘车（*Asterias rubens*）、紫贻贝（*Mytilus edulis*）、滨螺（*Littorina littorea*）、纵条矶海葵（*Diadumene lineata*）、紫海胆（*Strongylocentrotus droebachiensis*）及马粪海胆（*Psammechinus milliaris*），于2018年春季至秋季采自基尔峡湾、埃克恩弗德湾或卡特加特海峡。实验生物先在人工气候舱环境中驯化1周（盐度维持其原生栖息地水平、温度14℃、持续曝气），随后进行1至2周的盐度驯化，直至达到预设的最终盐度处理水平。之后将各组生物置于不同盐度处理条件下持续培养4周。实验期间定期记录水体理化指标（温度、盐度、pH值、亚硝酸盐、硝酸盐及磷酸盐含量）。实验结束后，采集海水及生物体液样本，使用渗透压仪（osmomat）测定总渗透压（单位：mosmol/kg），并测定无机离子含量（单位：mmol/l）；其中阴离子采用新型实验方案通过离子色谱法测定，阳离子采用火焰光度法测定。由于纵条矶海葵个体过小、体液量不足，未采集其体液样本。