Abundance, biomass, ingestion rates and daily ratios of Salpa thompsoni individuals sampled during POLARSTERN cruise ANT-XVIII/5b to the Eastern Belingshausen Sea

Distribution, density, and feeding dynamics of the pelagic tunicate Salpa thompsoni have been investigated during the expedition ANTARKTIS XVIII/5b to the Eastern Bellingshausen Sea on board RV Polarstern in April 2001. This expedition was the German contribution to the field campaign of the Southern Ocean Global Ocean Ecosystems Dynamics Study (SO-GLOBEC). Salps were found at 31% of all RMT-8 and Bongo stations. Their densities in the RMT-8 samples were low and did not exceed 4.8 ind/m**2 and 7.4 mg C/m**2. However, maximum salp densities sampled with the Bongo net reached 56 ind/m**2 and 341 mg C/m**2. A bimodal salp length frequency distribution was recorded over the shelf, and suggested two recent budding events. This was also confirmed by the developmental stage composition of solitary forms. Ingestion rates of aggregate forms increased from 2.8 to 13.9 µg (pig)/ind/day or from 0.25 to 2.38 mg C/ind/day in salps from 10 to 40 mm oral-atrial length, accounting for 25-75% of body carbon per day. Faecal pellet production rates were on average 0.08 pellet/ind/h with a pronounced diel pattern. Daily individual egestion rates in 13 and 30 mm aggregates ranged from 0.6 to 4.8 µg (pig)/day or from 164 to 239 µg C/day. Assimilation efficiency ranged from 73 to 90% and from 65 to 76% in 13 and 30 mm aggregates, respectively. S. thompsoni exhibited similar ingestion and egestion rates previously estimated for low Antarctic (~50°S) habitats. It has been suggested that the salp population was able to develop in the Eastern Bellingshausen Sea due to an intrusion into the area of the warm Upper Circumpolar Deep Water

2001年4月，德国科考团队搭乘“极星”号（RV Polarstern）极地科考船执行ANTARKTIS XVIII/5b号考察航次，前往别林斯高晋海东部海域，期间对浮游被囊动物汤氏海樽（Salpa thompsoni）的分布、种群密度及摄食动态开展了系统性调查。本次航次是德国对南大洋全球海洋生态系统动力学研究（SO-GLOBEC）野外作业的贡献项目。

本次调查共布设RMT-8网与Bongo网采样站位，其中31%的站位成功采集到汤氏海樽。RMT-8网采集样本中的海樽种群密度较低，最高仅达4.8个/平方米与7.4毫克碳/平方米；而Bongo网采集的样本中，海樽最大种群密度可达56个/平方米与341毫克碳/平方米。

在陆架海域记录到双峰型汤氏海樽体长频率分布，提示该海域近期发生过两次出芽繁殖事件，这一推测也通过单独体的发育阶段组成得到了验证。

群体型汤氏海樽的摄食率随口鳃腔体长从10 mm增长至40 mm时，由2.8 µg（色素）/个体/天提升至13.9 µg（色素）/个体/天，或由0.25 mg C/个体/天提升至2.38 mg C/个体/天，每日摄食量占体碳总量的25%~75%。

汤氏海樽的粪粒生产速率平均为0.08颗粒/个体/小时，且呈现显著的昼夜节律模式。体长13 mm与30 mm的群体型海樽日均排粪量介于0.6~4.8 µg（色素）/天或164~239 µg C/天。

体长13 mm与30 mm的群体型海樽的同化效率分别为73%~90%与65%~76%。

汤氏海樽的摄食与排粪速率与此前在南纬约50°的低纬度南极生境中估算得到的结果相近。有研究推测，本次调查区域受暖性环极深层水上层水团入侵影响，汤氏海樽种群得以在别林斯高晋海东部海域成功繁衍。