Journal Article Spatial distribution of Salpa thompsoni in the high Antarctic area off Adélie Land, East Antarctica during the austral summer 2008

12pp.69 - 78 , 2017-06
ISSN:18739652
Description
The salp Salpa thompsoni has the potential to alter the Southern Ocean ecosystem through competition with krill Euphausia superba. Information on the reproductive status of S. thompsoni in the high Southern Ocean is thus essential to understanding salp population growth and predicting changes in the Southern Ocean ecosystem. We carried out stratified and quantitative sampling from the surface to a depth of 2000 m during the austral summer of 2008 to determine the spatial distribution and population structure of S. thompsoni in the Southern Ocean off Adélie Land. We found two salp species, S. thompsoni and Ihlea racovitzai, with the former being dominant. S. thompsoni was distributed north of the continental slope area, while I. racovitzai was observed in the neritic zone. Mature aggregates and solitary specimens of S. thompsoni were found south of the Southern Boundary of the Antarctic Circumpolar Current, suggesting that S. thompsoni is able to complete its life cycle in high Antarctic waters during the austral summer. However, S. thompsoni was sparsely distributed in the continental slope area, and absent south of the Antarctic Slope Front, suggesting that it is less competitive with krill for food in the slope area off Adélie Land, where krill is densely distributed during the austral summer.
Salpa thompsoniはナンキョクオキアミEuphausia superbaとの競合関係が指摘されており、南大洋生態系に与える影響が懸念されている。そのため、南大洋高緯度域におけるS. thompsoniの生殖状態を把握することは、個体群動態や南大洋生態系の変化を予測するためには必要不可欠である。そこで2008年夏季の南大洋アデリーランド沖におけるサルパ類の空間分布と個体群構造を調べた。本研究ではS. thompsoniとIhlea racovitzaiが出現し、前者が優占した。S. thompsoniは陸棚斜面域北部に分布したのに対し、I. racovitzaiは沿岸域に出現した。S. thompsoni成熟個体は南極周極流の南縁よりも南側にまで出現しており、本種が夏季に南大洋高緯度域で生活史を完遂できることが示唆された。また、S. thompsoniは、E. superbaが多く分布する陸棚斜面域以南では非常に少なく、これら2種間には餌を巡る競合は殆どないと考えられた。

Number of accesses :  

Other information