2014年春末黄海中华哲水蚤(Calanus sinicus)的呼吸率与油脂积累

METABOLISM AND LIPID ACCUMULATION OF CALANUS SINICUS IN THE YELLOW SEA IN LATE SPRING 2014

春末是黄海冷水团中华哲水蚤(Calanus sinicus)度夏种群形成的关键时期。在此期间,中华哲水蚤C5期桡足类幼体(简称C5期)的油脂积累程度关系到种群能否顺利度夏。本文从呼吸率、油囊体积以及种群组成等角度,对春末黄海冷水团内外以及冷水团区表、底层的中华哲水蚤进行比较研究。结果表明,2014年5月底黄海冷水团初步形成,此时冷水团区中华哲水蚤C4和C5期幼体丰度占总体的62%—93%,种群处于度夏前的准备阶段。冷水团区C5期的平均呼吸率是近岸C5期的68%,同时冷水团底层C5期的油囊体积百分数是近岸种群的2.4倍。由此推测,冷水团区次表层较厚的温跃层(19—25m,0.3—0.5°C/m)以及冷水团的低温环境有利于C5期幼体降低呼吸消耗,进而增加油脂的积累。此外,冷水团区表、底层C5期的呼吸率相近,但底层C5期油囊体积百分数为表层的1.9—4.2倍,积累大量油脂的C5期偏向在冷水团底部活动。

Late spring is the key period for Calanus sinicus to prepare for over-summering in the Yellow Sea Cold Water Mass（YSCWM）, during which lipid accumulation at stage C5 copepodids（C5s） of C. sinicus would affect the success in over-summering. Oxygen consumption rates, oil sac volumes, and population composition of the C. sinicus were calculated to compare copepods inside and outside the YSCWM, as well as above and below thermocline in the YSCWM area in late spring. The YSCWM was formed as the thermocline developed in May 2014. The populations were dominated by C4 and C5 copepodids, being ready for over-summering. The proportion of C. sinicus at C5 s in the YSCWM area was 32% lower in metabolic rate and 1.4 times greater in oil sac volume than those in nearshore areas. Thus, the thick thermocline above the YSCWM（19—25m, 0.3—0.5°C/m） and the cold water inside the YSCWM would benefit the C5 s to increase lipid accumulation by reducing energy cost for respiration. In addition, the metabolic rates of C5 s above and below thermocline in the YSCWM area were similar, but the C5 s below thermocline had larger oil sacs, i.e., 1.9—4.2 times of those above thermocline. With large amount of lipid accumulation, C5 s preferred to stay in the bottom of the YSCWM.