南海西北部夏冬季浮游介形类的分布及其影响因素

海洋浮游介形类(Ostracods)是一类分布较广的小型甲壳动物, 在海洋碳循环中起重要作用。目前国内海洋浮游动物采样常使用505μm网目孔径的浮游生物网, 从而导致个体较小的介形类被忽略。文章根据2006年7—8月(夏季)和2006年12月—2007年1月(冬季)在南海西北部海域分别使用网目孔径为505μm和160μm浮游生物网采集的样品, 比较不同网目所获浮游介形类种类和丰度的差异, 分析介形类种类和丰度的分布特征, 探讨环境因素对其时空分布的影响。160μm网目采集的浮游介形类种类和丰度均高于505μm。基于160μm网目数据分析浮游介形类群落结构: 1) 鉴定浮游介形类32种, 其种数由近岸向外海递增, 等深线100m以浅海域的种数显著高于100m以深海域(p<0.01); 2) 夏季浮游介形类的丰度高于冬季, 夏季丰度高值区主要出现在雷州半岛东部和琼东近岸, 显著高于外海(p<0.05), 冬季介形类丰度分布较为均匀; 3) 优势种针刺真浮萤(Euconchoecia aculeata)是近岸高丰度的主要贡献种; 4) 介形类种数与温度和水深呈显著正相关, 丰度与叶绿素a浓度呈正相关, 而与温度和盐度呈负相关。夏季琼东沿岸上升流和粤西沿岸流有助于浮游介形类在雷州半岛和海南岛东部近岸海域形成较高的丰度, 最高达1252个·m^-3。同时, 建议今后研究浮游介形类采用网目孔径小的浮游生物网进行采集以便全面评估其群落结构特征。     

Vertical distribution of smaller macrobenthos and larger meiobenthos in the sediment profile in the deep-sea system of Suruga Bay (central Japan)

The vertical distribution of benthic organisms in the sediment profile was studied using horizontally sliced sediments collected at five stations at depths from 115 to 472 m in Suruga Bay, central Japan. Using sieves of 1.0 and 0.5 mm mesh, benthic organisms were divided into two size classes, smaller macrobenthos (>1mm, <1g wet weight) and larger meiobenthos (1.0 mm0.5 mm). The maximum depth of vertical distribution of organisms in the sediment profile was expressed by the 95 % intercept of the cumulative % curve of the number of individuals drawn with respect to depth in the sediment. It has long been supposed that benthic animals are concentrated in the surface centimeters of sediment in the deep-sea system, and the present study clearly substantiated this. Most benthic organisms of both of these two size classes were concentrated in the upper 5 cm of sediment. The vertical distribution was almost always deeper in the case of smaller macrobenthos than for larger meiobenthos. However the difference could not be substantiated statistically since the number of samples was insufficient. The maximum depth indices of polychaetes were found to be significantly larger than those of crustaceans in the case of macrobenthos, while in the case of meiobenthos, the difference was not significant. The maximum depth index of all benthic organisms was positively and significantly correlated with water-depth and the possible cause for this relationship is discussed.