Seasonal distribution of mesozooplankton in the upper 100 m of the northern Gulf of Aqaba in 2002 and 2003

The abundance and composition of the mesozooplankton were studied in the upper 100 m of the northern Gulf of Aqaba over a period of 22 months between February 2002 and December 2003. The samples were collected monthly with a Nansen net of 200 μm mesh size. The abundance of total mesozooplankton ranged between 245 and 3065 ind. m⁻³. Highest densities in 2002 were recorded in spring (March/April) and in autumn (October/November), while several peaks occurred in 2003 with maximum abundance in early summer (June/July). Copepods dominated the mesozooplankton community during the whole sampling period (~79%), followed by mollusc larvae (8%), appendicularians (2.5%) and chaetognaths (2.4%). Within the copepods, calanoids were predominant throughout the sampling period (41–83%). Cyclopoid copepods accounted for 17 to 59%, while harpacticoids occurred only in very low numbers (<1%). Within the calanoid copepods, Clausocalanidae, Paracalanidae and Acartiidae were abundant, accounting for 84 to 98% of the calanoids.

2002年2月至2003年12月的22个月监测周期内，研究人员对阿卡巴湾北部海域上层100米水体中的中型浮游动物（mesozooplankton）丰度与群落组成开展了调查研究。本次研究采用网孔孔径为200 μm的南森浮游生物网（Nansen net）进行月度采样。总中型浮游动物的丰度区间为245~3065 个·立方米⁻³。2002年的最高丰度密度出现在春季（3月/4月）与秋季（10月/11月）；2003年则出现多个丰度峰值，夏季初期（6月/7月）达到本次调查的最大丰度值。整个采样周期内，桡足类（copepods）均为中型浮游动物群落的优势类群，占比约79%；其次依次为软体动物幼虫（8%）、尾海鞘类（appendicularians，2.5%）与毛颚类（chaetognaths，2.4%）。在桡足类类群中，哲水蚤目（calanoids）为贯穿整个采样周期的优势类群，占比区间为41%~83%；剑水蚤目桡足类（cyclopoid copepods）占比为17%~59%，而猛水蚤目（harpacticoids）仅以极低丰度出现，占比不足1%。哲水蚤目中，亮羽水蚤科（Clausocalanidae）、小哲水蚤科（Paracalanidae）与纺锤水蚤科（Acartiidae）为优势类群，三者合计占哲水蚤类总丰度的84%~98%。