人工鱼礁对中小型浮游动物昼夜变化的影响

浮游动物有明显的昼夜垂直移动现象,这种生态习性会导致摄食浮游动物的某些鱼类昼夜垂直移动。为分析人工鱼礁对中小型浮游动物昼夜变化的影响,于2018年11月在防城港人工鱼礁区及附近海域进行了1个昼夜的中小型浮游动物采样,获取了14份样品。结果显示:(1)礁区和非礁区浮游动物种类组成相似度高、更替率低,且主要优势种相同,属于同一生态类型;(2)在人工鱼礁流场效应的作用下,礁区浮游动物的数量和多样性高于非礁区;(3)非礁区浮游动物数量的昼夜变化明显,呈明显的正弦曲线,以16:00数量最高,8:00最低,其垂直运动规律明显,可分为4:00～20:00的运动期和20:00～次日4:00的稳定期;(4)在礁体上方流速较快的水平层的阻隔作用下,礁区浮游动物数量始终处于波动状态,没有明显的昼夜垂直变化规律,在礁区上层保持较高的数量,可提升集鱼效果、促进生产力转换;(5)聚类分析和排序表明,礁区浮游动物为一个群落类型。而非礁区中小型浮游动物可分2个群落类型,一个是白天随浮游植物而上浮的以植食性种类为主要特征种的群落类型,另一个是晚上植食性种类下沉后以肉食性种类为主要特征种的群落类型。

Effects of an artificial reef on diel changes of micro- and meso-zooplankton

The apparent diurnal vertical migration of zooplankton leads to diurnal vertical migration of certain fishes that feed on zooplankton. In order to investigate the effects of an artificial reef on diurnal vertical migration of micro-and meso-zooplankton, we obtained 14 zooplankton samples from diurnal sampling in and outside an artificial reef area in the coastal Fangchenggang City, Guangxi Autonomous Region in November, 2018. The analysis showed that zooplankton compositions were quite similar between the artificial reef site and the control site, with the low species replacement rate and the same dominant species, indicating that the zooplanktons came from the same faunal assemblage. However, influenced by the flow-field effect of an artificial reef, zooplankton abundance and diversity were higher at the reef site than those at the control site. At the control site, zooplankton abundance showed apparent diurnal changes following a sinusoidal trend, with the highest abundance at 16:00 and the lowest at 08:00. There was apparent vertical migration between 4:00 and 20:00, while zooplankton abundance was quite stable from 20:00 to 4:00. At the reef site, due to the effect of horizontal fast flow field above the reef, zooplankton abundance fluctuated with time and no apparent diurnal vertical rhythm was observed. It is believed that higher zooplankton abundance above an artificial reef would enhance the reef''s fish-aggregating effect and promote the conversion of zooplankton productivity to fish. Cluster analysis and ordination of the 14 zooplankton samples identified one sample group for the reef site, but two sample groups for the control site, one being mainly composed of phytoplankton feeders following the upward shifts of phytoplankton during the daytime, the other being mainly composed of carnivorous species during nighttime after the phytoplankton feeders migrating downward.