泉州湾水域浮游植物群落的昼夜变化

对福建省泉州湾口、大坠岛以北水域的浮游植物群落作了准同步昼夜连续观测,观测时间分别在2001年11月至2002年8月内的秋(11月)、冬(2月)、春(5月)、夏(8月)季大潮期.结果表明,该水域的叶绿素a生物量(以下简称生物量)受湾内高生物量的影响在潮汐作用下出现波动,高潮期出现低生物量,低潮期出现高生物量.靠近内湾的站位生物量大于湾外的站位;底层水体中的生物量普遍大于表层,底栖硅藻成为生物量变化的重要部分.调查海区生物量呈现昼夜节律变化,生物量白天高于夜间.进一步的分析表明,在潮汐和昼夜变化综合作用下,浮游植物的群落结构发生相应变化,白天的多样性指数低于夜间,浮游植物昼夜群落的不相似度很高.群落中一些种类如中肋骨条藻白天大量增殖,出现较高的优势度,昼夜平均密度比值达到9,变化节律明显.研究认为,尽管海区潮汐和流向左右着生物量变化,浮游植物的生态学过程如细胞增殖、再悬浮、扩散等过程在昼夜生物量变化中仍产生较大作用.

Phytoplankton diel rhythm in the waters of Quanzhou Bay in Fujian, China

Twenty-four hour observations with three hour interval on the phytoplankton diel-rhythm at three stations in the north opening of Quauzhou Bay of Fujian were conducted seasonally from autumn of November in 2001,winter of February,spring of May and summer of August in 2002.The results show that chlorophyll a varied with tidal currents with higher biomass appeared at low tide period and lower biomass during the high tide period.Chlorophyll a was in general higher at the station in the side of inner bay than the outer ones,showing a high to low gradient of phytoplankton biomass from the inner bay to the outer.In the other hand,higher biomass was mostly found at the bottom water layer other than the upper water layer,where the biomass had partly contributed by the suspended benthic microalga,such as Paralia sulcata.Further analyses indicated that phytoplankton community changed in its structure with lower biodiversity index in the daytime than in the night.The dissimilarity of the phytoplankton communities between day and night was as high as 9,exhibiting an evident diel rhythm by some species,such as Skeletonema costatum that multiplies and dominates during the day.However,some benthic algae tended to have higher density during the night,suggesting the dispersion of alga cells by the currents at night after daytime growth.Cell multiplication,resuspension and dispersion process of phytoplankton should be considered as control factors in the diel rhythm though tidal currents could be the stronger factor.