Preliminary Study On Ecology Of Zooplankton Resting Eggs In Typical Waters Of Pearl River Estuary And The Eastern Guangdong Coast

By in situ survey and laboratory enclosure experiments, we studied thephysicochemical parameters, zooplankton community structure of three differentmarine ecological region, which belong to Pearl River Estuary and Zhelin Bay,Shen’ao Bay of eastern Guangdong. We also studied distribution and recruitmentpotential of zooplankton eggs bank and of the environmental factors. This studyreveal benthic-pelagic coupling with biogeochemical process of zooplankton andresting egg in the Guangdong coastal waters, and enriched the contents of thezooplankton ecology. The main results were included as following:1. In Wai Ling Ding and Guishan island areas, Pearl river estuary, the dominantspecies of zooplankton were Paracalanus parvus, Acartia spinicauda, Euchaetaconcinna, Temora turbinate While in Zhelin Bay and Shen’ao Bay, the dominantspecies were P. parvus, Paracalanus aculeatus, Acrocalanus gibber, Parvocalanuscrassirostris, Centropages tenuiremis, Oithona brevicornis.2. The recruitment potential ranged from8.36×105to3.86×106eggs/m3inGuishan island area. In the abyssal zone outside the breakwater the recruitmentpotential was higher than inside the culture area and in the shoal waters outside thebreakwater. The distribution of copepods resting eggs was closely related to the waterdepth and sediment particle size, and hatching species mainly included Acartiaspinicauda and Centropages tenuiremis. In Wai Ling Ding island area, therecruitment potential ranged from5.03×105to2.96×106eggs/m3, and species wasmainly Acartia spinicauda. Resting eggs of rotifer ranged from7.17×104to9.56×105eggs/m3in the two areas, much less than copepod resting eggs, and mainly belongedto Synchaeta stylata and Trichocerca sp..3. In our hatching experiments, the recruitment potential of hatching undercontrolled incubators of zooplankton resting eggs was higher than that in situ hatchingwith screen or without screen condition. Limnoithona sp., Corycaeus sp., Tisbefurcata, Microsetella sp. only hatched under in situ hatching condition. The hatching durationof copepods resting eggs was short, which belonged to synchronous hatchingpattern. And it was affected by the anaerobic, sulfide condition and sedimentembedding. Statistical analysis showed that zooplankton recruitment potential underin situ condition was lower than that under controlled incubators.4. The horizontal distribution of zooplankton resting eggs was uneven in ZhelinBay and Shen’ao Bay of eastern Guangdong. The recruitment potential ranged from3.05×105to4.7×107eggs/m3. In the Zhelin open bay the recruitment potential washigher than that in Shen’ao Bay area and Zhelin inner bay. Species mainly belongedto Acartia spinicauda. Resting eggs of rotifer ranged from0.46×105to26.07×105eggs/m3, much less than copepod resting eggs, and were identified as Synchaeta sp..Statistical analysis showed that the distribution of zooplankton resting eggs wasmainly affected by zooplankton structure, water depth, and sediment size in ZhelinBay.5. The vertical distribution of zooplankton resting eggs exhibited obviousdifference. The active resting eggs appear only on the surface (1-3cm) in Zhelin innerBay, while the vertical distribution appear “3-tier system” in Shen’ao Bay. Therecruitment potential and hatch rate dropped with the increase of sediment depth.Recruitment potential rank as surface layer>intermediate layer>sublayer. Copepodand rotifer resting egg can occur as deep as50cm and38cm, respectively. suggestingcopepod resting egg has better resistance to the adverse evironment.6. In Guangzhou-Zhuhai section of Pearl River Estuary, the salinity of Yuzhudock, Humen Bridge, Nansha19Chong, fish pond of Nansha and Xiangzhou dockincreased sharply in turn. Zooplankton eggs bank mainly consisted of copepodsresting eggs, of which recruitment potential ranged from3.1×104to5.5×107eggs/m3.Fish Pond of Nansha and Xiangzhou dock had higher recruitment than others, and theresting eggs mainly belonged to Acartia sp. and Sinocalanus tenellus. On thecontrary,, recruitment potential mainly referred to rotifer in Yuzhu dock, which was3.1×105eggs/m3, mainly including Brachionus calyciflorus, B. angularis and B.caudatus, and belong to Epiphanes sp. in the rest of the study area. Statistical analysisshow that the recruitment potential influenced by the salinity in Guangzhou-Zhuhai section of Pearl River Estuary.7. The embryonic development of Acartia sp. and Sinocalanus tenellus wereobserved and record for the first time. According to the morphological changes, theembryonic development could be divided into five stages, i.e. blastula stage, gastrulastage, appendage anlage formation, embryo with eye pigment, and pre-hatching stage.The duration of embryonic developmentin Sinocalanus tenellus and Acartia sp. were38h and46h respecitively.