象山港人工鱼礁区的网采浮游植物群落组成及其与环境因子的关系

Abstract

Xiangshan Bay(121°25′—120°00′E,29°05′—29°46′N),located on the east coast of China,is a long semi-enclosed bay with slow rate of water exchange.As one of the most important economic and aquaculture base in Zhejiang province,Xiangshan Bay has confronted a series of ecological challenge such as the development for coastal power plant,industrial construction,tidal flat reclamation and over-fishing.In order to restore the damage environment of Xiangshan Bay,the local government has begun to settle 230 concrete reefs(a total of 5000 air cubic meters) successively near the Baishi Island since 2008. Most researches so far focused on the artificial reef itself(e.g.body design,settlement area,pavement method and management) and its influence on the water quality,attachment organisms,benthos and fishery resource.However,report about the effects of artificial reef on phytoplankton is rare.Actually,the phytoplankton,as the basic and essential part of food chain,is very important for the ecological assessment and the community of phytoplankton should be taken into consideration of the artificial reef effects on the ecological restoration and fishery resource recovery. This paper represents the seasonal community composition of net-phytoplankton in artificial reef areas and their adjacent waters in Xiangshan Bay.The net-phytoplankton samples were collected in January(winter),April(spring),July(summer) and November(autumn) 2010,and a total of 8 phyla,74 genera,and 220 species were found,mainly including 168 diatom species and 38 dinoflagellate species,and other rare species such as Cyanophyceae,Chlorophyceae,Euglenophyceae,Chrysophyceae,Cryptophyceae and Xanthophyceae.The phytoplankton abundances in spring,autumn and winter(67.85,65.88 and 56.77×104 Cells/m3,respectively) were significantly higher than those in summer(7.19×104 Cells/m3).Coscinodiscus jonesianus,Cerataulina pelagica,Chaetoceros lorenzianus and C.lauderi were the main dominant species,especially C.jonesianus was the absolute dominant species in spring and winter.Both the phytoplankton community parameters(abundance,chl a concentration,species number,Shannon-Wiener diversity,Pielou evenness and Margalef richness index) and the environmental variables(temperature,salinity,transparency,pH value,DO,suspended solids,DIN,PO4-P and SiO3-Si levels) are seasonally different significantly(P 0.001) but no obvious difference between the artificial reef and control areas is found.The similar seasonal and spacial distributions of net-phytoplankton community are also shown by the results according to the clusters,multidimensional scaling and similarity analysis.Therefore,the artificial reefs at present have no significant influence on community composition of net-phytoplankton.It could be speculated that(1) the total scale(only 230 concrete reefs with a total of 5000 air cubic meters) and settle time(since 2008) of artificial reefs in this area are still not large and long enough to reflect the ecological effects;(2) the control area is close to the reef area,and the sampling stations are near the islands,so the influences of current and island effect on phytoplankton may overwhelm the influence of reefs.Canonical correspondence analysis(CCA) showed that temperature,nutrition(DIN and PO4-P),salinity and suspended solids were the main factors influencing net-phytoplankton community in turn.