Distribution And Germination Of Phytoplankton Resting Spore In Sediments From Typical Chinese Coastal Waters

Annual survey of phytoplankton resting spore in surface sediments and environmental factors was carried out in Daypeng Bay and Daya Bay,from April 2007 to March 2008.Sieved sediments between 20 and 125μm were incubated at 25℃for 20 d and 40 d.Five sediment cores about 15～40 cm in length were collected from the Changjiang River Estuary and adjacent waters in April and May 2005 to investigate the vertical distribution of dinoflagellate resting cysts.The purpose of this study is to understand the effects of resting spore on phytoplankton community,and to provide basic data for the mechanism of HAB Occurrence.A total of 83 types belonging to 47 genera of resting spores were identified during the annual survey of surface sediments from Dapeng Bay and Daya Bay. Fify-one dinoflagellate cysts were observed,and 29 types diatom resting spore or resting cell were analyzed.97 phytoplankton taxa(including speicies and varieties) were identified in germinated phytoplankton,including 50 diatom species,35 dinoflagellate species and other 12 ones.Scrippsiella trochoidea,Alexandrium.spp,Cochlodinium.spp were main HAB species in germinated phytoplankton and resting spore.Other species such as Hetereocapsa.spp,Pyrodinium bahamense,Gyrodinium.sp,Ostreopsis lenticularis were observed in both sea areas,indicating the potential of harmful algal blooms of these species.The density of resting spore ranged from 217.1 cells/cm³ to 6764.2 cells/cm³,with an average of 1337.9 cells/cm³.The cell number of germinated phytoplankton was from 0 cells/cm³ to 470660.6 cells/cm³ with averages of 16331.0 cells/cm³ and 17438.1 cells/cm³ respectively after 20 d and 40 d inoculation.The diversity and abundance of resting spore and germinated phytoplankton were generally higher in Daya Bay than those in Dapeng Bay.Rich diversity of dinocyst was observed in sediments from the Changjiang estuary and adjacent waters.46 different cyst morphotypes,representing 15 genera and 6 groups,were identified in this study.There were 19 autotrophic species and 27 heterotrophic ones.The results showed that the distribution of cyst was greatly influenced by complicated current system and environmental aspects in Changjiang estuary.Cyst abundance was low,with an average of 366.2 cysts·g^-1,and no regular pattern was observed in vertical profiles of cyst distribution in all sampling stations. Cyst species richness in Zhoushan Island area was higher than other sampling stations. Cyst of Scrippsiella trochoidea dominated in autotrophic cyst assemblages,with the average percentages from 17.0%to 28.9%.Cysts in genus Protoperidinium were predominant in heterotrophic group with average percentages ranging from 29.5%to 53.6%.Cysts of Alexandrium.spp distributed widely in all stations,but the abundance was low,with the maximum concentration of 68.1 cysts·g^-1.