Study on the dominant species of Pteropoda in East China Sea

Based on the data of four seasonal marine surveys in the East China Sea (23°30′–33°N, 118°30′–128°E)during 1997–2000, the author studied the ecological characters of dominant Pteropoda species in the area. Results showed that there were five dominant Pteropoda species, more in summer, less in autumn and even in other seasons. These species, though belonging warm water species, can be categorized into two dif- ferent groups in habitability. The first group was adapted in summer and autumn, including Creseis acicula, Desmopterus papilio and Creseis virgule, while the second group in winter and spring, represented by Limacina trochiformis and Agadina syimpsoni. The first group was more abundant than the second one. Besides, the first group contributed more to the Pteropoda abundance having higher occurrence frequency and aggregation intensity than the second. In horizontal distribution, the first group species reside in near- shore, and they could migrate to shallow place near estuary and aggregated in high density, while the second one was different: lower abundance, less occurred and aggregated because they were halophilic warm water species, and they were usually abundant in offshore area.

Identification of a marine woloszynskioid dinoflagellate Biecheleriopsis adriatica and germination of its cysts from southern Chinese coasts

A strain of small-sized dinoflagellates, isolated from the culture of sediment incubation collected from the coastal areas in southern China, has been identified under microscopical observation and r DNA sequence. Surface sediments from two sea areas in the southern Chinese coastal waters were incubated for 20 and 40 days, and germinated vegetative cells were observed. The cells were identified as species in the Suessiaceae based on the morphological characteristics, ultrastructural features of the cell, as well as its swimming behavior. The studied strain clusters into a well-supported clade together with six sequences of Biecheleriopsis adriatica in the phylogenetic tree based on the large subunit（LSU） rDNA sequence. Therefore, the strain has been identified as B. adriatica based on morphological observation and phylogenetic analysis. B. adriatica was the dominant dinoflagellate species in the germinated phytoplankton community from both sea areas,which contributed 50%–83% to the total germinated dinoflagellates averagely. However,B. adriatica has not been reported in previous phytoplankton surveys, and was probably ignored or misidentified due to its small size and thin wall. The frequent and abundant occurrence of B. adriatica in the germinated phytoplankton community of many sea areas of the southern Chinese coastal waters suggests its wide and abundant distribution in these sea areas.

Alkaline phosphatase activity in the phosphorus-limited southern Chinese coastal waters

Three fractions of alkaline phosphatase activity(APA),including phytoplankton APA(phyto-APA),bacterial APA(bact-APA),and free-APA,were examined in the sea surface microlayer(SML)and the subsurface water(SSW)from Daya Bay,Guishan Island,and Guanghai Bay of southern China.Relationships between APA and environmental parameters were analyzed.The growth of phytoplankton was significantly limited by dissolved inorganic phosphorus(DIP)in the three sea areas,especially in Daya Bay.TotalAPA ranged between 1.41 and 35.26 nmol/L/hr,and the highest value was found in Daya Bay.The increased APA in Daya Bay was the result of the increase of phytoplankton biomass and the response of phytoplankton to P limitation.Phyto-APA was the main contributor in Daya Bay,while phyto-and free-APA co-dominated in Guishan Island and Guanghai Bay.Bact-,phyto-,and total-APA showed a significant inverse power function relationship with DIP,and 0.2μmol/L was the threshold for DIP on particulates and totalAPA.Pearson correlation analysis suggested that DIP limitation together with high N levels enhanced APA.High water temperature and freshwater input accelerated APA as well.Principal component analysis clearly separated samples from the three sea areas,as well as from the SML and the SSW,which indicated the differences in environmental parameters and APA levels.Our results highlight the influence of phosphorus limitation and environmental parameters on APA.