Diversity And Annual Variation Of Skeletonema (Bacillariophyta) In Xiamen Harbor Waters

Abstract In Chinese coastline waters, species of Skeletonema Greville is one of the mostimportant phytoplankton blooms causing species, which plays an important role in marineecosystems. We have analyzed612strains of Skeletonema species which monthly sampled fromXiamen Harbor waters in2010. Six Skeletonema were identified based on morphological diagnosticfeatures approached by Transmission Electron Microscopy (TEM) and the Nuclear-encoded LargeSubunit (LSU) rDNA techniques. Our results show that, Skeletonema costatum (Greville),Skeletonema.tropicum Cleve, Skeletonema dohrnii Sarno et Kooistra, Skeletonema ardens Sarno etZingone, Skeletonema grevillei Sarno et Zingone and Skeletonema menzelii Guillard, Carpenter etReimann were found in Xiamen Harbor waters, and annual variations of these six Skeletonemaspecies was also reported in this thesis. S. dohrnii is a winter-spring species dominant in watersamples and disappeared in summer whereas other species tend to appear in summer and autumn.S. costatum is the single species present throughout the year.We also cultured seven species of Skeletonema including Skeletonema pseudocostatumisolated in Daya Bay in different conditions of temperature,irradiance and N/P ratio.The results ofthe culture emperiment act in accord with the annual occurrence of Skeletonema. To assess thediversity and germination requirement of resting cells of Skeletonema, we sampled the surfacesediments as well as isolated resting stages and incubated them into cultures of different conditions.Except S. grevillei, the other five species were successfully generated or incubated by abovemethods, implying that these five species produce resting cells。The resting cells of S.dohrnii andS.costatum are able to germinate under the temperature of15℃t o30℃whereas S. menzelii andS.ardens can only be able to germinate over20℃。S.tropicum was proved to be able to germinateunder very low temperature(about16℃).Resting cells of S. costatum and S. tropicum were actuallyobserved in the sediment.