夏季南海西部今生颗石藻

首次报道了南海西部上层水体今生颗石藻的物种组成、群落结构和分布。根据2007年9月在南海西部海域(11°—15°N,110°—114°E)32个站位采集的200m以浅208个颗石藻样品在偏光显微镜下的分析结果,研究了该海域颗石藻群落特征,并进行了颗石藻与环境因子的典范对应分析(CCA)。调查区共发现20种今生颗石藻,其优势物种为赫氏艾密里藻Emiliania huxleyi(Lohmann)Hay et Mohler、大洋桥石藻Gephyrocapsa oceanica Kamptner、深水花球藻Florisphaera profunda Okada et Honjo、纤细伞球藻Umbellosphaera tenuis(Kamptner)Paasche和艾氏桥石藻Gephyrocapsa ericsonii McIntyre et Bé。本次调查中,今生颗石藻的细胞丰度在2.97—32960.06cells/L之间,平均值为3340.75cells/L。整个研究海域中,今生颗石藻的分布呈现出一定的团块分布现象,调查区大部分站位均是赫氏艾密里藻和大洋桥石藻占有较高的相对细胞丰度,这两种藻的分布刻画了整个今生颗石藻群落在调查区的分布,它们多分布在50m和75m水层,且集中在西北部和西南部,水柱积分颗石藻平面分布也是如此。与以上两种藻的分布不同,深水花球藻则多分布于50m以深至200m,特别是50—75m水层的西北和东南部海域,而纤细条伞球藻则多集中在调查区25m水层的北部海域。

Production of dimethylsulfide and acrylic acid from dimethylsulfoniopropionate during growth of three marine microalgae

We measured the concentrations of dimethylsulfide(DMS),acrylic acid(AA),and dimethylsulfoniopropionate(DMSP) during growth of three microalgae:Prorocentrum micans,Gephyrocapsa oceanica,and Platymonas subcordiformis.The DMSP,AA,and DMS concentrations in culture media varied significantly among algal growth stages,with the highest concentrations in the late stationary growth stage or the senescent stage.In the stationary growth stage,the average DMSP concentration per cell in P.micans(0.066 5 pmol/cell) was 1.3 times that in G.oceanica(0.049 5 pmol/cell) and 20.2 times that in P.subcordiformis(0.003 29 pmol/cell).The average concentrations of AA were0.044 6,0.026 9,and 0.003 05 pmol/cell in P.micans,G.oceanica,and P.subcordiformis,respectively,higher than the concentrations of DMS(0.272,0.497,and 0.086 2 fmol/cell,respectively).There were significant positive correlations between cell density and AA,DMSP,and DMS concentrations.The ratios of DMS/AA and AA/(DMSP+AA) in the three algae differed significantly over the growth cycle.In all three microalgae,the DMS/AA ratios were less than 25%during the growth period,suggesting that the enzymatic cleavage pathway,which generates DMS,was not the main DMSP degradation pathway.The changes in the DMS/AA ratio indicated that there was a higher rate of enzymatic breakdown of DMSP in the early growth period and a lower rate during senescence.In all three microalgae,the AA/(DMSP+AA) ratio(degradation ratio of DMSP) decreased during the exponential growth phase,and then increased.The variations in these ratios can approximately indicate the cleavage mechanism of DMSP at different stages of algal growth.

西太湖W1A钻孔钙质超微化石的发现及意义

首次报道西太湖Ｗ１Ａ钻孔钙质超微化石，这一发现为研究西太湖成因及演化增添了新的古生物资料。钙质超微化石在西太湖的发现，证明大约１１２８０年前的全新世早期，西太湖湖盆曾遭受海侵，形成海湾环境。