The biomass, species composition and diversity of benthic diatom assemblages in mud-flat soils in Kalelia caTdel (L.) Dmce commu-ulfies with and without vegetation were stucrled seasonally at the Houyu Bayin Fudhlg City, Fujianth-ovhlce, China. Atotal of l03 taxa were identifed (including varieties). Eighty-fore-taxa were found in the mud-flat with vegetation and 74 taxa in the mud-flat with-out vegetation, while the biomass was large in January and April and decreased from July to October. The most abundant species in the mud-flat with vegetation are Nitzschia coccoTwiformis, Gyrosigma scaroides and N. fosciculata, compared with G. scaroides and N. obtusa var. scaelliformis in the mud-flat without vegetation. HighH'valuesat2sitesdmingallseasonssuggestthutdiatomassem-blages in the sediments of the Houyu Bay represent an original enviroiunent. Mulfi-dimensional scaling of diatom assemblages fi-ommud-flats with and without vegetation shows that a slight seasonal change and only a single association occur in the mangroves.

利用透射电镜对采自东黄海海域典型站位的微型硅藻（nanodiatom<20mm）进行了研究。观察到我国微型硅藻类的一个新记录属：微舟藻属Nanoneis R.E.Norris以及该属的一个新种：长微舟藻Nanoneis longta sp. nov.。该属的主要特征是：壳面两侧对称，具有不完全壳缝，壳面除中轴区外都有横肋纹或长室孔分布。本文描述该属的两个种，其中海斯微舟藻（Nanoneis hasleae R. E. Norris）为我国的新记录种，长微舟藻为新种，两种之间主要的区别特征是壳面外形、长宽比例以及壳面横肋纹的密度。并较详细地描述了该属种类的分类特征、生态习性和分布。

In a study of species composition of marine nanoplanktonic diatoms (<20tan) in water samples from the East China Sea and Huanghai Sea (Yellow Sea), four diatom species were identified by TEM as new records for China. They were Thalassiosira oceanica Hasle, Navicula Britannica Hustedt et Aleern, Nitzschia lhyi Fryxell and Synedra indica Taylor. Detailed description of the taxonomic characteristics with TEM photcgrapha of the four species and their ecological behavior and distribution is given in this paper.

2002年春季，在长江口附近海域典型赤潮高发区28个大面站位采集了53个样品，从中共鉴定出隶属于31个硅藻属的80个种和变种；其中种类多样性较高的属为圆筛藻属（Coscinodiscus），有17个种，斜纹藻属（Pleurosigma）,有8个种和变种；数量上较优势的种为柔弱拟菱形藻（Pseudo-nitzschia delicatissma），为3.48×103cells•L-1，占28.54%；具槽直链藻（Melosira sulcata），为1.43×103cells•L-1，占16.98%；尖刺拟菱形藻（Pseudo-nitzschia pungens），为0.71×103cells•L-1，占9.85%。它们在大部分站位中都有出现；柔弱拟菱形藻和尖刺拟菱形藻的高细胞密度区主要出现在1230E断面的站位，而具槽直链藻则主要出现在长江口的31～32°N断面的站位。浮游硅藻总细胞丰度变化于0.43×103～23.3×103cells•L-1，平均4.61×103cells•L-1；在123°E、30.5°N的DD15站位，无论表层还是中层,浮游硅藻总细胞丰度均最高（表层，1.85×104cells•L-1；中层，2.33×104cells•L-1）。从水平分布看，浮游硅藻呈不均匀分布态势，从垂直分布看，大部分站位的表层浮游硅藻丰度高于中层。

The extracellnlar dissolved organic carbon (DOC) and algal cell particfulate organic carbon (POC) of a marine nanoplanktonic diatom Chaetoceros sp. were determined in this study. The daily rhythm and the influence of light and temperature on the productim rate of DOC and POC were studied by growing the diatom under different laboratory controlled conditions of light and temperature. The results showed tlmt the production of DOC and POC varied with light and temperature and were generally higher at daytime than at night. Under culture conditions of 24L: OD light cycle and 3500 lx light intensity, the DOC and POC reached maximum (DOC: 17.27mgC/L; POC: 103.10mgC/L). While without light, they kept decreasing (DOC: 7.16-9.05mgC/L; POC: 37.71-51.14mgC/L). DOC and POC increased with temperature within the range of 16℃ to 300℃ (DOC: 7,45-12.66mgC/L; POC: 28.52-97.05mgC/L), and reached relatiwly higher value when the temperature was 25℃ to 30℃. It was found that generally about 10%-25℃ of the photosynthetic organic carbon was excreted into the culture solution as DOC. The relationship between the diatom biomass and the production rate of DOC and POC was also studied. Our results suggested that absolute production of DOC and POC was nearly linear with diatom biomass expressed either as cell density or as dried weight and had similar time-course tendency under diverse levels of light intensity and temperature. In general, we suggest that optimal environmental conditions for diatom growth and biomass increase will facilitate the increase of absolute production of POC and DOC. On the other hand, extreme environmental conditions are responsible for the high percentage of DOC excretion ahhough the absolute value of DOC is low.