武汉东湖颗粒悬浮物的结构与元素组成

STRUCTURE AND ELEMENTAL COMPOSITION OF DRY SESTONIN EAST LAKE, WUHAN

本研究于１９８９－１９９０对武汉东湖营养水平不同的二个湖区的颗粒悬浮物的干物质结构和元素组成进行了分析．综合平均值表明，浮游动物的现存量约为浮游植物的１／４，浮游动物群落以小型的原生动物和轮虫占优势．从年平均值来看，浮游生物的干重占颗粒悬浮物干物质的２．５—７．６％，浮游生物碳量占颗粒悬浮物碳量的４．０—９．８％；颗粒悬浮物的碳／氮比与一般浮游植物的比值相似，但明显大于多数浮游动物；颗粒悬浮物的碳与干物重之比约为一般浮游生物的３／４；颗粒悬浮物的灰分含量约为４５％，显著高于除硅藻以外的其它浮游生物。从数量上来看，有机碎屑是东湖生态系统颗粒悬浮物最重要的组成部分，而活体浮游生物只占颗粒悬浮物很小的一部分（＜１０％）；这意味着在东湖来自以浮游植物为核心的食物网的有机碎屑的形成速率显著大于有机碎屑的矿化速率．

The structure and elemental composition of dry seston were studied in 1989/90 at tWosampling stations with different trophic levels in East Lake.The annual average biomass ofzooplankton was ca.1/4 that of phytoplankton.The zooplankton communities were dominated by small protozoans and rotifers. On annual average, dry weight in living planktonconstituted 2.5-7.6% of the total dry seston,and plankton carbon only constituted ca.4.0-9.8 of the seston carbon;C/N ratio of the seston was near to that of phytoplankton,but obviously higher than most zooplankton;carbon/dry weight ratio was ca.3/4 that ofplankton; ash content of the seston(ca.45%)was remarkably higher than that ofphytoplankton with exception of diatoms.The present results indicate that organic detritus is quantitatively the most importantcomponent of the total seston in the ecosystem of East Lake, and living plankton constituteonly a small part of the seston(<10%),indicating that in the lake,the turnover rate of theorganic detritus from the food web dominated by phytoplankton is remarkably higher thanmineralization rate of the organic detritus.