Search

沉水植物和螺类都是水生生态系统的重要组成部分，两者的牧食关系也是水生食物网中重要的一环，而不同的基质类型可能会影响两者的生长和改变沉水植物对螺类牧食的防御策略.以耳萝卜螺（Radix auricularia）和苦草（Vallisneria spiralis）为对象，研究基质类型、螺类牧食对沉水植物的生长及防御策略的影响，以及基质类型及沉水植物对螺类生长和生理特征的影响.研究发现，螺类牧食和基质类型对苦草生长和元素特征具有显著的影响，存在螺类牧食时，泥沙基质和沙基质苦草的相对生长速率显著降低，泥沙、沙和泥基质苦草地上生物量分别减少了67.74%、58.58%和17.84%，根冠比分别升高了177.51%、217.23%和1.44%；且泥沙基质中苦草的叶片数显著低于无牧食组.不同基质类型下，牧食对苦草总碳含量无显著影响，但泥和泥沙组中，螺类牧食使苦草的总氮含量均显著降低，碳氮比均显著升高；沙基质下，螺类牧食使苦草总酚含量显著降低.基质类型对螺类的形态特征（除壳宽外）、生长及元素含量均无显著影响.总体来看，基质类型对耳萝卜螺牧食和苦草防御策略具有一定程度的影响，但对螺类的生长及元素特征基本无影响.本研究可以为牧食理论的研究提供基础数据支持，也可为沉水植被恢复、水生生态系统稳定提供参考，但基质类型对螺草牧食关系的长期影响，仍需进一步深入研究.

The phytoplankton of Lake Ulungur was investigated seasonally from November, 2006 to July, 2007. A total of 164 phytoplankton species (including a number of unconfirmed species) was detected, which belonged to 90 genera, 8 phylum. Among them, Anabaena bergii was a new record species of cyanophyta in Xinjiang Uygur Autonomous Region, and two species of bacillariophyta, Chaetoceros sp. and Thalassionema sp., belonged to marine algal. In each season, the phytoplankton composition was dominated by Chlorophyta and Bacillariophyta, secondly dominated by Cyanophyta, Euglenophyta, Xanthophyta, Chrysophyta, Cryptophyta and Pyrrophyta. The number of phytoplankton species was the highest in autumn (141 species), followed by the summer (128 species) and spring (121 species), the lowest in winter (95 species). There was an obvious seasonal characteristiscs for the dominant species. Raphidiopsis sinensia, Teraёdron minimum, Selenastrum minutum, Chlorella vulgaris and Synedra acus were dominant species in the whole year, while Synedra ulna could only be found in spring, summer and autumn. Kirchneriella contorta and Chlorella ellipsoidea dominated in summer, and Chlorococcum infusionum and Treubaria crassispina dominated in winter. The standing crop of phytoplankton peaked only in summer with a biomass of 6.77mg/L and the minimum biomass of 1.45mg/L occurred in winter. Compared with historical data, the phytoplankton composition had remarkable changes. The growth of green alga and diatom were most notable, while the number of the phytoplankton increased many fold in the past 30 years.

Daoguanhe Reservoir(30°52′N,114°59′E)situated in Wuhan, Hubei Province of China, is a mid- dle--sized hilly--lake reservoir built in 1968. X microlepis is the main fish and made up of 15% of fish product in the reservoir during 1985--1988. But the production of X microlepis declined in recent years, the fecundity of X microlepis from Daoguanhe Reservoir was studied for utilizing its resource sustainably during April to May 2001. The scales used as aged material. The indices were measured with the routine method. All data was analyzed with STATISTCA soft. Relationship between its' fecundity and indices imitated with 8 kinds of mathematic expressions. One hundred and ten specimens were colleted belonging to the age of 2~+ -- 5~+. Relationship between its' absolute fecundity(F) and body length(L), body weight(W) and age(A) could be expressed with the linear, logarithmic and exponential equation, respectively. Relationship between relative fecun- dity per centimeter(F_L) and body length, body weight and age could be described using the hyper- bolic, logarithmic and exponential equation, respectively. The equations(p 0. 01) as follow: F= -13. 414 + 0. 756 L R~2= 0. 8786 F_L= -1. 459 + 0. 521 lnL R~2= 0. 7664 F= -29. 322 + 6. 326 lnW R~2= 0. 8692 F_L= -0. 712 + 0. 168 lnW R~2= 0. 7626 F= 1. 012 A~(1.266) R~2= 0. 7877 F_L= 0. 0666 A~(0. 882) R~2= 0. 6824 The number of telative fecundity per gram mainly ranged from 150--250 and averaged 212. Mul- ti--regressive analyses showed its absolute fecundity and relative fecundity per centimeter were sig- nificant related with body weight and maturing coefficient, and relative fecundity per gram(F_W) only with maturing coefficient: F= -2. 846 + 0. 0192 W + 0. 216 GSI, (n= 110, H= 0. 9182, p 0. 00l) F_L= -0. 504 + 0. 000456 W + 0. 00942 GSI, (n=110, R~2= 0. 8553, p 0. 001) F_W= 78. 336 + 8. 415 GSI, (n = 110, R~2= 0. 4104, p 0. 001)