Nansi Of Macrobenthos Community Structure And Succession Laws

According to the investigation on macrozoobenthos of Nansi Lake in a full year, this thesispreliminary deals with analyzing the species number, standing crop, dominant species andfunctional feeding groups, and its Spatio-temporal variation. Compared with previous studies,succession of community structure of macrozoobenthos and its impact factors were explored. Inaddition, Water quality of Nansi Lake was also assessed using Shannon-Weaver index, Pielouindex, Margalef index and Simpson index. Those results can provide scientific information forconservation of hydrobios diversity and evaluation of ecosyterm health caused by theSouth-to-North Water Transfer Project. The main results show as follows:1A total number of40species were identified, of which,7species were oligchaetes,10species were mollusks,17species were insects, and others were6species. The number ofspecies in Weishan Lake was the largest among four lake regions, Nanyang Lake was thesmallest. The number of species in winter was the most in four seasons, while that in summerwas the least.2The mean density and biomass of macrozoobenthos in the Nansi Lake were1103ind/m2and82.09g/m2respectively. The average density and biomass of oligchaetes in the Nansi Lake were232ind/m2and0.48g/m2respectively; The average density and biomass of mollusks were71ind/m2and74.02g/m2respectively; The average density and biomass of insects were884ind/m2and6.59g/m2respectively. The standing crop of both oligchaetes and mollusks in Dushan Lakewas maximal, and the standing crop of insects in Nanyang Lake was maximal. Except WeishanLake, the changes of macrozoobenthos density of Nansi Lake were mainly affected by density ofinsects which occupied more than a half of total density. The changes of macrozoobenthosbiomass of Nansi Lake were affected by biomass of mollusks which occupied more than90%oftotal biomass.3The density of macrozoobenthos in Nansi Lake was significantly the highest in winter thanthat of the other three seasons, but the biomass in autumn was highest. The density and biomassof macrozoobenthos in Nansi Lake in summer were lowest. The average density of oligchaetes inwinter was397ind/m2, which was the highest of the four seasons. The density of mollusks wasdominant in summer with120ind/m2, and the biomass was dominant in autumn with123.82g/m2. The density and biomass of insect were significantly highest in winter while lowest insummer.4The dominant species of macrozoobenthos were Propsilocerusi akamusi, Limnodrilushoffmeisteri, Bellamya aeruginosa and Alocinma longicornis in Nansi Lake. All of four specieswere always denfinite patchiness. The dominant species of macrozoobenthos were Bellamyaaeruginosa and Propsilocerusi akamusi in Nanyang Lake. The number of dominant species of macrozoobenthos in Dushan Lake was one more than that of Nanyang Lake, which wasLimnodrilus hoffmeisteri. Copared with DushanLake, Alocinma longicornis and Anodontawoodiana woodiana are also among one of the dominant species of macrozoobenthos in WeishanLake and Zhaoyang Lake respectively. Limnodrilus hoffmeisteri and Bellamya aeruginosa werethe common dominant species in Nansi Lake all the year round. Propsilocerusi akamusi was nota dominant species in summer although it was absolute dominant species in winter.5Gather-collector was the main component of functional feeding groups in Nansi Lakesystem, accounting for87.6%of the total density in full year. The biomass of scrapers was54.39g/m2and the biomass of filter collectors was21.08g/m2, accounting for65.9%and25.5%of thetotal biomass in full year respectively. Direct collectors were dominant in density in all four lakes,while in biomass, Filter collectors were dominant in number in Weishan Lake and ZhaoyangLake, but Scrapers were dominant in number in other two lakes at all seasons.6According to K-dominant curve and biodiversity indexes, biodiversity of macrozoobenthoscommunity was that Weishan＞Dushan＞Zhaoyang＞Nanyang. Biodiversity ofmacrozoobenthos community in winter was fewer than in summer and autumn.7The macrozoobenthos communities in Nansi Lake showed a clear medium similarity. Themacrozoobenthos species had obvious differences at all seasons. Long-term trends in the densityand species composition of macrozoobenthos in Lake Nansi were examined using data fromprevious researches. Species number and standind crop of macrozoobenthos was dcreasedsignificantly; the dominant species in the lake has changed form intoleranet group to tolerantgroup.8Water quality was assessed using Shannon-Weaver index, Pielou index, Margalef index andSimpson index. It showed that the lake on the whole was moderately polluted. The degree ofpollution was Weishan＞Zhaoyang＞Dushan＞Nanyang. Water quality in the south of NaisiLake was relatively better than that in the north of Nansi Lake, because it is close to Jining City.The lake was moderately polluted all the year round expect for winter. The biodiversity indexvalues in winter were relatively low. It was caused by Propsilocerusi akamusi, unconcerningabout water quality.