Temporal dynamics of invertebrate and aquatic plant communities at three intermittent ponds in livestock grazed Patagonian wetlands

Ponds are recognized worldwide as biodiversity hotspots; nevertheless in Patagonia studies are still needed that reveal the composition and status of their communities. This paper analyses the temporal patterns of aquatic invertebrates and assesses the environmental factors that best predict the variation in community structure at three small intermittent ponds, subjected to ranching practices (summer stocking) in the Patagonian steppe. Variables identified as important in structuring community assemblages were related to environmental conditions (rainfall and water temperature), chemical features (conductivity and pH) and biotic factors (macrophyte coverage). During the connected phase only a small number of invertebrate species were present, in contrast to the 11 taxa that were frequent and abundant during the isolated period (Eucyclops chilensis, Hyalella curvispina and Rhionaeschna sp. were dominant). In this sequence the submersed Myriophyllum quitense and Lilaeopsis macloviana played a crucial role offering habitat and food resources. The present study provides valuable information that can contribute to minimizing the environmental damage and the development of strategies for the conservation of Patagonian wetlands.     

明清时期广西水利建设研究

明清时期广西特别重视水利建设。明清政府充分利用广西丰富的水资源和有利的地形,对灵渠、相思棣、陂塘、堰坝等进行多方面的修整,使广西的水利建设达到一个高峰期。     

稳定塘多池结构对藻类生长的影响

以模拟实验论论了多池稳定塘能够降低出水藻类，从而改善出水的卫生条件和透明度。进一步的研究表明，四池结构塘的出水保证率(藻类浓度100mg／1)达75％，是同容积单池塘的3倍。     

鮸状黄姑鱼人工繁殖与育苗技术的研究

鮸状黄姑鱼人工繁殖与育苗技术的研究表明：在网箱内培育3龄以上的亲鱼经激素诱导后可在网箱内自然产卵;催产激素LHRH-A和HCG,催产率达到100％;效应时间公36—40h之内;受精卵在水泥池充气孵化,平均孵化率为85．7％。在水泥池培育仔鱼的平均成活率为52％-75％,培育稚鱼的成活率为35％-45％,培育幼鱼的成活率为11％：使用土池培育早期仔鱼,15d仔鱼,22d稚鱼和27d稚色的成活率分别为8％,19％,30％和45％。在盐度30、水温24．2℃的条件下,从受精卵到孵化出苗需要23h30min,在试验期间海水盐度为20-34,水温18—28℃,DO6．5mg/L以上,pH值为8—8．5。