研究于2008年12月至2009年10月按季度对大通湖水质及软体动物资源监测,并通过纵向比较,探讨了集约化养殖对大通湖水域环境及软体动物群落的影响,以期为其渔业可持续发展提供理论依据。结果显示,大通湖水质全年呈碱性(8.62±0.07),具有较高的还原性[(?88.40±9.10)mv],属富营养水体。软体动物共计5科15种,梨形环棱螺(Bellamya purificata)、河蚬(Corbicula fluminea)和圆顶珠蚌(Unio doug lasiae)是主要优势种。软体动物平均密度和生物量具有明显的时空差异,时间上呈现由春夏季到秋冬季逐渐升高的趋势,空间上整体呈现由东北向西南逐渐递减的趋势。典范对应分析表明氧化还原电位、pH、溶氧、水深、电导率和水温与大通湖软体动物时空变化的关系最显著。与1960年相比,大通湖水体碱性显著增强(7.0—7.5 vs 8.4—8.8),电导率增加了9倍(0.25—0.27 vs 2.17—2.56 mS/cm),环境类型由氧化型转变为还原型。湖区喜好水草(白旋螺、光亮隔扁螺、萝卜螺)与流水生境(德氏狭口螺、湖沼股蛤、橄榄蛏蚌)的物种消失,软体动物优势种群呈现由双壳类向腹足类演替的特征。生境破坏和过度捕捞是大通湖软体动物资源面临的最大威胁,也是湖区渔业可持续发展所面临的核心问题。
Cadmium is a non-essential metal with a wide distribution that has severe toxic effects on aquatic animals. Changes in hematology and muscle physiology were examined in silver carp (Hypophthalmichthys molitrix) exposed to environmentally relevant levels of cadmium (0.01 mg L-1 ) for 96 h. Cadmium exposure induced significant increases in the red blood cell count, and in the plasma concentrations of cortisol, glucose, and lactate. This suggests that the dose of cadmium was sufficient to cause stress, possibly associated with impaired gas exchange at the gills. There were no changes in hemoglobin concentration or plasma protein concentration. Significant decreases in muscle energy fuels (ATP and glycogen), and increases in muscle lactate persisted until the end of the exposure period, respectively. The changes in muscle lactate and protein in silver carp differed from those observed in response to exposure of fish to cadmium and heavy metals in other studies. The study highlights the importance of selecting unpolluted release sites with suitable water conditions for the survival of newly released individuals for stock enhancement of the Xiangjiang River.
The frequency of algal blooms has increased in the mid and downstream reaches of the Xiangjiang River （Hunan, China）, one of the most heavily polluted rivers in China. We identified the bloom-forming species in a bloom that occurred mid-late September 2010. In addition, we determined the extent of metal bioaccumulation in the algae and measured the toxicity of the algae using a mouse bioassay. Water samples were collected at upstream （Yongzhou）, midstream （Hengyang）, and downstream （Zhuzhou, Xiangtan, and Changsha） sites. The dominant species was Aulacoseira granulata, formerly known as Melosira granulata. The heaviest bloom occurred at Xiangtan and Changsha, where the number ofA. granulata peaked at 1.3×10^5 filaments L-1 and chlorophyll a at 0.04 mg L-1. Concentrations of A1, Fe, and Mn were 4.4×10^3, 768.4, and 138.7 mg kg-1 dry weight in the phytoplankton. The bioaccumulation factor was 4.0×10^5, 7.7×10^5, and 3.2×10^3, respectively. The heavy metal Pb had the greatest tendency to bioaccumulate among the highly toxic heavy metals, with a concentration of 19.2 mg kg-1 dry weight and bioaccumulation factor of 9.6×10^3. The mouse bioassay suggested the bloom was toxic. The LD50 was 384 mg kg-1 and all surviving mice lost weight during the first 72 h after exposure. Our results demonstrate that blooms ofA. granulata in rivers contaminated with heavy metals pose a threat to freshwater ecosystems and human health. Thus, measures should be taken to control eutrophication and heavy metal pollution in such rivers.
LI JiePENG FuLiDING DongBoZHANG ShuBingLI DeLiangZHANG Ting
