Methane in the Changjiang (Yangtze River) Estuary and its adjacent marine area: riverine input,sediment release and atmospheric fluxes

Dissolved methane (CH₄) was measured in the waters of the Changjiang (Yangtze River) Estuary and its adjacent marine area during five surveys from 2002 to 2006. Dissolved CH₄ concentrations ranged from 2.71 to 89.2 nM and had seasonal variation with the highest values occurring in summer and lowest in autumn. The horizontal distribution of dissolved CH₄ decreased along the freshwater plume from the river mouth to the open sea. Dissolved CH₄ in surface waters of the Changjiang was observed monthly at the most downstream main channel station Xuliujing (121o2′E, 31o46′N), which ranged from 16.2 to 126.2 nM with an average of 71.6 ± 36.3 nM. The average annual input of CH₄ from the Changjiang to the Estuary and its adjacent area was estimated to be 2.24 mol s⁻¹ equal to 70.6 × 10⁶ mol year⁻¹. Mean CH₄ emission rate from the sediments of the Changjiang Estuary in spring was 1.97 μmol m⁻² day⁻¹, but it may be higher in summer due to hypoxia in the bottom waters and higher temperatures. The annual sea to air CH₄ fluxes from the Changjiang Estuary and its adjacent marine area were estimated to be 61.4 ± 22.6 and 16.0 ± 6.1 μmol m⁻² day⁻¹, respectively, using three different gas exchange models. Hence the Changjiang Estuary and its adjacent marine area are net sources of atmospheric CH₄.     

霍林河流域湿地土壤碳氮空间分布特征及生态效应

对霍林河流域湿地土壤有机碳及全氮空问分布特征及其生态效应的研究表明,有机碳和全氮的水平分异和垂直分异都十分显著,干湿交替周期是引起分异的关键因子;表层土壤有机碳与全氮含量显著相关(r=0．977),土壤碳氮比基本沿湿度梯度变化;土壤pH值对土壤表层碳氮含量及碳氮比值影响显著;流域湿地土壤与流域草原土壤碳氮比与土壤碳氮含量的相关性差异显著;其生态效应主要表现在生产效应和净化效应两方面．     

珠江口近海浮游植物生态特征研究

1998～1999年对珠江口近海浮游植物进行了5个航次现场调查,共鉴定出浮游植物239种．其中。硅藻最多,占72．4％,甲藻次之,占23．8％,其他门类合占3．8％．种类组成以暖水种和广温种为主;优势种季节更替明显,四季的主要优势种依次为伏氏海毛藻(Thalassiothrix frauenfeldli)、柔弱菱形藻(Nitzschia delicatlssima)、伏氏海毛藻、细弱海链藻(Thalassiosira subtilis)．细胞密度全年变幅0．2×10^4～2767．1×10^4cell·m^-3,四季平均98．7×10^4cell·m^-3,夏、冬季明显高于春、秋季．平面分布呈近岸明显高于外海趋势。密集区终年出现在西北海域上川岛附近．Shannon—Wiener指数、Pielou均匀度和多样性阈值四季均值变幅分别为2．63～3．17、0．53～0．71和1．74～2．23,群落多样性水平较高,结构较稳定．     

汉江中游江段四大家鱼产卵场现状的初步研究

为掌握汉江中游四大家鱼产卵场的现状,2004年5~8月分别设固定断面和流动采集鱼卵(仔鱼)。鱼卵漂流距离(S)用当时水温条件下胚胎发育经历时间(T)乘以江水平均流速(V)估算,即S=V.T,把产卵集中的江段确定为产卵场;产卵规模(M)根据采样点采获的相近发育期的鱼卵数(m)、采样点断面江水流量(Q)、采样网口流速(V′)、采样断面卵(仔鱼)密度系数(C)和采样网口面积(0.39)估算,即M=m.Q.C/0.39.V′。结果表明,汉江中游干流有四大家鱼产卵场5个,产卵场长度占该江段干流长度的36.22%,产卵总量为0.933×108粒,其中青鱼(Mylopharyngodon piceus)、草鱼(Ctenopharyngodon idellus)、鲢(Hypophthalmichthys molitrix)、鳙(Aristichthys nobilis)分别为7.28×106粒、6.125×107粒、2.067×107粒和4.10×106粒,左岸支流唐白河无四大家鱼产卵;四大家鱼产卵和产卵的规模与江水的温度、涨水持续的时间、流速、流态紧密相关;2004年四大家鱼的产卵量仅相当于1976年监测结果的6.71%,汉江中游四大家鱼资源已严重衰退。     

长江口北支大型底栖动物群落周年变化特征

分析了长江口北支滩涂大型底栖动物的群落结构和多样性变化特征。共采集大型底栖动物78种,包括环节动物7种、软体动物23种、节肢动物28种、脊索动物18种、其它两种,全年优势种有8种。密度为0.08 ind/m^2（1月）-1.24 ind/m^2（7月）,生物量为0.006 g/m^2（2月）-0.58 g/m^2（5月）,Margalef丰富度指数（D）为0.82（1月）-3.88（7月）,Pielou均匀度指数（J）为0.60（9月）-0.86（1月）,Shannon-Wiener多样性指数（H＇）为1.59（2月）-2.76（10月）。底栖动物密度与环境因子进行相关性分析显示,北支潮间带的大型底栖动物群落按照盐度、沉积特征等不同可分为3组,盐度和温度是影响底栖动物群落分布的主导因子。     

Impacts of the Yangtze River water transfer on the restoration of Lake Taihu

In order to improve the water quality and to abate the jeopardy of water bloom in Lake Taihu, China, two experimental water transfers from the Yangtze River to Lake Taihu were conducted in winter–spring 2002 and in summer–autumn 2003. In this study, an ecological model (EcoTaihu) was introduced to assess their environmental effects. First, the model was re-calibrated and reverified for the periods of the water transfer, then numerical calculations with and without the water transfer were carried out. The percentage of the area where water quality was improved by the water transfer was calculated in seven sub-zones of the lake. The results show that the experimental water transfers in both of the periods have notable positive effects on debasing the concentration of phytoplankton, total nitrogen and dissolved oxygen in some sub-areas. The positive effects fluctuated with the duration of the water transfer, and were different for different water quality parameters and in different sub-zones. Among the five water quality parameters considered, chlorophyll a achieved the most significant improvement. There are no notable positive effects on the total phosphorus in any sub-zones. Meiliang Bay, Gonghu Bay and Northwest Zone had more positive effects than the east epigeal zone and Dongtaihu Bay. As the water transfer results in net input of nitrogen and phosphorus to Lake Taihu, it can only be used as an emergency measure to abate the jeopardy resulting from water bloom. Otherwise, the water transfer would increase the risk of eutrophication in Lake Taihu if the concentration of phosphorus and nitrogen in the influent water was not cut down to a reasonable level.     

冀北高原闪电河流域上游不同介质体中总P分布特征

对冀北高原闪电河水库上游２０ｋｍ长的河段的多介质体中总Ｐ含量及其动态变化分析表明,同源水体的总Ｐ含量各段不一,其中最高量（０．０８２４ｍｇ·Ｌ（－１））为最低量（０．０２２８ｍｇ·Ｌ（－１））的３．６倍;不同介质体总Ｐ含量以土壤（３４０２ｍｇ·ｋｇ（－１））＞淤泥（１９９２ｍｇ·ｋｇ（－１））＞岩石（５４２ｍｇ·ｋｇ（－１））＞水体（０．０５５３ｍｇ·Ｌ（－１））的排序递减,并随温度升高而增高．     

古尔班通古特沙漠西部地下水位和水质变化对植被的影响

通过对比分析古尔班通古特沙漠西部3a地下水位和水质的变化特点,研究了地下水位和水质变化对地表土壤理化性质、植物多样性、及建群种梭梭种群生长与更新的影响。发现地下水位和土壤理化性质空间变异较大,最浅地下水位为3.3 m,最深可达24.2 m,主要集中在6-8 m;土壤电导率、pH值、Cl^-和SO₄^2-均在表层0-40 cm含量较高,变异系数随土层深度的增加而减小。在时间上地下水位受准噶尔盆地上游农田用水的影响,水位呈季节性波动。一年中最高水位出现在4月,最低水位在7月。玛纳斯河向下游输水对提高盆地地下水位具有明显作用,地下水位平均可升高4.3 cm,地下水矿化度平均增幅1 g/L。地下水位对退化区物种多样性影响不大,但对梭梭生长产生显著影响。梭梭生长的适宜地下水位为5-8 m,且地下水矿化度小于4 g/L。地下水位大于8 m导致梭梭种群衰退,而地下水位小于4 m时,地下水矿化度影响土壤表层积盐,进而显著地降低物种多样性,阻碍梭梭幼苗更新,导致梭梭种群衰败。总结认为准噶尔盆地上游的玛纳斯河断流和农业灌溉对古尔班通古特沙漠西部平原地区的地下水位和水质产生显著影响,梭梭退化与地下水位变化显著相关,必须引起高度重视。     

长江中下游地区水稻孕穗开花期高温发生规律及其对产量的影响

以长江中下游平原7个省(市)的19个地区作为样点,统计分析了各样点近36年(1970—2005年)水稻始穗前15d至始穗后20d内日最高气温≥35℃的时空分布特点;并根据全球气候渐变模型GISS GCM Transient B Runs生成的研究区域2030、2050年的气候渐变情景,分析了该地区未来水稻孕穗开花期≥35℃高温逆境的时空演变趋势。结果表明:近36年来长江中下游的早稻孕穗开花期出现高温日数的上升趋势显著,未来气候情景下水稻逆境指标出现日数最多的是单季稻,其次依次为早稻、后季稻;双季稻种植区,在未来气候变化中,长江中游地区温度逆境出现日数将大于下游地区。研究区域水稻气候产量的增减与该地区水稻逆境指标的关系说明,高温导致的颖花败育是水稻减产的重要原因;未来气候变化的两种(2030、2050)情景下,长江中游地区的减产幅度大于长江下游地区,减产幅度最大的是长江中游地区的后季稻。     

长江中上游主要经济鱼类的渔业生物学特征

根据1996－1999年长江中上游渔业资源监测资料,分析了青鱼,草鱼,链,鳙,铜鱼,圆口铜鱼,长吻Wei,河鲶,瓦氏黄颡鱼,鲤等10种主要经济鱼的渔业生物学特性,并应用von Bertalanffy公式,Key公式,Beverton-Holt公式等估计了生长参数,总死亡系数,自然死亡系数,捕捞死亡系数,总存活率,总死亡率,自然死亡率,捕捞死亡率和开发率,讨论了资源的开发状况,针对存在的问题,提出了渔业管理意见。