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B. R. Schne K. W. Flessa D. L. Dettman D. H. Goodwin 《Estuarine, Coastal and Shelf Science》2003,58(4):715-726
We studied how the extensive diversion of Colorado River water, induced by dams and agricultural activities of the last 70 years, affected the growth rates of two abundant bivalve mollusk species (Chione cortezi and Chione fluctifraga) in the northern Gulf of California. Shells alive on the delta today (‘Post-dam’ shells) grow 5.8–27.9% faster than shells alive prior to the construction of dams (‘Pre-dam’ shells). This increase in annual shell production is linked to the currently sharply reduced freshwater influx to the Colorado River estuary. Before the upstream river management, lower salinity retarded growth rates in these bivalves. Intra-annual growth rates were 50% lower during spring and early summer, when river flow was at its maximum. Growth rates in Chione today are largely controlled by temperature and nutrients; prior to the construction of dams and the diversion of the Colorado River flow, seasonal changes in salinity played an important role in regulating calcification rates.Our study employs sclerochronological (growth increment analysis) and geochemical techniques to assess the impact of reduced freshwater influx on bivalve growth rates in the Colorado River estuary. A combination of both techniques provides an excellent tool to evaluate the impact of river management in areas where no pre-impact studies were made. 相似文献
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Concentrations of some heavy metals and trace elements such as Cr, Ga, Ni, Zn, Mo, Cu, Pb, Yb, Y, Nb, Ti, Sr, Ba, Mn, Sc, Co, V, Zr, Fe, Al, W, Se, Bi, Sb, As, Cd in recent mollusk shells and factors affecting their distribution and deposits collected from various depths in the southern and southwestern parts of the Marmara Sea are investigated. The distribution of the elements in the shells is categorized into four groups. Of these, concentrations of 12 elements (As, Bi, Cd, Co, Ga, Mo, Nb, Sb, Se, Sc, W and Yb) are below zero [(0.053-0.79)×10^-6]; concentrations of seven elements (Cr, Ni, Pb, V, Y, Zr and Cu) are (1.0-6.0)×10^-6; concentrations of four elements (Ti, Mn, Ba and Zn) are 10- 20×10^-6; and concentrations of five elements (Si, Al, Fe, Mg and Sr) are (47.44-268.11)×10^-6. The taxonomic characteristics of the 29 elements were studied separately in mollusk shells such as Chamalea gallina (Linn6), Pitar rudis (Poli), Nassarius reticulatus (Linn6), Venerupis senescens (Coocconi), Mytilus galloprovincialis (Lamarck), Mytilaster lineatus (Gemelin in Linne) and Chlamys glabra. It was found that, in mollusk taxonomy, the elements have unique values. In other words, element concentrations in various mollusk shells depend mainly on the taxonomic characteristics of mollusks. In various bionomic environments different element distributions of the same species are attributed to the different geochemical characters of the each environment. Data obtained in this study indicate that the organisms are the most active and deterministic factors of the environment. 相似文献
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黄土中蜗牛壳Mn^2+的EPR研究及其古气候意义 总被引:2,自引:0,他引:2
对黄土高原陕西省洛川和甘肃省西峰剖面中黄土-古土壤层中的蜗牛壳进行了EPR波谱分析,同时对洛川地区的现代蜗牛壳也进行了测定。结果显示:(1)不同种类的蜗牛壳具有相近的EPR信号强度,表明不同种类的蜗牛对Mn^2+的吸收没有差异性。(2)黄土层中蜗牛壳的EPR信号强度远大于占土壤中的,即黄土中蜗牛壳所含的Mn^2+远大于古土壤中的蜗牛壳的Mn^2+的含量,说明前者生活在比较还原的条件下,后者形成环境的氧化性较高。因此本认为为蜗牛壳中Mn^2+的含量可反映其生长环境中Mn^2+的含量和氧化还原条件,对古气候的重建具有重要意义。 相似文献
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间齿螺(Metodontia)是我国现生陆生蜗牛的常见属, 也是黄土地层中常见的蜗牛化石, 汉山间齿螺(Metodontia huaiensis)和烟台间齿螺(Metodontia yantaiensis)是该属的两个常见种。我国现生间齿螺的地理分布调查取得了丰硕的成果, 为间齿螺化石作为夏季风气候变化的代用指标提供了依据, 但对现生间齿螺的数量分布和生态因子最适区域, 还缺少系统的研究, 限制了对间齿螺古生态古气候意义的深入理解。通过对黄土高原及周边地区356个表土蜗牛组合的研究, 揭示了间齿螺及其优势种的数量分布与气候参数的关系, 以及与经纬度和海拔高度的关系, 并利用加权平均方法定量估算了汉山间齿螺和烟台间齿螺的温度和降水量最适范围。结果表明, 在我们的研究区域内, 含量大于20% 的间齿螺, 主要分布在年均温大于11℃、年降水量550~850mm的地区, 36°N以南、110°E以东的地区, 海拔在750m以下的地区; 含量低于10% 的间齿螺, 在年均温5~15℃、年降水量380~700mm的地点都有分布, 主要分布在 33°~40.5°N、103.7°~117.5°E范围内, 海拔在2000m以下的地区; 年均温低于5℃、年降水量低于380mm的地区, 海拔2000m以上的地区, 基本上没有间齿螺生长; 汉山间齿螺和烟台间齿螺年均温度最适范围分别为10.2~14.1℃左右和8.9~14.0℃左右(实测值与推导值R2=0.70, 推导误差RMSEP=1.99), 年降水量最适范围分别为530~800mm左右和470~750mm左右(R2=0.81, RMSEP=90.87)。上述结果为间齿螺的古生态古气候研究和物种多样性保护提供了基础生态数据。 相似文献
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摘 分子遗传标记是随着分子生物学技术的发展而出现的遗传标记技术,它突破了形态和细胞水平上遗传标记的局限性,发挥着独特的优势。本文简要介绍了同工酶、RFLP、RAPD、AFLP、mtDNA、SSR等几种常用的分子遗传标记技术方法,并比较了各种技术的优点和局限性;概述了这些遗传标记技术在海洋经济贝类群体遗传结构和变异、遗传分化、遗传育种、种质鉴定、基因定位和构建遗传图谱研究等方面的应用和取得的研究成果。 相似文献
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广东湛江硇洲岛是典型的潮间带生态系统,属于热带气候,适宜底栖生物生存。底栖动物作为生态指标的一部分,可以反映出地理环境的多样性。于2011~2012年在硇洲岛潮间带五个位点进行底栖软体动物采样,以研究软体动物的季节演替变化,结果检出软体动物有4纲49科71属共104种。其中双壳纲39种,占总数的37.50%;腹足纲59种,占总数的56.73%;多板纲4种,占总数的3.85%;头足纲2种,占总数的1.92%。种类数秋季最多共61种,春季32种,夏季51种,冬季55种。各季节间共有种类数为19~33种。有8个种类为3个季节共有种,有12个种类为4个季节共有种,季节种间更替率为0.58~0.76,春秋季种间更替率最高,夏秋季种间更替率最低。优势种10种,其中1个物种为全年优势种,有2个物种为3个季节共有种。不同物种在潮间带分异明显,中潮区软体动物有58种,低潮区软体动物有44种,高潮区软体动物只有3种。调查显示各季节软体动物栖息密度变化明显,按降序排列为春季、夏季,秋季、冬季。季度Shannon-Wiener多样性指数变化范围为2.45~3.42,年均值为2.99;季度Pielou物种均匀度指数变化范围为0.53~0.66,年均值为0.58;季度Margalef物种丰富度指数变化范围为2.42~4.61,年均值为3.73; Simpson指数变化范围为0.69~0.80,年均值为0.76。调查显示各断面均受到不同程度的人为干扰,相关性分析发现栖息密度与悬浮物和总有机碳正相关(P<0.05)。优势种的转变与沿岸上升流的强弱以及养殖废水的不规则排放有关。软体动物的栖息密度与大型海藻的分布呈相反趋势,低潮区软体动物栖息密度小,与其结构和食性有关。 相似文献