Is fertility of hybrids enough to conclude that the two oysters Crassostrea gigas and Crassostrea angulata are the same species?

The distinction of the two cupped oysters Crassostrea gigas (Thunberg, 1793) and Crassostrea angulata (Lamark, 1819) into two species was chiefly due to their differing geographical distributions, C. gigas being present in Asia and C. angulata in Europe. Today it is commonly accepted that C. angulata and C. gigas are a single species according to morphological, genetic and F1 hybridization data. However, the demonstration of the fertility of their hybrids and the absence of any reproductive isolation remained to be investigated. Consequently, we studied the fertility of hybrids and sperm competition by performing three different experiments and producing G1 and G2 hybrid progenies between wild populations of C. angulata and C. gigas. Progenies showed very close developmental yields, at 24 hours after fertilization, according to dam taxa suggesting a strong maternal transmission of oocyte quality, but no reproductive isolation was observed between the two taxa. Significant decreases of developmental yields were noticed in C. angulata females with sperm competition, most probably due to early larval mortality. The fertility of hybrids C. angulata × C. gigas was demonstrated, which is further evidence that they are the same species. To definitively state the precise taxonomic classification of C. angulata and C. gigas, further studies are needed to (i) identify geographical zones where these taxa are in contact and (ii) assess their level of hybridization in these zones.     

广州市南沙区一次大雾天气过程分析

针对2010年2月26日出现在广州市南沙区的一次大雾天气进行了过程分析,结果表明:此次大雾天气属于平流雾的类型,低层偏南暖湿气流的移入是造成大雾天气的主要原因。在预报过程中,不仅要考虑湿度和风的条件,也要考虑前期地面至500 hPa相关的物理量场如逆温层等的变化对大雾天气的指示意义;另外,前期湿度的积累也为大雾的生成和发展提供重要条件。     

风云卫星系列及CLDAS土壤水分产品多尺度精度验证与评价：以青藏高原那曲地区为例

对风云卫星（FY-3B、FY-3C）系列土壤水分产品和中国气象局陆面数据同化系统CLDAS-V2.0（Chinese Land Data Assimilation System Version 2.0）土壤水分产品展开精度验证与评价,旨在明确中国土壤水分产品的时空序列精度特征,以期为后续土壤水分产品精度校正与反演模型改进提供参考。验证实验在青藏高原那曲地区开展,基于那曲地区大（1°×1°）、中（0.3°×0.3°）、小（0.1°×0.1°）三个尺度观测网中观测站点0-5cm、0-10cm和10-40cm土壤水分逐日观测资料进行评价,并加入全球陆面数据同化系统GLDAS-1（Global Land Data Assimilation System Vision 1.0）Noah土壤水分产品作为对比。结果表明：（1）时序性上,CLDAS-V2.0土壤水分产品表现出良好的时空连贯性,FY系列土壤水分产品空值普遍存在,在冰冻期尤为显著。FY及CLDAS-V2.0土壤水分产品多数时间存在高估现象,在降水事件发生后和植被生长期高估尤为明显。（2）各土壤水分产品在不同尺度观测网中的统计结果一致。但相较于大中尺度稀疏测站,各产品在小尺度密集观测网的评价结果更加稳定和优异。（3）0-5cm深度,CLDAS-V2.0土壤水分产品质量整体优于FY系列土壤水分产品,FY系列土壤水分日间观测产品精度高于夜间观测产品。10-40cm深度,CLDAS-V2.0土壤水分产品精度高于GLDAS-1 Noah土壤水分产品。结果表明中国自主研制的土壤水分产品数据集质量较为稳定、可靠。     

南沙群岛重点岛礁潟湖微型浮游动物的群落结构与摄食

潟湖是岛礁生物多样性演变的重要环境场,在岛礁水生态系统的物质循环和能量流动中发挥重要作用,而微型浮游动物的生态功能研究是解析南沙群岛岛礁水域潟湖生态系统初级生产力组成、流向、能量流动效率的重要研究内容之一。实验通过对南沙群岛重点岛礁渚碧礁、美济礁与永暑礁潟湖表层水域中微型浮游动物与生态环境调查,研究了其群落结构及其与环境因子的关系,并通过稀释培养实验研究了微型浮游动物的摄食压力。结果显示,调查水域共发现微型浮游动物20种,总丰度的范围为320～1 460个/L,以无壳纤毛虫丰度最高。无壳纤毛虫在渚碧礁潟湖西部水域（ZB-1）丰度最高,砂壳纤毛虫峰值则出现在永暑礁潟湖中部水域（YS-3）,桡足类幼体丰度最大值出现在美济礁潟湖北部水域（MJ-2）。聚类分析结果显示,3个岛礁潟湖中部区域的微型浮游动物群落相似度较高,溶解氧是影响群落结构的最重要因素,特别是对MJ-3站位影响最为突出。摄食实验结果显示,3个岛礁潟湖水域浮游植物生长率为0.22～1.36 d^-1;微型浮游动物摄食率范围为0.22～0.60 d^-1,微型浮游动物每天约摄食浮游植物现存量的...     

广东沿海养殖牡蛎中多氯联苯残留水平及人体饮食暴露风险评估

文章利用气相色谱质谱法测定了广东沿海主要养殖区(汕头、汕尾、深圳、珠海、江门、阳江、湛江)养殖牡蛎体内30种多氯联苯(Polychlorinated biphenys,PCBs)的含量,评价了其污染水平和致癌风险。结果表明,广东养殖牡蛎中普遍检出PCBs,检出率为97.6%,其质量分数为nd~8.62 ng·g^-1(湿质量,下同),平均值为(0.57±1.23)ng·g^-1,其中以深圳水域养殖牡蛎体内的PCBs含量最高,珠海次之,汕头、阳江、江门、湛江及汕尾较低。不同地区养殖牡蛎中PCBs的组成模式类似,均以五氯代和六氯代PCBs为主。与国内外部分沿海海域贝类相比,广东省养殖牡蛎中PCBs含量处于较低水平。广东省养殖牡蛎中PCBs残留量低于中国《食品安全国家标准食品中污染物限量》及欧盟国家的贝类卫生标准,食用牡蛎的致癌风险及危害商数均小于美国环保局(EPA)推荐的可接受风险水平,致癌风险处于可接受风险水平。     

广州南沙口岸进口大豆截获有害生物疫情分析

本文对广州南沙口岸2012-2018年入境的各来源国大豆中截获的有害生物进行统计分析,结果表明,进口大豆中携带的有害生物种类以杂草最多,约占76.8%;美国大豆截获的检疫性有害生物种类最多。针对分析结果提出相应的建议。     

珠三角地区养殖及野生淡水鱼类的甲基汞积累现状

汞（尤其是甲基汞）易在鱼体内富集,进而危害人类健康。为了解珠三角地区淡水鱼类的甲基汞积累现状,本研究对该区域内常见的养殖和野生鱼类进行了采样和甲基汞测定,并探讨了影响鱼类甲基汞积累差异的原因。结果发现,珠三角地区鱼类甲基汞含量总体较低,均未超过我国水产品食用安全标准,其中养殖鱼类肌肉甲基汞含量为0.26-331 ng g-1 dw,平均含量为62 ng g-1 dw;野生鱼类肌肉甲基汞含量为0.71-1 006 ng g-1 dw,平均含量为111 ng g-1 dw,养殖鱼类甲基汞含量显著低于野生鱼类。鱼类甲基汞累积主要受食物组成及食物甲基汞浓度影响,饲料甲基汞含量是决定养殖鱼类甲基汞水平的关键性因素。食用该地区鱼肉的甲基汞摄入水平总体较低,其中食用野生鱼类的甲基汞摄入水平较养殖鱼类高,食用野生鳜（Siniperca chuatsi)）存在甲基汞暴露风险。     

Vertical distribution of microbial communities under the canopy of two legume bushes in the Tehuacán Desert,Mexico

Prosopis laevigata and Parkinsonia praecox are the most abundant perennial shrubs in the Tehuacán Desert, forming ’islands of fertility’ that dominate the alluvial terraces. Both species exhibit very similar phenology, with the timing of litter foliage being the only difference between them. P. praecox litter occurs shortly after the rains, while P. laevigata maintains its leaves until the next wet season. As degradable organic matter (OM) is one of the leading factors determining soil biota composition and activity, because of the OM provided by littering, we expected that the vertical distribution of the microbial community in the vicinity of the root zone of P. praecox would be higher in comparison to P. laevigata. One soil sampling was performed; during the rainy season in August, soil samples were collected from a 0–50-cm depth at 10-cm intervals, in the vicinity of the root canopy of four individual plants of each species and the interspaces between them. Soil moisture, organic matter, and counts of bacteria and fungi under shrubs were found to decrease from the upper to deeper layers. Respiratory activity was higher in the deeper layers (p < 0.01) in all three sampling sites. Total bacterial, fungal, and heterotrophic diazotrophs were found to be significantly (p < 0.001) more numerous under shrubs than in the interspace soil. No nitrogen-fixing bacteria were isolated from interplant soils in comparison to the soil samples collected beneath the shrubs. Heterotrophic diazotrophs significantly (p < 0.01) reduced more acetylene under P. praecox (29.0 nmol/g soil) than under P. laevigata (20.1 nmol/g soil). Although the microbial numbers were unaffected by differences in plant phenology, greater nitrogenase activity under P. praecox may influence nitrogen distribution in this arid environment. Due to the fact that only one sampling was undertaken, this study elucidates the differences in the microbial community between the two shrubs, but the dynamics in the above community could not be shown.     

江南古典园林铺地艺术

本文阐述了江南古典园林铺地的形式、特点、图案和运用于不同环境中产生的不同作用，及其蕴含的中国文化，并简要介绍其对现代园林产生的影响。     

基于Clue-S模型的石马河流域东莞段生态系统服务价值变化情景模拟

[目的]探究生态系统服务价值演变的内在作用机制,旨在寻求以流域为单元的生态农业和城镇的优化配置模式。[方法]基于土地利用及生态服务价值相关理论与方法,以石马河流域东莞段2010-2020年土地利用数据为基础,利用Clue-S模型对2025年土地利用格局进行模拟,得出2025年区域在生态安全、耕地优先和建设发展3种情景下的土地利用空间布局和优化配置结果,分析各情景下流域生态系统服务价值时空格局。[结果]在2010-2020年,石马河流域东莞段生态服务价值下降了1.80×10⁷元,主要为耕地、林地、园地转出。2025年在耕地优先、生态安全、建设发展的情境下ESV分别为9.44×10⁷,9.62×10⁷,9.38×10⁷元,除了生态安全之外,其余两个情景较2020年生态系统服务价值ESV都有下滑。[结论]对处于快速城镇化发展且生态与发展矛盾突出的地区,进行流域生态系统服务价值进行模拟与分析,有利于增强对区域在不同发展模式下生态系统服务价值空间布局的认识和理解,为土地利用规划与生态经济协调发展提供宏观的参考。