Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change,genetic diversity and body condition     

J Keightley  S von der Heyden 《African Journal of Marine Science》2015,37(1):89-98

Successful aquaculture species are often chosen for their fast growth rates and fecundity, which are also characteristics of invasive species. The Pacific oyster Crassostrea gigas, which constitutes 80% of global oyster trade, has been confirmed as invasive in 17 of the 66 countries where it is cultured. The single study of its status in South Africa reported populations in six South Coast estuaries in 2001, dropping to three sites in 2003. We resurveyed these estuaries, visited others in the Eastern and Western Cape provinces, and sampled oyster tissue for molecular analyses of population structure. Pacific oysters have disappeared from Knysna and, following our collections, possibly also from the GouKou Estuary. Between 2003 and 2012, the Breede Estuary population decreased by 87%, from an estimated 184 206 to 23 760 individuals. Within this estuary, oysters 12 km upriver had denser shells and higher body condition indices than did those within 1.4 km of the river mouth, presumably reflecting higher availability of suspended organic matter. However, low salinity over most of the species’ range in the estuary probably inhibits recruitment. New populations of Pacific oysters in the Swartkops and Kaaimans estuaries urgently require monitoring and eradication. Haplotype (h) and nucleotide (π) diversities across all oyster populations sampled (h = 0.2300 [SD 0.0595], π = 0.0006 [SD 0.0007]) were lower than those of co-occurring indigenous Cape rock oysters Striostrea margaritacea from the GouKou and Breede estuaries (h = 0.9076 [SD 0.0386], π = 0.00589 [SD 0.00347]). Pacific oysters either have been introduced to South African estuaries infrequently, or have experienced genetic bottlenecks following river floods or human exploitation, or both. Populations growing outside culture infrastructure are restricted to estuaries in the Eastern and Western Cape provinces, with no evidence of occurrence in fully marine shelf environments. Given the species’ considerable socio-economic importance, estuarine and coastal surveillance coupled with aquaculture zoning are required to integrate biodiversity and food security considerations.  相似文献   

“十三五”时期黄河流域PM2.5时空分布规律及多尺度社会经济影响机制分析     

耿佳辰  沈石  程昌秀 《地球信息科学学报》2022,24(6):1163-1175

黄河流域生态保护与高质量发展是我国新时代的重大战略任务。探究黄河流域PM_2.5浓度的时空变化趋势,并分析其社会经济影响因素,对该地区的大气污染防治和实现高质量发展具有重要意义。本文采用时间序列趋势估计、空间自相关分析、地理探测器和地理加权回归方法,揭示了“十三五”时期年黄河流域不同尺度（全流域以及61个地级市）PM_2.5浓度值和变化趋势的时空分异特征,定量探究了社会经济因素对PM_2.5浓度的影响机制及其时空过程。结果表明：① 在“十三五”时期,黄河流域的PM_2.5污染情况整体好转,其浓度呈波动下降的趋势,平均每年下降约4.2 μg/m³,彰显了我国大气污染防治攻坚战取得的重要成效;② 山东、河南、山西和陕西的PM_2.5浓度值较高,但山东、河南改善速度较快,山西和陕西改善速度较慢;③ 以目前的改善速率推算,在黄河流域61个地级市中,54个市将能够完成“十四五”规划中PM_2.5浓度下降10%的目标,而咸阳、西安、榆林、太原、临汾、运城、晋城7市将难以完成;④ 人口密度、工业企业数、土地利用强度是导致黄河流域PM_2.5浓度升高的主要社会经济因素,其解释力均达到50%以上;⑤ 从2015—2019年,土地利用程度指数和人口密度的主要影响区域均转移至黄河流域中部地区,建议山西、陕西、内蒙古应作为下一阶段治理工作关注的重点区域;⑥ 促进与环境承载力相协调的城乡发展、控制工业规模并提高其环保水平,是进一步治理黄河流域大气污染的重要策略。  相似文献   

二倍体和三倍体太平洋牡蛎(Crassostrea gigas)繁殖前后生化成分及氨基酸组成的比较研究   总被引：3，自引：0，他引：3  

孔令锋  王昭萍  于瑞海  王如才 《海洋湖沼通报》2001,(4):44-49

对太平洋蛎二倍体和三倍体在繁殖前后的几种生化成分和氨基酸组成进行了比较研究，为牡蛎的生理生化研究提供了基础数据。结果显示：太平洋牡蛎的总糖，糖原，脂肪和蛋白的含量与其繁密切相关，二倍体牡蛎在繁殖后的总糖，糖原，脂肪的含量比繁殖前分别降低了24．31％，30．37％，14．91％，三倍体分别降低了9．45％，7．17％，20．29％，而二倍体和三倍体牡蛎粗蛋白的含量在繁殖后较繁殖前分别增高了14．91％，12．285，表明了糖类和脂肪是牡蛎殖能量的主要来源，繁殖前三倍体牡蛎的糖原含量比二倍体高23．30％，繁殖后二倍体糖原含量明显降低，三倍体的糖原含量比二倍体高了73．83％，表明三倍体牡蛎由于可育性低而体内一直保持较高水平的糖原含量，从而在繁殖季节也保持了鲜美的口味。二倍体太平洋牡蛎与三倍体的氨基酸组成和含量的分析比较也表明，二倍体牡蛎的氨基酸组分在繁殖前后变化较大，而三倍体的氨基酸组分相对稳定。  相似文献   

汕头港及其邻近水域潮间带海产动物体内重金属污染的调查   总被引：6，自引：1，他引：6  

孙萍  黄长江  乔永民  谢立民  董巧香 《热带海洋学报》2004,23(4):56-62

调查了汕头港及邻近水域潮间带常见海产动物体内的重金属含量。结果表明，翡翠贻贝(Perna viridis)体内的Ni、鳞笠藤壶(Tetraclita squamosa squamosa)体内的Cr和Zn、近江牡蛎(Crassostrea rivularis Gould)体内的Cu和Zn含量高于海洋生物污染评价标准。近江牡蛎的Cu污染因子质量分指数最高达6．01。可食性贝类中疣荔枝螺(Thais clavigera)体内的Cd、Zn，翡翠贻贝体内的Cd、Ni和Pb，小荚蛏(Siliqua minima)体内的Cd、Ni，近江牡蛎体内的Cd、Cu、Ni和Zn的含量高于人体食用限量标准。其中近江牡蛎体内的Zn含量最高，为限量标准的23．5倍。港内比港外污染严重，远离港口站位的生物体内重金属含量仍有超标现象，表明汕头港及其邻近水域的重金属污染严重。  相似文献   

Small-scale Spatial Distribution of a Pyramidellid Snail Ectoparasite, Boonea impressa, in Relation to its Host, Crassostrea virginica, on Oyster Reefs     

E.N. Powell    M.E. White    E. A. Wilson  S.M. Ray 《Marine Ecology》1987,8(2):107-130

Abstract. The pyramidellid snail, Boonea (= Odostomia) impressa (SAY), is an important ectoparasite of the oyster, Crassostrea virginica (G melin ). The small-scale spatial distribution of snails was examined in 11 oyster populations in the Copano Bay - Aransas Bay area of the Texas coast. Snails were contagiously distributed (s²/>1) and positively spatially autocorrelated. Patchiness was better developed and patches were larger on enclosed reefs than on more exposed open-bay reefs, probably because higher wave energy and increased distance between oyster clumps limited clump-to-clump movement by snails on open-bay reefs. Small snails were consistently distributed differently from large snails because small snails were less host specific. As the snails grow, a narrowing of host preference results in a substantial change in spatial distribution. Snails were consistently more contagiously distributed than their hosts; however, snail distribution was not host-density dependent. Factors determining the spatial distribution of the host had surprisingly little effect on the distribution of snails. Snail aggregates apparently form randomly by chance meetings of a few snails and then grow by attraction of additional snails. Consequently, snail behavior, which determines the size and length of time a patch retains its integrity, and the age distribution of the snail population may be the two most important factors, besides population size, determining the impact of B. impressa on oyster populations.  相似文献   

Satellite remote sensing of the geographical distribution of suspended particle size in an energetic shelf sea   总被引：2，自引：0，他引：2  

D.G. Bowers  C.E. Binding  K.M. Ellis 《Estuarine, Coastal and Shelf Science》2007,73(3-4):457-466

Natural and created Spartina brackish marsh habitats in the Guadalupe Estuary, adjacent to the Aransas National Wildlife Refuge, Texas, USA were surveyed during spring, summer, and fall 2004 to evaluate the equivalence of nekton assemblages in an old (>30 years) created marsh. During each season, six replicate samples were collected in each marsh type using a 1-m² drop sampler. Multivariate analysis revealed significant differences in nekton assemblage structure among marsh type, both within and across seasons. Species richness was significantly higher in the natural marsh in spring and summer but not in fall. Several species that were dominant in the natural marsh but rare or absent in the created marsh had strong correlations with the presence of oyster substrate that was only encountered in natural marsh samples. Although cumulative richness was greater in the natural marsh, eight species were collected only from the created marsh. Shrimp and fish biomass was significantly higher in natural marsh. Analysis of the density, biomass and size structure of three commercially important crustaceans indicated that the created marsh supported similar biomass of some species (white shrimp, blue crab); however, the size structure of some populations was variable among marshes (blue crab, brown shrimp). We conclude that lower substrate complexity (specifically oyster) and soil organic content in the created marsh reduced measures of nekton similarity and recommend that these features be addressed in future restoration efforts.  相似文献   

渤海湾西北岸全新世埋藏牡蛎礁建造记录中的间断及其解释     

范昌福  高抒  王宏 《海洋地质与第四纪地质》2006,26(5):27-35

渤海湾西北岸沿海平原的众多埋藏牡蛎礁体内部,除正常牡蛎壳堆积层外,还存在一些水平夹层,以往的文献对其成因有多种解释。对渤海湾西北岸埋藏牡蛎礁体中所含水平夹层特征进行了研究,并与江苏海岸南部现代活体牡蛎礁顶部沉积特征进行对比,结果表明渤海湾埋藏礁体中局部范围内分布的水平夹层与江苏海岸活礁体顶部的现代沉积相似,其特征与礁体生长时的局部水动力条件有关;但是,江苏海岸活牡蛎礁顶部的现代沉积特征不同于那些大范围分布于埋藏礁体内的水平夹层的特征,后者的成因尚待进一步研究。礁体剖面记录的垂向层序,在反映环境演化的同时,也反映了礁体生长时的平面特征。  相似文献   

超低温保存前后太平洋牡蛎精子(Crassostrea gigas (Thunberg))超微结构观察   总被引：1，自引：0，他引：1  

李赟  贺桂珍  王品虹 《中国海洋大学学报(自然科学版)》2002,32(4):526-532

应用扫描电镜和透射电镜技术 ,研究超低温冷冻前后太平洋牡蛎精子形态与超微结构。结果发现 ,受伤精子被膜肿胀、皱褶、破裂 ;顶体变形、囊泡化 ,顶体膜肿胀、局部断裂 ;核膜肿胀、破裂 ,核空泡化 ;线粒体嵴变形、消失 ,基质电子密度降低 ,结构模糊 ;精子鞭毛被膜膨胀 ,鞭毛自精子基部或主、末段断裂。结果表明 ,超低温冷冻和升温解冻 ,对牡蛎精子的膜结构损伤严重 ,导致精子活力和受精能力下降  相似文献   

厦门浔江湾牡蛎养殖区弧菌研究   总被引：4，自引：0，他引：4  

刘文华  叶德赞 《台湾海峡》1996,15(4):412-415

利用ＭＰＮ法及ＡＰＩ２０Ｅ系统对厦门浔江湾牡蛎养殖区的特牡蛎体、水体及底质三类榈进行弧菌分析。结果表明，三类榈的弧菌密度随季节呈春，夏〉秋，冬趋而变化。牡蛎体弧菌密度与水样、底质样弧菌密度之间的相关数值分别为０．８１４３和０．５９５５，二者都高于０．３２５，因此呈显著相关，而且前两者相关关系更密切。  相似文献   

Sedimentation flux from mariculture of oyster (Crassostrea Gigas) in Ofunato estuary, Japan   总被引：1，自引：0，他引：1  

Hayakawa  Y.; Kobayashi  M.; Izawa  M. 《ICES Journal of Marine Science》2001,58(2):435-444

  相似文献