(Table 1) Quantitative analysis of mollusk taxa from surface sediment samples in the Golfe d'Arguin

Ecological and taxonomic study of the mollusk-rich fauna of the Golfe d'Arguin, North Mauritania, investigates the various environmental influences affecting this tropical shelf. The upwelling of nutrient-rich waters leads to a highly productive environment under tropical conditions. The resulting mixed carbonate-siliciclastic sediment contains a large portion of calcareous components produced by heterotrophic organisms--e.g., mollusks, foraminifers, worms, barnacles--that are reworked on the open shelf. On the basis of mollusk assemblages, six taphocoenoses are defined, all being characterized by a mixed fauna of tropical (e.g., Tellina densestriata), subtropical (e.g., Macoma cumana) and temperate (e.g., Spisula subtruncata) species. Differences between the assemblages are related to the medium--grain size ranging from mud to gravel--that results from local hydrodynamic conditions and water depth. Among carbonate grains, Donax burnupi shells are very abundant in the swell-exposed, northern part of the Golfe d'Arguin and reflect the tropical to subtropical, high-energy, and high-nutrient waters. Mollusk assemblages are demonstrated to be a sensitive tool for deciphering complex environmental conditions in sedimentary archives.毛里塔尼亚北部阿尔金湾（Golfe d'Arguin）软体动物富集动物群的生态与分类学研究，旨在探讨影响该热带陆架的各类环境因素。营养丰富水体的上升流作用在热带环境下造就了高生产力的生境。由此形成的碳酸盐-硅质碎屑混合沉积物中，含有大量由异养生物（如软体动物、有孔虫、蠕虫、藤壶）产生的钙质组分，这些组分在开阔陆架上经历了再改造作用。基于软体动物组合，本研究划分出6种埋葬群（taphocoenoses），其均以包含热带（如*Tellina densestriata*）、亚热带（如*Macoma cumana*）与温带（如*Spisula subtruncata*）物种的混合动物群为特征。各组合间的差异与沉积物粒度相关，粒度范围从泥质到砾石，该特征由当地水动力条件与水深共同决定。在碳酸盐颗粒中，*Donax burnupi*的壳体在受涌浪影响的阿尔金湾北部区域极为富集，其指示了热带至亚热带、高能量且高营养盐的水体环境。研究证实，软体动物组合可作为解译沉积记录中复杂环境条件的灵敏工具。