Abstract The distribution of mid-Holocene, tropical benthic foraminiferal assemblages, including species' proportions, diversity, dominance and wall type, were analyzed for their correspondence to marine habitats and invertebrate facies. Benthic foraminifera are useful for paleoenvironmental reconstructions because the modern ecology of many species found as Quaternary fossils is known. Samples were collected from trenches in ~30,000 m2 of an excavated Acropora cervicornis-dominated, mid-Holocene reef with an age of ~6 kyr on Isla Colon (Colon island), bordering Almirante Bay in Bocas del Toro, Caribbean Panama. Bulk sediment samples were collected from a maximum depth of ~7 m below modern mean sea level and classified in the field into five invertebrate biofacies: 1) A. cervicornis-dominated reef, 2) molluscan mud, 3) Porites-Agaricia reef, 4) mixed coral, and 5) Lobatus-dominated seagrass. Sediment carbon and grain size analyses, a cluster analysis performed on the relative abundance of species per sample, and the Fisher's alpha diversity index were used to compare sample similarity and environmental variables to determine habitat relationships. Most samples contained high total inorganic carbon and poorly sorted, medium-coarse sediments. Principle component analysis of sediment grain size and carbon values did not show a clear correspondence among samples, habitat type or location of trenches. Foraminiferal assemblages in A. cervicornis and other reefal samples (categories 1, 3 and 4, above) had the greatest diversity and did not distinguish between the three reefal types, suggesting similar, normal marine conditions and/or mixing of coral fragments. Molluscan mud samples with high total organic carbon content were least diverse with dominant Ammonia and Elphidium taxa, though foraminifera in other molluscan mud samples showed a transition to proximal reef corals. Seagrass samples were differentiated from molluscan mud samples and had similar diversities and species assemblages to the Porites-Agaricia samples, and taxa known to be temporary grazers and living temporarily attached to seagrass blades are present in relatively greater amounts in these samples. Based on the distribution of foraminiferal species across this mid-Holocene coral reef, we conclude that it was a patch reef that included high-organic and seagrass facies similar to those of modern Almirante Bay. Results from this study can be compared to modern foraminiferal studies to investigate whether the modern habitats of BDT are significantly different from the pristine reefs of the mid-Holocene.

中文翻译：

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全新世中期珊瑚礁的有孔虫群落：科隆岛，加勒比海巴拿马

摘要 分析了中全新世、热带底栖有孔虫组合的分布，包括物种的比例、多样性、优势和壁类型，分析了它们与海洋生境和无脊椎动物相的对应关系。底栖有孔虫对于古环境重建很有用，因为作为第四纪化石发现的许多物种的现代生态学是已知的。样本是从约 30,000 平方米的沟渠中收集的，该珊瑚礁位于加勒比海巴拿马博卡斯德尔托罗的阿尔米兰特湾附近，位于科隆岛（科隆岛）上，年龄约 6 基尔的全新世中期珊瑚礁。从现代平均海平面以下约 7 m 的最大深度收集大量沉积物样品，并在现场将其分为五种无脊椎动物生物相：1) A. cervicornis 主导的礁石，2) 软体动物泥，3) Porites-Agaricia 礁石，4) 混合珊瑚，和 5) 以 Lobatus 为主的海草。沉积物碳和粒度分析、对每个样本物种的相对丰度进行的聚类分析以及费舍尔的 alpha 多样性指数被用来比较样本相似性和环境变量，以确定栖息地关系。大多数样品含有高总无机碳和分选不良的中粗沉积物。沉积物粒度和碳值的主成分分析没有显示样品、栖息地类型或沟渠位置之间的明确对应关系。A. cervicornis 和其他珊瑚礁样本（上面的第 1、3 和 4 类）中的有孔虫组合具有最大的多样性，并且没有区分三种珊瑚礁类型，这表明相似的、正常的海洋条件和/或珊瑚碎片的混合。具有高总有机碳含量的软体动物泥样品的多样性最少，主要是氨和 Elphidium 分类群，尽管其他软体动物泥样品中的有孔虫显示出向近端珊瑚礁的转变。海草样本与软体动物泥样本不同，具有与 Porites-Agaricia 样本相似的多样性和物种组合，已知为临时食草动物和暂时附着在海草叶片上的类群在这些样本中的含量相对较大。根据这个中全新世珊瑚礁中的有孔虫物种分布，我们得出结论，这是一个斑块礁，包括类似于现代阿尔米兰特湾的高有机相和海草相。