Modern Diatom Assemblages in Surface Sediments from Estuarine Systemsin the Southeastern Buenos Aires Province, Argentina
Modern Diatom Assemblages in Surface Sediments from Estuarine Systemsin the Southeastern Buenos Aires Province, Argentina
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阿根廷布宜诺斯艾利斯省东南部河口系统表层沉积物中的现代硅藻组合
DOI：
10.1007/s10933-005-6444-8
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发表时间：
2006
影响因子：
2.1
通讯作者：
F. Isla
中科院分区：
文献类型：
--
作者：
G. Hassan;M. Espinosa;F. Isla
阿根廷沿海地区全新世海平面变化的古生态重建主要基于从其他地区收集的生态数据，因为缺乏现代河口硅藻分布的信息。本工作的目的是评估硅藻组合在阿根廷的两个代表性的河口，以收集该地区的古生态重建的生态信息的空间变化。这两个选定的河口有不同的地貌特征和盐度制度：Mar Chiquita泻湖是浅的，这阻止了稳定的盐度梯度的发展，因为它发生在Quequén Grande河。表层沉积物样品取自选定的代表两个河口从入口到内流的环境梯度的站点。聚类分析确定三个硅藻区在三月Chiquita：海洋/半咸水组合占主导地位的入口（区I），盐度，潮差和流速较高。半咸水/淡水的tychoetonStaurosira pennatadomate的内泻湖（区II），其中环境条件非常多变，悬浮沉积物的浓度较高。微咸/淡水广盐性硅藻占主导地位的源头（第三区）。另一方面，Quequén Grande河被划分为三个硅藻区：沿海类群分布在入口（I区），而中部河口（II区）以半咸水/淡水广盐类群为主。在上河口区（Ⅲ区），淡水硅藻占主导地位，和盐nitzschia denticula的丰度值增加。硅藻的分布最密切相关的盐度梯度在Quequén Grande河比在三月Chiquita泻湖。化石数据的一个序列从三月奇基塔泻湖（拉斯Gallinas溪）进行了比较，以寻找化石和现代硅藻组合之间的相似性的现代数据集。DCA结果表明，化石硅藻组合具有现代对应物。Las Gallinas Creek的大多数硅藻组合属于Mar Chiquita III区，代表浅咸/淡水环境，盐度波动较低（~1-9‰），没有潮汐影响。因此，我们的现代硅藻数据提供了有用的类似物来解释该地区的古环境。
Paleoecological reconstructions of Holocene sea-level changes in Argentinean coastal regions were based mainly on ecological data gathered from other regions, as there was a lack of information on modern estuarine diatom distributions. The aim of the present work was to assess the spatial variation of diatom assemblages in two representative estuaries of Argentina in order to gather ecological information for paleoecological reconstructions in the region. The two selected estuaries have different geomorphologic features and salinity regimes: Mar Chiquita Lagoon is shallow, which prevents the development of a stable salinity gradient as it occurs in the Quequén Grande River. Surface sediment samples were taken from selected stations representative of the environmental gradient from the inlet to the inner reaches of both estuaries. Cluster analysis defined three diatom zones at Mar Chiquita: marine/brackish assemblages dominate the inlet (zone I), where salinity, tidal range and current speed are higher. The brackish/freshwater tychoplanktonStaurosira construensvar.venterandStaurosirella pinnatadominate the inner lagoon (zone II), where environmental conditions are very variable and concentrations of suspended sediments are higher. Brackish/freshwater euryhaline diatoms dominate the headwaters (zone III). On the other hand, the Quequén Grande River was divided into three diatom zones: coastal taxa are distributed at the inlet (zone I), while the middle estuary (zone II) is dominated by brackish/freshwater euryhaline taxa. At the upper estuary region (zone III), freshwater diatoms dominate, and the halophobousNitzschia denticulaincreased in abundance values. Diatom distributions were most closely related to the salinity gradient at Quequén Grande River than at Mar Chiquita Lagoon. Fossil data of a sequence from Mar Chiquita Lagoon (Las Gallinas Creek) were compared to the modern data set in order to search for analogies between fossil and modern diatom assemblages. DCA results showed that fossil diatom assemblages have modern counterparts. Most diatom assemblages of Las Gallinas Creek fall within Mar Chiquita zone III, representing a shallow brackish/freshwater environment, with low salinity fluctuations (~1–9‰) and no tidal influence. Therefore, our modern diatom data provide useful analogs to interpret paleoenvironments in the region.