Distribution of subfossil ostracod assemblages in lacustrine profundal sediments of north-eastern Poland

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• 作者：Tadeusz Namiotko^a ; ^{namiotko@biotech.ug.gda.pl} ; Lucyna Namiotko^a ; Anna Wysocka^b
• 关键词：Poland ; Lakes ; Profundal ostracods ; Eutrophication ; Bio-indication
• 刊名：Revue de Micropaleontologie
• 出版年：2012
• 期刊代码：98_00351598
• 类别：ear
• 出版时间：January-March, 2012
• 卷：55
• 期：1
• 页码：17-27
• 文件大小：1616 K

摘要

The distribution of ostracod valves was studied in seven short (<聽50聽cm) sediment cores collected from the sublittoral-profundal zones (depth聽>聽12聽m) of four lowland, dimictic lakes (Kamedu艂, Szelment Ma艂y, Szelment Wielki and Szurpi艂y) situated in the Eastern Suwa艂ki Lakeland of NE Poland. These postglacial channel lakes are still moderate in trophy level, but to some extent, they differ from each other in the increase of anthropogenic alterations, especially in their hypolimnion. The studied sediment sequences, corresponding roughly to the period of the last ca. 300 years, yielded ca. 5500 valves of 20 ostracod species, out of which only seven are here considered as the autochthonous profundal component of the fossil assemblages: Candona candida, C.聽neglecta, Fabaeformiscandona protzi, F.聽tricicatricosa, Bentocypria curvifurcata, Cytherissa lacustris and Limnocytherina sanctipatricii. Valves of the remaining species were most probably subjected to postmortem transport from shallow water deposits or from lakeside and/or subaqueous springs, and thus were not deposited in situ at the deep bottom. By clustering classification and multi-dimensional scaling ordination, three major assemblage types were recognised in the moderately eutrophicated parts of the studied lakes: (a) assemblage dominated by C.聽candida, (b) assemblage dominated by C.聽lacustris and (c) the most diverse assemblage, in which four species (C.聽lacustris, C.聽candida, F.聽protzi and C.聽neglecta) occur in more or less equal percentages. On the other hand, sediments of the most eutrophic basins of the lakes (especially in Kamedu艂 and Szelment Ma艂y) are characterised by the decline of total valve abundances and complete extinction of C.聽lacustris, a species indicative of low trophy, so that, in extreme cases, a few valves (if any) of more eurytopic or only allochthonous species could be found in some of the uppermost layers. Successional transitions of the recognised assemblage types are discussed according to the generalised model of the deep lacustrine ostracod succession previously established for the Polish lakes on the country scale. The recorded assemblages correspond well with the trophic diversity of the studied lakes, confirming inferences based on previously published data on other trophy indices from this area. Finally, additional data on modern profundal ostracod fauna from dredge samples of the studied lakes are also provided.