Spatial patterns of surface sediment variables in the littoral zone of Lake Constance (Germany)

Author： Schmieder K. Schünemann B. Schröder H.G.

Publisher： E. Schweizerbart'sche Verlagsbuchhandlung

ISSN： 0003-9136

Source： Archiv fuer Hydrobiologie, Vol.161, Iss.4, 2004-12, pp. : 455-468

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Abstract

A lakewide investigation of littoral surface sediments at Lake Constance gave information on spatial patterns of sediment composition and led to a better understanding of external and internal factors that affect sediment formation on a regional scale. Grain size analyses showed relations between both grain size means and the proportion of the silt and clay fraction at 2 m water depth and the intensity of wave action as described by the effective fetch of the main wind direction. Mean grain sizes of wind exposed northern littoral areas were higher than those of southern protected areas, which also featured higher proportions of silt and clay, resulting in a general north-south gradient of these two sediment characteristics. The sorting effect of the wave action on grain size composition was manifested in a depth gradient of the grain size means. Mineralogical analyses revealed negative correlations between calcite and siliciclastic as well as dolomite minerals. In particular, the linear regression between calcite and clay minerals displayed a high coefficient of determination and significant interactions with depth. The high correlations between the mineral constitutents were associated with an east-west gradient in sediment composition. The east-west gradient mainly resulted from two different processes: external input of dolomite, clay, and quartz minerals into Lake Constance from shore erosion and from eastern tributaries in the alpine and prealpine part of the catchment area, and biogenic calcite production by macrophytes and molluscs mainly in the western part. Areas of high sediment calcite content corresponded to the long-term distribution patterns of Chara contraria. Littoral areas near the few river mouths in the western part of Lake Constance were exemptions to the general pattern in sediment distribution.