Precipitated calcium carbonate was found in annual cyanobacterial mats developing on the beaches of the North Sea barrier island Schiermonnikoog (the Netherlands). A variety of different calcium carbonate morphs were found in the cyanobacterial mucous secretions and identified by light- and scanning electron microscopy and X-ray diffraction. Most of the calcium carbonate seemed to be associated with degrading extracellular polymer. It is conceived that supersaturation of calcium carbonate resulted from the periodic evaporation of the mats and from the release of calcium from the cyanobacterial mucous as a result of its degradation. The analysis of the carbon stable isotopic composition of the calcium carbonate showed only a slight depletion of (13)C, indicating that it did not in major part originated from the decomposition of organic matter. The delta(18)O values of the calcium carbonate confirmed the temperature differences between spring and summer but excluded the possibility that excessive evaporative events controlled precipitation. The precipitation of calcium carbonate could represent a potential factor enhancing the stabilization of intertidal siliciclastic sediments through cementing the sand. The discovery of massive calcium carbonate precipitation in these cyanobacterial mats was unexpected and hitherto unknown.

中文翻译：

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在北海的沙质潮滩中，蓝藻垫中的碳酸钙沉淀。

在北海屏障岛Schiermonnikoog（荷兰）的海滩上生长的一年生蓝藻垫中发现了沉淀碳酸钙。在蓝细菌的粘液分泌物中发现了各种不同的碳酸钙形态，并通过光学和扫描电子显微镜以及X射线衍射对其进行了鉴定。大部分碳酸钙似乎与降解细胞外聚合物有关。据认为，碳酸钙的过饱和是由垫子的定期蒸发和由于降解引起的蓝藻粘液中钙的释放所致。对碳酸钙的碳稳定同位素组成的分析显示，（13）C仅有少量消耗，表明它主要不是源自有机物的分解。碳酸钙的δ（18）O值证实了春季和夏季之间的温度差异，但排除了过度蒸发事件控制降水的可能性。碳酸钙的沉淀可能是通过固结沙子来增强潮间带硅质碎屑沉积物稳定性的潜在因素。在这些蓝细菌垫中发现大量碳酸钙沉淀是出乎意料的，而且迄今为止是未知的。