Cyanobacteria are widely known by the common name blue-green algae because of their historical classification. While they are technically prokaryotic bacteria and not true algae (which are eukaryotic), they were originally called algae due to their aquatic nature and ability to perform oxygenic photosynthesis similar to plants. Their blue-green color primarily comes from the presence of photosynthetic pigments like chlorophyll a (green) and phycocyanin (blue).

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