Marine Wildlife Encyclopedia
Black Tar Lichen Verrucaria maura
Black tar lichen is a smooth, black, crustose lichen that covers large areas of bedrock or stable boulders in a thin layer, making them appear as though they have been covered with dull black paint. Many types of lichen accumulate heavy metals, and the black tar lichen is no exception, having been found to have levels of iron that are about 2.5 million times more concentrated than the surrounding seawater. That may be an adaptation to deter grazers, such as gastropods, from eating it.