As the Spray Zone reaches toward the water, it overlaps with the Upper Intertidal.The Upper Intertidal is covered by water only briefly during the highest tides. Calothrix, one of the cyanobacteria (blue-green algae) thrives here. The rough periwinkle, Littorina saxatilis, ventures up out of the tidepools to feed on the nitrogen-rich Calothrix. The black color on the rocks is caused by the growth of many microsopic plants. Cyanobacteria and filamentous green and red algae dominate the plant growth. Many of these plants encase themselves in gelatinous or slimy coverings. Let's meet these plants...