Green algae. A mass of hair-like green algae (Chlorophyta), half immersed in water, clinging to rocks where a river enters the sea. These algae (probably Enteromorpha sp.) inhabit an intertidal zone where freshwater and seawater mix. They are adapted to exploit a habitat that is rich in nutrients and sunlight but subjected to severe environmental stresses. These stresses include constantly changing salinity and temperature, occasional drying out, and bashing by waves. Algae are primitive plants that have no true leaves, stems, roots, flowers or veins. Like higher plants they can photosynthesise (grow using the Sun's energy). Photographed in north-west Scotland.