Green algae. Hair-like green algae (Chlorophyta) clinging to rocks in a sandy estuary. These algae (probably Enteromorpha sp.) inhabit the intertidal zone, where freshwater from a river meets the sea. 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.