During low tide, wide and rapid changes of temperature are sometimes encountered on the shore. Strong sunshine can produce high temperatures on exposed shore surfaces, and the temperature of water standing on the shore when the tide recedes may be raised well above the normal limits of sea temperature. Shallow pools on English coasts sometimes reach a temperature of 25-30°C on hot summer days. In the tropics, temperatures of 50°C or higher have been recorded in shore water.
Intertidal organisms may also be exposed to severe frosts. When shore water freezes they face the additional dangers of moving ice which may scrape them off the rocks or crush them within their hiding places. In high latitudes the shore may be kept virtually barren by the effects of moving ice.
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