Marine Biology

TIDES

The tides are caused by the gravitational pull of the moon and sun on the waters of the ocean.  As the earth is continuously rotating, the water is heaped in some areas causing a rise in water level in some places and reduction in other areas.  The tides may appear once in 12 and half hours.  These tides are called diurnal tides. The lunar tides are almost double the size of the solar tides and normally mask them except on two days viz. full moon and new moon when the pulls work together and increase the height.  This is the reason why tides on the full moon and new moon days have larger amplitude.  Those on full moon will be larger than on new moon.  The tidal range in most of the places is in between 5 and 7 metres.

      The ecological effect of tides depends on two factors: (1) the duration of exposure or immersion, and (2) the time at which the exposure occurs.  If the duration of exposure is very long, it will affect the intertidal fauna very much by causing desiccation and osmotic problems.  Exposure during midday and that too in summer will also affect the fauna adversely.