Aquascope Facts
Cliff and rocky beach ecology

Variations in water level

Fisherman´s hut at low tide Fisherman´s hut at high tide
Those factors that we have shown earlier, that make it difficult for organisms to survive in the beach environment, are mainly due to the fact that the beach area is periodically flooded and drained - tides. These variations can take place during a period of a few hours, but at other times, the water level can remain unchanged over a period of several days. In the long term,sea level changes with changes in climate and land elevation.In the northern Baltic, where isostatic readjustment is most pronounced, land elevation is about 1cm a year.
    The highest high tide in relationship to the mean water level ever recorded in Swedish waters was +181 cm at Kalix in 1984. The lowest was -144 cm at Ystad in 1902.
    In Swedish waters, recurrent changes in sea level are mainly the result of three phenomenon:
  • Influx of water - Sometimes, the variations in the flow of freshwater to the Baltic are so great, they effect sea level.
  • Tides - due to the gravitational pull (movement and attraction) between the earth, sun and moon.
  • Weather - where differences in air pressure and wind intensity transport water and cause a slight inclination of the sea surface.

    The weather has most effect

    In the farthest reaches of the Baltic, tidal effect is of little importance, with variations of only a few centimetres. However, tidal differences increase further south in the Baltic, thereafter, even more in a northerly direction along the Swedish west coast. In northern Bohuslän, noticable tidal differences of up to 3 dm occurr twice daily.
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  • Cliffs and rocks are fantastic!
    Zoning and flecked occurrence
    Animals that are attached
    Modular construction
    Variation and change
    Variations in water level
    Wave exposure
    Both cliffs and rocks
    Freshwater and saltwater
    Geography, climate and history
    Organisms life cycles
    Organisms effect on each other
    Energy and the flow of material

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    Bo Johannesson | Martin Larsvik | Lars-Ove Loo | Helena Samuelsson