Aquascope Facts
Cliff and rocky beach ecology

Good and bad years

For those cliff and rocky beach organisms that have a planktonic distribution stage there are two factors that have a large effect on their population densities in different areas:
(1) The size of the population within a certain area is dependent of how many individuals survived the journey to the area in question, and
(2) how well they etablish themselves upon arrival.
Many organisms die during their journey. Many individuals are for example carried away from coastal areas and never get a chance to establish themselves on a beach. Others are eaten by other creatures during their journey. Many larvae are an important source of food for plankton and fish.
   Most larvae must live in the open water for a certain period of time to allow them to eat and grow before they can attach themselves to a solid foundation and became bottom dwellers. When a larva is mature enough to attach to some form of foundation it usually investigates the surroundings to determine if it is suitable. This moment, when it is falling towards the bottom is often critical and also a time when many larvae die. First they have to find a free area with the right stimulus to aid their change to a bottom-living stage. Then they have to survive the metamorphosis from a free swimming larva to an attached individual. Even if everything goes well, individuals still have to cope with living on its foundation until it reaches adulthood and can produce its own larvae in large enough quantities so that enough of them also reach adulthood and can themselves reproduce.
<A href="../../arter/mollusca/prosobra/gastveli/">[Watch a periwinkle larvae swim! 941 kB]</A> Cypris-larva 4 kB
In the film on the left, a perwinkle larva is seen. It is swimming around catching food so that it can grow into a fully developed bottom-living periwinkle. To the right, a barnacle larva (cypris) is seen. It has became so large and well developed so that it is looking for a place where it can attach itself and change to the adult stage. Both larvae have been magnified in a microscope.

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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