Good and bad years
(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.
|Cliffs and rocks are fantastic!|
|Zoning and flecked occurrence|
|Animals that are attached|
|Variation and change|
|Variations in water level|
|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|