DEPTH
Increase in depth reduces light intensity, which therefore reduces the ability of organisms such as algae to photosynthesize. Greater depths often result in slow, consistent growth rather than the rapid seasonal growth that happens nearer the splash zone.
TEMPERATURE
In general, a rise in water temperature will increase thegrowth rate of a colony. The growth rate approximately doubles with a 10 degree Celsius rise in temperature. There will of course be a limit and most organisms cease growth at 30-35 degrees Celsius. As the temperature variation is the greatest nearer the surface, this explains why there is more rapid seasonal growth.
WATER CURRENT
The speed in which the water flows over the surface plays an important part in the type of fouling colony that develops. There are two aspects to consider. The faster the current, the more food and nutrients the organisms get, so growth is accelerated. But, too fast a current and the larvae find themselves initially unable to attach themselves to the structure.
SALINITY
In nearly fresh water, fouling is usually confined to algae slime. As the salinity increases, so the amount and type of fouling. Sea water is usually of a salinity of approximately 3% - 3.5%. The higher the salinity(up to a limit), the higher the level and size of marine growth.
FOOD SUPPLY
Growth of the fouling is obviously dependant on the quality of nutriment available. Growth rates seem to be faster in coastal waters rather than those a few miles offshore where the water is much deeper. Investigations suggest that the slow currents that circulate around platforms become enriched with nutriments from sewage and other waste that will increase marine growth.