The density of the animal population in any area of the sea bottom must be closely related to the food supply available. An increase in food may be expected to lead to more rapid growth and to more prolific breeding, and a consequent increase in the number of animals sustained on a given area of the bottom.
The amount of food available to the “basic” bottom fauna, consisting of plankton, detritus and bottom microflora (cf. Hunt, 1925), depends upon the amounts of plant nutrients in the water, which limit photosynthetic activity in the presence of sufficient light. The addition of fertilizers to an enclosed area like Loch Craiglin (Orr, 1947) might be expected to lead to a greater food supply, and thus to a greater density of the bottom fauna.