SEASONAL AND TEMPORAL ASPECTS OF RECRUITMENT AND SUCCESSION IN AN INTERTIDAL ESTUARINE FOULING ASSEMBLAGE

The recruitment and succession of fouling organisms was examined on four substrata (concrete, plywood, fibreglass and aluminium) in Quibray Bay of Botany Bay in New South Wales, Australia. Eighteen 10x10 cm panels of each substratum were submersed in each of four seasons: January (summer), March (autumn), May (winter) and October (spring) 1992. Six of each substratum were retrieved after 1 month, 2 months and 4-5 months. Thus in this study, as a methodological improvement over many other studies of succession, samples were taken independently with regard to time. Seasonal recruitment was important in determining the pattern of succession and the composition of the assemblage. Sydney Rock oysters, Saccostrea commercialis (Iredale & Roughley), recruited in large numbers on panels submersed in January and, by their rapid growth, dominated the available space after 4-5 months. The greatest recruitment of the barnacle Hexaminius sp. and the greatest percentage cover of algae (six species) occurred on panels submersed from October to March. While panels submersed in January for a period of 4-5 months resulted in a single outcome, an oyster-dominated-assemblage, panels submersed in October for the same period of time resulted in a set of alternative outcomes depending on the relative abundance of barnacles and algae. The results of this study suggested that models and mechanisms of succession in the marine environment should be based on the traits of individual species (including seasonal recruitment, growth and ability to resist invasion) with respect to the limiting resource(s) in the system, which for many sessile marine species is the available space.