Zoology - Theses
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ItemEcological studies of barnacles in temperate mangrove forests( 1997)I have examined the horizontal distribution and abundance of Elminius covertus across three zones, landward, middle and seaward, of mangrove forests at Rhyll, Phillip Island, Victoria during 1995-1997. In the seaward zone of the forest, the vertical abundance of E. covertus between 0-15 cm from the bottom was also investigated. To determine what processes affect these horizontal and vertical patterns, presettlement, settlement and recruitment of E. covertus have been examined. The horizontal distribution of adults reflected the horizontal pattern of recruitment and settlement. The horizontal pattern of settlement was determined by larval supply and larval behaviour. Post-settlement factors had little influence on this pattern. Consequently, the horizontal pattern of adults were ultimately explained by patterns of larval supply and larval behaviour. The distribution of adults on pneumatophores reflected the vertical pattern of recruitment, but contrasted with the vertical pattern of settlement. Variability in the vertical distribution of settlers reflects larval settling behaviour not larval availability and the vertical pattern of recruits and adults is determined by post-settlement mortality. The patterns of settlement of E. covertus on seedlings of Avicennia marina in the seaward zone of the forest were also documented, with the greatest density of barnacles found on the stem, followed by the lower-leaf and upper-leaf surfaces. No further studies were undertaken to test what processes determine this pattern. The presence of E. covertus produced no negative effects on the survival and growth of seedlings of A. marina. Seedling survival appears to depend on other factors, such as, intermittent smothering by drift algae, seagrasses, and sediment as well as unfavourable climatic conditions, especially low temperatures and strong winds and currents.