Authors: Beaman, R.J.
Publication: PhD Thesis, University of Tasmania, Hobart, Australia, pp. 156.
Continental shelf waters are subject to the greatest impact by humans. If marine ecosystems are to be efficiently managed and protected from the adverse effects of human activities, then identification of the types of marine habitats and the communities they contain is required. Research cruise data and existing data were collected at three diverse study sites on polar, temperate and tropical continental shelves within Australia’s Exclusive Economic Zone (EEZ). This project conducted a multi-disciplinary analysis of satellite imagery, multibeam sonar, seismic profiles, oceanographic data, underwater video, and the results of sediment sampling. A Geographic Information System (GIS) was utilised to model the spatial boundaries of the physical and biological datasets. Spatial and multivariate statistical analyses were conducted on the GIS models and datasets to explore the relationships between abiotic and biotic patterns. GIS was used to map the spatial distribution of benthic habitats at each study site within a hierarchical context.
The East Antarctic continental shelf has had few studies examining the macrobenthos structure or relating biological communities to the abiotic environment. On the George V Shelf, GIS was used to map the geomorphology, surficial sediment and near-seabed water mass boundaries. A study of underwater photographs and the results of biological sampling provided information to infer the dominant trophic structure of benthic communities within geomorphic features. A hierarchical method of benthic habitat mapping was applied to the Geomorphic Unit and Biotope levels at the local (10s of km) scale. The study revealed that mud content, iceberg scour, and oceanic currents are the likely dominant abiotic factors in the broad-scale distribution of macrofauna on the George V Shelf.
To better understand the relationships between the geology of the seabed and associated biological communities, a multibeam sonar survey was conducted over New Zealand Star Bank, eastern Bass Strait, Australia. Through spatial and multivariate analyses of surficial sediment composition and underwater video, the biological assemblage patterns were related to the variation in geomorphology and substrate. A hierarchical method of benthic habitat mapping was applied to the Secondary Biotope and Biological Facies levels at the site (<10 km) scale. The major differences which control the distribution of biological communities in the New Zealand Star Bank area appear to be related to variations in substrate.
To help answer the question whether geophysical data from habitats can be used to predict the occurrence of benthic biodiversity, a multibeam sonar survey was conducted in the northern Great Barrier Reef – Gulf of Papua region. Multivariate statistical analyses were applied to the biological and physical datasets to determine patterns in the distribution of megabenthos, and the relationship with abiotic variables. A hierarchical method of benthic habitat mapping was applied to the Secondary Biotope and Biological Facies levels at the site (<10 km) scale. The combination of substrate type, sedimentary dynamics and physical processes related to nearseabed currents appear to be a dominant control on the benthic communities in the northern Great Barrier Reef – Gulf of Papua region.
Benthic habitat mapping plays a vital part in understanding marine ecosystems and the processes which influence the spatial distribution of benthos. The results of this research have made significant in-roads in the development of a framework for ecosystem-based management of the study areas, the contribution to the ongoing bioregionalisation of Australia, and through an examination of the use of geophysical proxies for the occurrence of biological assemblages, which are fundamental to the establishment of Marine Protected Areas.