Preface

Infauna is the name given to those animals that live within the sediments of the sea floor. The majority live within the first few centimetres of the surface where oxygen is more readily available. The most familiar animals are the easily visible macrofauna which include clams, worms, crabs, echinoderms and fish. These animals either ingest or displace the sediment particles around themselves as they move. At the other end of the size scale are those animals, often extremely numerous, which are less than 50 millimetres in size. These organisms, classed as microfauna, are normally studied with the aid of a magnifying tool, such as the microscope. Intermediate in size between the macrofauna and microfauna is a very abundant group of animals, called the meiofauna. The meiofauna are also referred to as interstitial animals, as they occupy the spaces between sediment particles.

In many locations, particularly at depths where insufficient light penetrates to stimulate plant growth, the organisms of the sea floor depend ultimately on the steady rain of food particles that descend from the upper layers of the ocean. The sea floor collects and accumulates plankton, waste material, and other plant and animal debris that sink from the waters above. A variety of worms, molluscs, echinoderms, and crustaceans obtain their nourishment by ingesting the accumulated detritus and digesting its organic material. Other organisms filter particles out of the surrounding water and some roam across the surface in search of prey or to scavenge dead, organic matter. These animals play an important role in the cycling of nutrients in the world’s oceans.

Research into the benthic ecosystems of the world’s continental shelves has been most comprehensive in temperate rather than tropic latitudes (see Alongi, 1990), notwithstanding some substantial work on the east and west coasts of India and along the west coast of Africa. Our knowledge of the Continental Shelf soft-bottom ecosystems of tropical Australia is quite restricted, derived from relatively shallow water research in the Great Barrier Reef province (e.g. Alongi, 1989a, b; Alongi and Hansen, 1985; Birtles and Arnold, 1983) and a handful of studies across the top end of Australia and the North-West Shelf (see Long and Poiner, 1994; Hanley, 1993, 1994). This Atlas adds to this still largely incomplete picture by documenting the benthic infauna at three sites on the Australian Continental Shelf in the Timor Sea, in water depths of greater than 50 metres.

A number of sites on the Continental Shelf, adjacent to the Big Bank Shoals, were sampled to determine the infauna of the region. Polychaetes and crustaceans were the dominant organisms found here, with the rest of the samples made up of various echinoderms, molluscs, nemerteans, sponges and fish. These communities, sampled from greater depths than other similar studies in the region, are consistent with what would be expected from Continental Shelf regions. In the following section we will discuss some of the general biology of infauna and the ways in which this may affect the communities of the Continental Shelf.

Methods
Regional infauna
Polychaetes
Crustaceans
Other infauna organisms