BENTHOS STRUCTURE ON TROPICAL TIDAL FLATS OF AUSTRALIA

General features of benthos communities of tropical tidal flats are de fined from northeast Australia, based on surveys from 1988 to 1991 in Hinchinbrook Channel and in the Haughton River estuary. A zonation of benthic communities is described. Total abundances for macrofauna aver aged 31 individuals 200 cm(-2), mesofauna (defined as infauna smaller than 0.5 mm and retained on a 0.25 mm sieve) averaged 16 individuals 1 0 cm(-2) and meiofauna averaged 231 individuals 5 cm(-2). The two stud y sites were similar in their abundance structures, but species number s were higher in Hinchinbrook Channel (227) than in the Haughton estua ry (96). This was due to a higher diversity of polychaeta in the Chann el (120 species, H' = 3.80 vs. 29 species and H' = 1.78 in the Haughto n estuary). Species densities were comparable at both sites and rather low (6 species 177 cm(-2), 2-7 species 10 cm(-2) and 5 meiobenthic Pl athelminth species 5 cm(-2)). Over 50 % of the species encountered wer e represented by less than three individuals. Deposit feeders dominate d the assemblages both in terms of individuals as well as species numb ers. Tropical tidal flats are compared with their temperate counterpar ts and approaches for future research in tropical benthos communities are recommended.