The Ecology and Distribution of Intertidal Organisms on the Rocky Shores of the Queensland Mainland

Abstract

This paper records investigations made on the ecology and biogeography of organisms found on rocky shores in eastern Queensland.

Traverses were made at selected localities along a region of the coast bounded by the New South Wales-Queensland border (lat. 28º 15' S.) to the south and Whitecliffs (lat. 16º 39' S.) to the north. An account of general physiographic features and environmental factors in this region is given.

It was found that the majority of typical Peronian organisms extended as far north as about lat. 25º S. North of lat. 25º S. tropical species occurred and the degree of overlapping of species from the two adjacent faunas was very small. However, the Moreton Bay-Caloundra region offered a refuge for some tropical forms.

Zonation patterns on either side of the biogeographical boundary differed. In southern Queensland the zonation picture was similar to that in New South Wales as described by Dakin, Bennett , and Pope (1948); but in northern Queensland an oyster zone dominated the upper half of the intertidal region, whilst in the lower half a barnacle zone replaced the serpulid zone found in southern Queensland and New South Wales.

The effects of various environmental factors on zonation on Queensland shores are discussed. It has been found that generalizations made by Evans (1947b) regarding zonation on British shores are only partially applicable to zonation in southern Queensland. Possible reasons for the differences noted are discussed. Also, the rate of change of percentage exposure to the air, which Doty (1946) has shown to be so potent a factor in determining the zonation of organisms at all levels in the intertidal region of the coasts of Oregon and northern California, apparently determines only the upper levels attained by organisms which extend above mean high water neap tide level on southern Queensland shores.

Analyses of the effects of varying environmental factors, including gross environmental changes relating to latitude, on faunistic composition have been made. These have given much information on the general ecology of many common Queensland rocky shore species. Moreover, they have thrown much light on the reasons for the existence of a biogeographical boundary near latitude 25º S. In particular they have shown that such factors as the degree of wave action and salinity are possibly of more importance than temperature in determining the position of this boundary.