Observations of relic intertidal assemblages in an inland marine-spring of Eyre Peninsula, South Australia

ABSTRACT

Marine-springs containing relic intertidal species can be used to observe how assemblages usually found only on open coasts are structured when free from disturbances associated with water movement. This study tested if two previously described patterns from disturbance-prone boulder habitats occurred within a South Australian marine-spring. I aimed to determine how species are associated with the interface between boulders and the surface of the bottom sediment, a habitat feature suggested to be important for some key benthic invertebrates. Testing species associations to this feature is normally difficult because boulders and sediment are regularly disturbed, but on stable marine-spring boulders, fine-scale associations of species with this interface could be measured. Also investigated was a previously described negative correlation of peracaridan (Crustacea) densities with boulder size. This could possibly occur due to variability in disturbance related to boulder-size/stability, in which case the correlation would not be expected in this sheltered lake. Seven rocky-benthic marine species were found. The boulder–sediment interface could be easily located on overturned boulders. An anemone (Isanemonia australis) was highly abundant within 5 mm of this interface, providing evidence of this habitat feature’s importance. As found previously, correlations were significant between boulder size and densities of peracaridans (in this case, the isopod Zuzara venosa). This correlation, which has been described widely for similar species, has previously been attributed to disturbance. This study found it occurring in extremely sheltered environments, however, so disturbance is unlikely to be involved. Additional larger-scale comparisons could provide further information about the effects of sheltered/exposed conditions on these taxa.

KEYWORDS:

• Benthos
• disturbance
• saline lake
• invertebrate
• boulder habitat

Acknowledgements

I am grateful to Professor Brian Timms for insightful discussion about Seagull Lake. I thank Clarissa Fraser for providing helpful suggestions on an earlier version of the manuscript. The staff at the Department of Environment, Water and Natural Resources Streaky Bay office provided resources for field work.

Disclosure statement

No potential conflict of interest was reported by the author.