Human activity and its effects on marine intertidal plant and animal populations: monitoring and management

This thesis examines the relationships between human use and biological changes in the rocky intertidal zone of the Bunurong Marine Park, Victoria between January 1990 and June 1991. The key areas of activities were to i) describe the types and patterns of human activities on the reef, ii) assess the impact and recovery of reef biota to these activities with particular focus on Hormosira banksii, the dominant algal community and iii) determine the natural fluctuations in reef communities to provide a baseline to detect future changes in response to protection.

Surveys of human activities between January 1990 and April 1991 found walking to be the most common activity. Levels of human use were greatest during school holidays followed by weekends and were lowest during term weekdays. During school holidays use varied with the time of day and use on term weekend depended on weather.

The impact of collecting intertidal gastropods and trampling were investigated. There was no relationship between the observed patterns of human use and variations in the size distributions of collected and non-collected intertidal gastropods. Experimental trampling showed that the dominant alga on these reefs, Hormosira banksii, was severely affected by trampling. The cover of Hormosira was reduced by trampling and the decrease in cover depended on the level of trampling. No significant effects of trampling were detected for any other species. Trampled beds of Hormosirra banksii took well over a year to recover to the same level as adjacent mats.

Algal monitoring showed that the cover of Hormosira was stable over time, except for a large decrease due to desiccation in summer. These findings are discussed in relation to the management of the Bunurong Marine National Park.