Biogenic habitats and their effects on native and exotic associated invertebrates

Denise Bunting (Supervisors: Assoc. Prof. Ross Coleman, Dr Will Figueira and Dr Emma Johnston)


Background
Denise & Fabiana in the field

Many organisms in terrestrial, freshwater and marine environments create structures with their living and/or dead tissues (e.g. coral reefs, seagrass meadows) that provide habitat and other resources that are utilised by many other organisms. Artificial structures in harbours and bays, such as pontoons, pilings and seawalls are often occupied by these habitat-forming organisms (for example; mussels and oysters) and generally have relatively large and diverse associated species assemblages. Organisms living amongst these habitats are from a wide range of taxa, including sessile species such as sponges and ascidians, and mobile species such as polychaete worms and crabs.
Non-indigenous (exotic) species are prevalent in harbours and bays worldwide and previous studies have shown that there are exotic species found on artificial structures than natural rocky shores. Few studies into the recruitment or presence of exotic species have considered which species (habitat-former) is the primary space occupier, which may be an important factor in explaining the successful establishment of exotic species.

Aims

To determine the effects of different biogenic habitat-forming species on native and exotic species assemblages, in order to increase our knowledge of mechanisms explaining distributions of exotic species.




Importance
Cirolana harfordi

Determining the effects of habitat-forming species on native and exotic species assemblages, will increase our knowledge of the processes and mechanisms behind the spread of non-indigenous species. Understanding some of these mechanisms will lead to more accurate predictions of changes in ecosystem biodiversity and may be useful in invasive species management.

Results

The data collected has shown that there are more exotic species living in the habitat created by an exotic mussel Mytilus sp. than in the habitat created by the native mussel (Trichomya hirsute) or habitat created by oysters. There was, however no difference in the numbers of exotic species within these habitats on artificial structures when compared to natural rocky shores. An exotic isopod found amongst the associated assemblages is being used as a model organism to test hypotheses about distribution and habitat use in the harbour and whether an exotic habitat-forming organism is facilitating successful establishment of other exotic organisms.