Marine Bioregions
The drowning of Bass Strait about 12, 000 years ago and the effects of the dominant physical influences of winds, seas, swells and tides on Tasmania have generated a number of strikingly different marine ecological communities.
Marine environments can be classified into a hierarchical system of large biogeographical provinces and smaller bioregions. At the broadest level, there are two distinct types of marine environments in Australia: the temperate south and the tropical north.
These overlap on the western and eastern coastlines of the Australian continent. In the south, which has been geographically and climatically isolated for around 35 million years, about 80–90% of species of most marine groups are endemic, whereas only 10% of species in most groups in the north are endemic. As a result, the marine environment of Tasmania and similar southern areas is in many ways more significant in world terms than tropical areas such as the Great Barrier Reef.
The Tasmanian marine environment has two biogeographical provinces: the Bassian bioprovince and, further south, the Tasmanian bioprovince. In addition, the waters around subantarctic Macquarie Island are in the Insulantarctic bioprovince. Based on the distribution of reef plants and animals, the Bassian and Tasmanian marine bioprovinces are each divided into four distinct bioregions.
A map showing the approximate locations of Tasmania's marine bioregions. 
Table illustrating the distinguishing characteristics of each of the Bioregions sourced from the State of the Environment Report 1996.
| Bioprovince | Bioregion | Distinguishing biota |
|---|---|---|
| Bassian | Boags | presence of the seagrass Posidonia australia |
| Otway | presence of species found in South Australian waters with significant similarities to intertidal invertebrate species at King Island and Cape Otway | |
| Flinders | regional affinities in the fish and plant communities | |
| Gippsland | shallow (<15m) reefs, encrusted by corralline algae and generally without macroalga; fish fauna from Victorian waters | |
| Tasmanian | Franklin | low diversity compared with the rest of Tasmania |
| Davey | distinct algal flora; low diversity of fish species | |
| Bruny | highest localised level of marine endemism in Tasmania (and probably Australia) leading to distinct reef and soft-sediment fauna assemblages | |
| Freycinet | several species, particularly fish, present there but not further south (fish include warm temperate species) | |
| Insulantarctic | Macquarie | marine biota almost completely different from that found elsewhere in Tasmanian waters |
