Cause Of Decline:

Driven by increased poleward penetration of the warm East Australian Current (EAC), the sea urchin Centrostephanus rodgersii (Diadematidae) has recently undergone a southern range extension in temperate south-eastern Australia. These urchins are able to eliminate macroalgal habitat and effect a catastrophic shift to an alternative sea urchin ‘barrens’ state. Thus, C. rodgersii grazing in eastern Tasmania is considered to pose a major threat to the structure and functioning of the biologically diverse macroalgal-dominated rocky reefs.

Site Observations:

Observation Date

19th Nov 2003 – 9th Nov 2005

Action Summary:

The long-spined sea urchin (Centrostephanus rodgersii) was removed from incipient barrens patches at an eastern Tasmanian site, and the macroalgal response and invertebrate diversity was monitored relative to unmanipulated barrens patches.

Project Outcomes:

In all incipient barrens patches from which C. rodgersii was removed, a structurally complex assemblage of foliose algae developed that was ultimately dominated by Ecklonia radiata and Phyllospora comosa. Filamentous algae and macroalgal sporophytes (height20 mm) recruited to available space and began to overgrow the substratum within 1 month. The pattern of re-colonisation for E. radiata (by cover) occurred consistently across C. rodgersii removal patches, while significant between-patch variability was detected for P. comosa and total canopy cover.

Key Reasons For Decline:

Overgrazing

Area of Restoration (Ha)

0

Indicator Data:

Indicator:	Ending Value:	Starting Value:
Kelp Cover	21.3213 %	0.0000 %

Observation Date

19th Nov 2003 – 9th Nov 2005

Action Summary:

Lessons Learned:

Removal of urchins can result in a macroalgal community that converges with natural kelp forests in diversity. Grazing activity of C. rodgersii results in an estimated minimum net loss of approximately 150 taxa (invertebrates and algae) typically associated with Tasmanian macroalgal beds in this region. Vertebrate diversity was not compared between groups.

Project Outcomes:

In barrens patches from which C. rodgersii was removed, there was a rapid proliferation of canopy-forming macroalgae (Ecklonia radiata and Phyllospora comosa), and within 24 months the algal community structure had converged with that of adjacent macroalgal beds where C. rodgersii grazing was absent. In the recovered macroalgal habitat, faunal composition redeveloped similar to that from adjacent intact macroalgal beds. In contrast, the faunal community of the barrens habitat is overwhelmingly impoverished. Grazing activity of C. rodgersii results in an estimated minimum net loss of approximately 150 taxa typically associated with Tasmanian macroalgal beds in this region.

Key Reasons For Decline:

Overgrazing

Area of Restoration (Ha)

0

Indicator Data:

Indicator:	Ending Value:	Starting Value:
Kelp Cover	48.7578 %	0.0000 %

University of Tasmania - Bicheno

University of Tasmania - Bicheno

Restoration Project

University of Tasmania - Bicheno

Restoration Objective:

Site Selection Criteria:

Cause Of Decline:

Overgrazing

Range expansion of a habitat-modifying species leads to loss of taxonomic diversity: a new and impoverished reef state

Organisation:

University of Tasmania

Site Observations:

19th Nov 2003 – 9th Nov 2005

Action Summary:

Project Outcomes:

Overgrazing

0

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Kelp Cover

3. Is Informed By Native Reference Ecosystems, While Considering Environmental Change

4. Supports Ecosystem Recovery Processes

6. Seeks The Highest Level Of Ecosystem Recovery Possible

19th Nov 2003 – 9th Nov 2005

Action Summary:

Lessons Learned:

Project Outcomes:

Overgrazing

0

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Kelp Cover

3. Is Informed By Native Reference Ecosystems, While Considering Environmental Change

4. Supports Ecosystem Recovery Processes

6. Seeks The Highest Level Of Ecosystem Recovery Possible