Deakin University - Warrnambool

Restoration Project

Deakin University - Warrnambool

Restoration Objective:

This study tested hypotheses associated with the model that H. banksii assemblages and coralline turfs are alternative stable states whereby the coralline turfs are maintained by exclusion of successful recruitment of H. banksii propagules through structural aspects of the turf.

Site Selection Criteria:

All selected sites were intertidal rock platforms of dune limestone/sandstone conglomerates in Victoria, Australia. Sites were chosen that had been historically impacted by sewage outfalls, with a resulting change in algal assemblages, while other sites had no sewage outfalls nearby.

Cause Of Decline:

In many parts of Japan, algal beds have been reduced by many factors, including grazing by herbivores, higher water temperatures/low nutrients, sedimentation and enhanced typhoons. In southern Japan, reduction of seaweed beds is becoming more serious than in other parts of the country. This is because the shallower waters experience higher water temperatures and they are largely oligotrophic, frequently affected by typhoons, and extensively inhabited by herbivorous fish and sea urchins.

Key Reasons For Decline:

Water Pollution

Scientific Paper

Restoration of the habitat-forming fucoid alga Hormosira banksii at effluent-affected sites: competitive exclusion by coralline turfs

A. Bellgrove, P.F. McKenzie, J. L., B.J. Sfiligoj
Marine Ecology Progress Series, Vol. 419.
https://doi.org/10.3354/meps08843

Organisation:

Deakin University

Australia

Site Observations:

Observation Date

15th Apr 2005 – 30th Apr 2005

Action Summary:

Sites were surveyed using quadrats to calculate percentage cover of the coralline algae Corallina officianis, the algae Hormosira banksii and rocky substrata. In addition, H. banksii zygotes were embedded into 10x10cm artificial substrata constructed to mimic rock, turf and coralline algae surfaces. Rock mimics were made of polyester resin cast from moulds of rock surfaces. Turf mimics were made from 4mm synthetic grass embedded in polyester resin. Dead coralline turf substrata were constructed from 10x10xm pieces of dense Corallina officinalis turf that had been dried at 60c for 24 hours to kill turf and infauna, and embedded in resin. Molluscan exclusion fences of copper-painted zincalume ant caps were placed beneath each of the panels in the field experiment to exclude herbivorous molluscs.

Lessons Learned:

This study showed removal of coralline turfs can improve restoration of H. banksii to shores that have been affected by sewage effluent.

Project Outcomes:

The percentage cover and number of individuals of H. banksii were negatively correlated with both the percentage cover and turf height of Corallina officinalis. In contrast, H. banksii was positively associated with rocky substrata and recruited well to rock-surface substrata. There appears to be a threshold abundance where the percentage cover of H. banksii rarely reaches above 20% cover amongst coralline turfs with >40% cover. In field and laboratory experiments, extensive coralline turfs (up to 4 cm thick) were shown to inhibit recruitment of H. banksii.

Key Reasons For Decline:

Water Pollution

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Juvenile Kelp Density

0.0022
/ m2
0.0000
/ m2
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