Seagrass Restoration Project 2002

Seagrass Restoration Project 2002

This was the first full scale seagrass transplanting experiment to be undertaken in Western Port. It was a partnership project between the Natural Heritage Trust, EPA Victoria and the Western Port Seagrass Partnership.

The project had four elements:

Identification of suitable sites for transplants.
Development of seagrass transplant techniques.
Establishment of procedures to cultivate seagrass in vitro.
Community education – (Elements of DRI “I sea, I Care” program).

Executive summary of all these activities – PDF
Full report on the research elements – PDF
Monash University paper on in vitro growth experiments – PDF

Key Research Conclusions

Transplants

Tim Ealey measuring seagrass plug growth

Transplanted seagrass cores

Site selection is critical to success with water quality and substrate being prime considerations and the site selection methodology seemed sound. The most successful transplant technique was the use of 15cm plugs, obtained by use of PVC tube corers at donor sites. Due to seasonal influences, Autumn appeared to be the optimal time to undertake transplants. Further work is required to determine optimal depths, light and nutrient levels. More work is required on how to minimize sediment movement and inundation of transplants. (Subsequently deemed impractical)

In Vitro Experiments and Post Experimental Observations

Seagrass plug showing radial growth. Photo: T. Ealey, WPSP

Seagrass growing in culture

Viable aseptic tissues of seagrass (Heterozostera tamanica) can be established in vitro with exhibited growth. Further work is needed to develop optimal levels of additives, improved physical growth conditions and alternative sterilization techniques to reduce toxicity effects.

During the course of this experiment, clear evidence of expanded seagrass growth beyond the initial cores was noted in many cases, indicating the technique worked, and the water quality was appropriate to support growth in the Coronet Bay section. However, most cores were eventually lost, being covered by sand drift due to tidal and storm events, showing that substrate instability was another factor to be considered with seagrass re-establishment efforts.

Subsequent Larger Scale Seagrass Planting

The WPSP went on to plant 1,000 seagrass plugs in a series of transects along the Coronet Bay coast in an attempt to discover the most suitable site for a larger experiment. These cores were monitored to record survival and growth. In October 2004 another 500 cores were planted in 10 rows of 50, two metres apart and at 2 metre centres. This planting was carried out where the initial trials had shown conditions were most suitable. A 10 gm dose of high potassium Osmocote was placed under each core with the objective of stimulating growth and seeding.

Some seagrass cores died, others were washed away and some smothered with sand, but many expanded from 15 cm to three metres in diameter. Seagrass produces seed in December, but no seeds were produced at these sites during the monitoring period even though seagrass seeds were found on a natural seagrass patch north of the experimental area. High potassium Osmocote continues to be injected beneath the experimental seagrass at six monthly intervals.