Seeds, an emerging approach to seagrass restoration

JOHN STATTON

UNIVERSITY OF WESTERN AUSTRALIA

Although seeding is a common technique in terrestrial restoration programs, it is a relatively new concept in seagrass habitat restoration. Given the massive scale of seagrass losses, development of scalable techniques is becoming increasingly necessary in order to tackle seagrass restoration programs at hundreds to thousands of hectares. In addition, seeds add versatility to current practices, emerging as an alternative and potentially cost-effective approach for replanting large areas and in difficult locations. 

Researchers from the University of Western Australia (Prof. Gary Kendrick and Postdoctoral researcher Dr. John Statton) were awarded successive ARC linkage grants (2013 and again in 2016) partnering with local and regional industry (Cockburn Cement, BMT Oceanica, Shark Bay Salt) and authorities (Rottnest Island Authority) which fostered ongoing collaborations with world renown restoration ecologists, Prof. Kingsley Dixon from Curtin University and Botanic Gardens and Parks Authority as well as  Prof. Robert Orth, an international expert in seagrass restoration ecology from Virginia Institute of Marine Science in the US. 

 Our approach follows the rigors of terrestrial seed science, but adapted to an underwater environment. We have been successfully developing approaches to (i) streamline techniques for seed collection and processing to improve the availability of large quantities of viable, ‘restoration ready’ seeds, (ii) deliver large quantities of seeds remotely to the seafloor, thereby enhancing the scale of seeding and improving our ability to restore locations that are difficult to access (deep, turbid, turbulent, or diver-restricted locations), and (iii) identify and overcome critical environmental factors militating against seedling establishment post-delivery to the seafloor. 
Currently, a two-year pilot-scale seeding trial has established seedlings to the juvenile stage (2 years old) with 1-2 plants established every m2 and they are growing, producing new shoots with larger leaves (see figure and images below). 

Figure: Collection, processing, delivery and establishment of Ribbon Weed (Posidonia australis) seeds in Cockburn Sound, Western Australia.

fig i

Mature clusters of fruit.

FIG iV

Clean seeds (no fruit husks) are
collected from the tank bottom
and held in aerated baskets.
 

FIG Vii

3-4 month old seedlings

FIG ii

100 litres of fruit (hand – collected 30 000 fruit in 4 hours), 

FIG v

Seeds delivered to the seafloor via a broadcast seeding method (seeds scattered by a diver for precision or from a boat to maximise coverage).
 

FIG VIII

7 month old seedlings

Fig iii

Automated fruit processing – agitation from aeration causes fruit to split and seeds sink to the tank bottom, empty fruit are removed from the surface. 
 

FIG VI

Seedlings with a developing shoot.

FIG IX

1 year old seedlings
producing new shoots