Seagrass transplantation in a high energy environment

M. van Keulen; E.I. Paling

This paper will briefly review some of the seagrass transplantation studies conducted by the Marine and Freshwater Research Laboratory at Murdoch University in the Success Bank region off the Perth metropolitan coast over the past eight years. Initial studies examined the role of transplant size and sediment stabilization on survival, arriving at the conclusion that larger transplants survive better, and that sediment stabilization is an important factor in transplant survival. These studies gave rise to the concept of mechanical transplantation of large blocks ("sods") of seagrass. "ECOSUB1" was the prototype developed as part of the Environmental Management Plan for Cockburn Cement Ltd., which mines shellsand on Success Bank. Improvements in the technology led to ECOSUB2, which consists of two machines operating simultaneously, one harvesting seagrass and the other planting it. A sod shuttle is used to transfer sods from one machine to the other which greatly increasing the efficiency of the operations. The theoretical maximum output of ECOSUB2 is 75 sods, or 40m2, per day. Experimental work to supplement the mechanical transplantation programme included studies on transplanting seagrass to different depths, and an examination of wave energy effects on survival. The depth studies suggested that it was possible to transplant seagrasses to greater depths than donor sites although wave energy was still instrumental in lowering survival. To examine wave energy effects, mechanically transplanted sods were deployed in an area of high wave energy, with spacing being used to modify the hydrodynamic regime. The results indicated no significant differences in survival or shoot density as a result of the spacing treatment, with poor survival once winter storms impacted the area. Monitoring of fluctuations in sediment height showed the presence of large sand waves passing through the region, and this is clearly a factor that needs to be considered when transplanting seagrass to areas of high wave energy. The studies conducted to date suggest that larger transplants (sods) are required when transplanting to areas of high wave energy, although smaller transplants (plugs and sprigs) may be appropriate in more moderate conditions. Major factors to consider in enhancing rehabilitation success would appear to be the appropriateness of the technique in regard to species, seasonality of weather and the range of sediment level fluctuation.

Seagrass transplantation in a high energy environment

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