Transplanting macrophytes to rehabilitate streams: experience and recommendations

Macrophytes play a key role in stream ecology and therefore efforts should be made to enable colonisation of plants to rehabilitate degraded streams. Our overall objectives in this study were first to add to the sparse published studies on the sustainability of transplanting macrophytes in-stream rehabilitation, and secondly to propose general recommendations for this purpose. We assessed the survival and growth of macrophytes after propagating and transplanting them into two streams, one of which was physically degraded and the other was a newly established stream part. We determined differences in colonisation success of different macrophyte species and of different bed sizes. Survival during propagation and after transplanting was 100% for four of the six species used in the experiment. Both survival and colonisation after transplanting six different plant species into a newly created headwater stream were high for Ranunculus baudotii × pseudofluitans, Callitriche cophocarpa, Potamogeton crispus and Myriophyllum spicatum but low for P. perfoliatus and P. pectinatus. After two years, the transplanted macrophyte species were all present and had spread along the stream. Ranunculus baudotii × pseudofluitans beds was more sustainable than C. cophocarpa at places where extensive sand transport occurred. After the second growing season, the smaller patches (0.12 m²) had both similar survival rate and size as the large patches (0.24 m²) for both R. baudotii × pseudofluitans and C. cophocarpa. Our study together with two previous ones from New Zealand enabled us to make general recommendations for transplanting macrophytes into streams. These include: (1) selecting suitable streams, (2) selecting and obtaining suitable plant species, (3) propagation technique and (4) transplanting technique.