An experimental assessment of slag as a substrate for mangrove rehabilitation

Rehabilitation of mangrove habitat has become common practice, but few stud ies have investigated the growth and survival of mangrove on artificial sub strates. Managers attempting to plant mangrove in sites containing artifici al substrates must remove substrates or risk poor performance of rehabilita tion efforts. This study compared propagule retention, early survival, grow th, flowering success, and nutrient concentrations of Avicennia marina (gre y mangrove) grown on sand, naturally occurring substrate, and rock blast fu rnace slag over two growing seasons at an experimental site near Newcastle, Australia. Nutrient concentrations of experimental plants were also compar ed to those of naturally occurring plants. Experimental results showed sign ificant differences (p < 0.05) in short-term survival, growth over the two growing seasons, and carbon and nitrogen concentrations between plants grow n on different substrates. Comparison of plants grown in slag and plants fr om reference sites suggests, however, that slag does not lead to anomalies in nutrient concentrations of young mangroves. Although the results identif ied some differences between plants grown on river sand, naturally occurrin g substrate, and slag substrate, the absence of consistent differences sugg ests that mangroves planted in slag are under no greater risk of future fai lure than mangroves planted in naturally occurring substrate.