Survivability and growth performance of using Rhizophora mangrove life stages in the revegetation of mangrove forest

Abstract

Mangrove forests play critical environmental, social and economic roles; however, these forests have been threatened globally for decades. In Nigeria, oil spills in mangroves are among the leading causes of mangrove degradation in the Niger Delta. This study analyses the survivability and growth performance of three Rhizophora racemosa mangrove life stages, propagules, sprouted propagules, and seedlings planted on a remediated mangrove forest. Three sites were used for the study; before planting, the total petroleum hydrocarbons (TPH) and nutrient concentration (Nitrogen, Phosphorus, and Sulphur) in the sediments of each site were analysed. Surface and subsurface composite sediment samples were analysed for TPH, while sub-surface sediment samples were analysed for nutrient concentration. A total of 100 propagules, 46 sprouted propagules, and 141 seedlings were planted in three sites. Monitoring for growth and survivability started after one month, and plants were monitored for one year. Growth monitoring (Increase in height and leave count) was limited to 20 tagged propagules, 5 tagged sprouted propagules, and 25 tagged seedlings, while survivability monitoring was done for the entire plant. The average TPH values at all sites were 192 mg/kg for surface samples and 145 mg/kg for subsurface samples. Nutrient concentration values slightly varied at all sites. A one-way ANOVA showed no significant difference in the TPH values (p = .205) and nutrient concentration values (p = .411) across the three sites. Sprouted propagules had the best growth rate and showed a significant height difference (p = .02) from propagules. Seedlings had a better growth rate than propagules after one year. Survival rates for sprouted propagule were 100%, while seedlings had a 95% survival rate, and propagule had a survival rate of 87% after one year of monitoring.