Impact of Polluted Soil on Herbivory of Leaves and Pneumatophore Growth of Black Mangroves (Laguncularia racemosa) at Eagle Island, River State, Nigeria

Abstract

Mangroves are ecosystem along the shoreline of Nigerian coast and area of active oil exploration in Nigeria. This study is on the impact of pollution on herbivory and pneumatophore growth in black mangrove at Eagle Island. Leave herbivory, pneumatophore growth, THC and heavy metal concentration in soil, root and leave were determined. The sample site was divided into: plot A (high muddiness), plot B (low muddiness), plot C (slight muddiness) and Control (little or no pollution). Random sampling was used in obtaining leaves, soil and pneumatophore from each plot. Pneumatophore height was taken with meter rule and the weight with weighing balance. The leaf image was taken using a digital handy scanner and was uploaded in a software called Image J to measure the area consumed. EPA Method 418 was used to test for Total Hydrocarbon Content (THC). Heavy metals (Cadmium, Lead, Zinc) were determined using AAS- Atomic Absorption Spectrometric method. Results revealed that control plot had highest leaf consumption (2.200±0.33cm2) compared to other plots. The heavy metals and THC concentrations in different plant parts (leaves and roots) revealed that THC was high in leaves (250.88±95.33mg/kg), while heavy metals were high in root  The pneumatophores were taller and heavier in Plot A compared to Plots B and C. This study shows that pollution affects herbivory and pneumatophores growth in mangroves forest. Mitigation measures should be taken to prevent these pollutants.