Salinity exacerbates oil contamination effects in mangroves.

Gonasageran Naidoo,Krishnaveni Naidoo

doi:10.1007/s11356-021-15450-9

Abstract

The effects of salinity (10 and 50% seawater) and oil in combination on three mangroves, Avicennia marina, Bruguiera gymnorrhiza, and Rhizophora mucronata, were investigated. In all species, plant height, number of leaves, and CO2 exchange were generally higher in 10% than in 50% seawater. Salinity and oil decreased plant height, number of leaves, chlorophyll content, and CO2 exchange, with reductions being greater at the higher salinity. In a second experiment, the effects of salinity (0, 10, and 50% seawater) and oil on concentrations of ions, polycyclic aromatic hydrocarbons (PAHs), leaf ultrastructure, and salt secretion in A. marina were investigated. Salinity and oil in combination increased concentrations of Na+ but decreased those of K+, Ca2+, and Mg2+. PAHs caused damage to cell membranes, disrupted ion concentrations, and reduced salt secretion. This study demonstrated that increase in salinity reduces growth of mangroves and that salinity and oiling in combination exacerbate growth reduction. In A. marina, oil was absorbed and translocated to the leaves where it disrupted membranes, ion accumulation, and salt secretion.

Highlights

Mangroves, which occur in sheltered, intertidal areas of the tropics and subtropics, are economically important as they provide food, timber, and medicine
Salinity and oil decreased plant height, number of leaves, chlorophyll content and CO2 exchange, with reductions being greater at the higher salinity
Plant height, chlorophyll content index (CCI) and CO2 exchange were generally higher in 10% than in the 50% seawater treatment (Table 1)

Summary

Introduction

Mangroves, which occur in sheltered, intertidal areas of the tropics and subtropics, are economically important as they provide food, timber, and medicine. Attenuate waves, sequestrate carbon and serve as nursery grounds for fish (Friess 2016; Barbier 2016)). Mangroves occupy low wave energy locations which are usually close to highly populated, industrialized cities. Mangrove habitats are exposed to organic pollutants such as polycyclic aromatic hydrocarbons (Ke et al 2011; Li et al 2014). Sources of PAH contamination include oil spills, atmospheric fallout, urban runoff and industrial effluents. Transfer of PAHs from mangroves to other trophic levels, via food chains, causes health problems. PAHs persist in the environment for long periods due to their insolubility in water and low rates of degradation (Lewis et al 2011)

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Discussion

Conclusion