Improving the Resilience of Black Mangrove Trees to Oil Pollution

Greg Howard
6th May, 2024

Improving the Resilience of Black Mangrove Trees to Oil Pollution

Image Source: Natural Science News, 2024

Key Findings

  • In Gabon's Ambowé mangrove, pollution reduces protective compounds in mangrove wood
  • Polluted mangrove wood shows structural changes, making it more prone to decay
  • The study indicates pollution may lower the carbon storage capacity of mangroves
Mangroves are unique coastal ecosystems that are not only crucial for maintaining biodiversity but also play a significant role in carbon sequestration, acting as a buffer against climate change. However, in Gabon, these environments are under threat due to pollution from activities such as fishing and waste disposal. A recent study by LERMAB at Université de Lorraine[1] has delved into the effects of hydrocarbon pollution—specifically from fishing engine oils—on the mangrove species Avicennia germinans in the Ambowé mangrove of Gabon's Estuary region. The study compared the impact of this pollution on the chemical composition and microstructure of the mangrove's wood to samples from two unpolluted sites, Oveng and Mamboumba. It found that the heartwood of the polluted mangroves contained significantly lower levels of certain extractives—chemical compounds that contribute to the tree's natural durability—when dissolved in dichloromethane and hexane. This suggests that the presence of pollutants can strip away protective compounds that are naturally occurring in the mangroves. Using confocal microscopy, researchers made a novel observation: the polluted heartwood exhibited changes in its microstructure, including the opening of rays and vessels. These structural changes could be the reason for the loss of extractives. Further analysis using ultraviolet light showed a significant decrease in these extractives when exposed to pollutants, while lignin—a structural component of wood—remained unchanged. The consequences of these chemical and structural alterations became evident when the wood's resistance to decay was tested. The polluted heartwood showed a higher mass loss when exposed to rot fungi, such as Trametes versicolor and Rhodonia placenta, compared to the unpolluted samples. This indicates a reduced natural durability and an increased vulnerability to decay due to pollution. These findings are concerning, particularly when considering earlier research[2] that highlighted the potential for mangrove sediments to accumulate trace metals, which could lead to bioaccumulation and toxicity issues for mangrove species and related fauna. The current study suggests that hydrocarbon pollution could be another factor contributing to the degradation of these ecosystems. Furthermore, the destruction of mangrove ecosystems has broader implications for carbon emissions. Previous studies[3] have shown that clearing mangrove areas, especially those with organic-rich soils, can lead to substantial CO2 emissions. The degradation of mangrove wood by pollutants, as observed in the current study, could exacerbate this problem by reducing the carbon storage capacity of these ecosystems. The research also resonates with findings from oil spill studies[4] that have assessed recovery rates in marsh environments. While many spills showed recovery within a few growing seasons, the presence of pollutants like hydrocarbons could lead to longer-term ecological damage, as seen in the decreased durability of mangrove heartwood. Lastly, the study indirectly touches upon the issue of environmental stressors affecting mangrove growth, similar to the factors influencing the productivity gradient observed in Avicennia marina in Richards Bay, South Africa[5]. The stress from pollution could potentially contribute to such gradients by impacting the trees' physiology and growth patterns. In conclusion, the research by LERMAB, Université de Lorraine, sheds light on the detrimental impacts of anthropogenic hydrocarbon pollution on the mangrove species Avicennia germinans. The loss of natural protective extractives and structural changes in the wood increase the vulnerability of these mangroves to decay and could have wider implications for the health and carbon sequestration capacity of these vital ecosystems. This study underscores the need for better management and conservation strategies to protect mangroves from the growing threat of pollution.

EnvironmentPlant ScienceMarine Biology

References

Main Study

1) Modification of the chemical composition and the natural durability of Avicennia germinans mangrove tree of the estuary region of Gabon exposed to marine hydrocarbons pollution.

Published 3rd May, 2024

https://doi.org/10.1016/j.marpolbul.2024.116196

Related Studies

2) Fate and effects of anthropogenic chemicals in mangrove ecosystems: a review.

https://doi.org/10.1016/j.envpol.2011.04.027

3) CO2 efflux from cleared mangrove peat.

https://doi.org/10.1371/journal.pone.0021279

4) Impacts, recovery rates, and treatment options for spilled oil in marshes.

https://doi.org/10.1016/j.marpolbul.2014.03.030

5) Factors contributing to dwarfing in the mangrove Avicennia marina.

Journal: Annals of botany, Issue: Vol 97, Issue 6, Jun 2006


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