Study Shows Oil and Dispersants Damage Mangroves Differently

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Florida Mangroves. (Photo by David J. Ringer, public use by creativecommons.org)

Scientists evaluated the effects of oil contamination on coastal mangrove plants. Their partially-submerged root system makes them vulnerable to pollutants. Scientists found that oil coated the mangrove roots and reduced water transport, leading to rapid plant dehydration.

The presence of dispersant allowed water that contained oil fractions to enter the roots, weakening and structurally damaging the root system in addition to reducing water transport and dehydrating plants. The team published their findings in Marine Pollution Bulletin: Decrease in osmotically driven water flux and transport through mangrove roots after oil spills in the presence and absence of dispersants.

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Cross sections of the mangrove root segments: a. Fresh cut root, b. root exposed to salt water for one week, c. root exposed to salt water and crude oil, d. root exposed to salt water, crude oil, dispersant at DOR=1:5. (Image provided by Berrin Tansel)

Researchers conducted laboratory experiments exposing mangrove roots to treatments of Louisiana crude oil and oil mixed with Corexit 9500A. They observed that roots in both treatments had reduced moisture content and exhibited drying at the roots’ top end as well as separation between the root’s outer layer (epidermis) and its innermost layer (endodermis).

Roots exposed to the oil only solution had an outside layer of oil that fouled the epidermis. Roots in the dispersant-oil solution had a higher water uptake than did roots in the oil only solution, but there was greater separation of the epidermis and endodermis tissues throughout the entire root segment below and above water, which significantly decreased structural integrity.

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Urpiana Koklonis (MS student) and Jillian Berbakov (undergraduate student) conduct calibration tests for the dispersant-oil mixtures in this study. Florida International University, Water Quality Laboratory, Engineering Center, Miami, FL. (Photo by Berrin Tansel)

The team explained that their methodology provides an explanation for observed symptoms in mangroves after an oil spill contamination – fast canopy loss and death are reflective of root epidermis fouling, while gradual canopy loss and slow death indicate root endodermis fouling. They recommended that in the event of a future major oil spill, quick isolation of contaminated areas may help minimize impacts on mangroves. Mangroves that do not have sufficient water movement from tides, waves, and currents and whose roots experience high oil exposure would most likely experience permanent structural damage.

The study’s authors are Berrin Tansel, Ariadna Arreaza, Derya Z. Tansel, and Mengshan Lee.

 

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This research was made possible in part by a grant from the Gulf of Mexico Research Initiative (GoMRI) to the Consortium for the Molecular Engineering of Dispersant Systems (C-MEDS).

The Gulf of Mexico Research Initiative (GoMRI) is a 10-year independent research program established to study the effect, and the potential associated impact, of hydrocarbon releases on the environment and public health, as well as to develop improved spill mitigation, oil detection, characterization and remediation technologies. An independent and academic 20-member Research Board makes the funding and research direction decisions to ensure the intellectual quality, effectiveness and academic independence of the GoMRI research. All research data, findings and publications will be made publicly available. The program was established through a $500 million financial commitment from BP. For more information, visit http://gulfresearchinitiative.org/