The Impact of Oil Spills from the Pontoon 300 Incident
on the Marine Ecosystem
Shigeyasu Tamaei
Aquaculture Expert
Japan International Cooperation Agency

In general, the impact of oil spills on the marine ecosystem can be divided into physicaland chemical ones. The physical impact is that oil directly affects marine life in theprocess of its floating on the sea surface, settling into the seabed, or stranding on theshoreline and is conspicuously visible. Marine life covered with oil suffers respiratory
failure and dies of suffocation. Because such marine life performs branchial respirationby taking dissolved oxygen in water through the gills and can hardly respire by their
being covered with oil. Similarly, when sea surface and beach are covered with oil, theoxygen supply from the atmosphere is cut off, suffocating and killing the organisms
living there such as fish eggs, fry, zooplankton, crabs, shellfish and clam worms.
Phytoplankton, seaweed, and corals are also affected when the oil slick cuts off thelight.
The chemical impact appears in some marine life when harmful substances in the oil
dissolve in the water and are accumulated in them through branchial respiration, or
when they also prey on small marine organisms in which those harmful substances
have been highly concentrated. This impact is very difficult to be detected because thedisorders occur internally after some periods of time. Especially when shellfish ingest
plankton that have taken toxic substances, the amounts of accumulated toxic
substances can rise to extremely high level, which is not detectable by theirappearances. When toxic substances are accumulated in some fish, their internalorgans tend to be damaged, particularly the liver and ovaries. Since the oil did not stayin the fisheries for such a long time in this incident, the physical impact was consideredhigher.
When the oil spill occurred, the fish swam away to safe waters, avoiding the spilled oiland the fish-eating sea birds did not stay in the contaminated area because they can notfind food. The marine life being damaged were those unable to swim such as plankton,
fry and fish eggs, and those living in the sands and rocks such as the shellfish, crabs
and clam worms.
The stranded oil on the coast seriously damaged the mangrove ecosystem thatcomprised the coastal ecosystem in the area. Mangrove forest waters provides

productive habitats for an abundance of tropical marine life, including fry, young
shrimps, young crabs and young shellfish. The waters are especially shallow, and thespilled oil even covered the exposed seabed at the low tide. Thus, the entire ecosystemfrom underwater to the seabed soil was affected. Physically speaking, the impact on themangrove forest with the stranded oil is that leaves and aerial roots essential to therespiratory processes are covered by oil, and photosynthesis and respiration areprevented. The oil covering the aerial roots is easily washed away by the ebb and flow of
the tide, but the oil adhering to the leaves and trunks can not be easily removed. The
younger and weaker trees covered entirely with oil gradually get worse to die off from
suffocation. Fortunately, many of the bigger and stronger trees are able to shed theircontaminated leaves to reduce their stress and survive only with the leaves thatremained clean In the upper position. The oil pollution this time killed the marine life
under the mangrove trees as well as young mangroves themselves, but many
mangroves have still survived with their leaves sparsely remained. With the survival ofthe forest, the damaged ecosystem is certain to recover in the near future.
It is a rapid recovery of oil that we should take first in case of an oil spill. This is theresponse to minimize damage to the marine ecosystem mentioned above and it isessential to increase equipment for oil recovery. Oil spills generally occur in roughweather, so recovery operations are often delayed. However, it is true that even partial
efforts for recovery can reduce the negative impact on the marine ecosystem. If
surfactants and dispersants with minimal environmental impact were to be used, thenegative impact on the ecosystem could be largely reduced. The use of surfactants isprohibited along the coastal waters, but people might nonetheless be tempted to use
such strong chemical agents to avoid charges of delays by mass media and localresidents. Yet, in view of the chemical impact on the life of the residents and theecosystem, this prohibition should be strictly observed. With dedicated efforts forrecovery operations and enough compensation for damages, local residents andvolunteers can effectively join the operations, and there will be a better chance of
restoring the trust of the local community.
The removal of the oil we failed to recover and of the chemical impact on the ecosystemshould be left to nature's own decontamination process. This natural process has
proceeded far more quickly than we expected in our laboratory investigation. Fish andcrabs started to return to their habitats in the water channels of the mangrove forest at
Umm Al Qaiwain about five months after the spill. As of October, the mangrove
ecosystem has been almost completely restored. This phenomenon tells us that theGreat Sun and the Mother Sea work together to clear up our mistakes.