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Oil spill effects on marine environment

Oh the occasion of the accident of the Russian fishing boat called Oleg Naydenov close to Grand Canary (Spain), the article of this week is about the effects of petroleum on marine environment. Here, I am going to talk about the origin of the petroleum in the sea, which are the transformations that suffer and the effects on marine fauna and flora. 

INTRODUCTION

The accident of the Russian fishing boat called Oleg Naydenov off of Grand Canary, which has finished with its sinking, is causing the appearance of oil in an area of 12 square km. The reason is that it sank with more than 1,400 tonnes of oil, 30 of diesel oil and 65 more of lubricant.

ORIGIN OF HYDROCARBONS IN THE SEA

Despite oil tanker accidents have a huge impact in the media, they represent a small portion of the amount of hydrocarbons that get in the sea. In general terms, these are the main sources of petroleum in the sea:

  • Industrial discharges and urban dredging: 37%.
  • Boat’s operations: 33%.
  • Oil tanker accidents: 12%.
  • Atmosphere: 9%.
  • Natural sources: 7%.
  • Exploration and production of hydrocarbons: 2%.

Although this values can vary depending of the sources, in general they represent quite good the proportions. It has been estimated that, each year, are poured into the sea 3,800 millions of litres of hydrocarbon, equivalent to 1,500 Olympic pools.

HYDROCARBON TRANSFORMATIONS IN THE SEA

When hydrocarbons are spilled into the sea (accidentally or deliberately), their features and shape change. This changes are physical, chemical and biological. This are the mechanisms:

  1. Evaporation: it allows that certain substances of the hydrocarbons go to the atmosphere, reducing about 40% its volume just in the first day. In any case, the surrounding atmosphere will be flammable.
  2. Dispersion: it consists on the fragmentation of the oil patch into small drops. When these drops are small enough, they remain in suspension and they mix with water and favours the biodegradation and sedimentation.

    La dispersió del petroli té un efecte positiu, doncs (Foto extreta de Ecosfera)
    Oil dispersion is positive because it allows the biodegradation (Picture from Ecosfera)
  3. Emulsification: consists on the absorption of water so the hydrocarbon’s volume increases between 3 and 4 times. This hampers the oxidation and biodegradation.
  4. Solution: depending on the product’s composition, the water temperature and its agitation. Only the more volatile components can be dissolved.
  5. Oxidation: the effect of the oxidation can produce a compound that is easier or more difficult to degrade.
  6. Sedimentation: consists on the down vertical displacement of the hydrocarbon’s particles. Depending on its density (with respect to water), the size and the agitation of the sea.
  7. Biodegradation: consists on the elimination of hydrocarbons by living beings, like bacteria and fungus.

PETROLEUM’S EFFECTS ON MARINE ENVIRONMENT

As we have said in the beginning of the post, the main goal of this is to comment which are the effects of petroleum (and other hydrocarbons) on marine fauna and flora. Let’s start!

The effects of petroleum on fauna are wide due to the high diversity of marine organisms. The main effects on the marine biodiversity are:

  1. Direct contamination: petroleum sticks on feathers, fur and scales, what make difficult the thermal isolation, movements and other important functions. As a consequence, this kills fishes, marine mammals and birds.

    Els mamífers marins es veuen efectats per la contaminació per petroli (Foto de Channel Island)
    Marine mammals are effected by petroleum pollution (Picture from Channel Island)
  2. Modification of gas exchange: the petroleum sheet reduces the content of oxygen in the water, what produce the dead of the plankton and fishes, what produce the dead of the organisms that feed on them.
  3. Alteration of seafloor: when petroleum is placed over the seafloor kills and produce sublethal effects on benthonic flora and fauna.
  4. Intoxication: petroleum poisons marine fauna, soaking into its digestive system and its skin and mucosa. The result is, on the one hand, the dead for suffocation and genetic disruptions on fishes, molluscs, marine mammals, reptiles and birds; and, on the other hand, the intoxification of other organisms like humans when they feed on them.

    Només una quarta part de les aus marines contaminades arriben a terra, la resta moren (Foto de Marine Photobank, Creative Commons).
    Only a quarter part of the contaminated marine birds achieve the earth, the rest dead (Photo: Marine Photobank, Creative Commons).
  5. Increase of the infections: because petroleum produces a reduction of the resistance to infections. This is specially important in birds because when they clean the feathers theirself, they swallow petroleum, so they present sublethal concentrations.
  6. Negative effects on fertility, reproduction and propagation of fauna and flora.
  7. Modification of the behaviour.
  8. Destruction of food sources.
  9. Incorporation of cancerous substances on food webs. 
  10. Effects on the availability of light: we cannot forget that the petroleum patch in the sea surface produce an important reduction of light in the water column. This causes a reduction or elimination of photosynthesis, essential process for the maintenance of food webs because the algae growth depends on light, which is consumed by herbivorous (and so on) and produce an oxygen input into the water. Moreover, we have to take in consideration that algae communities are shelter for many larvae and youthful fishes.
  11. Marine communities alteration: at community level, there is a gradient of vulnerability of oil spills. From less to more vulnerability, the communities are: exposed cliffs, exposed rock platforms, fine sand beaches, middle to big sand beaches, exposed tidal planes, big sand beaches, gravel beaches, protected rocky beaches, protected tidal planes, marshlands and mangroves, subtidal seafloors of sand and gravel, mud subtidal seafloors, batial and abyssal seafloors, infralittoral and circalittoral seafloors and reef corals.

REFERENCES

  • Notes of the subject Ecotoxicology and marine pollution of the Master in Oceanography and Marine Environment Management of the University of Barcelona.
  • EmerCoast Coast. “Training on marine pollution risks. Environmental risks in the littoral and marine environments”.
  • Course”Marine Pollution” from EuroInnova.
  • Greenpeace (2012). Environmental impact of petroleum (Brochuere).

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