Introduction to MARPOL

Introduction to MARPOL

This post is an introduction to MARPOL, which is the International Convention for the Prevention of Pollution from Ships. MARPOL stands for Marine Pollution, in case you were wondering.

It is a bit complex so what we have tried to do is put the rather dry, technical English into something we can all (hopefully) understand. The International Convention for the Prevention of Pollution from Ships is also ridiculously long so we are going to split it up into what we believe will be more manageable segments.

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Introduction to MARPOL

“The MARPOL Convention is the main international convention covering prevention of pollution of the marine environment by ships from operational or accidental causes. It is a combination of two treaties adopted in 1973 and 1978 respectively and updated by amendments through the years.

The International Convention for the Prevention of Pollution from Ships (MARPOL) was adopted on 2 November 1973 at IMO and covered pollution by oil, chemicals and harmful substances in packaged form, sewage and garbage. The Protocol of 1978 relating to the 1973 International Convention for the Prevention of Pollution from Ships (1978 MARPOL Protocol) was adopted at a Conference on Tanker Safety and Pollution Prevention in February 1978 held in response to a spate of tanker accidents in 1976-1977. (Measures relating to tanker design and operation were also incorporated into a Protocol of 1978 relating to the 1974 Convention on the Safety of Life at Sea, 1974).

The Convention includes regulations aimed at preventing and minimizing pollution from ships – both accidental pollution and that from routine operations.”

International Maritime Organization

We’ll start with where waste oil comes from, how it behaves at sea, and how it affects sea life.

Where Waste Oil Comes From

Let’s start with an overview in bullet point form.

  • Waste oil generated in a ship originates from various places; primarily from the sludge, slop, bilge, and ballast water system.
  • The discharging of oil into the sea from ship operations is due to both lawful and unlawful discharges.
  • Usually, ship-generated oily waste is taken to shore, burnt on board, and legally and/or illegally discharged into sea.
  • Oil tankers are used to transport hundreds of millions of tonnes of crude oil and refined products by sea.

I think you can see, there is no real mystery to where waste oil comes from. It should also be noted that most of the time, oil is transported safely and securely.

Obviously, this has not always been the case, which is why measures introduced by the International Maritime Organization (IMO) have aimed at making sure all oil tankers are securely constructed and operated. One of the other aims has been to reduce the amount of oil spilled when an accident occurs.

It is also worth noting that operational oil pollution; for example,  when tankers are cleaned out, has also been cut.

How Oil Behaves At Sea

Behaviour of Oil Spills

Image Credit: Coastal Environmental Assessment Regional Activity Centre

The consequences of oil spills on marine life are the result of either the physical presence of the oil (actual physical contamination and smothering) or by its chemical factors (toxic results and accumulation resulting in tainting).

Unfortunately, marine life may also be impacted by the operations to clean up the oil spill through the use of dispersants like detergents.

The key threat posed to animals and plants by oil spills is physical smothering. The maritime species most at risk are the ones affected by the contaminated sea surface. Additionally, maritime mammals and reptiles are also at risk of smothering. For example, birds that feed by diving; birds that form flocks over the sea; and maritime life on shorelines.

Animals and vegetation are also at risk in mariculture systems. This is “the specialized branch of aquaculture involving the cultivation of marine organisms for food and other products in the open ocean, an enclosed section of the ocean, or in tanks, ponds or raceways which are filled with seawater. An example of the latter is the farming of marine fish, including finfish and shellfish like prawns, or oysters and seaweed in saltwater ponds. Non-food products produced by mariculture include: fish meal, nutrient agar, jewellery (e.g. cultured pearls), and cosmetics.” Wikipedia – Click here if you’d like to read more about mariculture.

How Waste Oil Spills Affects Sea Life

Generally, the most harmful constituents of oil are disappear quickly by evaporation when oil is spilt. For this reason, lethal concentrations of toxins resulting in huge scale mortalities of maritime life are comparatively unusual. Additionally, when this does happen, it is only the immediate area that is affected and the effects do not last long.

Outcomes that hinder the ability of marine organisms to breed, reach maturity, feed, or complete other functions might be brought about by prolonged contact to the concentration of oil or oil elements which is far lower than the amount needed to lead to loss of life.


Less active animals in shallow waters such as oysters, mussels and clams, that regularly filter large volumes of seawater to extract nutrients are more likely to accumulate oil constituents. Although these constituents might not induce any rapid harm, their existence may possibly render these animals unpleasant to eat if they are consumed, due to the presence of an oily taste or odour.

It is a short-term problem since the constituents causing the unpleasantness disappear when things return to normal.

The next article in the series is coming soon. Don’t forget to bookmark this page.