Text and photos copyright (c) 2013 Erkki “Eric” Siirila, all rights reserved
Pioneering research has shown that plastic waste entering the ocean may have more serious negative effects on marine life than what was previously thought. Two studies published in Current Biology focus on the ecosystem effects of microplastic fragments less than 1 mm in diameter. The very small pieces of plastic have been polluting the ocean for about half a century.
Previous research has concentrated on the effects of bigger plastic objects in the marine ecosystem. This time the focus is on the fragments, which are produced for example as a result of gradual breakdown of plastic bottles in nature.
The tiny plastic particles are so small that wastewater treatment plants cannot stop them from entering the sea. A serious challenge for waste management is that this pollution does not originate only in what we normally consider plastic. The sources include synthetic textiles e.g. polyester – many of our clothes release a high number of microscopic pieces of plastic fibre when they are washed. Microbeads from cosmetic facial scrubs are one more source of harmful plastic particles. On the shores and in the sea, the microscopic plastic waste sinks into the sediments in high concentrations.
An additional problem with microplastics is that, in addition to the direct effects, they transfer harmful chemicals to marine organisms eating them. This was shown to take place in the case of lugworms by Mark Browne and his colleagues (link to Abstract). Lugworms (Wikipedia Lugworm) are an example of a common North Atlantic species using the sediments as food source. Starfish and sea cucumbers have similar feeding strategies. Mark Browne’s work was completed at Plymouth University, UK.
The harmful substances within the microplastics include antimicrobials, hydrocarbons and flame retardants, which are often persistent and may reduce health and biodiversity. Furthermore, minute plastic particles concentrate substances from the surrounding water on their surface: to name two examples, detergents and pesticides can be detected. The chemicals may be carried over to the next predators in the food chain – lugworms are eaten by flounders and wading birds. The harmful substances could also accumulate in the top predators, perhaps even in us humans. If lugworms are seriously affected, as they are, the whole food chain could be subject to significant adverse effects.
In the study by Stephanie Wright, University of Exeter, UK, and her colleagues, it was found that those lugworms which (in laboratory tanks) were subject to varying levels of plastic contamination, gained less weight than the worms in a clean environment. Consequently, the worms suffering from the consequences of plastic pollution had less energy for growth and reproduction. The worms were also likely to be less efficient in their important ecosystem service, i.e. in eating and keeping the sediments healthy and oxygenated for other animals. The article by Wright et al. is here: http://download.cell.com/current-biology/pdf/PIIS0960982213013432.pdf?intermediate=true .
When interviewed by the BBC, Dr Browne summarised his earlier findings relating to 18 sediment samples from the beaches in several countries: “We found that there was no sample from around the world that did not contain pieces of microplastic.”
Based on these two ground-breaking articles in Current Biology, there seems to be an urgent need to develop the use practices and waste management techniques of plastic products in our societies. This is an important coastal and marine conservation issue.
In addition to the material published in Current Biology, summaries published by the British BBC and The Guardian, were helpful in the preparation of this Coastal Challenges’ article.