ENVIRONMENT
is it carried away by currents? Some is in the sediment, some is in the fish, but we need to find out exactly how much plastic is there.’ In the study, Sabrina Beer, a
masters student at the University of Copenhagen, dissected more than 800 historical samples of fish and found microplastics in around 20% of them. This laborious process involved diluting the stomach contents in order to remove ‘organic’ materials, then checking the filtered contents under a microscope to determine the size and concentration of plastics. It illustrates the difficulty of quantifying plastics in any sample, says Gissel Nielsen. Finding microplastics is
challenging, as they can sometimes be of similar size to ‘natural’ species, from plankton to bacteria. ‘You must remove the biology to get a clear view of the plastics,’ he says. Most of the plastics found in the
samples were clothes fibres. The researchers assumed these pass un- digested through fish within 24 hours. They also concluded that the constant level of plastics pollution in the Baltic was linked to the fact that the local population has remained constant over that time – and that there was no correlation with the general increase in global plastics production. Nielsen is also critical of some studies that assess the effect of high concentrations of plastics on marine species, saying they do not replicate conditions in the real world. ‘All substances are toxic at a high enough level. It’s a matter of dosing,’ he says.
Searching high and low Researchers at the National Oceanography Centre (NOC) in Southampton, UK, led by Richard
JELLY TRAP
The study raises a number of questions, such as where the plastic has gone. Does it sink to the bottom, are there organisms that break it down, or is it carried away by currents? Some is in the sediment, some is in the fish, but we need to find out exactly how much plastic is there
Torkel Gissel Nielsen Technical University of Denmark 100,000t
Current estimated amount of microplastics on the surface layer of the sea worldwide – which is around 1% of the amount expected to flow into the sea every year
A scanning microscope with Fourier Transform Infrared capability promises to automate microplastics analysis with far higher speed and accuracy
Lampitt, are looking to answer a simple question: where are all the microplastics in the sea? ‘We don’t know if they are sinking, suspended, or whether they’ve already reached the sediment,’ he says. ‘We need to understand this, because there are huge uncertainties over their abundance.’ Current estimates of microplastics on the surface layer of the sea is around 100,000 tonnes worldwide, he says; which is around 1% of the amount expected to flow into the sea every year. ‘We can only account for a tiny proportion of this,’ he says. ‘One reason could be that we are sampling incorrectly.’ One common technique drags a fine net – with 300micron mesh size – through the water. However, it could be that most plastic has degraded into even smaller particles – but is still
Jellyfish mucus is effective at trapping
Researchers in a pan-European research project hope that a natural phenomenon – jellyfish blooms – might one day be useful in removing microplastics pollution. The aim of GoJelly is to exploit jellyfish
blooms. They are currently a problem – especially for the fishing and tourism industries. However, they could be turned into an opportunity by harvesting jellyfish for food, or as a source of raw materials for products like cosmetics or fertilisers – or for its mucus.
solid particles in water – so the researchers intend to exploit this by using it as a filter. ‘It could be used in wastewater treatment plants,’ says Nicole Aberle-Malzahn, of the Norwegian University of Science and Technology, one of the project partners. Rather than a physical filter – like a mesh – the mucous extract would be added to contaminated water to absorb solid particles – including microplastics – and form a sediment layer in a settling tank. This would leave a layer of clean water at the top.
there in high concentration. ‘That’s one way in which microplastics may have escaped detection,’ he says. To find the ‘missing material’, the NOC has been taking three main types of sample – some of them stretching back 20 years – to try and identify the location and concentration of microplastics. The first type of sample is from sediment cores, which are extracted from the sediment – sometimes at depths of 5km – and later recovered. The technique can be used to look up to 10,000 years into the past, he says. ‘You can take ‘slices’ and find the microplastic concentration in each layer. The ‘oldest’ samples contain no plastic, and will act as ‘blanks’ to ensure that our samples are good.’ The second type of sample is
from the ‘water column’. Here, water is collected from different depths – using a pump – for later analysis. The team has taken samples from the Porcupine Abyssal Plain Sustained Observatory (PAP-SO) in the North Atlantic, and at various points across the Atlantic Ocean. The third type of sampling is from sediment traps. These are moored at depths of 3km, and collect setting material.
Lampitt says that the collection phase is largely complete, and that his team will now move on to analysing the samples with a new tool in its armoury: a scanning microscope with Fourier Transform Infrared (FTIR) capability. This, he says, helps to automate the analysis with far higher speed and accuracy than before. ‘Earlier versions of the machine were just too slow in their analysis,’ he says. The new machine scans a sample; identifies microplastics; and assesses
The filter has yet to be developed, but
the researchers intend to do this over the course of the four-year project.
24 02 | 2018
TIHOMIR MAKOVEC
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