Microplastic workshop review

In 2010 the GESAMP (The Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection) met at UNESCO-IOC in Paris to discuss new and emerging issues affecting the marine ecosystem: the effect of microplastics was chiefly discussed.

Participants represented the scientific community, the plastics industry, policy makers and NGOs, creating a forum from which to inform GESAMP, who would in turn inform other agencies such as the FAO, IAEA, UN and UNDP.

Two principle sources of microplastic were offered:
1) Plastic resin pellets from plastics manufacturing, abrasives and cosmetics
2) Plastic fragments from the deterioration of larger pieces, mainly litter

Knowledge of the distribution of microplastics is currently emerging in scientific literature. Some recent articles discuss the characteristics and behaviour of various sized plastic particles and the role of said variables in determining the pollutants fate.

These will be explored in later blogs

Affect of oceanic pollution on marine biodiversity: in response to Laura Marriot

When considering the current state of the worlds ecosystems, it is proposed that 15 of the Earths 24 ecosystems area in decline, due to their reduction in biodiversity (Hooper et al, 2012). It is also estimated by Barnosky et al (2011) that in the next 2-300 years species will decline at a rate 100 times that of natural extinction rates. It is agreed in the literature that the loss of biodiversity is a global crisis requiring international solutions.

Why is this important?

The oceans ecosystems are no different. Anthropogenic impacts are affecting marine ecosystems and biodiversity in a big way.

With particular reference to the affects of oceanic plastic pollution it is estimated that at least 267 marine species are affected by entanglement or ingestion including seabirds, fish, turtles, seals and whales (Allsopp et al, 2006).

Within scientific literature it is agreed that plastics accumulate persistent, toxic contaminants such as PCBs, DDT and PBDEs (GESAMP, 2010). The large surface to volume ratios of plastic facilitate this chemical exchange. As such upon ingestion by marine organisms the material acts as a vector, passing toxins through the food chain.

This can have a potentially harmful impact on human health.

Other affects of oceanic plastic pollution are less obvious. Plastics when accumulated in near surface waters can act as a sanctuary for microbial communities, potentially introducing 'alien species' into the ecosystem. The accumulation of plastics can also lead to areas of oxygen becoming deoxygenated as gaseous exchange between the near surface ocean and atmosphere is reduced. This can lead to the asphyxiation of marine organisms and the creation of 'marine dead zones'.

Future predictions

With expected increases in the human population and concurrently plastic pollution the strain on the marine ecosystem will become increasingly worse. 

Micro plastics

These results confer with the findings of Jambeck (discussed in the earlier blog post 'How much of our trash ends up in the oceans), who found that only 2% of the worlds annually produced plastic waste ended up in the oceans.

Given a quadrupling of plastic production in recent years we would expect to see that oceanic plastic pollution has as such increased. Given the laxities of pollution legislation it seems unlikely that pollution levels have dropped. This conundrum leads me to ask the question: where has all the pollution gone?

Given the properties of plastic scientists have begun to consider that the relative abundance and mass of plastics within the oceans isn't as high as models predicted due to:

• Biodegradation of 'macro' sized plastic to smaller particles 'microplastics' (Law et al, 2010)
• Sinks of pollution

One potential sink of plastic pollution is proposed by Thompson et al (2004). Thompson identifies th presence of micro plastic accumulation on shorelines and in the water column, whereas comparatively large plastic pieces accumulate in near surface waters. Thompson continues in later work to identify the presence of plastic on the deep sea floor and in other remote regions of the globe, after exploring sites in the Mediterranean Sea and the Indian and Atlantic Oceans.  Thompson concludes that every square kilometre of deep ocean contains 4 billion plastic fibres, compared with a billion fibres found in surface and coastal waters. Thomson results show a large prevalence of microfibres within the ocean system, stating that its presence is ubiquitous in the deep sea.

Since the work of Law and Thompson the NOAA in the USA has defined microplastics as plastic fragments less than 5mm in diameter (Arthur et al, 2009).

Work by Goldstein et al (2012) confers with the work of Thompson in agreeing that micro plastic abundance is increasing in the oceans.

Shifts in paradigm

Within academia the mal effects of oceanic plastic population began to be recognised during the 1970s.

Plastic pollution literature ranges from describing the effects of beach litter (Gabrieldes et al, 1991) to studies on the sea floor plastic accumulation (Galgani, 1995) and offshore floating debris.

Recently the topics discussed within literature have expanded, due to new discoveries and developments within technology. A Scopus review of the most cited marine pollution articles of the past 5 years shows a paradigm shift towards discussion regarding the size of plastics, with microplastics (those under 1mm) and their effects being explored.

The first 'International workshop on the Occurence, Effects and Fate of Microplastic' occurred in 2008. This was the first international setting in which microplastics were agreed to pose a significant problem to the marine environmental, due to the longevity of the material and potential to be ingested by marine organisms.

How much of our trash ends up in the worlds oceans?

As a follow up to last weeks blog this week I have been researching the volume of plastic that is estimated to be in the worlds oceans.

Public environmental literature often states that 8 million tonnes of plastic enter the oceans each year (Parker, 2015).

However within scientific literature the abundance and distribution of marine plastics is often deemed 'unknown'. There are several studies which attempt to clarify estimates, however agreement between papers is often quite dicey.

Jambeck and colleagues from the University of California created a successful model to estimate the abundance of oceanic debris, through the combination of population and economic data from 192 coastal countries. They estimate via the use of per capita production of plastic pollution in coastal countries that the annual input of oceanic pollution as fluctuating between 4.8-12.7 million metric tonnes (MT), with an estimated 9.1 million MT inputted during 2015. If pollution rates continue to increase with population and plastic production growth, then by 2025 they estimate that 155 million MT will be inputted into the worlds oceans. This estimate is over 10 times the quantity of current levels, extrapolated from the same exponential increase in pollution as seen in recent years. Arguably it seems unlikely that exponential increases in plastic pollution will occur given environmental legislation and future mitigation schemes.

Where does all the pollution come from?

There has been a recent shift in where the production of plastic pollution originates. Typically the majority of marine debris originated from more developed countries with high industrial output, whilst less developed more rural economies produced less non organic waste. Industrialisation in developing countries has lead to high levels of plastics and synthetics being produced elsewhere, shifting the spatial source of pollution.

(Parker, 2015)

This chart reflects the highest amounts of plastic waste flowing into the oceans annually. Bangladesh ranks 10th overall, with 867,879 tons inputted into the oceans annually.

Issues of scale

When attempting to assess the scale of the pollution existent within the oceans several major problems become apparent:

1. Lack of data

This problem arrises due to the scale of the investigation. The oceans cover 361 million km2 of the Earths surface, physically measuring and mapping plastic pollution within seems a difficult and costly venture. Globally there is an asymmetry in the location of data collection, with greater amounts of data collected in the northern hemisphere. Within the literature there is a call for increased data collection in the southern hemisphere and remote areas.

The scale of the oceans provide a fundamental issue concerning the methodology of estimating global pollution. The scaling up of direct measurements and modelling techniques are often used, though like any extrapolation issues ensue. Data collection consists of the measurement of plastic concentrations at various points along boat routes and extrapolated to provide global estimates.

One such attempt to estimate global plastic pollution is evident in Eriksen et al (2014), whereby they collected plastic pollution data via surface net tows and visual survey transects.

Field locations at 1571 sites

As can be seen in the image above field locations cover only a small fraction of the ocean surface and so modelling extrapolations from field data may be erroneous. Eriksen et al estimated used primary and secondary data to estimate that the ocean contains at a minimum 5.25 trillion particles of plastic, weighing 268,940 tons. This minimum predicted is just 0.1% of global plastic production (288 million tons of plastic produced globally in 2012) and so this figure seems an underestimate and possibly erroneous.


    2.   Diversity of methodologies in assessing plastic pollution

Currently within literature several methods are utilised when attempting to assess marine plastic pollution, which can lead to varying results and estimates. From collecting plastic in plankton nets to assessing plastic pollution via a by sight 'transect' to taking water samples.