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Fishing for microplastic

17 Jan 2021

  • Nearly 80% reduction in fish stocks in 40 years 
  • Marine pollution becomes key issue to be addressed
By Sarah Hannan  Sri Lanka already seems to be experiencing the consequences of microplastics in its marine environment, as it is witnessing a reduction in fish stocks by nearly 80% between a span of 40 years as indicated by two surveys conducted in 1978 and 2018.   The Ellen MacArthur Foundation and the New Plastics Economy, in their 2017 article titled “The new plastics economy: Rethinking the future of plastics and catalysing action”, predicted that if steps are not taken to reduce the usage of plastics, the entire ocean will contain one metric tonne of plastic for every three metric tonnes of fish by 2025.   “We all have a responsibility towards reducing the littering of polythene and plastic into the environment which later ends up in the ocean. Recently, Sri Lanka was labelled among the top 20 ocean polluters by an international organisation, and it is time that we paid serious attention to reduce the usage of plastic as well,” Environment Minister Mahinda Amaraweera, speaking to The Sunday Morning, explained.   Amaraweera said that one of the main reasons for the decline in fish population was the increase in microplastics in the ocean. He stated that a recent survey had found the presence of microplastics in 70% of the 60 water samples taken from the ocean off the southern coast of the country.  Recalling an incident during his tenure as the Minister of Fisheries, Amaraweera noted that there was a time when about 24,000 plastic bottles were collected per day in the vicinity of the Dikkowita Fishing Harbour.   “I conducted an inquiry, and later imposed a ban on fishermen taking plastic containers with them when they went to sea. This year, we are imposing the ban on single-use plastics and sachets that are found to contribute towards dispersing plastic pollutants to the environment,” Amaraweera elaborated.  Pollution all around   In 2018, National Aquatic Resources Research and Development Agency (NARA) carried out a survey supported by the Norwegian Institute of Marine Research and found that the north-western region of Sri Lanka was more polluted with microplastics than any other region in the country.   Preliminary results of the survey had revealed that the coastal water of the West was more polluted with microplastics compared to the East, with the highest abundance in microplastic particles in samples collected from the north-western coastal waters (0.85 particles/㎥). The Central East was slightly more polluted (0.27 particles/㎥), compared to the Northeast (0.18 particles/㎥) and the Southeast (0.25 particles/㎥).    Microplastics found in the southern waters were low (0.12 particles/㎥) and the overall average abundance of microplastics in Sri Lankan waters was estimated to be 0.31 particles/㎥ of surface water.   The findings published on the above survey also suggested that microplastic contamination could have contributed to a depletion of fish stocks, which was evident when compared with the fish resources estimation recorded between 250,000 to 350,000 tonnes during the survey carried out in 1978-1980 against the fish resources that amounted to 53,000 tonnes at the culmination of the survey.  The data that is made available by the Department of Fisheries indicates that the fish production around the island has fluctuated over the years, although there have not been any direct claims that it was due to the increasing pollution that is taking place.  Fresh survey this year   Based on the study that was conducted in 2018 with the involvement of the Norwegian Institute of Marine Research, NARA is to conduct a further study with an improvement in research protocol in 2021. Samples are to be obtained and data sets are to be analysed.   During their previous study, the researchers had collected three types of samples – one was from the surface water, the other was a deep-water sample where samples were collected from different depths of the water column, and the final one was sediment samples which are from the ocean bed.   What the research team had found was that the chemical composition of the categories from the surface was quite different from what was found in the water column sample and the sediment sample.   The plastics with less density were on the surface, while there were a lot of plastics in the water column, and the heavier ones were on the sediment layer.   Therefore, in the next phase of the study that will be launched in 2021, they plan to pay more attention to sediments and the water column using manta trawls to collect samples from the surface. The surveyors are planning to employ a proper method to quantify and understand the larger impact microplastics could have on biota such as zooplankton, phytoplankton, and ichthyoplankton. 


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