Author: T. Šarčević
We finally have results from the first expert analysis of collected data on litter on Lastovo!
For a reminder, in autumn 2019 we have collected data on litter from beaches on island Lastovo (beaches Kremena, Saplun and Sito) and from sea surface on the surrounding sea. This was a first field work, from total of four planned, for the purpose of collecting data on litter as part of our project, and also it was a first research with unified methodology on Lastovo archipelago.
At the beach Sito 3,495 pieces of litter per square meter was recorded, while on beach Saplun 1,251 piece/m2 and on Kremena 0,664 kom/m2.
The analysis showed that the most common recorded item was Polystyrene particles size category 2.5 – 50 cm which made 32% (n=2348 pieces) of total recorded litter. Other most common categories were: Other plastic items (12%), Sponges (10%) and Plastic particles size category 2.5 – 50 cm (5%). It should also be noted that only items/particles whose size was 2.5 cm or larger were taken into account and only on the transects that were monitored – on a determined area. Unfortunately, we have witnessed large quantities of litter, mainly plastic, that was smaller in size than 2.5 cm.
According to the sources of collected litter from beaches, analysis showed that most of the litter can be associated with fishery and maricultural activities (50%) since most of the recorded items are commonly used in these types of activities (polystyrene packaging for fish, nets for shell culture).
Clean coast index (according to Alkalay et al 2007)* estimates is the beach clean base on number of items per area unit. According to this index, beaches Saplun and Sito are “very dirty” beaches while beach Kremena is “dirty”.
During monitoring of the sea surface, total of 251 items of floating litter was recorded which means that the average density per square kilometre of floating litter was 753 items.
There are no clean sea surface indexes developed for floating litter for sea surface. It will be only possible to assess the trend, increase or decrease of floating litter on the sea surface, comparing these results to the ones from future researches.
When analysing sources of recorded litter (both on beaches and on sea surface) 49% of it can be related to fishery and mariculture, 28% with coastal activities while 9% is from and unknown source and it also showed how this litter is associated to other activities like tourism and recreational activities, poor waste management, sewer and boat traffic.
The most common material is definitely plastic, with 92% occurrence frequency on beaches and 97% on sea surface. At beaches most frequent subcategory was Styrofoam – Polystyrene particles size category 2.5 – 50 cm that made 32% of total litter collected on beaches. Most frequent subcategory recording on sea surface were Polyurethane granules** that made 40% of total letter recorded at sea surface.
Through this project we hope that interest in sea and coastal pollution and sensibility about that topic will get bigger and bigger in local community and visitors and in the end result in decrease of litter. We all have the same interest – clean and healthy sea and coast!
*- Alkalay, R., Pasternak, G., Zask, A. (2007) Clean-coast index-A new approach for Beach cleanliness assessment. Ocean and Coastal Management. 50 (5–6), 352–362.
** – “According to the type of monomers and conditions of the production, polyurethanes of various structures and properties are obtained, from hard and foamy to elastomeric and fibrous materials, binders, coatings and adhesives. The most important is the so-called polyurethane foam, which results from the reaction of the final isocyanate groups with water, which causes carbon dioxide to crosslink, which leaves voids in the polymer mass. It is a soft, semi-hard or hard cellular material for thermal and acoustic insulation, for the manufacture of mattresses, furniture components (soft seats and armchairs), etc. Foam with integral lining (with compact outer layer) is used for the interior of the vehicle and for sports shoes and equipment.” – https://www.enciklopedija.hr/natuknica.aspx?ID=49248