Marine floating litter refers to items that have been produced and used by humans and have been intentionally or unintentionally discarded or lost at sea, in rivers, or on the shore. These items can be transported to the sea through various means such as wind, rainwater, rivers, or sewage.

Monitoring of floating marine litter (FML) in the south-western Black Sea was carried out in the period 09.2021 - 12.2023. Eight transects, each with a length of 2250 m and an area of 13500 m² were observed.  A total of 502 objects were described. 88.72% of the floating marine litter was made of plastic. The amount of FML varied between tansects and values ranged between 168 - 730 Items.km-2. The average amount of floating marine litter over the entire monitoring period was 403 ± 692 Items.km-2.

Seasonal and annual differences in the amount of floating debris were observed. In 2022, the amount varied between 0 and 252 Items.km-2, with an average of 120±191 Items.km-2 across all transects. In 2023, the floating marine litter in the transects ranged from 352 to 1407 Items.km-2, with an average of 791±957 Items.km-2.

The highest concentration of FML during the monitoring period was observed in September, with a concentration of 636± 1053 Items.km-2. The lowest concentration occurred in April, with a concentration of 70± 145 Items.km-2. The most common types of litter, in order of relevance, were plastic pieces measuring 2.5 to 50 cm, cover/packaging, plastic bags, wood boards, plastic bottles, synthetic rope, cups and cup lids, plastic caps and lids, balloons and balloon sticks, and food containers.

The concentration of FML in the sea is strongly influenced by local  severe weather events, which can result in concentrations 2 to 3 times higher than the average values. These higher concentrations were recorded in September 2023 (870±559 Items.km-2) and November 2023 (1481±1458 Items.km-2).