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Fig. 1. Location of A) Cabo Verde in relation to the African coast, B) location of Säo Vicente within the Cabo Verde archipelago and C) beach debris composition 
during the subsequent surveys based on densities (left pie chart) and masses (right pie chart). Dark blue = plastic, orange = paper, dark green = wood, light blue = 
metal, purple = glass, light green = others (including medical and sanitary waste, pottery, rubber, and cloth). Beach debris abundances are averaged across the nine 
surveys that were carried out between 22nd May and 29th June 2023. Numbers in the pie charts indicate the contribution of each debris category to the total density 
or mass in percent (contributions <10% are omitted). Numbers in boxes indicate the average accumulation rate as density Litems/m?/d] (dark grey) and mass [g/m?/ 
d] dight grey) of debris on a beach. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) 
able 1 
Zeach characteristics, average accumulation rate and average mesoplastic density at the six surveyed beaches. 
Beach Coordinates Orientation Beach use Topography at the back Average accumulation rate macrodebris Average mesoplastic density 
items/m?/d g/m*/d particles/m” 
357° N Low Main road 0.11 + 0.05 0.6 + 0.6 77.22 + 110.96 
351° N Medium Sand dune 0.01 + 0.005 0.02 + 0.02 48.22 + 111.55 
32° E High Parking lot 0.04 + 0.01 0.09 + 0.06 13.77 4:20.15 
57° E Low Stone formations 0.12 + 0.07 0.4 + 0.2 224.55 4352.15 
183° 5 None Open valley 3.0002 + 0.0002 9.001 + 0.001 0.44 + 0.53 
>3Q0 TAT High Lake 3.002 + 0.001 ABA LANA 0.88 + 1.05 
Lazareto 16° 52’N, 25° 00’ W 
Salamansa 16° 54’N, 24° 56’ W 
Bala das Gatas 16° 54’ N, 24° 54' W 
Praia Norte 16° 52’N, 24° 54' W 
>alha Carga 16° 47'N, 24° 57'W 
Säo Pedro 10 A0°MN Oro 97 5AT 
OSPAR beach survey sheets assign a debris item to one of ten main 
categories (plastic, rubber, cloth, paper, wood, metal, glass, pottery, 
sanitary waste, medical waste) and identify it as one of 116 objects 
(Wenneker and Oosterbaan, 2010). Large items that could not be 
:ransported or were buried in the sand were left behind, but were noted 
on the survey sheet. They were not recorded again during the following 
surveys. The number of items per square meter describes the dehris 
density. 
On each beach, we carried out an initial cleaning (18th to 24th May 
2023), in which the transects were cleaned from all debris that had 
accumulated over an unknown period of time prior to the start of this 
study. This was a prerequisite that enabled us to quantify debris accu- 
mulation rates during the four-day intervals that intersected the 
following nine surveys that were conducted from 22nd May to 29th June 
2023. The data from the initial cleaning were not included in the sta- 
tistical analyses but they can provide an overview of the general 
pollution level on Säo Vicente and facilitate comparisons with other 
studies. Hence, an extensive analysis of the data from the initial cleaning 
is included in the supplements (Appendix B). 
After all surveys were completed, the collected debris was sorted 
again by beach, date of survey and debris category and each of the 
resulting batches was then weighed to the nearest 0.001 g to gather 
information about accumulated debris mass. After that, debris was 
disposed into the public waste management system of Mindelo. In total, 
LO replicates were collected per beach (including the initial cleaning), 
»ach spaced 4 days apart, resulting in 60 samples overall.