S. Acksen et al. 
u 
500 
0 
an 
+ 
zz 
A 
Zudem m BR 2 ME vn mm 
O00CUZ>CO<LLON 
020995030528 
5355 3°25°535 
2 555 S5 72 
le 
2000 ı 
5 in 
3 
A 
5 1000 
500 
Q - 
„ WO 
A 
Mm 
NE EN 
Marine Pollution Bulletin 228 (2026) 119525 
2000 ı 
© 
N 
© 
+ 1500 
S 
D, 
5 1000| 
500 | 
3! 
zo 
En 
De 
EESäo Pedro IESalamansa IEPraia Norte EIPalha Carga IElLazareto IEBaia das Gatas 
Fig. 5. Mesoplastic particle characteristics with regard to colour (A), shape (B) and polymer type (C). Colors indicate the surveyed beaches (light blue = Säo Pedro, 
green = Salamansa, purple = Praia Norte, yellow = Palha Carga, red = Lazareto, dark blue = Baia das Gatas). (For interpretation of the references to colour in this 
figure legend, the reader is referred to the web version of this article.) 
(Supplement Appendix B). According to this, the sites in Sao Vicente can 
ve classified as low polluted beaches, compared to beach debris data 
from across the world (Ansari and Farzadkia, 2022). 
Weidlich and Lenz (2022) conducted a beach cleaning on Sao Vice- 
nte in 2020, comparable to our initial cleanings, on five of the six bea- 
ches included in our study, and found a pollution distribution similar to 
ours, with the same beach exhibiting the highest pollution level. In their 
study, Praia Norte also had the highest debris load (83.91 items/m”), 
ollowed by Salamansa (10.72 items/ m”), Lazareto (0.49 items/m”?), Säo 
2edro (0.25 items/m”) and Palha Carga (0.01 items/m. However, as 
‘he authors surveyed debris items >0.1 cm instead of >1 cm, the 
abundances they observed were substantially higher than the ones that 
we found. 
4.2. Accumulation rates of macrodebris 
The average accumulation rates gathered in this study provide new 
knowledge on anthropogenic debris accumulation on African oceanic 
„slands. We display our findings in different metrics to allow comparison 
between different studies (Table 2). The accumulation rates found on 
Sao Vicente are comparable to accumulation rates on Rapa Nui (Thiel 
et al., 2021) on the Barrier islands (Wessel et al., 2019) and on beaches 
of the Lofoten islands (Haarr et al., 2024). Higher accumulation rates 
than in our study were found at the Selayar island coast (Hermawan 
et al., 2017), in Jericoacoara National Park, Brazil (Brabo et al., 2026) 
and in Hawai‘i (Currie et al., 2023). 10-100 times lower accumulations 
rates than on Säo Vicente were found on Sub-Antarctic Island beaches 
(Eriksson et al., 2013), on the Seychelles (Dunlop et al., 2020) and at 
Mediterranean costs (Prevenios et al., 2018). This shows the high vari- 
ability between debris accumulation rates all around the world (Table 2) 
and highlights the importance of local environmental conditions for 
ınderstanding the accumulation on single beaches. Assessing the 
amount of debris that accumulates on a beach in a given time period is 
essential for reliably estimating pollution levels. It also helps to adjust 
che frequency of debris surveys and to improve debris management 
activities such as beach cleanings. 
In our study, counts and masses generally yielded a similar picture of 
he pollution status of beaches on Säo Vicente. However, reporting 
debris loads in both units is meaningful and should become a common 
practice, since it facilitates comparisons to older surveys, which often 
report only the one or the other. This, in turn, would allow to discern 
long-term developments in the abundance and composition of beach 
debris from existing data. 
Discrepancies in the pietures drawn by count- and mass-based data 
usually go back to differences in the physical density of the collected 
materials. Heavy items in our surveys were pottery (43.27 g/item) and 
wood (13.69 g/item), while paper (1.76 g/item), medical waste (2.07 g/ 
item), and plastic (2.70 g/item) were light (Supplement Table A3). The 
metal items we collected had a rather low mass (5.1 g/item), because 
they were mainly small and thin objects like bottle caps. Hence, light 
materials can dominate debris compositions when these are count- 
based, while they play a minor role when masses are considered. On 
che beach in Lazareto, e.g., 46% of all items were made of plastic, while 
‘his fraction only represented 23% of the total debris mass. At the same 
beach, wood made up 19% of the items, but 48% of the mass. 
The items that clearly dominated the beach debris in Säo Vicente 
were made of plastic (83% of all items), and this was the case regardless 
?f beach orientation. This value is comparable to the share of 75.6% 
found in West Iceland (Burlat and Thorsteinsson, 2022), Sand Island in 
the Midway Atoll/North Pacific (91%) (Ribic et al., 2012), or from the 
Azores (87%) (R{os et al., 2018). Interestingly, on Säo Vicente those 
beaches that are characterized by low levels of beach use, but which are 
ariented towards the north-east (i.e., Palha Carga, Salamansa and Praia 
Norte) showed higher shares of plastic items (71-98%) than beaches 
with other debris sources (35-47% for Baia das Gatas, Sao Pedro and 
.azareto). 
4.3. Variation in mesoplastic abundances 
We found a total of 2701 mesoplastic particles (1-10 mm) in the 
sediment samples from Säo Vicente. The average density was 121.7 + 
339.1 particles/m”, while the minimum was 0 and the maximum 1694 
particles/m?, These abundances are 4-8 times lower than those reported 
from other oceanic islands (Table 3), even though the studies at the 
Canary Islands considered particles from a smaller size range (Herrera 
at al., 2018; Älvarez-Hernändez et al., 2019). Furthermore, mesoplastic 
particle abundance was assessed across three different beach sections, 
where samples collected near the waterline exhibited very low abun- 
dances, thereby lowering the overall average. This limits the compara- 
bility to different studies. Almost all studies observed a very high 
variability in mesoplastic density between sampling locations even on 
small spatial scales (Table 3). Hence, it is still unclear which spatial 
resolution is required in beach surveys to obtain reliable information 
about mesoplastic pollution. It is likely that the spatial distribution of 
these particles is generally patchy, while the level of patchiness may 
depend on local conditions such as the prevailing wind regimes, level of 
beach use and beach topography. As a consequence, surveys of these 
small-sized particles would need to be tailored to the specific situation at