S. Acksen et al.
environments such as beaches (Thushari and Senevirathna, 2020). For
nany oceanic islands, tourism is an important economic branch and
nunicipalities often try to reduce debris loads through cleanups
(Sheavly and Register, 2007). However, these measures are expensive
and therefore difficult to implement in particular at high frequencies
(Rodriguez et al., 2020).
The assessment of the abundance, composition and accumulation
rate of debris in coastal environments as well as understanding the
processes that determine these variables is crucial for an appropriate,
cost-effective management of anthropogenic waste by the affected mu-
ıcipalities, to inform policy makers about the extent of the problem and
:o provide baselines for future surveys. While numerous studies have
documented the occurrence of marine debris in various regions of the
world, surveys in African countries, including Cabo Verde, have so far
been scarce. The first study on marine debris on shores of the Cabo
Verdean Island of Säo Vicente was published in 2022 (Weidlich and
lenz, 2022). This study involved a single beach-debris cleanup con-
ducted on five beaches on Säo Vicente, during which all debris larger
:han 1 mm was collected. This approach provides a snapshot of debris
pollution at one point in time; however, it does not allow for the
assessment of debris accumulation rates (Weidlich and Lenz, 2022).
ATence, our study serves as a comprehensive follow up, in which we
nvestigated the abundance, composition and short-term accumulation
:ate of beach debris on the island in repeated surveys that were con-
ducted in May and June 2023. At the same time, the abundance and
composition of mesoplastic particles in the beach sediments were
assessed. While beach debris can originate from both land- and ocean-
based sources (Prevenios et al., 2018), ocean-based inputs are particu-
‚arly important to consider on remote oceanic islands. To identify the
potential origins of floating items that were transported to the beaches
via ocean currents, backward ocean modeling techniques were
employed to track the pathways of particles using the PARCELS frame-
work (Delandmeter and Van Sebille, 2019). This approach focuses on
large-scale open ocean currents and can give a first rough estimate of
main prevailing ocean currents that transport marine debris while
neglecting small scale processes, wind transport and extreme events
(Van Sebille et al., 2020). This study aims to address existing knowledge
gaps on debris accumulation rates and the relationship between the
sources and transport pathways of macro- and mesoplastics, with a
particular focus on African oceanic islands. Following Hartmann et al.
2019) we define macrodebris as all non-natural objects >10 mm and
nesoplastics as plastic particles in the size range of 1-10 mm throughout
our study. Using Säo Vicente as a case study, we integrate three com-
lementary approaches — macrodebris beach-cleaning surveys, meso-
olastic particle sampling, and particle tracking simulations with
>ARCELS —- to provide a comprehensive assessment of coastal pollution
levels. Results are presented using multiple metrics to enable robust
comparisons across methods and spatial scales.
2. Methods
Säo Vicente is one of the ten Cabo Verdean islands and it is located in
:;he northwest of the archipelago. Situated in the North Atlantic
approximately 500 km off the coast of Senegal, the island is strongly
ınfluenced by ocean currents (Pena-Izquierdo et al., 2012). Through
strong wind interactions within the Cabo Verde archipelago and high
mesoscale eddy activity originating from the West African coast, the
Cabo Verde archipelago is a biological hotspot with high mixing, many
internal waves and high tidal energies (Schütte et al., 2025). Mindelo,
Sao Vicente's capital city, has approximately 75,000 inhabitants (INE,
2024) and is one of the most important seaports of Cabo Verde. While
che tourism industry grew during the last decades, Säo Vicente still has
many natural beaches with relatively low human activity.
Marine Pollution Bulletin 228 (2026) 119525
2.1. Survey locations
Between May 18th and June 28th, 2023, six beaches on Sao Vicente
were inspected for beach debris (> 10 mm) and mesoplastics (1-10 mm)
to obtain a comprehensive picture of the prevailing pollution levels
along its coastline and to identify factors that determine the composition
and abundance of debris items (Fig. 1).
Characteristics that determined the choice of sampling locations
were the orientation of the beach, accessibility, sediment grain size (i.e.,
the ability to sieve the sediment), wave and wind exposure, as well as the
level of beach use. Prior to the initiation of the surveys, eight beaches on
5a0 Vicente were visited and characterized based on a predefined set of
zriteria (Supplement Fig. A1). Six of these beaches were then selected to
include in the study, ensuring representation of a broad range of beach
types and environmental conditions across the island.
Lazareto (16° 52’N, 25° 00’ W), which, among the beaches that we
surveyed, is nearest to the city of Mindelo, is influenced by activities in
the adjacent marina, ship traffic, and a proximate main road. It faces
north and, due to low public use, it is seldomly cleaned (Supplement
Big. A2A). Salamansa (16° 54’N, 24° 56’ W) is oriented to the northeast
and is characterized by a large dune in its back section and a wide
beachfront. It is occasionally frequented by wind- and kite surfers and
features a small bar and a restaurant (Supplement Fig. A2B). Bafa das
Gatas (16° 54’ N, 24° 54’W) faces southeast and is separated from the sea
by a shallow lagoon. It is a popular destination for Mindelo residents,
leading to high numbers of visitors on weekends (Supplement Fig. A2C).
Praia Norte (16° 52’N, 24° 54’ W) faces east and is difficult to access.
Hence, the level of use is low and the beach is infrequently cleaned. This
'eads to the accumulation of debris and macroalgae that are deposited
here by winds and waves (Supplement Fig. A2D). Palha Carga (16° 47’
N, 24° 57’ W) is oriented to the south, and requires a 30-min offroad trip
with a 4WD vehicle to access. It is characterized by high waves that
accasionally inundate the entire beachfront, leading to the retention of
zeawater in its back section. There is no beach use at this location
“Supplement Fig. A2E). Finally, Säo Pedro (16° 49 N, 25° 3’W), which
faces the west, serves as the starting point for turtle-watching excursions
and therefore experiences a high level of use (Supplement Fig. A2F). It is
regularly cleaned by locals and the owners of the various restaurants and
food outlets in the adjacent village of Säo Pedro (Sina Acksen, pers.
abs.). Like Palha Carga, Säo Pedro experiences high wave action that
5ccasionally floods the entire beachfront and leads to the accumulation
’»f water in its back section (Table 1 and Fig. 1). Prior to our surveys,
:ommunity representatives, the university, and the local community
were informed about the study in order to avoid additional cleaning
activities during the sampling period. However, we cannot guarantee
the absence of additional cleaning activities during that time.
2.2. Beach debris surveys
Macrodebris, i.e., items >10 mm (Hartmann et al., 2019), was sur-
veyed at each of the six beaches every four days on 10 subsequent oc-
2asions following the OSPAR protocol for beach debris monitoring
‚Wenneker and Oosterbaan, 2010), with no modifications applied to the
protocol. For this, a transect was chosen at each location, which ran
parallel to the waterline and was always 100 m in length. The exact start
and end points of the transects were identified by GPS and nearby
landmarks, such as buildings or fences. The width of these transects,
however, varied between survey dates due to fluctuations in wave action
and water levels. On each survey date, the width was measured at the
ands of the transect from the waterline to the back of the beach. The
latter was identified by topographic features, such as a road, sand dunes,
or rock formations. With the help of these data, the surveyed area was
zalculated (Supplement Fig. A3). Debris surveys were always conducted
by two persons, who walked in parallel to the waterline. Every item
larger than 1 cm was collected, protocolled on the survey sheets, stored
ın a bag and then transported to the Ocean Science Center Mindelo. The
