A. Zonderman et al.
assumption that galvanic anodes introduce significant amounts of
various metal(loid)s into the marine environment (Deborde et al., 2015;
Kirchgeorg et al., 2018; Reese et al., 2020). A recent study estimates that
the current European offshore wind capacity results in annual emissions
of 3219 t a”* Al, 1148 t a”! Zn and 1.2 t a7! In, the three main com-
ponents of Al-alloy GACP systems, under the assumption that GACP
accounts for around 90 % of applied corrosion systems (Watson et al.,
2025). However, in German OWFs, metal emissions are in general
reduced through use of ICCP systems or GACP systems with substructure
coating in order to limit the total emissions (BSH, 2023). Thus, the
German proportion of emissions is likely smaller than estimated. In a
previous study, several metals have been identified as possible tracers
for OWF activity, particularly Al, Zn, Ga, Cd, In and Pb (Reese et al.,
2020).
Anode components, as well as any other chemical output from OWFs,
may enter and accumulate in multiple compartments, namely the dis-
solved fraction in seawater, suspended particulate matter, sediment, and
marine biota. The fate and consequences of metal(loid)s and other
chemical contaminant emissions are heterogeneous. Therefore, the
investigation of chemical contaminants in multiple compartments and
data concerning transport pathways of OWF chemicals in the environ-
nent are necessary to understand and predict the environmental im-
pacts of offshore-wind-induced emissions.
Due to rapid colonization by fouling organisms, turbines themselves
provide an opportunity to study the uptake of contaminants through
their role as artificial hard substrate for sessile species such as mussels
(Coolen et al., 2022; Dannheim et al., 2019; Degraer et al., 2020). On
offshore wind turbines, blue mussel (Mytilus edulis) individuals appear
within months after the installation of the structure and are dominant in
he shallow subtidal zone, a phenomenon which has already been
‚.nvestigated from an ecological perspective, primarily in the Belgian
North Sea (De Mesel et al., 2015; Krone et al., 2013; Mavraki et al.,
2020). Due to their distribution and life as sessile, filtering organisms,
‘here is a long history of using Mytilus species in monitoring programs. In
the North Sea, time series are available including the OSPAR Coordi-
aated Environmental Monitoring Programme (CEMP) and the German
Environmental Specimen Bank (Umweltprobenbank). Mussel-based
monitoring is also conducted globally, including the United States Na-
tional Oceanic and Atmospheric Administration (NOAA) for the analysis
of contaminants of concern (Farrington et al., 2016).
As of now, little is known about the in-situ uptake of chemicals
released from OWF structures by marine organisms. Gomiero et al.
'2011, 2015) suspected the dissolution of galavanic anodes as a cause
for increased metal mass fractions (Ni, Zn and Cd) in Mytilus gallopro-
vincialis from offshore gas rigs in the Adriatic Sea. A number of labora-
tory experiments specifically targeting the effects of dissolution of
galvanic anodes on marine organisms have been performed in recent
years (Bell et al., 2020; Caplat et al., 2010; Levallois et al., 2022;
Levallois et al., 2023; Mao et al., 2011; Nivelais et al., 2023). However,
che experimental concentrations of Al and Zn producing negative effects
in model organisms fall generally outside of measured dissolved metal
concentrations in the North Sea (BSH and Hereon, 2022; Ebeling et al.,
2025). Therefore, this study attempts to address the knowledge gap
concerning the uptake of metals originating from OWF corrosion pro-
tection in-situ.
ın this study, a dataset concerning the distribution of 46 metal(loid)s
in M. edulis collected from offshore wind foundations is presented. The
wide range of analytes and multiple sampling locations provide an op-
portunity (a) to investigate the feasibility of detecting metal emissions
from OWF corrosion protection in fouling species and (b) to evaluate the
overall metal burden of OWF-colonizing mussels and the possible im-
plications e.g. for future multi-use scenarios.
Marine Pollution Bulletin 218 (2025) 118216
2. Experimental
2.1. Reagents and standards
The mussel tissue certified reference materials (CRMs) BCR-668
Institute for Reference Materials and Measurements, Geel, Belgium)
and NIST SRM 2976 (National Institute of Standards and Technology,
Zaithersburg, USA) were used as quality control (QC) for the
microwave-assisted acid digestion (MWAD). The CRMs NCSZC-73034
‘prawn; China National Analysis Center for Iron & Steel, Beijing,
China) and NIST SRM-1566a (oyster tissue; National Institute of Stan-
lards and Technology, Gaithersburg, USA) were used to further validate
the versatility and robustness of the digestion protocol (Wippermann
at al. 2023).
Further information concerning preparation of materials, contami-
nation mitigation protocols, and element standards can be found in
previous publications (Wippermann et al. 2023; Klein et al., 2021).
2.2. Mussels
A total of 196 individual mussels were analyzed for their mass
fractions of 46 metal(loid)s. The mussels were collected by divers from
15 single wind turbines located in eight OWFs within three OWF areas
(N-2, N-3 and N-5) located in the German North Sea (see Fig. 1) in
autumn 2021. Mussels were located approximately one meter (all wind
turbines), five meters (eight wind turbines) and ten meters (one wind
turbine) below the water surface. Applied cathodic corrosion protection
systems in sampled wind farms are either galvanic anodes in combina-
tion with coatings or ICCP systems (BSH, 2023). Detailed information
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Fig. 1. Sampling areas within OWFSs in the German Bight (grey areas) within
(he exclusive economic zone (EEZ) (dashed line). Areas are labeled in accor-
lance with the site development plan for the German North Sea and Baltic Sea
BSH, 2023).
