Science of the Total Environment 878 (2023) 162902 
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Science of the Total Environment 
ournal homepage: www.elsevier.com/locate/scitotenv 
Ecological effects of offshore wind farms on Atlantic cod (Gadus morhua) in 
the southern North Sea 
A. Gimpel *?*, KM. Werner®, F.-D. Bockelmann“, H. Haslob*, M. Kloppmann®, M. Schaber®, V. Stelzenmüller® 
* Thünen Institute, Federal Research Institute for Rural Areas, Forestry and Fisheries, Institute of Sea Fisheries, Herwigstraße 31, 27572 Bremerhaven, Germany 
> Federal Maritime and Hydrographic Agency, Department Management of the Sea, Divison Assessment and Monitoring, Section Ecosystem Analyses, Neptunallee 5, 18057 Rostock, Germany 
? Helmholtz-Zentrum Hereon, Institute for Carhon Cycles, Department of Applied Modelling and Quantitative Methods, Max-Planck-Str. 1. 21481 Geesthacht, Germany 
HIGHLIGHTS 
- Unravelling the effects of offshore wind 
anergy on demersal fish species is key for 
marine spatial planning. 
Offshore wind farm effects on Atlantic cod 
‘Gadus morhua) were studied at different 
spatial and temporal scales. 
Results indicate that cod frequents off- 
;hore wind farm areas for feeding in sum- 
‚ner and spawning in winter, 
Offshore wind farms have positive effects 
on the resilience of local cod populations. 
Our simplified setup may provide valu- 
able details for the design of future moni- 
;oring and area-based management 
zoncepts. 
ARTICLE INFO 
Editor: Rafael Mateo Soria 
Keywords: 
Artificial reef effect 
Atlantic cod 
Offshore wind farm 
Reproduction 
Southern North Sea 
GRAPHICAL ABSTRACT 
Samples taken at different spatial and temporal scales using a combination of techniques to study the ecological effects 
of an Offshore Wind Farm (OWF) on Atlantic cod (Gadus morhua) around in the southern North Sea. Samples were 
taken inside the OWF during summer (OWF summer, yellow) and winter (OWF winter, blue) as well as at reference 
stations in the German Bight (GB) during summer (GB summer, red) and winter (GB winter, grey). While results on 
2,g. “the length at age and *the carbon isotopes 813C and nitrogen isotopes 8315N indicated positive effects on food 
availability during summer, *the maturity stages of cod adults (dark blue = females, light blue = males; all taken dur- 
ing winter) and *the origin of eggs (OWF or GB) suggested reproduction during winter. Concluding that offshore wind 
“arms provide local positive effects on cod populations, we contribute to urgently needed observational evidence re- 
garding the ecological impact of offshore windfarm installations to inform area-based management and future moni- 
toring activities. 
Ecological effects of offshore wind farms on cod 
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ABSTRACT 
Zvaluating the ecological effects of the rapid expansion of offshore renewables at local, regional and ecosystem-wide 
;cales is essential to understand the overall socio-ecological trade-offs also for other sectors such as fisheries. Hence, 
ittle is known about the ecological impact on demersal fish. To shed light on this topic, we studied the effects of an 
offshore wind farm in the southern North Sea on different life stages of Atlantic cod (Gadus morhua) using a combina- 
:ion of sampling methods at varying spatial and temporal scales. Our investigations of diet composition and trophic 
ıiches indicate that cod utilizes wind turbine piles with scour protection as feeding grounds. Furthermore, collected 
nformation on cod adults and early life stages during winter spawning season suggest that spawning activity occurred 
'n winter across the wider wind farm area. We conclude that wind turbine foundations with a scour protection can 
unction as artificial reefs that have local positive effects on the resilience of local cod populations. With our study 
ve contribute to urgently needed observational evidence regarding the ecological impact of offshare wind farm instal- 
ations to inform area-based management and future monitoring activities. 
* Corresponding author at: Thünen Institute, Federal Research Institute for Rural Areas, Forestry and Fisheries, Institute of Sea Fisheries, Herwigstraße 31, 27572 Bremerhaven, Germany. 
E-mail address: antje.gimpel@bsh.de (A. Gimpel). 
http://dx.doi,org/10.1016/j.scitotenv.2023.162902 
Received 23 September 2022; Received in revised form 12 March 2023; Accepted 12 March 2023 
Available online 17 March 2023 
0048-9697/© 2023 Elsevier B.V. All rights reserved.