Effects of offshore wind turbine foundations on mobile demersal megafauna and pelagic fish - research at the alpha ventus offshore wind farm

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1 Effects of offshore wind turbine foundations on mobile demersal megafauna and pelagic fish - research at the alpha ventus offshore wind farm Roland Krone and Sören Krägefsky Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research

2 Changing German Bight Up to 5,000 offshore wind turbine foundations 20% of the German EEZ Planned Approved Under construction Operating Depth EEZ German exclusive economic zone, German Bight

3 Impact on mobile demersal megafauna and pelagic fish?. Dominated by soft bottom associated communities 5,000 new habitats introduced New communities, increase in reef organisms?! How react pelagic fish? StUKplus challenges Monitoring the effects of construction and operation on pelagic fish Quantification of mobile demersal megafauna at the artificial habitats

4 Effects of construction and operation on pelagic fish

5 Questions Do construction and operation redistribute pelagic fish? Do pelagic fish feed on reef organisms inside alpha ventus? Does hydro acoustic generate new findings?

6 Methods Hydro acoustic survey with ship-mounted multifrequency echosounder (1) sampling with net catches (pelagic trawl) (2) stomach content analysis of fish caught outside and within the area of alpha ventus

7 Results: net catches Strong similarity in species composition between net catches in alpha ventus and at reference sites.

8 Results: hydro acoustic surveys Indication for strong relative decline in abundance of pelagic fish in the alpha ventus area compared to the surrounding area during construction phase Relative abundances inside/outside alpha ventus day night

9 Results: stomach content analysis Biofouling organisms from the foundations are a diminutive component of the diet of Atlantic mackerel and Atlantic horse mackerel Purple A. mackerels ref Green A. mackerel within av Red A. mackerel at FINO1 Blue A. horse mackerel at FINO1 Atlantic mackerels within the wind farm had ~ 50% lower fullness compared to mackerels outside the wind farm (operation phase)

10 Mobile demersal megafauna at offshore wind turbine foundations

11 Questions How do demersal megafauna communities at foundations (reef fauna) differ from those on soft bottom? How large are the stocks of mobile demersal megafauna at alpha ventus foundations? New findings by scientific diving?

12 Methods 2 nd year after construction (2011) Sampling in spring and autumn Fauna 1cm (megafauna) Towed video camera on sand bottom 6-27 recordings inside av; 7-27 outside Diving belt transects 3-4 tripods and jackets per season Abundances per foot print

13 Results: foundation comparison 2 nd year after construction av spring ref spring av autumn ref autumn Tripod spring Jacket spring Tripod autumn Jacket autumn Communities on soft bottom and foundations are not similar Community structure at tripods and jackets are similar Communities on soft bottom inside and outside are similar

14 Results: seasonal and differences Percentage share > 90% Spring Soft bottom Autumn Spring Foundations Autumn Lars Gutow/AWI Two years after construction. Seasonal variability or ongoing development?

15 Result: large stock potential for mobile demersal megafauna 2 nd year after construction Standing stock in alpha ventus ~20,700 Brown crabs (different size)

16 Result: large stock potential for mobile demersal megafauna Example: Brown crab colonizing future wind farms 5,000 Tripods = 11.7 Mio. individuals Soft bottom + wrecks = 4.2 Mio. individuals inside EEZ* + 275% Brown crab Increased predation pressure More fishery targets *Krone et al., 2013

17 Results: Brown crab nursery and production? Large individuals exclusively inhabit the bottom area! Large numbers of small individuals inhabit the upper sections! Upper sections functioning as larvae collectors, increasing production?!

18 Summary and outlook Construction phase potentially effects pelagic fish! The offshore wind power foundations provide habitat for thousands of mobile demersal reef organisms! New challenges What happens after two years? What happens in other German Bight areas? Production and redistribution? Alain Norro/RBINS How does reef fauna develop at other foundations (e. g. with scour protections)? Literature Krone R, Gutow L, Dannheim J, Brey T, Schröder A (2013) Mobile demersal megafauna at artificial structures in the German Bight - likely effects of offshore wind farm development. Estuarine Coastal and Shelf Science 125: 1-9. Krone R, Schröder A (2011) Wrecks as artificial lobster habitats in the German Bight. Helgoland Marine Research 65:

19 Acknowledgements We thank Dr. Alexander Schröder, Dr. Lars Gutow, Gabriele Dederer, Philipp Krämer, Christof Schneider, Philipp Kanstinger and Sebastian Fuhrmann for their contribution to the project work. Funding: Federal Ministry for Environment, Nature Conservation and Nuclear Safety, research project RAVE Ecology (grant no A) Coordination: Federal Maritime and Hydrographic Agency (BSH) Supervision: Project Management Jülich (PTJ) Dr. Roland Krone phone Thank you for your attention!

20 Forschungstaucherische Beprobungen Projektlaufzeit Projektbewilligung StUK plus (für 2,5 Jahre der Betriebsphase) Projektverlängerung (Modifikation und Erweiterung des Beprobungsschema) Errichtungsarbeiten Betrieb Kampagne Jul Sept Okt Apr Mai - Jul Sept Apr Okt/ Nov Mär Sept bis Jul Umspannw erk Tripods Tripods Jackets Betriebsphase I II II IV V VI VII Tripods Training 2 Training 4 3 Jackets 3 3 Training FINO 1 Training 1* Wrack 1* Umspannwerk Bodenvideoeinheiten [n] alpha ventus Referenz Basisdaten, Ersatzuntersuchungen & Methodentraining Bauphase Bauphase 1. Betriebsjahr Hauptuntersuchung 2. Betriebsjahr

21 Spring Autumn