Ecological research at the alpha ventus offshore test site

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Ecological research at the alpha ventus offshore test site




When the first applications for offshore wind farm projects were submitted to the Federal Maritime and Hydrographic Agency (BSH) many questions concerning possible impacts were far from being answered satisfactory. Although some practical experience had been gained in other European countries, concrete data was difficult to obtain and difficult to apply to German projects which were located up to 150 km offshore and at water depths of up to 50 m. With more approvals being granted and the first wind farms under construction, cumulative evaluation of possible impacts became more and more important.

Ecological research at alpha ventus is brought together in the StUKplus research project, funded by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU). This project supplements the mandatory ecological monitoring by wind farm operators according to BSH Standard for Environmental Impact Assessment (StUK). The StUKplus project sets a wider frame in size, scope and content than ‘ordinary’ monitoring. In 2008, BSH was put in charge of coordinating the StUKplus project over a time period of almost six years - from May 2008 to March 2014.

During the extensive field research programme, novel observation methods and technologies such as new bird migration radars were applied for the first time in German waters. The pur-pose of the ecological research was to gain a better understanding of possible environmental impacts of offshore wind farms and to evaluate the second update of the StUK standard (StUK3, BSH 2007) which was used for the first time in an offshore wind farm during con-struction and operation.

The main research topics aimed to provide answers to the following questions:

  • How do habitats change for benthic organisms and fish close to the foundations? How are these organisms influenced by the artificial reef structures? How do habitats change as a result of fisheries being excluded from the wind farm area?
  • How do birds react to the rotating, illuminated wind turbines? Is there a risk of migratory birds colliding with the turbines at sea? Will resting birds avoid the wind farm area?
  • What impacts will noise-intensive construction work have on marine mammals? Will they continue to use the wind farm area as habitat and how can they be protected from noise? How do they react to operating noise?

Research on
benthic organisms

Research on

Research on

Research on
migratory birds

Research on
marine mammals

Research on
underwater noise


See reports (in German)


Research on benthic organisms

Benthos-related research at alpha ventus was carried out by the Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research. Benthic fauna were surveyed within the wind farm area and in a reference area between 2008 and 2011. Soft-bottom epifauna - mostly mobile, invertebrate organisms such as crabs, shrimps and starfish that live on top of the seafloor - were sampled with a beam trawl. Soft-bottom infauna - animals such as clams, tubeworms and burrowing crabs that live inside the sediment - were sampled using a van Veen bottom grab. Assemblages of fouling organisms such as mussels and sea anemones colonising turbine foundations and mobile demersal megafauna were sampled by scientific divers. The mobile demersal megafauna were also surveyed visually along belt transects extending on the seafloor away from the turbine foundations.


scientific divers

Colonisation of the foundation structures of offshore wind turbines was thoroughly investigated by scientific divers.
(photo: Roland Krone)

Colonisation of the FINO1 research platform in 5 meters water depth with blue mussels and sea anemones.
(photo: Sebastian Fuhrmann)

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Research on fish

A study on fish was conducted by the Alfred Wegener Institute (AWI), Helmholtz Centre for Polar and Marine Research, covering the pre-construction phase, the construction period and the first years of the operational phase at alpha ventus. Multi-day ship-based hydroacoustic surveys were carried out in spring, summer and autumn inside and outside the wind farm. The measurements were supplemented by a recently developed stationary long-term hydroacoustic measurement system. Additional net catches with a pelagic trawl allowed the fish species composition and size distribution to be identified. The stomach contents of horse mackerel and mackerel were analysed to examine the influence of the wind farm on the feeding behaviour of pelagic fish.

Local accumulation of mackerels at the FINO1 research platform.
(photo: Lars Gutow)


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Research on resting birds

Comprehensive studies on resting birds were conducted by the Research and Technology Centre (FTZ) at Büsum, an institute of Kiel University. Multiple-day ship-based surveys and aerial surveys were carried out in the area of the alpha ventus wind farm and in a reference area to determine changes in seabird abundance and distribution patterns. Data from all EIA studies in and around alpha ventus was also evaluated. Flight heights were measured with a rangefinder, and detailed observations of seabird behaviour were recorded during boat counts. Digital aerial surveys using HiDef technology were conducted to test new survey techniques for German offshore EIA monitoring.

The common guillemot (Uria aalge) was one of the key species monitored at the alpha ventus offshore test site.
(photo: Mathias Putze)

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Research on migratory birds

One of the reasons for refusing approval for an offshore wind farm project is if the wind farm poses a threat to bird migration (Section 5 (6) (2) of the German Marine Facilities Ordinance). In light of this, bird migration was investigated in four research projects carried out by Avitec Research GbR and the Institute of Applied Ecology GmbH (IfAÖ). Bird migration was investigated at the wind farm using video and heat imaging, as well as various radar systems to monitor birds encountering the rotor-swept zone and to capture evasive bird movements. Various remote sensing techniques were installed on one of the wind turbines, the transformer station and the nearby FINO1 research platform. The aim was to determine to what extent the presence of the twelve alpha ventus wind turbines influences bird migration in the German Bight during spring and autumn. The fact that most migratory birds are fairly small in size and that two-thirds of them prefer to fly by night posed a special challenge for the investigations.

Video and thermal cameras on the
transformer station in direction of rotating blades.
(photo: Reinhold Hill)

Examples of video tracks taken on the transformer station: A) single bird track;
B) several bird tracks; C) lesser or great black-backed gull; D) possible evasive movement of a bird. (photo: Reinhold Hill)

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Research on marine mammals

Research on marine mammals primarily focused on underwater noise. Investigations into the impacts of pile driving and operational noise on harbour porpoises were carried out by University of Veterinary Medicine Hanover. The presence of harbour porpoises was surveyed by means of aerial and boat counts in the pre-construction phase, during the construction period and in the first years of the operational phase. These surveys covered a large sea area. To account for possible changes in habitat use, a comprehensive passive acoustic monitoring programme was carried out. The collected data allows conclusions to be drawn as to the spatial and temporal scale of displacement caused by the installation of a wind farm.

A habitat modelling project was conducted by DHI to evaluate data on distribution and abundance of harbour porpoises gathered during EIA studies in accordance with StUK3. The EIA data and the StUKplus research data was then combined for long-term analysis and modelling of harbour porpoise distribution in the German Bight – the alpha ventus test site area and adjacent waters.


Harbour porpoise at the transformer station during a pile-driving break.
(photo: BSH)


Research on underwater noise

Construction and operation of offshore wind farms produce underwater noise that is potentially harmful to marine fauna. Most offshore wind turbines are installed by means of impact pile driving, which causes strong, impulsive noise. The foundations at the alpha ventus test site were driven up to 30 m into the seabed. Using hydrophones positioned in the water column, the underwater noise was measured before and during the pile driving work as well as during the operation of the wind turbines. The measurements were carried out by the Institute for Technical and Applied Physics GmbH (itap) during the construction of alpha ventus in 2009 and during the second year of operation in 2011. Most measurements were made with autonomous recording systems deployed 800 to 2,400 m from the alpha ventus test site.


Measurements of underwater noise were made with autonomous recording systems deployed 800 to 2,400 m from the alpha ventus test site.
(photo: itap GmbH)

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