Thursday, February 7, 2013

If wind blows, will fish grow? – Part 1

The GLC-sponsored Offshore Wind – Understanding Impacts on Great Lakes Fishery and Other Aquatic Resources Workshop* was held on Nov. 28-29, 2012, at NOAA’s Great Lakes Environmental Research Laboratory in Ann Arbor, MI. The workshop was well attended by roughly 50 participants representing resource management agencies, utilities, universities and policy experts.

The first workshop session was devoted to presentations by European experts on wind farm development and impact on marine and freshwater resources. Two of the three invited speakers, Åke Petterson Frikberg and Tore Wizelius, representing Sweden’s Rewind Offshore utility company, gave an informative presentation on development of the first operational wind farm in a freshwater environment. They highlighted how and where in Lake Vanern the wind farm was constructed, and discussed potential impacts of the farm on bird and bats, fishery habitat and fish populations.

Much of their presentation was devoted to issues of construction and cost as they represented the private sector. Åke and Tore discussed tradeoffs between developing wind in freshwater versus salt water. In marine waters, wind farms have stronger, more sustained winds and less interaction with birds or bats, and no ice, but must deal with salt erosion and difficulties in siting farms in deeper depths. They emphasized lowering construction costs as much as possible, which they accomplished by building forms for the pylons onshore and then towing them out to the site by reconverted barge.  Their company also received support of 7% of total costs from the Swedish government. The wind farm was located in shallow waters (4-12 m depth) and over bedrock, which is likely different than where wind farms likely will be sited in the Great Lakes. Construction of wind farms in Lake Vanern was halted during spawning season of the vendace, a member of the coregonid family which includes lake whitefish and cisco.  Åke and Tore noted no significant impacts of wind farms on birds or bats, as these animals do not normally fly at wind speeds > 4m/sec which are most optimal for powering the turbines.

Dr. Erwin Winter, a fisheries scientist from Wageningen University, The Netherlands, reviewed studies of potential impacts of wind farms on marine resources (birds, marine mammals, fish, benthos) in coastal waters of the Netherlands.  He noted there were impacts on bottom fauna and vegetation while construction took place, but not afterward. He noted impacts on phytoplankton biomass due to sediment disturbance, although effects on zooplankton were negligible.  Fish and marine mammals tended to move away from the area during wind farm construction, and returned after construction was completed. In one extensive study, Dr. Winter compared fish abundance, species composition, length and behavior outside and inside of wind farms, and used hydroacoustics to study fish behavior around the wind farm. Results indicated some fish species, principally demersal flatfish, avoided scour bed habitats created by currents swirling around the pylons, while other species such as cod and edible crabs were attracted to the scour beds. There were no detectable effects of the wind farm on the fish community, in fact most species appeared indifferent to its presence. Although the studies described by Dr. Winter were well designed, and used a before/after/control/ impact (BACI) design, they had relatively low statistical power of detecting an impact of wind farms. 

I felt that the presentations by the European visitors addressed several concerns of the Great Lakes community about wind farms. The European studies indicated there were few significant impacts of wind farms on birds, bats, or benthos. Fears about electromagnetic fields generated by power cables were unfounded as the cables were shielded which minimized the electric field. Dr. Winter did note some significant impacts on fauna from underwater sound and habitat disturbance from construction activity, and collision with rotor blades from birds. Potential beneficial impacts of wind farm construction included increase in new reef habitat, and closing areas to fishing near the wind farms.
Dr. Edward Rutherford

Research Fishery Biologist

Part - 2 coming next week!

The main financial partners were the Great Lakes Commission, Great Lakes Wind Collaborative, Great Lakes Fishery Trust, Great Lakes Fishery Commission, DT Energy and National Wildlife Federation.

No comments:

Post a Comment