NARRAGANSETT — Rhode Island is still the only state in the country with an offshore wind farm, but that will change in the coming years as wind farms are built along the entire Eastern Seaboard, from Virginia all the way up to Maine.
Now five years old, the Block Island wind farm, consisting of just five turbines, has been the subject of considerable study as scientists determine what impacts, if any, the construction of the facility and the turbines themselves are having on the ecosystem. Researchers are also looking to the future, when thousands of wind turbines will be coming online.
At the second of four webinars in the 17th annual Ronald C. Baird Sea Grant Science Symposium, scientists from the University of Rhode Island and elsewhere heard from researchers in Europe, where offshore wind power has been commonplace for decades.
Entitled “Offshore Renewable Energy — Changes in Habitats and Ecosystems,” the June 15 symposium focused on the impacts of individual turbines and larger-scale wind energy installations on the diversity and interactions of marine species.
Emma Sheehan of the University of Plymouth in the United Kingdom and Jan Vanaverbeke of the Royal Institute for Natural Sciences in Belgium presented some of the findings of their research on the environmental impacts of large-scale commercial wind and wave energy farms.
The discussions were moderated by Jennifer McCann, director of U.S. coastal programs for the Coastal Resources Center of the University of Rhode Island; David Bethany, executive director of the Commercial Fisheries Research Foundation; Julia Livermore, supervising biologist from the Rhode Island Department of Environmental Management; and Andrew Lipsky, acting chief of staff of the Northeast Fisheries Science Center at the National Oceanic and Atmospheric Administration.
“In the next 20 years there will be more than 2,000 wind turbines off the coastline,” McCann said in her introduction. “As we experience this growth, however, we see that state and local decision-makers, resource users and other end-users are struggling to keep up with the decisions they’re having to make and also understand the potential impact that may come on existing activities and natural wildlife.”
Vanaverbeke studies plankton, the microscopic plants and animals that form the base of the marine food chain. He has also looked at the changes that wind turbines make to the sandy sediment on the ocean floor.
The first thing that happens when a turbine is installed is the colonization by what Vanaverbeke called ‘fouling organisms,’ small animals that attach themselves to the structure, the same way they would attach to a ship’s hull.
“We have huge numbers of these,” he said, “so this means we have high densities and at a certain stage, we also have a very high biodiversity, which means we have lots of species. This increased biomass will also attract other animals.”
Vanaverbeke set out to determine the impacts of such high densities of organisms. Young fish and shellfish, such as cod, are attracted to the turbines because they provide shelter, but also, food.
“This investigation also showed that the diversity in food items for the higher tropic [food chain] levels was the highest,” he said. “It’s not just shelter.”
The turbines also have an effect on the benthic, or bottom sediment, not only when they are driven into the sea bed but also because of the waste generated by all the organisms that colonize them.
“We actually know that flora and fauna are filter feeders so they re-take a lot of organic material from the water column,” Vanaverbeke said. “And that introduces fecal pellets and fecal pellets are given back to the water column and they will sink.”
Sediments close to the bases of turbines are altered by the quantity of organic matter to the point where they become depleted of oxygen, or anoxic.
Understanding how turbines, both individually and in large aggregations, affect marine ecosystems, helps policy-makers decide where wind farms should and should not be built.
“Where is the best place, from an ecosystem perspective, and the other thing, of course, is can you combine that marine space that’s occupied by offshore wind farms? Can you combine with aquaculture? … And you can also use that knowledge for the better design of these offshore wind farms.”
In the United Kingdom, Sheehan’s research focuses on marine protected areas and how offshore wind farms might impact those areas by excluding fishing close to the turbines.
“It’s so important for us to consider the the benthos, the seabed, in these communities, because it really is the foundation for the whole marine ecosystem,” she said. “It provides nursery habitat, feeding habitat for several species of commercial and conservation importance.”
Sheehan studies the impacts of offshore renewable energy, including wave energy, on fish populations. She has also considered the impact of England’s first large-scale offshore mussel farm.
“In areas that were heavily degraded seabed, we’ve seen that the mussel shell fallout onto the seabed habitat seems to be increasing biodiversity,” she said. “It’s restoring the benthic habitat. It’s also increasing the benthic commercially valuable species such as lobster and crab on the seabed, but it’s also increasing commercially valuable species in the water column.”
Sheehan likes the idea of having offshore industries located at the same sites.
“We think there’s lots of potential for environmental benefit of putting offshore aquaculture together with offshore renewable — from an environmental point of view, but also from an economic point of view,” she said. “Sharing space is going to be the only way I think we can move forward in this industry … If managed to exclude bottom-type fishing from the whole site, offshore development can have positive effects on the ecosystem."