For Cod and Windmills
Offshore windmills are increasing our renewable energy capacity to power homes and neighborhoods, but did you know that with thoughtful design, windmills also create some of the largest new marine habitats and artificial reefs in our history?
Here’s how it works: Over a period of seven years, more than 663,970 individual fish spanning 61 species were collected around the six wind turbines built on the sandy shoaling waters off Block Island, Rhode Island. Schooling forage fish like butterfish and Atlantic herring made up 74% of the catch. Among the 113,752 invertebrates sampled, 52% were longfin squid, followed by Jonah crab, rock crab, sand dollars, and sea scallops.
There were no negative effects on bottom-dwelling fish populations during the construction or operational phases of the wind farm. The structures provided a substrate that was heavily covered by barnacles above and mussels below. Shelter and protection were created for young fish. Divers photographed in transects black sea bass, little skate, windowpane, and winter flounder congregating around the structures in large numbers. An increase in Atlantic cod was also observed, but not enough to draw definitive conclusions.
The windmill café serves three types of diners, representing three dietary guilds. Planktivores and crustacivores consume the vertical fouling community, which includes anemones, bryozoans, tube worms, tunicates, and amphipods. Too few of these fish were observed for analysis.
Benthivores feed on a seabed enriched by a fall of mussel and barnacle shells, along with other tasty bits for crabs. Scup, winter flounder, little skate, winter skate, Atlantic herring, yellowtail flounder, and haddock were seen scavenging the ocean floor.
The piscivores are fish that eat other smaller fish. Chowing down near the windmills were weakfish, striped bass, summer flounder, spiny dogfish, bluefish, monkfish, and silver hake. Unfortunately, spiny dogfish are voracious predators that prey on commercially important species, including Atlantic cod, Atlantic herring, squid, butterfish, and Atlantic mackerel.
Windmill companies are taking steps to increase marine life by adding artificial reef balls, cubes, layer cakes, and mats to their structures.
Orsted US Offshore Wind operates the Block Island Wind Farm. Orsted is involved with building one of the largest offshore wind farms in the world, the Anholt Offshore Wind Farm, about fifteen miles offshore of Jutland towards Sweden. Working in collaboration with WWF Netherlands, Reef Design Lab, and the Italian company D-Shape, a dozen reef structures are on the seabed between the wind turbines, designed to create habitats for cod.
With cod populations so low, we’ve forgotten how vital cod are to Atlantic Ocean ecosystems. Cod are benthivores feeding on crabs. Without many cod, green crabs have flourished, eating the seeds of eelgrass. Crabs also eat sea snails, including periwinkles that graze algae off eelgrass. The loss of eelgrass means fewer juvenile fish survive, the grasses photosynthesize less oxygen, and the seabed is no longer stabilized. The Baltic Sea is one of the world’s largest brackish, shallow seas, where eelgrass once flourished. Large portions of the Baltic today have severe oxygen depletion, creating ocean “dead zones.” Restoring cod populations would restore the eelgrass beds and the marine coastal ecosystems we depend on.
By building with nature in mind and failing to resist jokes about something fishy in Denmark, we can transition our energy economy, create clean energy jobs, and support a thriving fishery and ocean ecosystems!
As we grapple with the effects of climate change, we need to be smarter, more nature-savvy. Designing wind turbines to support ocean health is precisely the kind of ingenuity required to build a clean, green and healthy future for all.
