The Elasmobranch Puzzle: Navigating the Balance Between Energy Production and Environmental Sustainability

By Erika Pietrzak, July 1, 2024

Offshore wind energy stands as a promising alternative to meet the nation's energy demands, but its integration should prioritize a symbiotic relationship with the existing marine ecosystem.

Background

There are currently 127 species of sharks, rays, and skates (elasmobranchs) in United States waters. The elasmobranch subclass is one of the oldest living vertebrate groups, composed of thousands of species that have evolved independently for millions of years. This has given them a pivotal position in affecting the marine ecosystem. Their long-standing impact is also seen in the presence of coastal livelihoods and more recently through eco-tourism. Notably, their slow reproductive and growth rates render their populations unable to efficiently recover from rapid declines. The critical ecosystem role is imperiled, as evidenced by a dramatic decline in their populations due to habitat degradation and unregulated fishing. Ocean shark and ray populations have plummeted 71 percent since 1970 and one-third of the world’s shark populations are threatened with extinction.

The landscape of wind energy has surged, experiencing a fivefold increase in productivity from 2005 to 2012. Offshore wind experiences an annual growth rate of over 25 percent globally and is expected to grow another 25 percent by 2030. This growth is pivotal to diversifying our energy grid and “avoid[ing] releasing harmful greenhouse gases that contribute to global climate change and harmful air pollutants, such as nitrogen oxides (NOx), sulfur dioxide (SO2), and fine particulate matter (PM2.5), that can cause serious localized health impacts, such as respiratory disease, cardiovascular disease, and premature death.” Wind farms are a 40- to 50-year commitment from site survey to eventual decommissioning. In 2021, the Biden administration announced its efforts to reach 30 gigawatts (GW) of offshore wind capacity by 2030 and 86 GW by 2050. This abundant clean energy source can provide a great opportunity for 83,000 new jobs by 2030 and bring in billions of dollars while combating climate change. Offshore wind produces energy without emitting carbon dioxide or burning any fuel, making its growth crucial to meeting growing electricity demands without worsening the already dire climate situation. Offshore wind in particular is important because of the high winds at sea, little visual impact from land, and high populations near the coast. One acre of offshore wind also brings 12,500 percent more for taxpayers than one acre of oil land while creating more energy. The industry has also worked diligently to close all loopholes for their workers in order to create safer working conditions with unions and bargaining agreements. With approximately 80 percent of Americans residing within 200 miles of the coastline, offshore wind represents a tangible and environmentally friendly alternative to current energy needs in the United States. Offshore wind helps us breathe better, have healthier oceans, create jobs, reduce extreme heat, and live healthier.

Habitat Loss

Irrespective of the method used to construct wind turbines, alterations in wind currents are inevitable, leading to changes in the surrounding habitat. When currents are altered, they develop differing bed forms, including ripples, sand ribbons, and hollows that then may attract or repel benthic species such as many elasmobranchs. While offshore wind farms are far from the greatest threat to marine habitats, with the creation of these farms, fauna and flora in the area will be disturbed due to sediment removal and habitat loss. Turbidity and concentration of suspended solids in the area will also increase, blocking the sunlight from floor life. All of these disruptions can damage the ecosystem and result in evacuations of the area.

These evacuations have resulted in starvation in seals and cetaceans due to mothers leaving their young behind when leaving the area. Stress induced by starvation, habitat alteration, noise disturbances, and changes in habitat quality diminishes an organism's immune responses, rendering it more susceptible to pollutants and diseases.

Many elasmobranchs are benthic species, staying low to the sea floor. The possibility of long-term damage from offshore wind farm creation “due to permanent changes in the current patterns and the transportation and deposition of sediments around the new structure on the seabed” presents a troubling issue. Offshore wind farms tend to have harsh bedrock and very coarse sediments, causing benthic species to avoid these zones.

In a 2012 study, researchers explored how bull sharks utilized natural versus artificial habitats. Though bull sharks utilized both habitats, more than 80 percent of adult bull sharks preferred the natural habitat compared to the artificial habitat. While the preference was less pronounced in juvenile bull sharks, they still gravitated toward natural habitats almost 60 percent of the time. Researchers hypothesized that these results occurred because of “the presence of riparian vegetation, … and well-established tidal flows which greatly contrast with the canals where riparian vegetation is almost non-existent and tidal flow is greatly modified resulting in the deoxygenation of the bottom layers, a strong deterrent to demersal species such as the bull shark.”

Habitat Creation

While offshore wind farms may create some habitat loss, they are ultimately considered fish aggregating devices, with several species congregating around the structure post-construction. In an initially relatively featureless basin, algae and fixed-living invertebrates rapidly colonize cables, piles, and structures, creating the base of the ecosystem and attracting other animals. Some invertebrates have been assembled up to tens of centimeters thick, resulting in some scientists hypothesizing that wind turbines may act as plankton collectors. These new habitats may increase biomass and species richness throughout the water column while creating new food webs. With limited fishing in the area, offshore wind farms present a protected habitat for these animals. Only when frond scouring is used do the farms experience a net habitat loss (-12.5m2), while gravel and boulder scouring increase habitat areas by 650m2 and 577m2 respectively. This net gain occurs because of the “significant increase in surface area which is achieved by the three-dimensional structures created by the boulders and gravel, which cannot be created by the installation of the synthetic frond mats, which are simply placed around the base of the turbine, directly onto the sea floor.”

Some studies have found seasonal attractivity of fish species to offshore wind farms, which were then used by seals as feeding grounds. This attractivity of fish and other prey to offshore wind farms can additionally create an opportunity for new elasmobranch feeding grounds. As well as seasonal activity, wind farms provide extra protection from fishers, making them an ideal location for juveniles and large fish. The tall structure occupying the water column also increases encounters with juvenile fish, making these locations excellent hunting grounds for many elasmobranchs. For example, areas around turbines experience 10-100 times higher catch rates of tuna than in the open ocean. However, these habitats have not been utilized by elasmobranchs as they experience 2.5 times lower predation rates, but further investigation is needed to understand why this is. One hypothesis for why elasmobranchs are not habituating these areas as much as other animals is the benthic nature of many of these animals being disturbed by wind farms in other ways like noise and electromagnetic fields.

However, the creation of these habitats is under question. The stresses and evacuations aforementioned make the congregation of animals particularly confusing to many scientists. Myberg in 1990 hypothesized that marine animals congregate around wind farms “because they have been deafened to the point where they would not be able to hunt or avoid predation if they were to enter the open water,” though this has not been proven and is vehemently disagreed on by many other scientists. Furthermore, fish have aggregated around oil platforms at higher rates than natural reefs because of the platform’s protection from fishing, which wind turbines offer as well, but proves that it is not necessarily unique to these farms.

Conclusion

For the harmonious coexistence of elasmobranchs and offshore wind energy, it's imperative to gain a deeper comprehension of the impacts that offshore wind operations exert on these species. This necessitates a concerted effort involving voluntary initiatives and policy changes without hindering the necessary growth of the offshore wind industry. Offshore wind energy stands as a promising alternative to meet the nation's energy demands, but its integration should prioritize a symbiotic relationship with the existing marine ecosystem. Striking this balance demands a thorough understanding of the effects of offshore wind activities on elasmobranchs and a commitment to implement measures that safeguard their well-being, many of which we should look to our European comrades for advice on as their industries have been further developed and further researched.

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