August 14, 2024 — Over the next ten years, thousands of wind turbines will be installed along the Atlantic coast of North America. This will be the biggest change to the sea floor in the area since the last Ice Age ended about 14,000 years ago.

A new research study, conducted by Kevin D. E. Stokesbury, N. David Bethoney, Felipe Restrepo, Bradley P. Harris, and sponsored by the Commercial Fisheries Research Foundation has been conducted to:

1. Understand the differences between the sea floor in areas where wind turbines will be built and other locations;
2. Help scientists predict how the ecosystem might change when the turbines are installed;
3. Provide a detailed picture of the current sea floor, so future changes can be measured accurately after the turbines are in place. 

To understand what the sea floor is like now, scientists combined two large sets of data. One set comes from underwater camera surveys done from 2003 to 2019, and the other set is from geological studies dating back to 1966. They used this information to create detailed maps of the sea floor from Virginia Beach to the Gulf of Maine, down to a depth of about 300 meters. These maps show the probability of finding different types of materials on the sea floor, like rocks or sand, in specific areas.

Background

Offshore wind energy development goals are set to bring thousands of wind turbines to the North American Atlantic coast over the next decade. Such rapid development will significantly change the underwater environment. For example, currently soft seabeds (mud, sand, etc.) will have new hard structures introduced by wind farms (towers, foundation base materials, etc.). To understand the impact of wind farm development on marine habitats, we need to gather baseline information on the current state of these underwater areas.

What We Did
We studied the ocean floor along the East Coast of the United States using historical data. This involved using data collected from 2003 to 2019 by camera surveys from the University of Massachusetts Dartmouth School for Marine Science and Technology and marine sediment data from the United States Geological Survey dating back to 1966. We wanted to map the composition of the ocean floor before wind farm development began, so we looked at the percentages of mud, sand, gravel, cobble, shell, and rock in different areas. Then, we created maps to show where each of these types of substrate are found.

Photo: The six substrate types based on the Wentworth scale for the SMAST drop camera samples. Credit: Stokesbury, K. D. E., Bethoney, N. D., Restrepo, F., & Harris, B. P. (2024). Anticipating the winds of change: A baseline assessment of Northeastern US continental shelf surficial substrates. Fisheries Oceanography, e12693

What We Found
1) Across all of the areas we mapped, sand was the dominant bottom type (found in 59% of areas), followed by mud (34%), and gravel (6%).

2) Areas slated for wind farm development had different substrate types than the rest of the continental shelf. For example, wind farm lease areas predominately had a mix of sand (99% of areas) and shell (92%) as their substrates.

Looking Forward

Wind farm lease areas currently consist mainly of soft-bottom habitats with low percentages of harder substrates such as gravel, cobble, and rock. Wind farms will add a lot of hard structures to these areas, potentially altering the habitat and species that inhabit these areas, which will likely affect fisheries. The maps created in this study will help us monitor changes to the substrate after wind farm construction. This will provide a more comprehensive view of the impacts of offshore wind on ocean ecosystems.

The published paper on this research, which was led by Dr. Kevin Stokesbury. Dean of the University of Massachusetts Dartmouth School for Marine Science and Technology, is available here: “Anticipating the winds of change: A baseline assessment of Northeastern US continental shelf surficial substrates.”