Coastal Virginia Offshore Wind
Foundation Monitoring Survey - 2023
Overview
The Coastal Virginia Offshore Wind (CVOW) Pilot Project consists of two 6-megawatt offshore wind turbine generator monopiles, the first installed in United States federal waters. This Pilot Project will inform future developments of large-scale offshore wind in the adjacent Virginia Wind Energy Area leased by Dominion Energy (CVOW Commercial Project). Project permits include research requirements as a condition for approval. Therefore, the Coastal Virginia Offshore Wind Pilot Project facilitates research, including foundation monitoring surveys, which evaluate marine growth on monopile surfaces and associated scour protection layers. Pilot project results will inform the Bureau of Ocean Energy Management’s permitting work and guidance for monitoring plans at larger-scale wind projects proposed in US offshore waters. INSPIRE Environmental prepared this report in support of Siemens Gamesa Renewable Energy (SGRE) and Dominion Energy.
Overview of lease area: A01 is 1.32 km from A02
The foundation monitoring surveys include two components: 1) above the waterline, including the splash zone and intertidal zone, and 2) below the waterline, including monopile surfaces, scour protection layer, and surrounding sediments. This visual report describes spatial (e.g., vertical zonation) and temporal (i.e., successional change) patterns in biotic presence and abundance. Also, this report highlights the presence of non-native species, sensitive taxa, and species of concern.
The INSPIRE and SGRE teams in the field.
Above the Waterline
The SGRE team surveyed the foundation above the waterline. The INSPIRE team created mosaics of the images and analyzed biotic growth in this region.
Physical conditions were considered "good" to "fair" at all locations. Conditions were considered “fair” when paint was scratched or flaking, leading to exposed and rusted metal in some cases.
Every year, the extent of biotic growth increased in both the splash zone and intertidal zone.
Algae dominated the biotic community in the splash zone and intertidal in all years, with greater coverage in the intertidal.
The survey detected few taxa above the waterline, with minimal increases in diversity from 2020 to 2023.
Below the Waterline
Fish
Atlantic Spadefish & Greater Amberjack| Jacks & Barracuda | Scad
The survey detected a variety of fish, including jacks (above & below, black sea bass (below), cunner (below), tautog (not pictured), scad (above), barracuda (above), sheepshead (not pictured), banded rudderfish (not pictured), Atlantic spadefish (above), greater amberjack (above).
The survey documented predictable vertical zonation in the fish community. Scad and jack (blue runner) dominated the fish community in shallow water (12 m).
The fish community also predictably varied with distance from the foundation (Z1 to Z4): taxa occurred frequently in the middle of the scour protection layer (Z2), and frequency declined in either direction away from Z2.
Black sea bass occurred throughout the scour protection layer and at all depths > 8 m. Black sea bass is a species of concern given its importance to recreational and commercial fishermen.
Jack (Blue Runner) | Black Sea Bass |Cunner & Black Sea Bass
Monopile
In 2022, mussels nearly completely covered the foundation, but in 2023, the survey detected bare space on the foundation.
The anode cage provided a complex habitat for mobile taxa, including fish, and this habitat changed little between 2022 and 2023.
Algae dominated the biotic community on the foundation in 2020; abundance declined with depth, as expected for these photosynthetic taxa. However, mussels dominated the community in 2022 and reached 100% coverage at most depth intervals. By 2023, mussel abundance declined at multiple depths and algae regained dominance in shallow water. In contrast with algae, the mussels greatly increased the biovolume of the biotic community.
Diversity increased every year. Notably, sea stars feed on mussels and the abundance of these predators (sea stars) and the abundance of the prey (mussels) increased in 2023. The 2023 survey also detected an increased abundance of colonial tunicates, a putative non-native species.
Scour Protection Layer
In 2023, mussel abundance dramatically increased near the base of the foundation on the scour protection layer.
While mussels dominated the scour protection area near the foundation in 2023, biota sparsely colonized the scour protection area in all other zones and across all years.
The scour protection area supported the greatest biotic diversity. Similar to the monopile, diversity increased every year. Also in this region, the 2023 survey detected an increased abundance of tunicates and coral. The tunicate is possibly the non-native, Didemnum vexillum. The coral is likely the northern star coral, a sensitive species.
Large mussel gap | Algae on monopile | Mussels and sea stars on monopile | Mussels near base of monopile
Summary
This survey found abundant fish and algae near the surface, mussels on the monopile, and the greatest biotic diversity on the scour protection layer. Compared with 2022, the 2023 survey detected large and small mussel gaps, increased sea star abundances, and increased biotic diversity. Sea stars prey upon mussels, which was observed in the video. In addition to the elevated sea star presence, the biotic diversity included coral, urchins, tunicates, gastropods, and a variety of fish. Finally, the survey observed more particulates in the water column in 2023 compared with 2022.
This survey supports the following conclusions.
- The infrastructure supports a diverse ecosystem, with predator-prey dynamics common to natural hard habitats.
- The infrastructure supports a productive ecosystem, which could lead to advanced infauna communities in surrounding sediments, mediated by increased carbon transport.
- The infrastructure could alter connections between populations, illustrated by the presence/abundance of the coral (northern star coral), potentially non-native tunicate (Didemnum vexillum), and fish near the northern edge of their geographic range (barracuda and greater amberjack).
Putative non-native tunicate | Mussels growing on scour protection layer | Scour protection layer
