Abstract
Benthic assessment techniques utilized in soft sediment areas are of limited utility in glacial moraine habitats that are structurally complex and largely composed of hard substrata. We present a multi-modal approach consisting of multibeam bathymetry, video, and still imagery that collectively provides the knowledge base necessary to perform impact assessments in these habitats. Baseline and post-construction surveys were conducted adjacent to the Block Island Wind Farm to develop and test these methodologies within the context of offshore wind development, specifically for detecting and documenting anchoring-related impacts to moraine habitats. Habitat data were evaluated using the substrate and biotic components of the national classification standard, the Coastal and Marine Ecological Classification Standard, recommended by federal regulators, with modifications to present results in terms of predicted vulnerability to disturbance. Habitats near the wind farm were diverse and patchy, ranging from rippled gravelly sand to continuous cobble/boulder fields with high biotic cover. Anchor furrows were detected in moderate value habitats in bathymetric and video data. The multi-modal survey approach tested at the Block Island Wind Farm and presented here is now specifically recommended by federal agencies and is being used to inform efforts currently underway to map and assess benthic habitats for a number of U.S. projects seeking federal permits.
Highlights
With increasing recognition of the consequences of climate change and the need to reduce dependence on fossil fuels, countries around the world are investing significant resources in developing renewable energy supplies (Barrie et al 2014; Szulecki et al 2016; Voormolen et al 2016)
These patterns are consistent with a glacial history, with topographic highs representing moraines comprised of cobble/boulder ridges with low sediment availability (O’Hara and Oldale 1980), and with deeper sandy areas characterized by high sediment availability and frequent reshaping by physical forcing, e.g., storms, tides
Topographic highs were evident in the northwest corner of the survey area with a ridge line extending into the maximum anchoring extent boundary and in the area immediately southwest of the wind turbine generator (WTG)
Summary
With increasing recognition of the consequences of climate change and the need to reduce dependence on fossil fuels, countries around the world are investing significant resources in developing renewable energy supplies (Barrie et al 2014; Szulecki et al 2016; Voormolen et al 2016). Offshore wind installations remain in Europe, markets in Asia and North America are growing rapidly (GWEC 2019). Addressing environmental concerns and studying the effects of offshore wind farms on marine habitats and resources is paramount to the success of each development and the industry as a whole (Barrie et al 2014). Among concerns related to ocean sprawl most pertinent to offshore wind farms are interruptions to marine population connectivity (Bishop et al 2017) and alteration of sedimentary environments and biotic communities (Heery et al 2017). Research on how offshore wind farms affect marine environments has largely taken place in northern Europe and established monitoring programs there were generally designed to meet regulatory benchmarks across ecosystem components rather than to address targeted questions related to ecosystem function
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