Multi-Disciplinary and Multi-Scale Assessment of Marine Renewable Energy Structure in a Tidal System

Abstract

The French coast of the Atlantic and English Channel (EC) is promising for the development of Marine Renewable Energy (MRE), including wind, wave, and tidal stream, due to the high velocity of currents in some parts of the area. This paper, focusing on wind and tidal energy, discusses how the implementation of MRE converters influences biodiversity, and vice versa, through biofouling and reef effects. The understanding of these interactions requires the knowledge of the hydro-sedimentary conditions and the macrofauna. The research on these topics, performed at the Continental and Coastal Morphodynamic laboratory (M2C) (UNICAEN, France), is presented through a multi-disciplinary approach by i) studying the hydrodynamic conditions and the macrofauna in Alderney Race, ii) studying the biofouling effects on tidal turbines and their influence on the turbulent wake, iii) assessing the hydro-sedimentary impacts induced by the offshore wind farm, like scouring, and iv) taking an ecosystem approach on MRE, such as the reef effect. From an ecological perspective, the reef effect can be responsible for changes in the structure and function of the ecosystem. Although several studies have analyzed this effect at the species-or community-scale, the propagation of the reef effect at the ecosystem-scale remains unclear. Thus, understanding these ecosystem-scale effects is urgent for future research. From an engineering perspective, biofouling changes the structural characteristics (i.e., supplementary mass) of the converters and thus, affects their performance.

A Multidisciplinary Approach for A Better Knowledge of the Benthic Habitat and Community Distribution in the Central and Western English Channel

“…The French government has announced in early March 2022 a 'target 40 gigawatts of marine renewable energy in service in 2050', which is the equivalent of about fifty offshore wind farms (OWF) to be installed in the French Metropolitan coastal waters. Four OWFs were under construction along the French side of the EC at a distance between 15 and 20 km from the coastline [59,60]. In the future, there is a plan to build OWF at a greater distance from the coast (around 50 km), similar to the area prospected during the VIDEOCHARM surveys offshore the Bay of Seine where two new OWF sites have been investigated [59].…”

“…Four OWFs were under construction along the French side of the EC at a distance between 15 and 20 km from the coastline [59,60]. In the future, there is a plan to build OWF at a greater distance from the coast (around 50 km), similar to the area prospected during the VIDEOCHARM surveys offshore the Bay of Seine where two new OWF sites have been investigated [59]. Similarly, aggregate extraction areas are planned at a greater distance from the coast, such as the area located to the north of the Bay of Seine [13].…”

“…Data on the biomass of the benthic macrofauna should be completed by data on other biological components such as phytoplankton, zooplankton, suprabenthos and fishes to understand fluxes between these components (e.g., by studying fish stomach contents) to provide an ecosystem approach of such an offshore system in the central part of the EC. The development of the marine renewable energy structure in the EC will be for the researchers an opportunity to increase the knowledge of the functioning of such offshore coarse sediment, which has remained, once again, poorly investigated [59][60][61].…”

No Observed Effects of Subsea Renewable Energy Infrastructure on Benthic Environments

“…A fundamental consideration for approval of the development of MRE technology by regulators and stakeholders is the effect during the different stages of construction, operation and decommissioning on existing benthic ecosystems [5,6]. The introduction of infrastructure into a relatively pristine fast-flow marine environment [7] has the potential to change surrounding ecological characteristics [8][9][10]. Subsea introductions, in particular, have the capacity to act as 'artificial reefs', which may alter local hydrodynamics, sediment transport patterns and indigenous flora and fauna [11,12].…”