Monitoring of the nature enhancement project in offshore wind farm Borssele III/IV, T3 2023

Leewis, L. (2024). Monitoring of the nature enhancement project in offshore wind farm Borssele III/IV, T3 2023. Report by Eurofins. Report for The Rich North Sea - De Rijke Noordzee.

@techreport{Leewis-2024-2130898,
author = {Leewis, L},
title = {Monitoring of the nature enhancement project in offshore wind farm Borssele III/IV, T3 2023},
institution = {Eurofins},
year = {2024},
month = {feb},
address = {Amsterdam, Netherlands},
url = {https://toolbox.therichnorthsea.com/app/uploads/2025/01/BW-Final-report-T3.pdf},
keywords = {Wind Energy, Fixed Offshore Wind, Ecosystem Processes, Invertebrates},
}

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TY - RPRT
TI - Monitoring of the nature enhancement project in offshore wind farm Borssele III/IV, T3 2023
AU - Leewis, L
AB - The Dutch government has a responsibility for the state of the North Sea environment, following from the EU’s Marine Strategy Framework Directive and Habitat and Birds Directive. In order to utilize the momentum of the large-scale development of offshore wind farms, a commitment was therefore explicitly included in the site decisions for developers. This enables them to contribute to the strengthening of nature, and the preservation and sustainable use of species and habitats that originally existed in the Netherlands (Blauwwind, 2019).Blauwwind is currently operating the Borssele III and IV wind farm on the southern edge of the Dutch exclusive economic zone. Blauwwind developed its vision on how to design and construct the Borssele III and IV wind farm in such a manner that it matches the vision mentioned above, with the goal of contributing to a strong, healthy, and biodiverse North Sea (Blauwwind, 2019). In partnership with The Rich North Sea programme, a nature enhancement project is carried out and monitored.In October 2020, biodiversity was monitored around eight wind turbines in the Borssele wind farm, site III and IV (T0). In addition, living flat oysters were installed at the scour protection of four wind turbines in site III. In July 2021, a second monitoring campaign (T1) was carried out and the scour protection of the eight wind turbines, consisting of different sizes of rock, was also partly covered with shell material to create settlement places for flat oysters. The eight wind turbine locations in sites III and IV were studied again in 2023 (T3) and are scheduled to be monitored and decommissioned in 2028. The scope of this monitoring entails measuring growth of the oysters, taking water samples for larvae and eDNA analysis, oyster samples from the baskets (for reproduction and Bonamia status), and a combined video and photo survey of the scour protection with an ROV.Research questions which could (partly) be answered in the T3 are:What is the survival and growth rate of flat oysters?Do the flat oysters stay free of the parasite Bonamia?Do the flat oysters produce larvae?Do oyster larvae settle on different scour protection substrates (armour layer, filter layer and empty shells)?Do they have a preference for any substrate type?Can the oyster spat and/or larvae also be found in the control zone?How is the general biodiversity developing on the different substrate variations?Can patterns be found in oyster larvae settlement or species-specific responses in relation to the prevailing current?Is the species data found by ROV (remotely operated vehicle) video and photo analyses correlated to the eDNA data? Which species are not found or only found by a certain method?How fast does succession of a hard substrate community occur in the Borssele area?The current report will describe the T3 monitoring in August 2023 in terms of a description of the observed site and a comparison with the T0 and T1 data (Schellekens et al., 2021; 2022). Methods are described in more detail in the next chapter, followed by the results and a discussion.
CY - Amsterdam, Netherlands
DA - 2024/02//
PY - 2024
SP - 57
PB - Eurofins
UR - https://toolbox.therichnorthsea.com/app/uploads/2025/01/BW-Final-report-T3.pdf
LA - English
KW - Wind Energy
KW - Fixed Offshore Wind
KW - Ecosystem Processes
KW - Invertebrates
ER -

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Abstract

The Dutch government has a responsibility for the state of the North Sea environment, following from the EU’s Marine Strategy Framework Directive and Habitat and Birds Directive. In order to utilize the momentum of the large-scale development of offshore wind farms, a commitment was therefore explicitly included in the site decisions for developers. This enables them to contribute to the strengthening of nature, and the preservation and sustainable use of species and habitats that originally existed in the Netherlands (Blauwwind, 2019).

Blauwwind is currently operating the Borssele III and IV wind farm on the southern edge of the Dutch exclusive economic zone. Blauwwind developed its vision on how to design and construct the Borssele III and IV wind farm in such a manner that it matches the vision mentioned above, with the goal of contributing to a strong, healthy, and biodiverse North Sea (Blauwwind, 2019). In partnership with The Rich North Sea programme, a nature enhancement project is carried out and monitored.

In October 2020, biodiversity was monitored around eight wind turbines in the Borssele wind farm, site III and IV (T0). In addition, living flat oysters were installed at the scour protection of four wind turbines in site III. In July 2021, a second monitoring campaign (T1) was carried out and the scour protection of the eight wind turbines, consisting of different sizes of rock, was also partly covered with shell material to create settlement places for flat oysters. The eight wind turbine locations in sites III and IV were studied again in 2023 (T3) and are scheduled to be monitored and decommissioned in 2028. The scope of this monitoring entails measuring growth of the oysters, taking water samples for larvae and eDNA analysis, oyster samples from the baskets (for reproduction and Bonamia status), and a combined video and photo survey of the scour protection with an ROV.

Research questions which could (partly) be answered in the T3 are:

What is the survival and growth rate of flat oysters?
Do the flat oysters stay free of the parasite Bonamia?
Do the flat oysters produce larvae?
Do oyster larvae settle on different scour protection substrates (armour layer, filter layer and empty shells)?

Do they have a preference for any substrate type?
Can the oyster spat and/or larvae also be found in the control zone?

How is the general biodiversity developing on the different substrate variations?
Can patterns be found in oyster larvae settlement or species-specific responses in relation to the prevailing current?
Is the species data found by ROV (remotely operated vehicle) video and photo analyses correlated to the eDNA data? Which species are not found or only found by a certain method?
How fast does succession of a hard substrate community occur in the Borssele area?

The current report will describe the T3 monitoring in August 2023 in terms of a description of the observed site and a comparison with the T0 and T1 data (Schellekens et al., 2021; 2022). Methods are described in more detail in the next chapter, followed by the results and a discussion.