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 explicitly included in the site decisions for developers. This enables them to contribute to the strengthening of a healthy sea and the preservation and sustainable use of species and habitats that originally existed in the Netherlands. (Blauwwind, 2019).
Blauwwind is constructing Borssele III and IV wind parks on the edge of The Netherlands’ exclusive economic zone. Blauwwind developed its vision on how to design and construct the Borssele III and IV wind parks in such a manner that it matches the vision mentioned above, trying to contribute to a strong, healthy and biodiverse North Sea. (Blauwwind, 2019).
With this in mind, the Borssele III & IV project aimed to install and monitor living flat oysters inside the Borssele Wind Farm Zone, Site III&IV as well as the monitoring of the surrounding epibenthic fauna, and investigating the success of oyster installations and different scour protection. The main monitoring effort concerns status of flat oysters, as it is indicated as an umbrella species, assuming enhancement of the biodiversity in general.
The operational objective of this pilot was to increase the empirical evidence of the influence of habitat conditions on native biodiversity and flat oyster bed development by implementing various scour protection designs. This called for a scientific approach where the effects of various scour protection designs (treatments) can be investigated statistically to draw conclusions on what is the most effective approach (Blauwwind, 2019).
Based on this the monitoring objectives are:
- What is the survival and growth rate of the live oysters introduced (as larvae source) in the wind farm?
- Do oyster larvae settle on the various design substrates (scour protection and empty shells)? And if so, which scour protection variations are the best for oyster settlement?
- How is biodiversity in general developing on the various design substrates (scour protection and empty shells)? Are there differences on the different scour and empty shell variations?
The main monitoring effort concerns status of flat oysters, as it is indicated as an umbrella species, assuming enhancement of the biodiversity in general.
The Blauwwind Pilot scientific scope (2019) consists of the monitoring of the Borssele 3/4 project in order to find answers to the monitoring objectives. This scope entails taking larvae samples, oyster samples from the racks, video surveys with an ROV including grab samples and writing reports. This type of monitoring is to be executed in the specified windows during Year1, 3 and 8.
In this study however, that functions as the T-0, monitoring like mentioned above was yet conducted. Here, live oysters were placed in cages on installations and lowered to the sea floor at 4 different windmills. The methods are described in more detail in the next chapter. The ROV surveying and e-DNA sampling that was conducted will serve as a baseline for biodiversity at the research sites to compare to the future campaigns.