Samenvatting

Oyster reefs were once abundant in European waters, but they are now rare. In Zeeland, the wild population of the native flat oyster (Ostrea edulis) has declined significantly in recent decades, with serious implications for coastal water health in relation to biodiversity and water quality (Colsoul et al., 2020; Kamermans, 2019; Native Oyster, 2019). Oyster reefs are critical components of ecosystems. These reefs provide habitat for a variety of marine species, helping to increase biodiversity. Furthermore, oysters have the unique ability to purify hundreds of liters of water per day thanks to their filtering capacity (Native Oyster, 2019; Project Proposal, 2024;Bishop et al., 2023). A pilot project for Oyster Reef restoration started in 2024 in the Veerse Meer, Zeeland, in collaboration with HZ University of Applied Sciences, Oyster Heaven, Stichting Zeeschelp, and Van de Kreeke Palinghandel. During research into a suitable location in Zeeland to develop a pilot reef, the Veerse Meer was one of the selected locations where the flat oyster was still naturally present in some parts, and it was later decided to be the most promising option for a pilot for the return of the flat oyster. Despite its promising appearance, the Veerse Meer presents challenges that must be investigated and, if necessary, addressed in order to develop a self-sustaining reef and a healthy flat oyster population. The most significant challenges to this restoration are the deteriorating oxygen balance, the presence of large quantities of jellyfish and seaweed, and the presence of predators. Particularly young oysters are vulnerable to these threats.

The focus of the internship is: Impact of oxygen depletion: How long can the flat oyster (Ostrea edulis) survive in a low or oxygen depleted environment? The goal is to create a laboratory set-up that could test the survival of the flat oyster (Ostrea edulis) in hypoxic (≤2 mg/L O₂) and low oxygen (<5 mg/L O₂) conditions and to get preliminary results that would serve as possible guidelines when the project is further continued after the internship is finished.