DEFINE III

DEvelopment oF Integrated measures for Nature conservation and Ecosystems

Project duration: 15.06.2026 – 15.05.2029

Building on the results and methodologies developed within DEFINE I and DEFINE II, DEFINE III focuses on the development and field validation of standardised methods for assessing the carbon storage potential of subtidal biogenic oyster reefs in the German North Sea.

Biogenic reefs formed by the European oyster (Ostrea edulis) provide important ecosystem services, including habitat formation, biodiversity enhancement, water filtration and sediment stabilisation. However, their role in marine carbon cycling and their potential contribution to long-term carbon storage remain insufficiently understood. In particular, standardised field-based methods for quantifying carbon sequestration and storage in subtidal oyster reefs are currently lacking.

DEFINE III addresses this knowledge gap through an in situ, multi-season field experiment at the AWI MARGate test site near Helgoland. Experimental reef units containing living oysters, shell material and control treatments will be used to investigate how oyster reefs influence the delivery, retention, transformation and burial of carbon at the seafloor.

The project comprises one work package focusing on:

• quantifying organic carbon accumulation and burial in sediments beneath subtidal oyster reef structures;
• evaluating inorganic carbon storage through shell growth, burial and dissolution;
• investigating dissolved inorganic carbon dynamics and sediment geochemistry;
• distinguishing the biological effects of living oysters from the structural effects of reef habitat; and
• developing and validating standardised protocols for monitoring and assessing carbon storage in subtidal biogenic reefs.

Measurements will include organic and inorganic carbon in sediments and biodeposits, changes in shell mass, sedimentation rates, dissolved inorganic carbon, total alkalinity and relevant environmental parameters. By comparing oyster reef treatments with appropriate controls across different seasons, DEFINE III will provide a field-based assessment of the role of restored European oyster reefs in marine carbon cycling.

The resulting standardised and transferable methods are intended to support future monitoring of restored oyster reefs and strengthen the scientific basis for assessing their potential contribution to both marine nature conservation and natural climate protection. The project thereby contributes to linking biodiversity restoration with climate protection objectives and supports the Aktionsprogramm Natürlicher Klimaschutz (ANK).

DEFINE I & DEFINE II