From the sixties, growing general awareness arose concerning the negative effects of chemical pollution in the marine environment. This led to international regulation in Europe starting with the Oslo and Paris convention in the seventies and leading to several research projects and monitoring programs. In the Belgian Part of the North Sea (BPNS), modern oceanography, with systematic campaigns for assessing the quality of the marine environment, started with the “Projet Mer/Projekt Zee” (PMPZ) in 1970. Within this first phase of the Belgian Federal North Sea Research Program, all compartments of the marine ecosystem were studied. This initial program was followed by other research actions, programs and monitoring campaigns, resulting in a large set of valuable historical data on the marine environment of the BPNS.

As part of the 4DEMON project (4 Decades of Marine Monitoring), a massive amount of marine pollution data in sediment and biota has been centralized from various data sources. A quality check was performed on the data (coordinates, units, duplicates,…) resulting for biota in a dataset of no less than 82000 analyt values with metadata including those of heavy metals and polychlorinated biphenyls (PCBs). The data were valorized by performing long-term trends modelling on a defined subset of the data.

When collecting 40 years of pollution data, variability in the dataset is large and various issues have to be addressed to intercalibrate the data: sampling locations and species changed over time, major method changes occurred and essential metadata might be missing. Therefore, a linear mixed effect model was used to integrate all data into consistent long-term time trends, including the parameters season, sampling location and analysis method as model variables. The selected species for most contaminants were blue mussel (Mytilus edulis), brown shrimp (Crangon crangon), flounder (Platichthys flesus), and swimming crab (Liocarcinus spp). The model output gives a view on PCB and heavy metal pollution on a large time frame.

Acknowledgement

We want to thank the Belgian Science Policy Office (BELSPO) for the financial support of the 4Demon project.