4DEMON Workshop on data analysis on January 26th 2016 | 4DEMON

4 decades of Belgian marine monitoring

uplifting historical data to today's needs


The Belgian scientific community has, in the last four decades, built up considerable expertise in marine sciences (see Compendium Coast and Sea). Numerous scientific expeditions at sea have resulted in a vast quantity of scientific data related to different topics and important publications in the scientific literature about the marine environment of the Belgian Continental Shelf. Many valuable, historic data however still remain inaccessible to the larger scientific community, being available only on paper in various institutions. These sources are essential for understanding long-term changes in the quality of the marine environment. The 4DEMON project aims to centralise, integrate and valorise data on contamination, eutrophication and ocean acidification compiled during expeditions in the BCS over the last four decades, forming an important Belgian scientific heritage.

In the first phase of the project an extensive data inventory will be created and relevant historic data and metadata will be searched for in archives and digitized when needed.
Continuous remote sensing chlorophyll a and turbidity data sets will aid the data interpretation and intercalibration as they have a much higher spatial and temporal resolution.
Van Mechelen: Old Cruise summary reports provide useful sampling information.
1000-points map: Map of 1970-1976 sampling grid.


4DEMON Workshop on data analysis on January 26th 2016

Added on 14 Mar 2016
During the workshop on data analysis, each WP presented its progress and the results were discussed in the frame of further analyses within the project.
WP3 Contamination: need for normalization of pollutant concentrations

In order to determine temporal or spatial changes in pollutant concentrations in sediments, a correction is needed for the grain size effect. In fact, coarse components in sediments (which normally have low levels of heavy metals and organic pollutants) produce a downward shift of the concentration in the total sample. Since sediments of different origin vary in grain size composition, this shift in non-uniform between locations. Therefore, pollutant concentrations should be normalized. One way of doing this is normalizing all data towards a “standard seafloor”.

The figure above shows the relation between the concentration of the contaminant Hg and the normalizing parameter (TOC in this example) on different locations on the Belgian Part of the North Sea. For each location, different grain size compositions were analyzed for Hg concentration and for TOC. In this way, the concentration of Hg for each location can be standardized towards the standard seafloor (which contains 2.5% TOC) and results can be compared between each other.

WP4 Eutrophication: zonation of the BCZ

For the statistical analysis and to investigate spatial and temporal variations in the phytoplankton composition and dynamics, it was decided to divide the BCP into 6 zones (see Figure below). Zonation was based on a ‘common sense’ approach in order to cover as much as possible geomorphological (e.g. the inshore-offshore depth gradient) and environmental (e.g. the impact of the Scheldt river plume on water turbidity and nutrient concentrations) gradients in the BCP. The study in variations of CHL dynamics in the BCP between different pixels observed in the Earth Observation supports the chosen zonation.

The results on data analysis for WP4 will be presented by Anja Nohe on the 16th VLIZ Marine Scientist Day (see poster above).
Two main trends were observed:
  • An upward trend can be observed on the dinoflagellate/diatom abundance ratio for the last decade; higher ratios are also observed during summer months
  • A shift in genera composition between 1970s and 2000s
With regard to the Chlorophyll a, results need to be intercalibrated due to the different methodologies used through time for its measurement.

WP5 Ocean acidification: seasonal pH variations in the Belgian Coastal Zone

The analysis of pH data shows seasonal variations that seems consistent with the biological activity (see Figure).

Figure 3


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