Monitoring of hazardous substances in marine biota

Background and Objective

The European Marine Strategy Framework Directive (MSFD) demands "good environmental status" in european seas. To reach this goal MSFD descriptor 8 includes contaminants to be monitored in fish. Thünen Institute of Fisheries Ecology samples fish in North Sea and Baltic Sea using own research vessels every year. In these samples - mainly in dab, herring an cod - contaminants were investigated. Some of these investigations last for 25 years so time series have been established and we can reveal potential temporal trends. The goal is to describe spatial and temporal contamination in fish as well as an assessment of the contamination level and of the "good environmental status" as demanded by MSFD.

Approach

The reseach cruises take place every year in late summer - a time when biological changes in fish are low and environmental year-to-year differences have minor influence on the results. Fish samples were taken to the lab to investigate selected organis contaminants as well as heavy metals. We also investigate biological parameters like age, condition and health of the fish.

Data and Methods

The methods used differ for every contaminant under investigation. They are state of the art and typically used in modern labs for environmental trace analytics. We use among othes liquid chromatography with fluorescence detection as well as atomic absobtion spectroscopy. Analytical quality assurance is always a part of what we do. Therefore we use certified reference materials and take part in international intercalibration trials.
The results were delivered to national and international data bases like MUDAB to contribute to current environmental assessments.

Our Research Questions

• To which extend marine fish from the North Sea or from the Baltic are contaminated?
• Do spatial differences in contamination level or composition exist?
• Do temporal trends in contamination level exist?
• Which biological factor influence data interpretation?
• Can sources of contamination be identified?
• How can the environmental status be asseds on base of the contaminantion level?
• Do problems arise for human consumers from the contamination level in fish?

Preliminary Results

To which extend marine fish from the North Sea or from the Baltic are contaminated?
Results for the heavy metal mercury (in german) are presented here.

Do spatial differences in contamination level or composition exist?
Yes, fish from coastal regions in the North Sea are higher contaminated than fish from the open North Sea.

Do temporal trends in contamination level exist?
This differs with the regions: While in some off-shore regions of the North Sea trend are negativ, shallow or not detectable, Hg levels in dab from the German Bight rise significantly in the last 25 years.

Which biological factor influence data interpretation?
Fish species and the age of animal play a role. Hg accumulates in fish with age. Ths means that older fish are higher contaminated than younger ones from the same species (bioaccumulation).

Can sources of contamination be identified?
In one study (Kammann et al., 2021) concerning dumped munition in the Baltic Sea it could be shown that Hg-contaning fuses of this munition are no source for elevated Hg in fish living there.

How can the environmental status be asseds on base of the contaminantion level?
The good environmental status for Hg in biota has not been reached yet.

Do problems arise for human consumers from the contamination level in fish?
No, EU food threshold of 500µg Hg/kg wet weight) is usually not exeeded. This is true for all above mentioned fish species and regions.

More results concerning different contaminats can be foud here.

Links and Downloads

www.ospar.com

www.helcom.fi

www.ices.dk