Report: “Pollutants in flatfish – Long-term measurements (1988-1999)”
Description
Since 1988, as part of a regular monitoring of coastal waters at six (later five) fishing areas along the Lower Saxony coast, flatfish samples have been taken once a year (July/August) for pollutant determination. These are the species Limanda limanda, Platichthys flesus and Pleuronectes platessa. The results of the study on the heavy metals copper, zinc and mercury in muscle tissue for the period 1988 to 1999 are presented. In addition to sampling failures, different distribution patterns or difficult points as well as the selected classification into size classes allow only limited statistical analysis. Overall, however, no increased loads can be observed compared to other test results from the North Sea or Nordic waters. For copper, there is a uniform trend at all sites, for all species and in all size classes: After a decrease from 1988 to 1990, there are constant values with a partly slightly negative correlation between body length and heavy metal content. A constant load is observed with zinc, whereby a slightly negative correlation between body length and heavy metal content can also be seen here. There is no clear pattern in the long-term development of mercury; comparable to results from other studies. The measured values move in the range of the background value, but show, at least in Limanda limanda and Platichthys flesus, in contrast to Cu and Zn, a possible positive correlation between body length and metal content. A revision of the sampling strategy is recommended. Within the regular monitoring of coastal waters, flatfish samples are taken once a year (in July/August) since 1988 at six (later five) fishing grounds along the coast of Lower Saxony to determine contents of noxious substances. Examined are the species Limanda limanda, Platichthys flesus, and Pleuronectus platessa in this preferred order. The results for the heavy metals copper, zinc, and mercury in the muscular tissue are presented for the period of 1988 to 1999. Additional to incomplete data collection, varying distribution patterns and main area of distribution as well as different size classifications allow only limitedstatistical analysis. Altogether, no increased levels can be determined in comparison to survey other results from the North Sea or Nordic Seas. The element copper shows a uniform trend for all the sites, species, and size classes: After a decrease from 1988 to 1990, the values are now almost constant between 0.20 and 0.35 mg kg FW (fresh weight) with a partly slight negative correlation between body length and heavy metal content. A steady content of zinc varying between 5.0 and 10.5 mg kg-1 FW is recorded, so showing a slight negative correlation between body length and heavy metal content. Comparable to the results from other studies, no clear pattern can be found for mercury in the long term development. The measured values range from 0.05 to 0.2 mg kg-1 FW. Whereas there is a tendency to a negative correlation for Cu and Zn, a positive correlation between body length and metal content indicates for the element Hg in the species Limandalimanda and Platichthys flesus. A revision of the sampling method is recommended.
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Tags
- plattfisch-limanda-limanda-kliesche-platichthys-flesus-flunder-pleuronectes-platessa-scholle-plattfischfang-sublitoral-blmp-schadstoffe-schwermetalle-organische-schadstoffe-nlwkn
- wilhelmshaven-mellum-innenjade-langeoog-baltrum-emsästuar