Report: Macrozoobenthos: Unterweser; Bremerhaven to Bremen (1980)»
Description
Summary: In 1980 a survey of the intertidal bottom fauna was carried out in the upper reaches and the Limnic tidal area of the Weser estuary between Bremerhaven and Bremen. The upper reaches are part of the natural estuarine brackish water zone. The Limnic Tidal Area can no longer be viewed as a true fresh water habitat, because in recent years the entire course of the Weser has received a brackish character by wastes from potassium mining.
From the 38 Benthic animal species found, 16 species are oligochaetes, which are also in quantitative respect are the most important group. A faunal break near Rodenkirchen, where the average chloride concentration is about 1 to 1.5, divides the area in a lower and an upper section. In the lower section the brackish water Oligochaetes Tubifex costatus, Paranais litoralis and Peloscolex heterochaetus are the dominat species. The upper section (which includes the formerly Limnic, but now briny area) is dominated by the Limnic Oligochaetes Limnodrilus hoffmeisteri and Tubifex tubifex, also Paranais litoralis, Tubifex costatus and larvae often the dipterous Ceratopogonidae are common and abundant.
In the intertidal banks the following habitats can be distinguished:
Reed beds; Mud flats; Mixed bottom; Sandy flats; Hard bottoms;
Concerning the productivity of the investigation area the following conclusions may be drawn: In the upper reaches and the Limnic tidal area of the Weser reed beds and mud flats are the only habitats where a considerable production of the Benthic fauna takes places. The Large Sandy Banks of the Main River Bed represent a habitat which is extremely poor or even uncolonised.
Discussion and summary:
In 1980, an inventory of the soil fauna in the cotton linings of the Lower Weser took place. Of the 50 km long river route, a lower part (Bremerhaven – Brake) belongs to the natural brackish water, an upper part, which is also subject to the tide (Brake – Bremen) was formerly limestone, but is currently wnadlet by wastewater from the Kali industry into a weak brackish water.
Of the 38 species of soil fauna found in the area, the oligochaetes with 16 species form the strongest and most important group in quantitative terms. The distribution of animal species shows an accumulation of deposit limits and abundance jumps in Rodenkirchen, average chloride content 1 to 1.5 Ω. At this point, the subwesers were divided into a lower and an upper section.
In the lower section (natural brackish water with seaward rising concentrations) the brackish water oligochaetes Tubifex costatus, Paranais litoralis and Peloscolex heterochaetus are the dominant species. In the upper section (partly weakly concentrated, natural brackish water, predominantly formerly Limnish, now artificially salted area), the Limnodrilus hoffmeisteri and Tubifex tubifex predominant oligochaetes predominate and Paranais litoralis, Tubifex costatus and larvae of the dipterene family Ceratopogonidae are further steady and frequent soil animals.
The banks of both sections have the following eulitoral habitats:
Ried stocks; Sludge floors; Mixed floors; Sandy soils; Secondary hard floors;
From a production biological point of view, it should be concluded from the results: Red stocks and siltties of the Lower Weser are the only sites where a significant production of the soil fauna takes place, as the sandy soils of the banks of the main stream are weak or not at all populated.
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Tags
- weser-unterweser
- makrozoobenthos-abundanz-makrofauna-artenzusammensetzung-nlwkn-biologische-kartierung-eulitoral