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The macrophytic vegetation of the major rivers of Luxembourg. Bulletin Societé Naturalists Luxembourge, 88 (1988), 3—54.


Purpose of survey

This survey was commissioned by the Ministry of Environment of Luxembourg following complaints by anglers of a decrease in vegetation (a loss of Ranunculus being particularly mentioned). The possibility of damage from herbicides was raised particularly that from atrazine, since this is used in maize fields and maize-growing has much increased in recent years.

The aims of the survey were twofold: Firstly, to establish a base-line inventory of the actual aquatic vegetation of macrophytes in the main rivers of Luxembourg, in order to be able to follow future changes.

The second aim was to assess the amount of vegetation damage in the main rivers of Luxembourg and whether this pollution could be ascribed to a particular type or source. The comparison with earlier investigations in 1977-80 shows some changes and trends in this pollution damage during the recent past.


On looking at a river, one of its most obvious features is its 'weed' (macrophytic vegetation). This may be pleasing or displeasing to the eye and be useful as creating habitats for invertebrates and fish and hence for anglers, or be useless for man's purposes, as when it creates a flood hazard or prevents easy angling. All organisms, including these larger plants, grow in conditions favourable to themselves and avoid habitats too unfavourable. Therefore, once the habitat preferences of species are known, the living communities present in any river can be used to interpret the conditions of that river as they affect them.

The quality of rivers can be assessed in many ways. These include chemical analysis of water (or soil), invertebrate surveys and indices, macrophyte (large plant) surveys and indices, diatom surveys and indices, fish surveys, chemical analysis of molluscs and analysis of mosses, among others. If a river is completely clean, this will be shown on all indices. If a river is grossly polluted by a range of chemicals, likewise all methods will indicate this gross pollution.

However, when pollution is mild or consists of only a small range of chemicals, different methods will lead to rather different results. This does not mean any of the methods are wrong; it means that the different methods are assessing rather different aspects of pollution.