ALBERT

Notes: Summary Observations of a correlation between the distribution of certain aquatic invertebrate species and different water pollution levels are — perhaps contrary to the expectation — not very recent. One could even say that such observations are older than ecology itself; as early as 1848 it was correctly concluded that the absence of caddis larvae from a stream can be caused by the presence of a city upstream (KOLENATI, 1848). The term ‘ecology’ was blended in 1866 by Ernst Haeckel, together with a definition of the field to be studied by this new science. In the last decades of the 19th century these observations were more and more assembled into systems and methods to estimate water pollution levels and in 1908–1909 a first elaborated scheme for biological water quality assessment was published, the well-known ‘Saprobiensystem’ (KOLKWITZ and MARSSON, 1908; 1909). In this system the range of organic pollution is divided into four levels and for every level a list of characteristic organisms is given; the invertebrate fauna is represented, but is only a fraction of all listed species. On basis of later investigations new indicative species were added to the list (LIEBMANN, 1960; SLADECEK, 1973). While the system was used more and more widely, a marked disadvantage was noticed, especially with respect to the invertebrate fauna, since the ‘Saprobiensystem’ is a result of research in running waters in Central Europe. When sampling in other types of water (e.g. stagnant) or other parts of Europe one can meet two problems: (a) relatively few of the sampled species will be mentioned in the system as a consequence of either the limited geographical distribution of most invertebrate species or their limitation to running water; (b) those species mentioned in the system may have another behaviour towards pollution in not-running (or otherwise different) waters. In the past twenty years several large sampling programs have resulted in better adapted systems to estimate water quality on basis of invertebrate fauna (WOODIWISS, 1964; TUFFERY, and VERNEAUX, 1967; MOLLER PILLOT, 1972). One may conclude that the problem of limited geographical distribution of indicative species can be solved by constructing different systems for zoogeographically too different regions. ‘Too’ different means in this context so different that a saprobic system on the taxonomical level of the species cannot be suitable for both regions by sheer lack of common organisms. On a higher taxonomical level (genera or families) it may be possible to construct a system with a very broad applicability, but the degree of resolution with respect to pollution levels may not be very high in this case. The second problem-restriction of species to certain types of water-could be dealt with in a similar way,i.e. a ‘Saprobiensystem’ for every type of water. The almost philosophical problem of defining what a ‘type’ is, should be avoided for practical purposes by adopting a tractable number of easily recognizable types and accepting the fact that a saprobic system loses its applicability for the more extreme representatives of a type. Some types of water may be found, for instance large open water, where invertebrate fauna is not a very convenient group for water quality assessment. On the other hand, types of water where invertebrates are virtually the only group present also exist (glacier streams). In general the group seems to be highly suitable for the estimation of organic pollution in many kinds of surface water (‘limnosaprobity’,sensu SLADECEK, 1973). Apart from saprobity there are some other properties of surface waters that can be faunistically detected and/or characterized. (a) Nutrient status (oligotrophic, eutrophic, etc.). However, invertebrate species with a clear preference for a specific nutrient level are not very numerous as compared to phytoplankton or macrophytes. (b) ‘Integrity’ or other criteria to express the extent to which the potential biological richness of a geomorphologically defined type of water is realized. This can be important when an indication is wanted of the value of an aquatic ecotope as compared to other representatives of the type. Again, knowledge of the optimal biological development is needed as a reference, as in the case of a saprobic system. Thus, a typology or classification of types of water, accompanied by some sort of indication about the optimal (often ‘natural’) situation, would not be a purely scientific topic. A classification can serve as a basis for the monitoring as well as the evaluation of aquatic ecotopes (MOL, 1977; 1979). The large number of species and the vast geographical and ‘typological’ distribution of aquatic invertebrates justifies the expectation that the group will play an important part in any biological classification of surface waters.

Notes: Abstract The factors determining life conditions in running waters can be arranged in a hierarchical scheme. One of the main factors is stream velocity, which is described by Manning's formula. By transformation of the formula a set of variables is acquired with which a diagram is constructed to contain all hydraulic conditions in running water. By measuring the ground slope and the hydraulic radius at a certain station this station can be placed in the diagram. Data from Dutch streams and rivers form definite clusters enabling us to describe types of running waters on this base. The distribution patterns of stream organisms in accordance with stream hydraulics can be fit into the diagram as well.