Changes in biologically controlled carbon fluxes in a small stream following continuous supply of excess organic load

Abstract

The consequences of a constant supply of organic load from a pigsty to a small 2nd order stream are analysed through simultaneous consideration of amount of carbon stored in benthic biomass and of main biologically controlled carbon fluxes .The results show that the allochthonous load induced a general increase in all fluxes and therefore stimulated processes of carbon elimination from the receiving system .The increase of biologically controlled fluxes was due to qualitative changes of populations toward specialization for an optimal use of the newly supplied organic substrates . This was especially evident in this stream for macro-invertebrate biomass production and for insect emergence .Effects of trophic pollution ranged from drastic modifications near the input of the pig waste to a place where the additional supply of organic substrate increased the numbers of individuals of macroinvertebrate populations without any change in their specific diversity .Variations of CO 2 production appeared to be more related to biomass of microbial populations in the downstream station and to macroinvertebrates in the upstream station .Although the allochthonous load caused significant increases in several processes involved in its own elimination, the magnitude of these increases was small compared to the influx of organic carbon from upstream and from the pigsty . 123