In limnological studies the measure of sedimentation fluxes of seston
is neglected, in spite of the importance it can have in determining wa
ter quality, studying biogeochemical cycles, evaluating the distributi
on of chemical species, etc. Often sedimentation is obtained only from
mass balance models, not taking into account the fact that the uncert
ainty of determining inputs and outputs makes this evaluation from the
ir difference rather unreliable; other factors of the balance, such as
exchanges with the atmosphere, between water and sediments, are equal
ly difficult to define. Though the direct measurement of sedimentation
also presents some methodological and logistic difficulties, such as
resuspension of material from the bottom, grazing, etc., this does not
justify the very scarce attention paid to this kind of determination.
This paper reports the sedimentation fluxes of 39 lakes, in different
parts of the world, having different limnological and trophic charact
eristics (0.4 < TP < 369 mu g L-1; 0.5 < chlorophyll a <50 mg m(-3)).
The fluxes of PM, C, N and P show a log-log relationship (r approximat
e to 0.6, p less than or equal to 0.05) with the common trophic variab
les (Secchi disk, total phosphorus, chlorophyll and primary production
), independently of the morphometric characteristic of lakes. Hence se
dimentation seems not to be an intrinsic property of the environment b
ut is related to the trophic state of the system. The results achieved
tend to confirm that the nature of sedimenting seston is generally au
tochthonous, even though the poor correlation between PM and the same
trophic variables suggests that PM is more influenced by allochthonous
material.