Changes in bacterial processing and composition of dissolved organic matter in a newly-flooded reservoir (a three-year study)
Richardot, M.; Debroas, D.; Jugnia, L.B.; Tadonléké, R.; Berthon, L.; Dévaux, J.
published: Apr 14, 2000
ArtNo. ESP141014802004, Price: 29.00 €
The temporal changes in hydrolytic activities, the concentration and nature of DOM and the influences of these variables on bacterial production were studied over three years (1996 to 1998) in the euphotic zone of a newly-flooded reservoir (Sep, France). The dissolved combined amino acid concentrations (DCAA) changed little from year to year 5.3 (3.3-7.6) mg/L. In contrast, the concentration of polysaccharides (DCCHO), probably of allochthonous origin as shown by the low value (0.41) of the ratio a-Glucosidase activity/β-Glucosidase activity (⍺GlcA/βGlcA) were high in the first year (0.2-4.7, average 2.4 mg/L) and then decreased greatly. The increase in the value of the ratio ⍺GlcA/βGlcA (0.75) indicates that there was a change in the origin of the DOM with time. The hydrolytic activities of Leucine aminopeptidase activity (LAP), a and βGlcA were particularly high in 1996, being 498.3 (119.4-1302.9), 11.9 (2.4-28.5) and 27.2 (6.5-51.1) nM/h, respectively. Compared to the first year, the hydrolysis activity rates of the second and third years were about two to three times lower. The positive correlations between DCCHO and LAP (r = 0.59, n = 40, P < 0.0l), ⍺GlcA (r = 0.57, n = 40, P < 0.0l) and ⍺GlcA (r = 0.35, n = 40, P < 0. 05), and also between DCCHO and bacterial production (r = 0.49, n = 36, P < 0.05) indicate that enzyme activities and bacterial production were regulated by the supply of polysaccharides. In this type of ecosystem, organic matter, therefore, seems to play a key role in controlling bacterial communities through resources.