CHANCES IN ABUNDANCE AND BIOMASS OF THE ATTACHED BACTERIAL COMMVNITY THROUGHOUT THE DECOMPOSITION OF THREE SPECIES OF AQUATIC MACROPHYTES

Abstract

Aiming at observing the variation in abundance and biomass of the attached bacterial community throughout the decomposition of plant material, three species of aquatic macrophytes were selected as substrate: Eleocharis interstincta (emergent), Potamogeton stenostachys (submersed), and Nymphaea ampla (floating 1eaves). These species were selected since they occupy different habitats in the aquatic environment and exhibit different chemical compositions, Samples were set up under water as a small depth, allowing for the passage of light, in plastic bottles with lateral openings, and rubber hoses were used as a control substrate. The chemical composition of the substrates (concentration of C, N and P) as well as the rate of dry weight loss were estimated from separate samples, incubated in litter bags. The bacterial community exhibited different values of each analyzed variable (density, biovolume, biomass, secondary productivity) in each substrate. The artificial substrate always exhibited lower values of density, biomass and secondary productivity. N. ampla was the best substract for the bacterial community regarding its density and biomass, followed by P. stenostachys and E. interstincta. This pattern was also found in the curves of dry weight loss of the detritus of these species, indicating a relationship between the process of decomposition and the bacterial colonization. Any relationship was found between the chemical (concentrations of C, N, and P) and bacterial variables. The values of density and biomass of the attached bacterial community were approximately 10 times greater than those registered in the bacterial community of the water column, in a comparison of area x volume (cm² x cm³). The increase of bacterial biomass in the surface of the detritus probably results in an improvement of its nutritional quality, with implications for the higher trophic levels.