Biomass and abiotic variables change in phytotelmic environment in the tank-bromeliad Nidularium longiflorum Ule in tropical forest

Aim Phytotelm plays an important role in plant growth and ecosystem functioning, but this natural aquatic microcosm is poorly known. We evaluated the seasonal (dry and rainy seasons) and spatial variations (forest trail and stream sites) of the phytotelm in Nidularium longiflorum, bromeliad that occurs in the Atlantic Forest. Methods Abiotic and biotic variables were measured in tank-bromeliad phytotelms. The biomass was analyzed by ash-free dry mass and chlorophyll-a concentration. Results Abiotic variables measured in the phytotelmic environment of bromeliads varied between sampling sites and seasons. Temperature, electrical conductivity and total nitrogen values were significantly different between seasons and sites. Chlorophyll-a and ash-free dry mass (organic matter) in phytotelm were significantly different between sampling sites. Eleven genera of algae in the phytotelm were identified. PCA axis 1 ordination evidenced the seasonal variation of environmental conditions. Conclusions Our findings suggest that environmental and micro-environmental conditions do not favor the development of algal community in the phytotelm. Biomass and abiotic variables in phytotelm of Nidularium longiflorum change seasonally, however biomass accumulation was strongly influenced by site characteristics.

Use of the aqueous extract of Eucalyptus microcorys for the treatment in microcosm, of water containing Enterococcus faecalis: hierarchisation of cells' inhibition factors

An experimental study in aquatic microcosm was carried out to determine the major factors involved in the inhibition of Enterococcus faecalis in the presence of aqueous extract of Eucalyptus microcorys. The planktonic bacterial cells remained in various concentrations of the aqueous solution at light intensities which fluctuated between 0 and 3,000 lx and incubation periods which ranged from 3 to 24 hours. A hierarchisation of studied factors revealed that the aqueous extract concentration, followed by experimental temperature, light intensity and incubation duration influence the inhibition of E. faecalis cells, respectively, with a rate of 86.82%, 7.03%, 5.25% and 0.90%. The cell abundances dropped significantly at 1.5% (λ = 0.491 and F = 5.518) and 2% (λ = 0.568 and F = 4.055) concentrations coupled with 1,000, 2,000 and 3,000 lx. The highest light intensities and extract concentration produce the highest log removal values. The disinfectant properties of E. microcorys were evaluated by the Chick–Watson model. This Chick–Watson model so obtained varied between log (N/No) = −0.09 Ct and log (N/No) = −0.17 Ct for extract concentrations of 1, 1.5 and 2%. Aqueous extract of E. microcorys could be used for water disinfection.

Impact of two disinfectants on detachment of Enterococcus faecalis from polythene in aquatic microcosm

<p><strong>After cell adhesion processes in microcosm, the impact of sodium hypochlorite (NaOCl) and hydrogen peroxide (H₂O₂) on the detachment of <em>Enterococcus faecalis </em>from polythene fragments immersed in water under stationary and dynamic conditions was assessed. The abundance of planktonic cells was also evaluated. The density of <em>E. faecalis</em> adhered in absence of disinfectant fluctuated between 2 and 4 units (Log CFU/cm²). </strong><strong>After living in disinfected water, </strong><strong>the density of <em>E. faecalis</em> remained adhered to polythene sometimes reached 2 units (Log CFU/Cm²)</strong><strong>. </strong><strong>This highest abundance of cells remained adhered was recorded with cells coming from the lag, exponential and stationary growth phases in water treated with 0.5‰ NaOCl. In H₂O₂ disinfected water, the highest value was recorded at all cells growth phases with 5‰ H₂O₂concentration. Adhered <em>E. faecalis</em> cells have been sometimes completely or partially decimated respectively by NaOCl and H₂O₂ treated water. Considering separately each experimental condition, it was noted that increasing the concentration of disinfectant caused a significant decrease (P≤0.01) in abundance of cells stay adhered after living in water disinfected by the two disinfectants. Changes in disinfectant concentrations in different experimental conditions had an impact on the detachment of <em>E. faecalis</em> cells from the substrates. </strong></p>