Oxygen uptake during mineralization of photosynthesized carbon from phytoplankton of the Barra Bonita Reservoir: a mesocosm study

Abstract

This study aimed to discuss and describe the oxygen consumption during aerobic mineralization of organic products (cells and excretion products) from five unialgal cultures: Cryptomonas sp., Microcystis aeruginosa, Anabaena spiroides, Thalassiosira sp. and Aulacoseira granulata. These species were isolated from Barra Bonita reservoir (22° 29' S and 48° 34' W) and cultivated in the laboratory. From each culture, two decomposition chambers were prepared; each chamber contained about 130 mg.L -1 of carbon from water samples of the reservoir. The chambers were aerated and incubated in the dark at 20.0 °C. The concentration of dissolved oxygen, pH values and electrical conductivity of the solutions were determined during a period of 10 days. The results indicated increases in oxygen consumption for all the solutions studied and also for electrical conductivity. The pH values presented a decreasing tendency throughout the experiment. Oxygen consumption varied from 43 (Aulacoseira granulata chamber) to 345 mg O 2 g -1 C (Anabaena spiroides chamber). Decrease in pH values was probably due to increase in CO 2 concentration from microbial respiration. Increase in electrical conductivity might be due to the liberation of ions during decomposition. The results demonstrate the potentiality of the studied genera in influencing oxygen availability followed by a die-off event.It also indicates the possibility of changing of the electrical conductivity and pH values in the water column due the aerobic algae mineralization.

Modeling chlorophyll-a and dissolved oxygen concentration in tropical floodplain lakes (Paraná River , Brazil)

“…Increases in decomposition rates and decreases in oxygen usually occur during high water periods, when decomposing organic matter input to the lakes increases (Taniguchi et al, 2004;Thomaz et al, 2004a;Townsend, 2006). This process rapidly leads to a change in water quality, an increase of ions due to the leaching of detritus and a decrease of dissolved oxygen due to microbial respiration (Godshalk and Wetzel, 1978;Carvalho et al, 2005;Bianchini et al 2008;Cunha-Santino et al, 2008). In addition, oxygen depletion promotes the release of ions from sediment (e.g., reactive phosphorus), increasing electrical conductivity.…”

Production of bio-fertilizer from Ascophyllum nodosum and Sargassum muticum (Phaeophyceae)

“…Despite being devoid of leaves, stems, roots or vascular system, seaweeds are photosynthetic organisms, primary producers and one of the main sources of organic matter for aquatic ecosystems, playing a crucial role in the carbon cycle as they fix it through photosynthesis. This permits to make an analogy between the values of seaweeds in marine ecosystems as good as higher plants in terrestrial ecosystems (Cunha-Santino et al, 2008;Silva, 2009;Akila and Jeyadoss, 2010).…”

Aerobic and anaerobic decomposition of Pistia stratiotes leachates from a tropical eutrophic reservoir (Barra Bonita, SP, Brazil)

“…Then, oxygen consumptions were estimated from the sum (CO-HMM DOM × 0.39 + CO-LMM DOM × 0.61). The half-time (t 1/2 ) of oxygen consumption was calculated according to Cunha-Santino et al (2008).…”