Prolonged high biomass diatom blooms induced formation of hypoxic-anoxic zones in the inner part of Johor Strait

Anoxic zones are designed for the removal of nitrogen in nitrifying activated sludge plants. This can be carried out either to achieve a nitrogen discharge consent or to eliminate the problem of rising sludges. The rising sludge problem is mostly encountered in medium and small size plants in warm conditions and there is limited information as to the appropriate design of anoxic zones to protect against rising sludges in the secondary sedimentation tanks. Therefore a series of batch experiments were undertaken in order to establish the critical concentration of nitrate-nitrogen which causes rising sludge in the secondary settling tank and the effect of environmental factors such as temperature (15°C to 30°C) and residual carbon source (100 to 600 mg/1 COD) were examined. Based on the results of these experiments an empirical equation was presented which can be used to size an anoxic zone to eliminate rising sludges. The application of this equation at full-scale plants is discussed.

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Interactions between a planktivorous fish and planktonic microcrustaceans mediated by the biomass of aquatic macrophytes

Journal of Plankton Research ◽

10.1093/plankt/fbaa061 ◽

2021 ◽

Author(s):

Bárbara Angélio Quirino ◽

Franco Teixeira de Mello ◽

Sabrina Deosti ◽

Claudia Costa Bonecker ◽

Ana Lúcia Paz Cardozo ◽

...

Keyword(s):

Aquatic Macrophyte ◽

Plant Biomass ◽

Flow Speed ◽

Trophic Niche ◽

Planktivorous Fish ◽

Low Flow ◽

High Biomass ◽

Predator Prey ◽

Cladoceran Species ◽

Macrophyte Biomass

Abstract Habitat complexity is recognized to mediate predator–prey relationships by offering refuge or not. We investigated the availability of planktonic microcrustaceans and the diet of a planktivorous fish (Hyphessobrycon eques) at different levels (low, intermediate and high) of aquatic macrophyte biomass. Sampling was carried out in a river with low flow speed, located in a Neotropical floodplain. We collected fish and microcrustaceans in macrophyte stands with variations in biomass. There were no differences in microcrustacean density in the water among the levels of macrophyte biomass, but microcrustacean richness and diet composition of H. eques differed. Microcrustacean richness and trophic niche breadth of the planktivorous fish were higher in high biomass stands. There was high consumption of a small cladoceran species in low macrophyte biomass, which was replaced by larger species, such as copepods, in intermediate and high biomass. Thus, the selection of some species was different among the biomass levels. These results suggest that plant biomass plays an important role in the interaction between fish and microcrustaceans, and prey characteristics such as size, escape ability and energy value make them more or less subject to predation by fish according to habitat structuring.

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Metabolic engineering in woody plants: challenges, advances, and opportunities

aBIOTECH ◽

10.1007/s42994-021-00054-1 ◽

2021 ◽

Author(s):

Shu Yu ◽

Cody S. Bekkering ◽

Li Tian

Keyword(s):

Renewable Energy ◽

Metabolic Engineering ◽

Ecosystem Services ◽

Plant Transformation ◽

Woody Plants ◽

Woody Plant ◽

High Biomass ◽

Generation Times ◽

Wide Range ◽

Biochemical Diversity

AbstractWoody plant species represent an invaluable reserve of biochemical diversity to which metabolic engineering can be applied to satisfy the need for commodity and specialty chemicals, pharmaceuticals, and renewable energy. Woody plants are particularly promising for this application due to their low input needs, high biomass, and immeasurable ecosystem services. However, existing challenges have hindered their widespread adoption in metabolic engineering efforts, such as long generation times, large and highly heterozygous genomes, and difficulties in transformation and regeneration. Recent advances in omics approaches, systems biology modeling, and plant transformation and regeneration methods provide effective approaches in overcoming these outstanding challenges. Promises brought by developments in this space are steadily opening the door to widespread metabolic engineering of woody plants to meet the global need for a wide range of sustainably sourced chemicals and materials.

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Microbial N2O consumption in and above marine N2O production hotspots

The ISME Journal ◽

10.1038/s41396-020-00861-2 ◽

2020 ◽

Author(s):

Xin Sun ◽

Amal Jayakumar ◽

John C. Tracey ◽

Elizabeth Wallace ◽

Colette L. Kelly ◽

...

Keyword(s):

Kinetic Parameters ◽

Substrate Affinity ◽

N2o Production ◽

Anoxic Waters ◽

Production And Consumption ◽

Consumption Rates ◽

Anoxic Zones ◽

First Time ◽

Microbial N

AbstractThe ocean is a net source of N2O, a potent greenhouse gas and ozone-depleting agent. However, the removal of N2O via microbial N2O consumption is poorly constrained and rate measurements have been restricted to anoxic waters. Here we expand N2O consumption measurements from anoxic zones to the sharp oxygen gradient above them, and experimentally determine kinetic parameters in both oxic and anoxic seawater for the first time. We find that the substrate affinity, O2 tolerance, and community composition of N2O-consuming microbes in oxic waters differ from those in the underlying anoxic layers. Kinetic parameters determined here are used to model in situ N2O production and consumption rates. Estimated in situ rates differ from measured rates, confirming the necessity to consider kinetics when predicting N2O cycling. Microbes from the oxic layer consume N2O under anoxic conditions at a much faster rate than microbes from anoxic zones. These experimental results are in keeping with model results which indicate that N2O consumption likely takes place above the oxygen deficient zone (ODZ). Thus, the dynamic layer with steep O2 and N2O gradients right above the ODZ is a previously ignored potential gatekeeper of N2O and should be accounted for in the marine N2O budget.

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