L32: Aquatic Microbes Flashcards
Prokaryotes
Bacteria, Archaea
10^6/ml total at sea surface
Archaea < Bacteria
No. decrease with depth
Eukaryotes
Protists (protozoans and microalgae); fungi
10s to 1000s/ml (surface waters)
Few in marine waters
Viruses
Virioplankton
10^7/ml
Bacterial no. x 10
(Mostly bacteriophages)
Environmental factors involved affecting aquatic microbes
Light: tropical sunlight and high UV to total darkness
Temp: hydrothermal vents (113 degrees) to ice flows (-15 degrees)
Pressure: atmospheric pressure (surface) to 1100 atmospheres
Salinity: freshwater/estuarine/marine/hypersaline lakes
pH: soda lakes (pH 12) to acid springs (pH 1)
Nutrients: oligotrophic (low nutrients; open ocean, mountain streams) to eutrophic (rich; estuaries, polluted rivers)
Oxygen: aerobic to anaerobic
Most abundant biological ‘entities’ in oceans
Viruses
World’s largest bacteria
Thiomargarita namibiensis (Namibia): up to 750 um diameter
Epulopiscium fishelsonii: >500 um long
Ecological Importance of Aquatic Microbes
- Nutrient generation
- Nutrient cycling
- Affecting environmental conditions: oxygen depletion; microbial activities affect oceanic climate
- Aquatic food webs
Winogradsky column
A model of microbial nutrient formation and cycling, emulating processes at global scale. Illustrates combined and integrated cycling of nutrients by microbial populations
Ingredients: natural mud and water (containing microbes and inorganic nutrients), cellulose, sulphate, light
Winogradsky column steps
- Oxygen is removed by heterotrophic bacteria (produces CO2)
- Oxygen removal -> allows anaerobes to ferment cellulose to organic acids (produces CO2)
- Organic acids support growth of sulphate-reducing bacteria, which produce sulphides
- Sulphides used by anaerobic photosynthetic bacteria for anoxygenic photosynthesis (fix CO2; adds organic C)
- Some sulphides used by chemolithoautotrophic bacteria to fix CO2 (adds C)
- Phototrophic protists and cyanobacteria fix CO2 entering via air diffusion. Adds organic C and O2 at surface
- Photosynthetic and chemoautotrophic bacteria feed other microbial pop
Aquatic Food Webs
Bacterias important secondary producers in aquatic ecosystems and control ‘microbial loop’ by which dissolved nutrients returned to food chain
Phytoplankton: main primary producers in aquatic ecosystems
Phagotrophic protists graze on other microbes and transfer carbon and energy up food chain -> lead to fish
Use in wastewater treatment
Aims to remove or reduce pollution from wastewater
Typically utilises aquatic microbes
Primary treatment step
Physical/chemical process
Removal of insoluble particulate materials by settling, screening, addition of alum and other coagulation agents and other physical procedures
Cheapest, less complex and low effluent quality
Secondary treatment step
Largely microbiological processes
Biological removal of dissolved organic matter: trickling filters, activated sludge, lagoons, extended aeration systems and anaerobic digesters
Tertiary treatment step
Physical/chemical and/ or biological process
Biological removal of inorganic nutrients
Chemical removal or inorganic nutrients
Virus removal/inactivation
Trace chemical removal
Secondary wastewater treatment
- Microbes degrade organic matter in waste stream as: biofilm on solid surfaces (trickling filter) or as flocs suspended in water column (aerated tanks)
- Products of microbial degradation of organic matter are formed (CO2, microbial biomass and any intransigent organic matter: sludge)
- Sludge further processed: used to seed secondary treatment process; further digested often by anaerobic microbial processes. Effluent is now liquid largely free of organic matter and is disposed of to ocean, rivers etc or tertiary treated
- Anaerobic digestion (different anaerobic bacteria pop work in sequence to degrade sludge. Organic polymers fermented to organic acids -> converted to acetate, CO2 and H2 -> converted to methane: biogas
- Biogas harvested and used in heating and electricity generation
