Role of Microbes in Aquatic Systems. H 2 O Structure Hydrogen Oxygen - ++ 105 o.
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Transcript of Role of Microbes in Aquatic Systems. H 2 O Structure Hydrogen Oxygen - ++ 105 o.
Role of Microbes in Aquatic Systems
H2O Structure
Hydrogen Hydrogen
Oxygen
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105o
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Hydrogen Bonding
Water Properties
1. Hydrogen bonding2. Density anomaly3. Thermal features4. Surface effects5. Viscosity6. Solvent
Aquatic BiomesFreshwater
Lakes (lentic)Wetlands (lentic)Rivers (lotic)
How are lakes formed?
1. Tectonic2. Volcanic3. Landslide4. Solution basins
Lake types
5. Fluviatile6. Aeolian7. Meteorites8. Animals9. Glacial
Lake Habitats
Terms
Littoral – near shore area
Pelagic – open water out from littoral
Profundal – deep water area in stratifiedwater
Aquatic Functional Groups (lentic)Benthos – living on or in bottom sediments
Plankton – small organisms in pelagic zone, movement controlled by wind
Phytoplankton – AlgaeZooplankton – Animals
Nekton – large invertebrates and fish capable of swimming independently
Neuston – organisms associated with top water layer
Macrophytes – Large plants
neuston zooplankton
phytoplankton benthosmacrophyte
Food chain example
phytoplankton
zooplankton
Big fish
minnows
Four steps are common
Lakes can be classified by productivity
Production = biomass (wt)/area (volume)
Lake classification is a continuum ranging From oligotrophic to eutrophic
ultra-oligotrophic
oligotrophic
mesotrophic
eutrophic
hypereutrophic
high productivity
low productivity
MN Lakes production
Oligotrohphic
Mesotrophic
Eutrophic
Why is it this way?
Oligotrophic Eutrophicdeep shallowclear not clearlow production high productionlow nutrients high nutrients
General Trends
TOO MUCH PRODUCTIVITY A BAD THING?
High nutrients lead to high amounts of algae
These algae eventually die and sink to bottom
Bacteria use oxygen when decomposing algae
Can lead to fish kills
Remember, high nutrients levels are natural in rich soil
Anabaena
Aphanizomenon
Microcystis
The Players
Annie, Fanny, and Mike
Cyanobacteria
Can produce their own nitrogen
“drown” out other algae and plants
Ecosystem: community of different speciesand their abiotic environment where energyflows and matter cycles
What happens in a lake is a complex interaction of many variables.
Temperature, wind, soil, nutrients, biota, etc.
Water temperature and density
Water is most dense at 4o C
Ice (solid) is less dense than liquid
Warm water is much lighter than cold water
Water mixingWhen the water temperature is uniform the water column will completely mix with a little help from the wind. This is because the density of the water is equal throughout the water column.
Nutrients from bottom are circulated throughout lake
0
30
Temp C300
Dep
th m
Lake surface
Lake bottom
Water mixingDuring the summer the surface water warms faster than the rest of the lake due to poor transfer of heat in water
At some point the density difference is too great for wind to break
Called summer stratification
0
30
Temp C300
Dep
th m
Lake surface
Lake bottom
Depth m
0
30
Hypolimnion
Metalimnionor
Thermocline
Epilimnion
Summer temperature stratification zones
Temp C 300
Oxygen and temperature cycle in a Dimictic Oligotrophic lake
0 4 8 12 16Oxygen concentration mg/L
0 4 8 12 16 0 4 8 12 16 0 4 8 12 16
Temperature, C
surface
bottom
ICE
0 4 8 12 16 18
Winter
0 4 8 12 16 18
Spring
0 4 8 12 16 18
Summer
0 4 8 12 16 18
Fall
Oxygen and temperature cycle in a Dimictic Eutrophic lake
0 4 8 12 16Oxygen concentration mg/L
0 4 8 12 16 0 4 8 12 16 0 4 8 12 16
Temperature, C
surface
bottom
ICE
0 4 8 12 16 18
Winter
0 4 8 12 16 18
Spring
0 4 8 12 16 18
Summer
0 4 8 12 16 18
Fall
Winter-Summary
Ice forms barrier to oxygen (no photosynthesis or diffusion)
oligotrophic lakefewer organisms so low respirationlarge body of water so lots of oxygen
eutrophic lakelots of organisms (especially bacteria on bottom)
so high respirationsmaller volume of water so less oxygen
Summer-SummaryMetalimnion or density gradient prevents oxygen from movingbetween epilimnion and hypolimnion
Epilimnion has plenty of oxygen from air and photosynthesisin both lakes
Hypolimnion-oligotrophic lakefewer organisms so low respirationlarge body of water so lots of oxygen
Hypolimnion- eutrophic lakelots of organisms (especially bacteria on bottom)
so high respirationsmaller volume of water so less oxygen
Lake Nyos, Cameroon
Meromictic, top 50 m mixes, bottom 150m loadedwith sodium and carbondioxide
Lake Nyos, CameroonIn 1986 a huge cloud of carbon dioxideBurped up from the bottom and movedDown the valley killing 1700 and livestock
Lake Nyos, Cameroon
Trying to prevent again by mixing the water
Cultural Eutrophication
Eutrophication
Oligotrophic Eutrophicdeep shallowclear not clearlow production high productionlow nutrients high nutrientsHigh oxygen possible low oxygen
Lakes are basins, and naturally change fromOligotrophic conditions to Eutrophic ones
Time
Lake Baikal
Cultural Eutrophication
Artificially fertilizing lakes so eutrophication sets in sooner
Characteristic is blooms of blue-green algae
Cultural Eutrophication
2 big causes are N and P from:Municipal wasteFertilizer runoff (can have many forms)
Cultural EutrophicationProcess is positive feedback
More nutrients leads to more algae
Treated sewage
Lower algaeDie and sink
Cultural EutrophicationProcess is positive feedback
More nutrients leads to more algae
Treated sewage
Bacteria decompose algae using oxygen and releasing nutrients that willmix into water column again causing more algae growth
Cultural Eutrophication
Effects:When water not mixing oxygen disappearsAestheticsToxinsOnce started very hard to stop due to positive feedback
Cultural Eutrophication
Some Solutions:Treat wasteControl runoff from agriculture/livestockAllow native riparian vegetationDon’t drain wetlands
Minnesota River carries nutrients down to Gulf of Mexico, These with other rivers drain about 1/3 of the continental US
Dead Zone
High nitrogen content of spring runoff from agricultural land
Less dense fresh water floats on ocean water and algae bloom
Dead algae and zooplankton sink to bottom and are decomposed by heterotrophic bateria
Any animal life that can not move will die
Dead Zone SolutionsReduce fertilizer use
Buffers
Reestablish wetlands
Municipal waste treatment
Will it happen??
Ethanol
EthanolIs it a net energy gain???
EthanolIt apparently is a net energy gain
A study at the U of MN found:Ethanol from corn produced 25% more energy than inputs
This only uses the sugar from the grain
Future technologies could use cellulose which is found in many plants that are much more environmentally friendly to grow than corn
Switch grass
EthanolWill it end our dependence on foreign oil?
No way:If all U.S. corn went into ethanol that would offset 12.3% of gas
Most corn now goes to feed livestock
Significant environmental effects (fertilizers, pesticides, etc.)
Only part of the solution, need to explore cellulose production
BIODIESELDiesel fuel made from a blend of biological oil and diesel fuel
BIODIESEL vs ETHANOL
BIODIESELETHANOL
Energy yield 25% 93%Green house gas reduction 12% 41%Dedicated production supply 12% 6%
Synfuel hydrocarbons or cellulosic ethanol, if produced from low-input biomass grown on agriculturally marginal land or from waste biomass, could provide much greater supplies and environmental benefits than food-based biofuels