Role of Microbes in Aquatic Systems

H2O Structure

Hydrogen Hydrogen

Oxygen

-+ +

105o

+

+-

++

-+ +

-

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