ES 105 Exam #2 Redox Reactions and Microbial Biogeochemistry

Reductions-Oxidation (redox)Reaction

• A chemical reaction in which the oxidation states of the atoms are changed.

• Oxidation is the loss of electrons

• Reduction is the gain of electrons

Stages of the Microbial Nitrogen Cycle

N2 gas —> Nitrogen fixation—> organic nitrogen—> ammonification—> Ammonium(NH4) —>Nitrification—> Denitrification

Alternative electron acceptors to Oxygen in order of decreasing energy yields:

(NO3-) Nitrate, (Fe²+) iron, (so4²-)Sulfate, (co2) Carbon dioxide

What processes are these electron acceptors involved in?

Oxidation or breakdown of organic matter by bacteria and archaea.

What are hot spots/hot moments?

Locations or times of intense biogeochemical processing due to electron acceptors and donors coming together under just the right conditions (redox state)

Hydrology of riparian wetlands

Seasonal flood pulses

Inundated during spring floods and heavy summer rain.

What did the Hubbard brook experimental forest discover?

That there were huge spikes in nutrient concentration in the stream after there was no more trees or plants to suck up the nutrients and use them so the nitrate spiked and ran off. there was nothing left to decompose. caused eutrophication in the pond where the water would run into.

What does the study of watersheds/catchments look at?

Effect of water on the landscape

effect of landscape on the water

the interaction of land and water in relation to biota

What parts of watersheds influence water quality?

soils, geology, weather and climate, topography, nutrients, groundwater and surface water, water chemistry: pH, alkalinity, carbon, redox, impervious surfaces, anthropogenic pollution

How do watersheds influence organisms in them?

Through ecology, energy cycling, ecosystem services, biodiversity and biodiversity crisis

How are water ecosystems generally classified?

Salinity, temperature, dissolved oxygen, current/waves, light, nutrients, pH

Lotic system

Systems which contain flowing waters

Headwater streams are typically…

shallow, fast, and highly oxygenated.

Rivers are typically…

deeper, slower flowing, less dissolved oxygen, “cloudier”

Ecosystem services for flowing freshwater ecosystems are…

drinking water, nutrient cycling, agriculture, recreation and hydropower

River continuum concept

Gradient of physical, chemical, and biological features headwater to mouth.

Lentic systems

A body of standing water/no downhill flow: lakes and ponds

Littoral zone

shallow area around shore, lots of plants

Limnetic zone

deeper water, phytoplankton is the base of the food chain, less plants

Profundal zone

Below light penetration, mucky, no plants/algae

are wetlands typically lotic or lentic?

Mostly lotic

What are some ecosystem services of wetlands?

Flood control, recharge groundwater, filtering water

Biodiversity hotspot

Geographic area that harbors a disproportionate number of species, usually endemic.

Drunken kangaroos punch children on family game shows

Domain, kingdom, phylum, class, order, family, genus, species

Species richness

The number of different species represented in an ecological community, landscape or region

Species Evenness

measure of species with their proportions

5 main things leading to biodiversity crisis

Land use change

Invasive species

Over exploitation

pollution

climate change

I=PAT

Impact= Population* affluence * technology

Things to know about freshwater microbes:

Vary with abiotic factors (especially temp and pH)

• Bacteria, protozoa, fungi, viruses, algae, and cyanobacteria

Most abundant and diverse group of organisms

Critical to nitrogen cycle!!!!

Microbes are responsible for which parts of the nitrogen cycle?

N fixation, denitrification, and nitrification

Why do we care about diversity of microbes?

Nitrospira oxidize nitrite into nitrate (nitrification)

Removes ammonia (toxic to aquatic life) from wastewater

Freshwater microbes influence water pH and oxygen level

• photosynthetic bacteria produce oxygen as a byproduct—> aerobic conditions

• Anaerobic bacteria—> contribute to N and S cycling influencing pH

What is anammox?

When microbes convert ammonium and nitrite into nitrogen gas and skip over the process of denitrification. No longer waste.

What do microbes do in lentic systems?

Anammox processes

Degradation of organic pollutants

control pathogen populations

maintain nutrient balance

sequester carbon

food source for organisms

bioremediation

What does eutrophication lead to?

Excess nutrients

algae bloom

oxygen depletion

dead zones

What does metabolism depend on?

Gettin energy to drive reactions and getting C to build biomass.

Classification A

Physiological classification of life based on energy and carbon sources

Classification B

Aquatic habitat

“epi” (upon, on, or over)

“symbiotic” = living with

Classification C

Taxonomy of Freshwater Organisms

example: is it a virus or bacteria or algae or protozoan or macrophyte or fungi or vertebrate, etc

Classification D:

Trophic classification of aquatic biodiversity

Food chain

trophic level

food web is the most accurate

Classification E

Organisms by Functional Significance

ex: autotrophic versus heterotropic

chemoautotrophic versus photoautotrophic

Ecological Succession

Predictable, orderly change in an ecosystem following a disturbance

Stages of freshwater succession

1) Open water phase

2) Submerged vegetation phase

3) Emergent vegetation phase

4) Wetland phase

5) Terrestrial phase

Ecological integrity

The capacity of supporting and maintaining a balance, integrated, adapted community of organisms having a species compositions diversity, and functional organization.

What are the components of ecological integrity?

Biological assessment

physical assessment

chemical assessment

How could you measure ecosystem integrity with biology?

Aquatic Benthic Macroinvertebrates which are EPT species that are generally intolerant of many types of pollution.

What happened with the Nile perch in Lake Victoria?

Great Lake in Africa with 400 species of fish.

1954 Nile perch (predator) was introduced into the lake

in the 1980s the population exploded

Lake went from being a complex food system to being dominated by just three fish species which were predators. Most of the cichlids are now extinct.

Do nutrients control primary productivity?

Yes they do

Autochthonous Inputs

Algae, mosses, vascular macrophytes (rooted plants)

Allochthonous inputs

Leaves and needles

• herbaceous

• shrubs

• trees

Wood

Fine particulate matter

• Frass

• soil

Organisms that fall into the water

In Hubbard brook experiment, nitrate went from nothing to 50mg per liter in the water. What aspect of the nitrogen cycle could explain this?

The microbes in the soil were not killed and were taking organic forms of nitrogen and mineralizing it into ammonium but there was no vegetation to take up the ammonium so then nitrifying organisms turned it into nitrate.

Why did Baxter et al. put greenhouse covers over sections of stream water?

In order to stop stream insects from getting into the forest and first insects from getting into the stream. Cut off food in 2 directions.

What did the introduction of non-native rainbow Trout cause in the Baxter experiment?

All the spiders in the trees to go hungry and die. Because the rainbow trout and the charr were now competing for food which means that more benthic insects are being eaten by the fish and then there is no food left for the spiders. Then this leads to more benthic algae because the benthic insects are not there to eat it anymore. this leads the algae to use up the co2 when its alive and o2 when it decomposes so there is less oxygen at the bottom.