unit 3.2

matter in an ecosystem- nutrients

nutrients are available in limited amounts on earth= need to be constantly recycled

biogeochemical cycles

biotic→abiotic→biotic

depend upon the nutrient and trophic structure of the ecosystem

• absorbed by plants and assimilated into them, eaten by consumers

• excreted by animals back into air and soil

• decomposers breakdown dead organisms also returning nutrients back into soil

reservoir

where nutrient spends most of time in cycle

global scale

can spread worldwide

-atmospheric or oceanic portion: includes carbon, oxygen, sulfur, calcium, and nitrogen

local scale

tend to not spread as quickly

-soil or rock is main abiotic reservoir: phosphorous, potassium, and other trace elements

general model of nutrient cycling

4 reservoirs with two characteristics each

• organic or inorganic form of nutrient

• available or unavailable

reservoir 1

living organisms/ detritus

• organic and available

reservoir 2

fossil (coal, oil, peat)

• organic and unavailable 

reservoir 3

atmosphere/ soil/ water

• inorganic and available

reservoir 4

mineral in rock

• inorganic and unavailable

carbon

essential to living organisms and is one of 4 elements making up 96% of human body

• found in living organisms, oceans, air, soil, rock (most in rock) 50,000 gigatons of total carbon pool in the biosphere

• less than 1% actively circulating… because in rock

carbon % of where it is

80% in oceans as CO2 or calcium carbonate

10.6% as fossil fuels

3.3% as soil

2.0% as phytoplankton

2.5% as plant and animal matter

1.6% in atmosphere

4 types of processes involved in cycling of carbon

biological processess

geological processess

biogeochemical processess

human activity

biological processess

photosynthesis CO2→C6H12O6

cellular respiration C6H12O6→CO2

consuming plants or animals by animals 

decomposers breaking down organic material into soil 

geological processess

release of CO2 by volcanoes

weathering, erosion, and sedimentation

biogeochemical processess

fossilization of organisms

human activity

burning fossil fuels

cutting down and burning trees

nitrogen cycle (how nitrogen enters)

80% of earths atmosphere, most N2 which plants cannot use (triple covalent bond)

• atmospheric deposition by lightning

• nitrogen fixation

atmospheric deposition by lightning 

5-10% of nitrogen enters this way

forms ammonium (NH4+) and nitrate (NO3-) which is added to soil and dissolved by rain or settles as dust

nitrogen fixation

N2→NH3 by nitrogenase (nitrogen fixing bacteria) which is active in absence of oxygen

NH3→NH4+ which can be used by plants because of acidic soil or water donating H

NH4+→NO2- (nitrite) → NO3- (nitrate) nitrification

symbiotic relationship

1- bacteria free-living (soil, marine cyanobacteria)

2- plant roots

• bacteria does this for energy needs and excess NH3 and NH4+ used by other organisms

uses of nitrate

NO3-: used by plants to make amino acids and nucleotides and other organic molecules

animals get nitrogen from consuming plants or animals

denitrifying bacteria

use of NO3- as an oxygen source during anaerobic conditions producing N2 and nitrous oxide N20 gases back into atmosphere

4 ways humans disturb the nitrogen cycle

nitric oxide with fuel for cars and jet engines

nitrous oxide live stock waste & commercial fertilizer

agricultural runoff from sewage

remove nitrogen from topsoil by harvesting nitrogen rich crops

human added nitric oxide

NO, combining N2 and O2 by burning fuel for cars and jet engines= atmosphere

converted into nitrogen dioxide (NO2) and nitric acid vapor (HNO3) which helps form acid rain

human added nitrous oxide

N2O, added as anaerobic bacteria, “feeds on” livestock waste and commercial fertilizer in soil= atmosphere

N2O warms atmosphere (greenhouse gas) and depletes ozone

human added nitrates

agricultural runoff (water with chemicals and pollutants→ nearby bodies of water) and discharge from municipal sewage adds excess nitrates to aquatic ecosystem

human removed nitrogen

remove nitrogen from topsoil by harvesting nutrient rich crops, irrigation run off, and burning forests and grasslands for farming

1950-2000

quadrupled annual release of nitrogen from land→environment

• fertilizer use to feel population

• expected to double from 2000-2050

reservoirs acting as sources and sinks

source: gets rid of 

sink: takes in

phosphorous cycle

primarily a local cycle (not in water or atmosphere)

not common in biosphere, rare in usable form

plants can have 2% but get it from soil or water that is .000003% usable phosphorous 

levels of phosphates

organisms are sensitive to changes in their levels causing huge effects

= phosphate is limiting factor in plant growth

where is phosphorous found in living organisms

essential to living organisms

• dna

• rna

• bone

• shells

• teeth

how does phosphorous enter

mostly in rock, soil, and sediment so doesn’t normally enter atmosphere

• orthophosphate H2PO4^-

• inorganic phosphate PO4^-³

erosion releases from rock and washes it into streams/rivers where it is dissolved

fertilizers and detergents

by humans, cause algal blooms in aquatic systems then possibly dead zones

algae/phytoplankton use up P→ die→bacteria break it down and uses up O2→algae and phytoplankton toxins which poison fish and shrimp so they die→bacteria pulls out oxygen and things suffocate because no O2

phosphorus in plants and plankton

pick up out of soil or water with help from fungi

phytoplankton can use dissolved marine phosphates

plants and plankton put phosphate into organic molecules

how consumers get phosphorus

eating organisms and utilize their phosphate-containing organic molecules

• put back into soil by decomposers breaking down organisms

sulfur cycle

most found as sulfate S04²- stored in rock

converted by plants, fungi, various prokaryotes into sulfhydryl groups R-SH

sulfur found in…

proteins, vitamins, and several hormones

hydrogen sulfide 

H2S added to atmosphere by anaerobic prokaryotes in swamps and mudflats, added by volcanoes too

sulfur dioxide

SO2 added to atmosphere through volcanoes

volatile dimethyl sulfide

marine algae produce (DMS) CH3SCH3

helps form cloud condensation

DMS can be convertied

DMS

can be converted into sulfur trioxide gas in the atmosphere SO3 and sulfuric acid H2SO4 (acid rain)

human impact on sulfur cycle

sulfur dioxide SO2 by burning coal and other fossil fuels through the production of gasoline

heating oil

converting sulfur contain ore into copper, lead, and zinc

mining: loosens rock, extraction, releases SO2