biology 403: principles of ecology (nutrients & biogeochemical cycles)

BIOLOGY 403: PRINCIPLES OF ECOLOGY

(Nutrients & Biogeochemical Cycles)

NUTRIENTS & NUTRIENT CYCLING

• NUTRIENTSelements (C, H, N, etc.) and simple inorganic compounds of these elements (H2O, CO2, etc.) that are essential for life

• FOODSOrganic compounds (contain carbon, hydrogen, often oxygen, and sometimes other elements) that organisms use to fuel their metabolism. Foods would include lipids (fats and oils) carbohydrates (sugars, starch, etc.), proteins and other classes of organic molecules as well.

Essential Minerals (Nutrients)

Major Elements Trace Elements(= Macronutrients) (= Micronutrients)Carbon (C) Nickle (Ni) Hydrogen (H) Manganese (Mn)Oxygen (O) Zinc (Zn)Nitrogen (N) Molybdinum (Mo) Phosphorus (P) Chlorine (Cl)Calcium (Ca) Copper (Cu)Potassium (K) Vanadium (V)

Sulfur (S) Silicon (Si) Iron (Fe) Cobalt (Co),

Sodium (Na) Boron (B), Fluorine (F) Magnesium (Mg) Iodine (I), Chromium (Cr) Tin (Sn), Selenium (Se)

BIOGEOCHEMICAL CYCLES (I)

• The more or less circular paths of the chemical elements passing back and forth between organisms and environment are known as Biogeochemical Cycles (also called Nutrient Cycles).

• Essential elements are rarely (if ever) homogeneously distributed, nor present in only one chemical form throughout an ecosystem. These materials exist in compartments or pools which have varying exchange rates between them.

BIOGEOCHEMICAL CYCLES (II)

• From the standpoint of the earth as a whole, Biogeochemical Cycles fall into two groups:

• Perfect (= gaseous) cyclescycles (nitrogen, carbon, oxygen) which have a large gaseous, rather easily exchangeable, reservoir which makes them less likely to get out of balance

• Imperfect (= sedimentary) cyclescycles (calcium, phosphorus, iron) which involve the more earthbound elements and large portions of the supply may become unavailable for long periods of time, thus disturbing the cycle

AVAILABILITY OF NUTRIENTS

• Even if the nutrient elements are in the soil and/or water of an area, they may be unavailable to organisms.

• Some organisms can only utilize an element when it is present in a specific compound.

• pH also affects the availability by either changing the chemical form of the element and / or by interfering with the uptake of that substance

pH & RELATIVE NUTRIENT AVAILABILITY

NUTRIENTS AND pH

• Low pH (acid or ‘sour’) soils --- H+ ions replace Ca+ +, Mg++ and K+ on soil colloids and these may then be lost by leaching

• Low pH (acid) soils may make Aluminum, Iron (and things like lead) so soluble as to be in toxic quantities

• High pH (basic, alkaline or ‘sweet’) soils --- may result in the presence of such large quantities of available calcium compounds that they interfere with the uptake of necessary nutrients (such as iron)

EXAMPLES OF BIOGEOCHEMICAL CYCELS

• Generalized Cycle

• Sedimentary Cycles– Calcium– Phosphorus– Sulfur

• Gaseous Cycles– Nitrogen– Carbon

GENERALIZED BIOGEOCHEMICAL CYCLE

NUTRIENTS IN PRECIPITATION

PPM Open under Aspen under Pine

• K 0.5 11.3 10.4

• Ca 1.0 4.0 5.6

• NO3 0.1 2.8 0.2

• Cl 0.7 2.8 13.8

• SO4 1.0 10.1 16.3

• B 0.0 0.04 0.3

CALCIUM CYCLE

TRANSECT THROUGH A GLADE

GLADE ANALYSIS

• Soil pH is 8.2

• Soil Analysis: N, P, K, Fe, & Mn quantities are similar throughout

• Foliage Analysis:

– CaCO3 increases toward the glade

– Mn shows no correlation

– K & P tend to be deficient toward the glade

– N & Fe are strongly reduced toward the glade

SOIL pH STATIFICATION

• Leaching of calcium may lead to acid top strata and more basic lower strata

• Can then find shallow-rooted acidophiles growing next to calciphiles (that are deeper rooted)

• Some plants benefit by having some roots in each zone

• Role of earthworms in calcium (and other nutrients) cycling

PHOSPHORUS CYCLE

RADIOPHOSPHORUS MOVEMENT

RADIOPHOSPHORUS MOVEMENT

• Very rapid movement from H2O to plankton (within 2 hours 50% of phosphorus had been taken up)

• Movement was slower into attached algae

• Tracer eventually moved into grazing animals and then into carnivores but more slowly than into algae

• Although the RATE OF UPTAKE may decrease along a food chain, the concentration ratio at equilibrium may be very high

• Eventually decay organisms began to recycle some of the phosphorus but there was a net movement into the sediments

TROPHIC LEVEL CONCENTRATION

• DEFINITION: The selective retaining of certain elements or

compounds by an organism so that the concentration builds up in these organism above what it is in their immediate habitat and/or food

• Also known as trophic level magnification, biological concentration or biological magnification

• T.L. Concentration can occur for non-essential materials and toxic materials as well as for essential materials.

TROPHIC LEVEL CONCENTRATION

SULFUR CYCLE I

SULFUR CYCLE II

1 -- primary production (sulfates are the principal available form reduced by autotrophs & incorporated into organic molecules)

2 -- decomposition (sulfur often released as H2S)

3 -- animal excretion

4 & 5 -- specialized chemosynthetic bacteria obtain energy by converting sulfides to elemental sulfur & sulfates

SULFUR CYCLE III

6 -- Desulfovibrio bacteria (anaerobic SO4 reducers) convert SO4 to H2S

7 -- Thiobacillus bacteria (aerobic sulfate oxidizers) convert H2S to SO4

8 – INTERACTION of P & S cycles: Phosphorus is converted from the insoluble ferric phosphate to a more soluble form aiding the cycling of PhosphorusH2S + FePO4 H2PO4 + FeS2

NITROGEN CYCLE (I)

NITROGEN CYCLE (II)

• N2 gas NH3 NO2 NO3

I IIa IIb

• I ---- Nitrogen Fixation (Azotobacter, Clostridium)

• II --- Nitrification --- a two-step process IIa --- Nitrosomonas IIb -- Nitrobacter

• Denitrification --- a multistep process in which specialized bacteria (such as Pseudomonas) take NO3 compounds and release N2 gas

NITROGEN CYCLE (III)

NITROGEN CYCLE (IV)

NITROGEN CYCLE (V)

CARBON CYCLE (I)

CARBON CYCLE (II)

GREENHOUSE EFFECT AND GLOBAL WARMING

• Is the Earth warming?

• Yes.• Is this due to human activities or to some cycle that

can affect climate?

• ??????????

• What are the major greenhouse gases?

• CO2, N2O, CH4, CFC’s, (H2O ?)• Could the Earth also cool from human activities

and enter an ice age?• Yes - and there have been ‘recent’ short duration

cooling events!• Global warming could be a positive feedback

system!!!!!

GREENHOUSE EFFECT

AUTUMN EFFECT (NUCLEAR WINTER)

SOME POINTS CONCERNING THE EARTH’S TEMPERATURE

• current average surface temp. is 150C (= 59OF)

• without an atmosphere it would be -180C (= 0OF)

• estimated average temp. during coldest part of last ice age was only 5OC (9OF) lower than today

• last major ice age ended 12,000 years ago

• Today sea levels are 300 feet higher than at the peakof the last ice age (and are still rising!)

• greenhouse gases have increased dramatically since 1850 (actually since 1950!)

• CO2 has gone from 280 ppm to 360 ppm since 1850(a 28.6% increase) ???? Highest Ever ????

THE MAJOR GREENHOUSE GASES• Gas % human residence impact compared

input time to CO2 per molecule

• CO2 49 500 years 1

• CFC’s 14 65-111 years 10,000 to 20,000

• CH4 18 7-10 years 25

• N2O 6 150 years 230

PROJECTED GROWTH OF GREENHOUSE GASES

CHANGING PATTERN OF GLOBAL CO2 EMISSIONS

CHANGING PATTERN OF GLOBAL CO2 EMISSIONS

INCREASE IN GLOBAL TEMPERATURE

RISE IN ATMOSPHERIC CO2

INCREASE IN GLOBAL TEMPERATURE (overlay)

So……….?

HUMAN ACTIVITIES THAT CAUSE GLOBAL WARMING