Transcript BIOLOGY 154: ECOLOGY and ENVIRONMENTAL ISSUES

BIOLOGY 403:
PRINCIPLES OF ECOLOGY
(Nutrients & Biogeochemical Cycles)
NUTRIENTS & NUTRIENT CYCLING
• NUTRIENTS
elements (C, H, N, etc.) and simple inorganic
compounds of these elements (H2O, CO2, etc.)
that are essential for life
• FOODS
Organic 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
(= Macronutrients)
Carbon (C)
Hydrogen (H)
Oxygen (O)
Nitrogen (N)
Phosphorus (P)
Calcium (Ca)
Potassium (K)
Sulfur (S)
Iron (Fe)
Sodium (Na)
Magnesium (Mg)
Trace Elements
(= Micronutrients)
Nickle (Ni)
Manganese (Mn)
Zinc (Zn)
Molybdinum (Mo)
Chlorine (Cl)
Copper (Cu)
Vanadium (V)
Silicon (Si)
Cobalt (Co),
Boron (B), Fluorine (F)
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) cycles
cycles (nitrogen, carbon, oxygen) which have a large
gaseous, rather easily exchangeable, reservoir which
makes them less likely to get out of balance
• Imperfect (= sedimentary) cycles
cycles (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
•
•
•
•
•
•
K
Ca
NO3
Cl
SO4
B
Open
under Aspen
under Pine
0.5
1.0
0.1
0.7
1.0
0.0
11.3
4.0
2.8
2.8
10.1
0.04
10.4
5.6
0.2
13.8
16.3
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 Phosphorus
H2S + 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 peak
of 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
input
residence
time
impact compared
to CO2 per
molecule
• CO2
49
500 years
1
• CFC’s
14
65-111 years
• CH4
18
7-10 years
25
• N 2O
6
150 years
230
10,000 to
20,000
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