Transcript Basic Limnology Concepts - Independent School District 196

Nutrient Systems/Cycles
Water, Nitrogen, Carbon, Oxygen,
and Phosphorus
Water Cycle
Fueled by the sun and gravity
The Water Cycle
Water leaves the oceans and
other bodies of water through
evaporation and the leaves of
plants through transpiration.
– Solar energy powers this
part of the water cycle.
Water vapor cools and
condenses to make cloud
droplets or ice crystals that
merge to form rain and other
forms of precipitation.
– Gravity pulls the
precipitation back down to
the surface.
See U.S.G.S for a quick summary:
http://ga.water.usgs.gov/edu/watercyclesumma
ry.html
Precipitation can be rain, snow, sleet
or hail
Precipitation
falls
to the Earth
 and either infiltrates into
the ground,
 becomes runoff that
moves across the surface,
 lands in a body of water
 or is evaporated back up
into the sky
Can
G?
you label A -
Rita Haberlin’s Lecture notes:
http://members.aol.com/rhaberlin/hcpptnts.htm
We Impact
the Water Cycle
Developing land reduces the
amount of water that can sink into
the ground, infiltration and
increases the amount of runoff that
occurs.
This causes other problems such
as:
Soil erosion
Loss of ground water recharge
Flooding
Pollution of lakes and streams
Judith Earl slideshow:
http://managingwholes.com/photos/erosion/pictures/slide17.html
Nutrient cycles - Carbon
Carbon is the chemical backbone of
organic molecules
– Proteins, hydrocarbons, lipids,
carbohydrates
Carbon in carbon dioxide and the
carbonate ion (C03) provide a buffering
system for lakes to absorb excess acid
Carbon dioxide
Carbon dioxide enters water from 3 sources:
– the atmosphere
– the weathering of carbonate rocks such as limestone
– Respiration of organic matter by all organisms
– Is released from bottom sediments from bacterial
decomposition
The warmer the water, the more carbon dioxide is
driven into the atmosphere
Carbon dioxide is used by plants in photosynthesis and becomes
part of the plant tissue or glucose that is used for energy
Organic Carbon returns to the
water
When algae die organic carbon is
returned to the water as dissolved
organic carbon (DOC)
– Some is converted to Carbon dioxide
– Some is eaten by zooplankton
– Used for making shells of calcium
carbonate
– When they die, they get buried and turn to
limestone
Human Impact on the Carbon
cycle
Deforestation or removing trees mean
less carbon dioxide is taken up during
photosynthesis, so more Carbon dioxide
enters the atmosphere.
Also, if trees are burned, this adds CO2 to
the atmosphere.
(slash and burn in rain forest)
Photosynthesis and respiration
Photosynthesis
In algae and green plants
– Called the primary producers because they
create the organic material needed for all
organisms higher up on the food chain.
Oxygen is the waste product of
photosynthesis and is needed for
respiration in the cells of all aerobic (air
breathing) organisms
Oxygen
Colder water holds more oxygen than
warm water
Oxygen enters the water at the surface
from wave action
The only oxygen introduced into deep
water in a lake is from photosynthesis
– if the light does not penetrate there will be
no producers there and oxygen may get
depleted
Decomposers
Bottom dwelling decomposers may use
up the oxygen in the process of
respiration (getting useable energy from
their food.)
This may lead to anoxic conditions on
some lake bottoms in the summer
Nutrient cycles - Phosphorus
Phosphorus cycle
P moves slowly from phosphate deposits
on land and in shallow ocean sediments
to living organisms and then back very
slowly to the land and ocean
Most soils contain very little phosphate
therefore it is a limiting factor for plant
growth
– Organic P is bonded to carbon in animal
and plant tissues
– Inorganic P is the type needed by plants
Excess Phosphorus enters lakes
in:
Runoff of animal wastes from feedlots
Runoff of fertilizers from farms, lawn or
gardens
Sewage discharges from leaky/faulty
septic systems or municipal sewage
The phosphate ion binds tightly to soil
particles and commonly enters bodies
of water with eroded soil
Eutrophic lakes are:
Nutrient rich, shallow, warm temperature,
poor water clarity, high productivity.
Cultural eutrophication – Normally lakes age slowly over 1000’s of
years
– We add nutrients that speed the process
up
– Nutrients such as fertilizers, sewage,
organic wastes
Eutrophication of lakes
Effects of excess P and N on
lakes
Sources Used
For nutrient cycles:
– http://clab.cecil.cc.md.us/faculty/biology/jason/phosc.htm
– http://www.agnr.umd.edu/users/agron/nutrient/Factshee/Phosphoru
s/Eutrop.ht
Water on the web - Understanding Lake Ecology
– Http://wow.nrri.umn.edu
A Primer On Limnology, second ed. Bruce Munson, Water Resources
Center, 1992
Living In the Environment, 12th ed. G. Tyler Miller, Jr, Brooks/Cole
Thomson Learning, 2002
“Basic Limnology Concepts,” 10/5/00, Barb Liukkonen
[email protected]
Nutrients
Dissolved mineral nutrients are absorbed
from the water by algae and from the
water and sediment by plants
– Nitrogen and phosphorus are usually the
most important nutrients and are present in
the lowest concentrations unless the lake
is polluted
– Other minerals needed such as calcium,
magnesium, sodium and potassium along
with trace metals are generally there in
sufficient concentrations.
Biological communities
A typical food chain in a lake
Sampling lakes to determine
biodiversity and the relative
abundance of taxa that are
tolerant, moderately tolerant
and intolerant to pollution is
a good indicator of water
quality
Healthy communities have
high biodiversity and a
number of species that are
intolerant to pollution
The Ecologyical pyramid
This shows the transfer of energy.
1. Producers take in nutrients that
decomposers make available and
use sunlight, carbon dioxide and
water to make glucose
(photosynthesis)
2. Herbivores eat the producers
and transfer 10% of the energy.
3. Planktivores -are carnivores that
eat the herbivores and transfer
10% of the energy to the next level
4. Piscivores - are carvivores that
eat fish
Many organisms are
omnivorous and feed
at different levels of
the pyramid. Also,
many organisms
change their food
source over the
course of their life
cycle. In the
example, a larval fish
eats algae and then
switches to larger
zooplanton and then
eventually other fish.