Transcript 04-16-14

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GEOG 370
April 16, 2014
Peer
review of
group
presentations
Human impacts on Water as ecosystem processes
•
•
Open-system self-regulating Ecosystems’ overall stability “dynamically” maintained by 3 chief
mechanisms:
–
Controlling the rate of chemical and material cycling with the “water” system
–
Controlling the rate of energy flow through the “water” system
–
Maintaining a diversity of species & food webs so that system stability is not affected
seriously by the loss of some food web links and/or species
Human-induced alterations of “natural” water systems
–
Disruption of essential material/nutrient cycle:
•
Changing the rate of cycling by material overloads or leaks in the system
•
Breaking the cycle
•
Introduction of human-made chemicals into the water, especially those with no natural
decomposition chain
–
Disruption of energy flow(s)
•
Entropy or heat build-up in the system by consumption of too much energy by human
society
•
Changing properties and/or composition of the atmosphere leading to an increase or
decrease in the solar energy input involved in hydrological cycle
•
Altering drainage systems (quality, quantity, direction of flow, etc.)
–
Disruption of the ecosystem by destruction of species diversity and/or the food web
Levels of organization of
matter
Second law of (energy)
thermodynamics
Comparative Energy
Efficiency
Simplified Biogeochemical
cycles
Energy flow to and from the
earth
Freshwater pond ecosystem
Ecosystem of a field
Detritus feeders
Ecosystem structure and
function
Ecosystem structure and
function
Range of tolerance for a population of organisms
A food chain
Greatly simplified food web
Generalized model of main
one-way flow energy
pathways through ecosystems
Energy flow pyramids
Biological magnification
DDT in fish-eating birds
25 ppm
DDT in large fish 2 ppm
Concentration
has increased
10 million times
DDT in small fish 0.5 ppm
DDT in zooplankton 0.04 ppm
DDT in water 0.000003 ppm
or 3 ppt