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Ecosystems Ch 54 U119PP
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Depends on the recycling of essential chemical elements ... gull eggs. 124 ppm. Zooplankton. 0.123 ppm. Phytoplankton. 0.025 ppm. Lake trout. 4.83 ppm ... – PowerPoint PPT presentation
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Title: Ecosystems Ch 54 U119PP
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Ecosystems- Ch 54 U119PP
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- Concept 54.4 Biological and geochemical
processes move nutrients between organic and
inorganic parts of the ecosystem - Life on Earth
- Depends on the recycling of essential chemical
elements - Nutrient circuits that cycle matter through an
ecosystem - Involve both biotic and abiotic components and
are often called biogeochemical cycles
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A General Model of Chemical Cycling
- Gaseous forms of carbon, oxygen, sulfur, and
nitrogen - Occur in the atmosphere and cycle globally
- Less mobile elements, including phosphorous,
potassium, and calcium - Cycle on a more local level
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- A general model of nutrient cycling
- Includes the main reservoirs of elements and the
processes that transfer elements between
reservoirs
- All elements
- Cycle between organic and inorganic reservoirs
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Biogeochemical Cycles
- The water cycle and the carbon cycle
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- Water moves in a global cycle
- Driven by solar energy
- The carbon cycle
- Reflects the reciprocal processes of
photosynthesis and cellular respiration
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- The nitrogen cycle and the phosphorous cycle
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- Most of the nitrogen cycling in natural
ecosystems - Involves local cycles between organisms and soil
or water - The phosphorus cycle
- Is relatively localized
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Decomposition and Nutrient Cycling Rates
- Decomposers (detritivores) play a key role
- In the general pattern of chemical cycling
- The rates at which nutrients cycle in different
ecosystems - Are extremely variable, mostly as a result of
differences in rates of decomposition
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Vegetation and Nutrient Cycling The Hubbard
Brook Experimental Forest
- Nutrient cycling
- Is strongly regulated by vegetation
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- Long-term ecological research projects
- Monitor ecosystem dynamics over relatively long
periods of time - The Hubbard Brook Experimental Forest
- Has been used to study nutrient cycling in a
forest ecosystem since 1963
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- The research team constructed a dam on the site
- To monitor water and mineral loss
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- In one experiment, the trees in one valley were
cut down - And the valley was sprayed with herbicides
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- Net losses of water and minerals were studied
- And found to be greater than in an undisturbed
area - These results showed how human activity
- Can affect ecosystems
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- Concept 54.5 The human population is disrupting
chemical cycles throughout the biosphere - As the human population has grown in size
- Our activities have disrupted the trophic
structure, energy flow, and chemical cycling of
ecosystems in most parts of the world
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Nutrient Enrichment
- In addition to transporting nutrients from one
location to another - Humans have added entirely new materials, some of
them toxins, to ecosystems
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Agriculture and Nitrogen Cycling
- Agriculture constantly removes nutrients from
ecosystems - That would ordinarily be cycled back into the soil
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- Nitrogen is the main nutrient lost through
agriculture - Thus, agriculture has a great impact on the
nitrogen cycle - Industrially produced fertilizer is typically
used to replace lost nitrogen - But the effects on an ecosystem can be harmful
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Contamination of Aquatic Ecosystems
- The critical load for a nutrient
- Is the amount of that nutrient that can be
absorbed by plants in an ecosystem without
damaging it
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- When excess nutrients are added to an ecosystem,
the critical load is exceeded - And the remaining nutrients can contaminate
groundwater and freshwater and marine ecosystems
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- Sewage runoff contaminates freshwater ecosystems
- Causing cultural eutrophication, excessive algal
growth, which can cause significant harm to these
ecosystems
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Acid Precipitation
- Combustion of fossil fuels
- Is the main cause of acid precipitation
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- North American and European ecosystems downwind
from industrial regions - Have been damaged by rain and snow containing
nitric and sulfuric acid
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- By the year 2000
- The entire contiguous United States was affected
by acid precipitation
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- Environmental regulations and new industrial
technologies - Have allowed many developed countries to reduce
sulfur dioxide emissions in the past 30 years
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Toxins in the Environment
- Humans release an immense variety of toxic
chemicals - Including thousands of synthetics previously
unknown to nature - One of the reasons such toxins are so harmful
- Is that they become more concentrated in
successive trophic levels of a food web
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- In biological magnification
- Toxins concentrate at higher trophic levels
because at these levels biomass tends to be lower
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- In some cases, harmful substances
- Persist for long periods of time in an ecosystem
and continue to cause harm
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Atmospheric Carbon Dioxide
- One pressing problem caused by human activities
- Is the rising level of atmospheric carbon dioxide
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Rising Atmospheric CO2
- Due to the increased burning of fossil fuels and
other human activities - The concentration of atmospheric CO2 has been
steadily increasing
IS the world warming? Nine of the 10 warmest
years on record have occurred since 1995 Does
the mean anything? Science not clear where do
you measure from?
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How Elevated CO2 Affects Forest Ecology The
FACTS-I Experiment
- The FACTS-I experiment is testing how elevated
CO2 - Influences tree growth, carbon concentration in
soils, and other factors over a ten-year period
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The Greenhouse Effect and Global Warming
- The greenhouse effect is caused by atmospheric
CO2 - But is necessary to keep the surface of the Earth
at a habitable temperature
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- Increased levels of atmospheric CO2 are
magnifying the greenhouse effect - Which could cause global warming and significant
climatic change
- Recent studies show or predict
- Climate change could wipe out premium wine grape
growing in California - Vines (such as poison ivy, Japanese honeysuckle,
and kudzu) will grow stronger and more poisonous
(as well as increasing their ranges). - Poison ivy grew at 2.5 times its normal rate
under predicted levels of CO2 and became more
allergenic to humans
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Depletion of Atmospheric Ozone
- Life on Earth is protected from the damaging
effects of UV radiation - By a protective layer or ozone molecules present
in the atmosphere
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- Satellite studies of the atmosphere
- Suggest that the ozone layer has been gradually
thinning since 1975
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- The destruction of atmospheric ozone
- Probably results from chlorine-releasing
pollutants produced by human activity
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- Scientists first described an ozone hole
- Over Antarctica in 1985 it has increased in size
as ozone depletion has increased
Figure 54.28a, b
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- If current trends continue, 1 in 5 Americans will
develop skin cancer during their lifetime.
Melanoma continues to rise at an alarming rate.
In 1930, 1 in 5,000 Americans was likely to
develop melanoma during their lifetime. By 2004,
this ratio jumped to 1 in 65. Today, melanoma is
the second most common cancer in women aged 20 to
29.
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