Nutrient Cycling

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Nutrient Cycling Pollution

• BS 111
• Ecology Biodiversity

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• Operation Wallacea will be giving a presentation
  and information session about how students from
  UK universities can contribute to biodiversity
  research conducted in remote areas of Indonesia,
  Honduras, Egypt, South Africa, Cuba and Peru next
  summer.
• Presentation/information session
• Wednesday 5 November
• At 5pm
• In Lecture Theatre B5
• Essex University
• For Advanced Information call
• 01790 763194

Come join us on expedition Summer 2009!
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Learning objectives

• Describe different types of pollution and their
  effect on the environment
• Describe the various ways in which human
  populations can disrupt nutrient cycling

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Human populations Disrupting chemical cycles

• Human pop. Growth 6.6b increasing by 75 m each
  yr (4 yrs adds another US!) 7.8 -10.8 b by
  2050.
• Activities/tech. capabilities have intruded into
  dynamics of most ecosystems
• Disrupted trophic structure, energy flow,
  chemical cycling
• Most chemical cycles are now influenced more by
  human activities than natural processes

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Pollution?????

• Pollution usually occurs when certain substances
  are either too abundant or not plentiful enough
  as a result of human activity
• Pollutants 3 types
• substances that occur naturally in nature, e.g.
  CO2
• 2. toxic substances produced that are not found
  in nature, e.g. pesticides
• 3. substances themselves not toxic but released
  into atmos. through human activity with
  unfortunate consequences, e.g. CFCs.

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Agriculture and Nitrogen cycling
N is main nutrient lost through
agriculture Ploughing mixes soil speeds up
decomposition of organic matter releases N that
is then removed when harvested Human activities
more than doubled Earths supply of fixed N
available to PPs Industrial fertilizers provide
largest addition to N source Fossil fuel
combustion also releases N oxides enter atmos.
dissolve in rainwater
To replace nutrients removed in crops farmers
must apply fertilizers, organic, e.g. manure or
synthetic
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Too much of a good thing???

• Remove nutrients from one part of biosphere add
  them to another - Depletion of key nutrients in
  one area, excesses in other places
• Eutrophication release of large amounts of
  phosphate/nitrate/organic matter into water
  resulting in lowering O2 levels/change in fauna
• Critical load amount of added nutrient that can
  be absorbed by plants without damaging ecosystem
• Nitrogenous mineral in soil that exceed critical
  load eventually leach into groundwater or run off
  into FW marine ecosystems
• Nitrate concs. in groundwater increasing in most
  agricultural areas, sometimes exceeding safe
  drinking levels

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Venice lagoon

• Eutrophication localised in Med., coastal waters,
  close to urban areas with discharges direct to
  sea
• Venice lagoon 55 000 ha av. Depth 1 m
• Fed by a series of rivers on landward side,
  linked to Adriatic sea by 3 inlets
• Water warmer, 2/3 less saline than surrounding
  sea
• Waste from agri., industry, urban sources 80-90
  nutrient load entering lagoon

First ecology plate 7.3
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• Excess nutrients have changed plant community
• Blooms of Ulva rigida displaced lagoons natural
  veg.
• Dwarf eelgrass (Zostera noltii) spp. Charac. Of
  good quality brackish water disappearing
• Urbanisation, prev. natural buffer of
  woodland/marshland helped protect from
  sediment/pollution
• Measures - GIS
• Removal of Ulva hoping let Zostera (eelgrass)
  re-establish
• Ulva harvested at peak of biomass whilst aerating
  the water to maintain O2 conc. Above 5 mg/l for
  the eelgrass to establish
• Medium term measures Reduce erosion, introduce
  filter feeders to remove nutrients, long-term
  reduce nutrient loads at source (effluent
  treatment facilities)

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Contamination of aquatic ecosystems
winter
summer
The dead ring zone arising from N pollution in
the Mississippi basin Sat. images from 2004 red
orange represent high concs. Of phytoplankton
and river sediment in the Gulf of Mexico. Extends
much further from land in summer than in winter
When the phytoplankton die decomposition rates
creates extensive dead zone of low O2
availability along the coast Fish, shrimp etc
disappear from economically imp. waters
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Toxins in the environment

• Humans release immense variety of toxic chemicals
  including synthetic compounds unknown in nature
• Organisms acquire toxic substances from the env.
  Along with nutrients and water
• Some metabolised and excreted, some accumulate in
  specific tissues, esp. fat
• Become more conc. In successive trophic levels of
  food chain biological magnification
• Biomass at any trophic level produced from a much
  larger biomass ingested from the level below
• Top level carnivores most affected

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Chlorinated hydrocarbons industrially
synthesised compound include industrial chemical
PCB polychlorinated biphenyl Used as coolants
and insulating fluids, PVC coatings of electrical
wiring and electronic components
Great lakes conc. Of PCBs in herring gull eggs
at top of food chain is x 5000 that in
phytoplankton
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• Initially introduced to eradicate Malaria
• large doses were intensively applied
• led to mosquito resistance within 5 years
• Biomagnification DDT moved up the food chain
  (fat soluble)
• As it moved up the food chain the effects
  intensified.

Poisons in food chains DDT (Dichloro-Diphenyl-T
richloroethane)
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DDT

• reach predators via number of routes various
  sub-lethal effects.
• Pesticides used in seed dressings - eaten by a
  sparrow - eaten by a hawk.
• Sprays contaminated leaves eaten by a pigeon -
  pigeon eaten by hawk.

Fall onto soil absorbed by worm - eaten by
blackbird -eaten by a hawk. Enter watercourses
concentrate in aquatic inverts. - eaten by
wagtail-eaten by a hawk. No bird species
analyzed in Britain over the last 30 years has
been free of OCs
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• campbell

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Effects conclusions

• Widespread eggshell thinning followed intro.
• detected by comparing recent clutches with museum
  specimens.
• Thinnest shells SE England where DDT use
  greatest.
• Thin shells often break in nest or fail to hatch
  (reduction in breeding success)
• In some areas the problem became great that
  regional extinctions occurred.
• The effects of DDT continued long after it was
  banned.
• It is still in use in some areas.

Clutch of mallard eggs contaminated by DDT. The
accumulation of DDT in many birds causes
reproductive difficulties.
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Acid rain

• Burning of wood and fossil fuels releases oxides
  of sulfur and N that react with water in the
  atmos forming sulfuric and nitric acid
• Unpolluted rain pH 5.6 due to presence of
  dissolved CO2
• Polluted rain pH 4-4.5 due to nitrogen, sulphur
  from fossil fuels, e.g. petrol in vehicles, coal,
  oil, gas in power stations
• Lowers pH of streams/lakes affects soil
  chemistry/nutrient avail.
• Regional prob. Arsing from local emmisions

Changes in the pH of precipitation at Hubbard
brook. Although still very acidic the
precipitation in this NE US forest has been
increasing in pH for more than 3 decades env.
Regulations and technologies reduce sulfur
dioxide long recovery
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Responses to CO2 increase

• Decreased calcification in marine orgs., e.g.
  molluscs, crustaceans, echinoderms, corals,
  calcareous algae, foraminifera, some
  phytoplankton
• Reduction in availability of chemical
  constituents needed for calcified shells/plates
  making more acidic(may also affect physiology)
• Primary productivity changes in availability of
  nutrients - growth of photosynthetic orgs.

Increase in atmos. Carbon dioxide conc. At Mauna
Loa, Hawaii. (far from cities, high enough for
atmos. To be well mixed) Aside from normal
seasonal fluctuations the CO2 curve (blue) has
steadily increased from 1958-2007. Though
average global temps. (red curve) fluctuated a
great deal over the same period there is a clear
warming trend
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Depletion of atmospheric ozone

• Protected from UV by a layer of ozone molecules
  located in stratosphere (17-25 km above Earth)
• Ozone depletion results mainly from accumulation
  of CFCs chemicals used in refrigeration and
  manufacturing
• When the breakdown products from these chemicals
  rise to the stratosphere the chlorine they
  contain reacts with ozone reducing it to
  molecular O2
• Subsequent chemical reactions liberate the
  chlorine allowing it to react with other ozone
  molecules in a catalytic chain reaction

Thickness of ozone layer over Antarctica in
Units called Dobsons satellites show gradual
thinning since 1975
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First described in 1985 The ozone hole over
Antarctica is visible as the dark blue patch in
these images based on atmospheric data Most
apparent over Antarctica in Spring where cold,
stable air allows the chain reaction to
continue Increased intensity of UV - PPs
phytoplankton DNA damage reduction in
phytoplankton growth Montreal Protocol ended
production of CFCs now slowing
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Oil pollution

• Response contain the oil, clean it up
• 1967 Torrey Canyon on Cornish coast
• Methods bombing vessel with napalm to set fire
  to the oil
• Remainder of slick treated with detergents,
  dispersants (over 10 000 t chemicals used)
• Turned out to be more more toxic than the oil
• Some parts of coastal comm. 10 yrs to recover
  from effects

Photo of tanker oil spill in Prince William
Sound, Alaska. 1989, the Exxon Valdez supertanker
grounded on Bligh Reef, spilling 11 m g crude oil
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• Slick on the water limits O2 diffusion anoxic
  condits. beneath
• O2 levels also fall as the microbial comm. begins
  to decompose the oil
• Oil smothers, obstructs, weighs down living orgs.
• Amoco Cadiz 1978. ¼ m tonnes into English
  channel
• Reluctant to use detergents so physical mopping
  up used relying on natural degradative processes
• More successful

Table 7.3 first ecology
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Summary

• Human pop. disrupting chemical cycles
• Eutrophication, Venice lagoon as e.g.
• Biological indices
• Agricultural effects on nutrient cycling
• The use of chemicals in agriculture, DDT as case
  study
• Acid rain
• Responses to CO2 increase
• Oil pollution

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Recommended reading

• Campbell Reece, Chapter 55, pp1244
• Beeby Brennan, Chapter 7, p230-255

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