Changes to Ecosystems Flashcards
Process of eutrophication
- The water body is low in nutrients. These nutrients could be organic or inorganic in origin.
Organic – faeces, litter, bread, oil, petrol, diesel, grass clippings, detergent
Inorganic – urine, inorganic fertiliser - Decomposers break organic matter down into inorganic nutrients.
- Nutrients are added, particularly NO3- and PO43- these stimulate growth of plants and algae in the water body.
- Initially this is good because it improves productivity. More photosynthesis leads to more food and oxygen production, more organisms can live in the area.
- However, if nutrients continue to be added, the levels of NO3- and PO43- continue to rise. Leading to more producer growth. Algal blooms occur. These block the light from reaching producers lower in the water body.
- Organisms tend to die. Oxygen is used by decomposers to break down the bodies of the dead organisms. O2 levels decrease.
- As the levels decline less life can be supported and conditions become anoxic.
Causes of eutrophication
Fertiliser, detergents, waste spread on the land.
Washed into water, excess nutrients in water.
Consequence of eutrophication
Overgrowth of algal blooms that block out the sun.
Death of aquatic plants due to no light, and fish in lake due to no oxygen.
Loss of biodiversity.
e.g. Dowling’s farm in Dryandra
Process of land salinization
- Deep-rooted vegetation is replaced with annual pastures and crops. These plants do not have deep roots and use less water than the deep-rooted vegetation.
- Some rainfall goes past these roots and adds to the water table, leading to a rise in the water table.
- As the water rises through the soil, it dissolves salts that are stored deep in the soil.
- As a result, when the groundwater reaches the surface it is salty.
- Salt crusts then form when the water evaporates due to heat = land salinization.
Causes of dry land salinity
Land clearing, causes the water table to rise up bringing the salt with it.
Evaporation concentrates saline groundwater at the surface.
Impacts of dry land salinity
Loss of plant life and biodiversity.
Loss of habitats for animals.
Land erosion.
Examples of dry land salinity
Wellington dam south of Perth has become too saline for domestic or agricultural use.
Causes of climate change(greenhouse effect)
Carbon dioxide - exhaust from cars, combustion of coal wood and oil, burning rain forests.
Methane - plant debris, growing vegetation, belching and flatus of cows.
Chloro-fluoro-carbons, a leaking coolant from refrigerators and air conditioners.
Greenhouse effect - natural process by which heat is retained within the atmosphere by these greenhouse gases, which act as a thermal blanket around the Earth letting in sunlight but trapping the heat that would normally radiate back into space.
Impacts of climate change
Warming of the Earth’s surface.
Core temperature of Australia has risen by 0.9 degrees over the past 100 years.
Heat stress - white-tailed black cockatoos and budgies drop dead to the ground.
Sea levels rising 1.5mm/year in Fremantle.
Examples of impacts of climate change
Mountain nursery frog: live in rain forests which are constantly in the clouds, lay eggs in moist leaf litter. Cloud level is rising with climate change, losing habitat.
Shearwaters, Heron Island - Great Barrier Reef: Adults deserted chicks, starved to death in burrows. Sea surface temperature rises, means a decrease in food. Less plankton = less small fish to eat.
Mountain pygmy possum: Live in snowy mountains, snow duration is decreasing. Snow forms a blanket to insulate possums during hibernation. 1 degree rise in temperature = less insulation for possums due to less snow.
How has fire changed over the years?
Indigenous australians: small, frequent fires. Used fires to manage their food resources, after a fire there is the reshooting of plants. This helps to attract animals. Lead to a fine/patch burn mosaic.
European Australians: tried to stop fire, put out fire. Changed the plant/animal dynamic, introduced species have changed the way that fire happens. Build up of fuel loads as a result of trying to suppress fire. The change of plants has also led to this. Led to climate change, rising temperatures.
Fire now: big fires, tendency to have fires much closer together in time.
4x more frequent, 2.5x longer fire seasons, 6.5x larger fires
What are the benefits of fire?
Fire stimulates new growth, provides food, germinates weeds.
What is biomagnification?
The increasing concentration of a substance, such as a toxic chemical, in the tissues of organisms at successively higher levels in a food chain.
Biomagnifying substances persist, they don’t break down. They are not biodegradable.
Biomagnifying substances bioaccumulate, they don’t leave the body along with your faecal matter, they stay in the body.
Impacts of biomagnification
Biomagnifying substances increase in concentration the further along the food chain you go. Considering how many there re in parts per million of an organisms body measures this.
Many highly persistent chemicals are not readily excreted and instead are stored in fatty tissues, showing increasing progressive concentration in food chains.
This is biomagnification, putting higher order consumers at risk of accumulating substances into their tissues at harmful/lethal levels.
Examples of biomagnification
Vultures and Diclofenac – grass –> cow(people give cows the diclofenac) –> vulture. Diclofenac is widely used to treat illness and injury in livestock in India, vultures are highly susceptible to the drug and die from renal failure after feeding at carcass dumps, the traditional method of livestock disposal in the area.
Aquatic ecosystems and DDT – DDT is a highly toxic, it is now banned for use as a pesticide in most developed countries. Enters lakes as runoff and accumulates in producers. Then concentrates progressively in subsequent trophic levels(biomagnification). Higher order consumers may be exposed to toxic levels of a chemical because they eat a larger number of lower order consumers. Algae and aquatic plants –> plant eating fish –> carnivorous fish –> fish-eating birds
Persistent organic pollutants(POPs) and Killer whales – Accumulates in the thick layer of blubber in whales as POPs are stored in the fat of animals that consume them. Not only passed through food chain but also from female to calf during gestation and nursing. Mainly transferred via the rich, fatty milk produced by the mother. Harmful to the calf but females reduce their contaminate load significantly every time they rear young. Phytoplankton –> Zooplankton –> Small fish –> Large fish –> Killer whales
