Eutrophication L6 Flashcards
Give an example of natural eutrophication.
In streams in Iceland algae sometimes covers the floor of the stream, preventing anything else from growing. The stone is volcanic and is naturally enriched in nutrients causing the algae coverage. Other plants wouldn’t be able to grow here anyway because it’s too hot (50 degrees C).
Define oligotrophic
relatively poor in plant nutrients and containing abundant oxygen in the deeper parts.
Define eutrophic
rich in nutrients and so supporting a dense plant population, the decomposition of which kills animal life by depriving it of oxygen.
Define eutrophication.
A process in which an increased of algae biomass is caused as a response to nutrient enrichment. So the trophic status is changed from oligotrophic to eutrophic.
What is cultural eutrophication?
anthropogenic nutrient enrichment causes a change in algae biomass and production.
Define trophic status
The nutrient levels in an aquatic system and the algal biomass (i.e. primary production) as well as the heterotrophic activity.
Why are nitrogen, phosphorus and carbon macronutrients?
Because they are disproportionately important (especially to primary producers).
Why are macronutrient cycles important?
They are pivotal in the stability of global biogeochemical cycles in sustaining natural resources and in protecting human health and biodiversity.
Where does phosphorus come from?
1) Agricultural land (fertiliser run off). More than 13 Tetragrams per year
2) Domestic sewage (3T/yr)
3) Landuse change (e.g. deforestation)
Where does nitrogen come from?
1) Fertiliser (50T/yr)
2) Legumes (crop)
3) Atmospheric ammonia from livestock farming areas
What does an increase in phosphorus do in the oceans?
1) Leads to increase in phytoplankton (esp. cyanobacteria)
2) This leads to reduction in light and an accumulation of dissolved organic matter leading to a bacteria increase
3) This leads to an oxygen decrease and negative impacts on fauna e.g. fish
Give an example of dead zones being caused by eutrophication.
The Mississipi carries so many nutrients that when it meets the ocean it fertilises the ocean, resulting in dead zones (everything dies there except for cyanobacteria because the cyanobacteria shade the water)
What does an increase in phosphorus do in rivers and streams?
1) Causes periphytic algae and macrophytes to increase leading to an increase in cyanobacteria
2) This reduces light and dissolved organic matter accumulates leading to bacteria increasing
3) This causes oxygen to decrease and negatively impacts fauna e.g. salmonids need high oxygen
List some negative effects of eutrophication
1) Declines in coral reef health
2) Reduction in species diversity
3) Reductions in harvestable fish and shellfish biomass
4) Taste, odour and drinking water problems.
Describe an experiment investigating the effects of nitrogen and phosphorus.
Whole lake experiments in Ontario investigating acidification and eutrophication by DW Schindler
