Freshwater Flashcards
(33 cards)
What are nitrogen and phosphorus used for in ecosystems?
What the different zones (ecological features) of a deep lake? (light/stratification/nutrients/communities)
Littoral Zone:
* Edges of water bodies
* Macrophytes, periphyton, epiphytes, biofilms
Central/Pelagic Zone
* Surface biofilm, neuston community
* Epilimnion, phytoplankton
Benthic zone
* Bacteria, protozoa, heterotrophic
Epiliminion, metaliminion and hypoliminion
—
Aphotic zone (no light), Photic zone
What are the implication of stratification?
Implications of stratification
* Epilimnion, low organic nutrients cuz of primary production
Hypolimnion no primary but high nutrients
How do the ecological features of a shallow lake differ to that of a deep lake?
- Shallow lake is all i the photic zone
- limited distinction between littoral and central zone
- turbulent mixing throughout summer
- mainly autotophic benthic community
What are the ecological differences between depositional and erosional systems?
Erosional system
* photic zone throughout
* LIttoral and central zone not so defined
* Autotrophic benthic community, epibenthic algae
* Coarse sediment - aerobic community
* Non-stratified water
Depositional
* pronounced littoral and central zone
* Macrophytes
* Neuston community
* Fine anoxic sediment
Summarize the nitrogen cycle in freshwater ecosystems
There are four reactions taking place
- Nitrification
- The conversion of ammonia to nitrate or nitrite
- Carried out by specialised bacteria such as nitrobacter
- nitrate taken up by plants etc
- excreted as ammonia
- Ammonification
- The conversion of nitrates into ammonia by Saprobionts when an organism excretes or dies
- Denitrification
- The conversion of nitrate into nitrogen gas is carried out by denitrifying bacteria in anaerobic conditions
- Nitrogen fixation
- Conversion of Nitrogen gas into ammonia
- Carried out by nitrogen-fixing bacteria that have a symbiosis with plants
- Nitrates can come internally or externally
- Assimilation - the incorporation of nitrogen into living tissues
- Nitrate from agriculture, sewage, groundwater into lakes/streams
- Ammonium from ammonification by decomposers
- Uptake by phytoplankton
- Passed through zooplankton, insect/larvae and fish.
Excreted as ammonium (NH3)
What are the main anthropogenic impacts on the nitrogen cycle?
- Surface run off
- Eutrophication
- Haber process for fertilizer, increasing stores in agriculture
- acidification of soil/water
- increased Nr toxic for organisms that absorb nutrients directly from the environment
Describe the allochtnous and autochontous loading of nitrogen and phosphourus into freshwater ecosystems.
Allochonthous
* Nitrogen: Rainfall, aerial deposition, dust particles, fertiliser application (as N03);
burning of fossil fuels, planting N-fixing crops, wastewater disposal (as NH4)
* Phosphorus: From weathering of rocks, fertiliser use/run off, pollution i.e detergents
Autochonthous
* Nitrogen: nutrient cycling by Nitrosomonas/Nitrobacter
* phosphorous: Sediments, nutrient cycling
Describe acidification from nitrogen.
Early life stages of fish and aquatic invertebrates can be especially sensitive to acidification, but direct and indirect impacts have been reported at all higher trophic levels, including zooplankton, benthic invertebrates, amphibians and birds
Aquatic ecosystems with a low acid neutralizing capacity (primarily freshwater) can be acidified by atmospheric deposition of reactive N and S.
With a sharp decline in sulfur emissions beginning in the mid-1980s, Nr has become the major component of acidic deposition in many areas of Europe and North America, and a growing problem in many developing countries.
With persistent acidification, species composition at the base of the food chain is shifted, and often simplified, to favour acid-tolerant macrophytes and phytoplankton.
Describe the soluble and insoluble forms of phosphate.
Soluble
* most common is orthophosphate
* also monophosphate and dihydrogen phosphate
Insoluble
* attached to bacteria, plants, suspended solids
Describe the sources of phosphate in rivers
- Agricultural runoff
- small amount of erosion from rocks
- lots from sewage and run off from cities (96%)
- Dead Pom, detritus etc
How do macrophytes modify the phosphate cycle.
Macrophytes modify p cycle by transporting PO4 from sediments to water, internal loading. Also uptaking the orphophosphate through the leaves when the water is rich in P04.
How is phosphate measured?
Name an example of a classic eutrophic lake and an oligotrophic lake
Oligotrophic lake
* Wastewater in Cumbria, mountainous infertile, deep
* however there’s declining sechhi depth, possibly increased dissolved carbon
Eutrophic lake
* Esthwaite water in cumbria
* surrounded by cultivated land, shallow
* upgrades to waste water treatments and removal of fish farm
Describe the seasonilty in phytoplankotn production
What are the different functional feeding groups of macroinvertebrates?
And what oxygen concentrastion to trout and salmon die below?
3 mgl-1
How do combines sewage overflows (CSOs) effect freshwater systems.
CSOs
* Back up storage tank
* High precipitation means water flows out into the river washing organic and industrial pollutants and surface contaminants from the roads and drains
* have been shown to increase BOD when released
How is BOD measured?
- BOD can be found by collecting water sample
- Measure oxygen concentration
- Incubate water sample in the dark for 5 days @ 20’C
Measure oxygen concentration
Describe the waste water treatment process.
Preliminary, primary, secondary, tertiary.
* Preliminary, screen for debris * Primary, allowed to settle, sludge is formed * Secondary, activated sludge with aerobic bacteria * Sedimentatino again Tertiary with maybe UV or filterbeds
What challenges are faced when factories etc use water systems.
Challenges:
* Regulation
* Enforcement
* Too much abstraction
* Too much/not clean effluents
Effluents often used for cooling so are hot, too hot for the organisms that live there
* Affording the treatment * Afford the monitoring * Enforcing regulations * Putting the neccesery regulation through the government with interested parties not wanting to spend * Maintaining facilities Different priorities
What water quality indicators are there?
In what way was the EU water collective a success?
- large decrease in ammonia concentrations
- 60% decrease in BOD since 1990
- large reduction in orthophosphate
- but no trend in nitrate concentrations
What are the advantages and disadvantages of using BMWP to monitor pollution in waters.
Biological Monitoring Working Party (BMWP):
* Broad, responds to inorganic pollutants
* Doesnt include abundance for individual taxa, operates at family level
BMWP Scores, low is bad, high is unpolluted and unimpacted
