Components of freshwater ecosystems Flashcards
Give four examples of services that water ecosystems provide humans
Transport, irrigation, hygiene, waste disposal
Describe lentic ecosystems
Stationary/slow flowing water. Closed system.
Name three types of water ecosystem
Lentic and lotic ecosystems and wetlands
Give three examples of lentic ecosystems
Lakes, ponds, and pools
Give three factors that can be used to classify lentic ecosystems
Age, size, and nutrient richness
Describe lotic ecosystems
Running water. Open systems
Give three examples of types of lotic ecosystems
Rivers, streams, and springs
Describe how lotic ecosystems affect water chemistry.
Their catchment area influences river contents. They transfer, transport, and dilute materials and chemicals.
Describe wetlands
Areas of standing water that support aquatic plants. The interface of terrestrial and aquatic ecosystems. Can be permanent or temporary, natural or artificial, and flowing or stagnant.
How do wetlands alter stream hydrology?
They impede flow and enhance sediment deposition.
Give three examples of wetland ecosystems
Marshes, swamps, bogs
How do wetlands contribute to the release of detritus downstream?
They transform inflowing nutrients into organic forms
Define epibenthic
Attached or clinging to plants
Define neuston
Resting or swimming on the surface
Define epipelic biofilms
A biological complex of autotrophs and heterotrophs
What are benthic macroinvertebrates?
Organisms that inhabit the substrate for at least part of their lifecycle.
What size mesh can benthic macroinvertebrates be caught in?
200-500μm
What role do benthic macroinvertebrates play in freshwater ecosystems?
Key components of aquatic food webs (linking organic matter and nutrient resources)
Describe zooplankton
Minute aquatic animals that either drift or are very week swimmers.
Give three types of zooplankton
Rotifers, Cladocerans, and Copepods
What type of organism is useful in the detection of changes in the environment and why?
Zooplankton because they are very sensitive.
Give three categories of plants found in freshwater ecosystems
Phytoplankton, periphyton, and macrophytes
Describe the environment where phytoplankton are found
Slow-flowing rivers with high temperatures and light intensity
What are periphyton?
Unicellular and filamentous algae.
Where can periphyton be found?
Living on the substrate or on larger plants
What can macrophytes be used for?
Pollution indication
What are the four types of macrophytes?
Emergent leaves, floating leaved, free floating, and submerged
What types of organisms make up the major biological communities in lake and pond ecosystems?
Plankton and nekton
What types of organisms make up the major biological communities in floodplain and permanent wetlands?
Plankton, nekton, epiphyton, benthos
What type of organisms make up the major biological communities in rivers and streams?
Benthos
What types of organisms make up the major biological communities in estuaries (mudflats)?
Epipelic biofilms
What types of organisms make up the major biological communities in estuaries (outflow)?
Plankton, nekton
What can be influenced by the physical and chemical properties of freshwater ecosystems?
Abundance, distribution, and biodiversity
Describe the three layers of water depth
Epilimnion (surface, warmer), metalimnion (thermocline), hypolimnion
How does water flow and how is the flow measured?
Flows in an open channel and is measure in discharge (volume of water passing through a given point per unit time)
How does the velocity of flow in a river relate to depth?
Inverse proportionality
What can flow also be influenced by?
The type of sediment bed, seasonal precipitation, catchment geology, bed slope, floods, human impacts
What kind of flow picks up more silty and sandy substratum?
Rapid river flows
What type of substrate has a greater range of invertebrates than silt-rich pools?
Stony substrate
What reduces an organism’s habitation and how?
Silt deposition alters an organisms’ habitation because it alters water movement and reduces oxygen levels and food availability
What scale is used to classify rock particle sizes?
Wentworth Scale
What is the effect of low water velocity?
Net deposition, forming a deposition zone
What is the effect of high water velocity?
Net resuspension, forming an erosional zone
Why are some organisms able to sit on top of the water’s surface?
The water has high surface tension (7n28Nm^-1) and the organisms attach with the least surface area possible
What is primary production rate influenced by?
Light availability
What tool is used to measure transparency in lentic ecosystems?
Secchi disc
What are the respective names for the depths of water that are penetrated and unpenetrated by light?
Photic and aphotic zones
What is conductivity the result of?
The concentration of ions
How much more conductive is seawater than freshwater?
20% higher
What is the conductivity of freshwater?
150-500µSeimens cm^-1
What does high specific heat capacity and poor thermal conductivity result in?
Moderate diurnal and seasonal changes in water temperature and a decrease in the rate of decomposition of matter
How does an increase in discharge affect conductivity?
Decreases conductivity by dilution by precipitation. Precipitation doesn’t pass through the geology, therefore does not pick up an ions.
When is dissolved oxygen especially limiting to sensitive biota?
At high temperatures
Give two reasons for low levels of dissolved oxygen in water?
Can be limited in stratified water due to lack of transfer to lower layers and can be depleted at night due to plant respiration.
How does temperature affect levels of dissolved oxygen?
Higher temperatures result in low levels of dissolved oxygen.
How do organisms the prefer lower levels of oxygen have an advantage over those that need more?
They can produce with lower oxygen availability
What ions result in water ‘hardness’?
Ca2+ and Mg2+
What ions result in permanent water ‘hardness’?
Cl- and CO4 2-
What is the pH of hard water?
pH>8.5
Give two examples of factors that impact water pH levels
Soil geology and human activity
Give three examples of human activity that can influence water pH
Cement and steel industries, potassium ion fertilisers, and sodium ion wastewater
What is the pH of freshwater?
Ideally pH 4.5-10.0 but generally pH 6.5-8.5
Give two examples of processes that can lower water pH
Acid mine drainage and acid runoff (which can be increased by sphagnum mosses in wet swamps and peaty areas)
Describe particulate organic matter (POM)
0.2µm-1mm, allochthonous organic matter
What is the size of coarse particulate organic matter? Give four examples of CPOM
> 1mm. Includes living and dead planktonic organisms, leaf litter, twigs, and fruits
What is the size of fine particulate organic matter (FPOM)?
0.2µm-1mm
What size is dissolved organic matter (DOM)?
<0.45µm
Give four examples of types of DOMs?
Anions, cations, viruses, and fine organic debris
What material makes up major components of CPOM, FPOM, and DOM?
Microorganisms
Define allochthonous organic matter
External materials
Define autochthonous organic matter and give three examples
Indigenous plant material. Includes; periphyton, plankton, and macrophytic detritus
Give five examples of micronutrients
Na, Mg, Si, K, Ca
Give six examples of macronutrients
C, H, O, N, P, S
What are C, H, O, and S usually available for?
Growth
What is the ideal N:P concentration ratio in freshwater?
7:1
What is nitrogen used for by organisms?
Amino and nucleic acids
Define heterocyst
Differentiated cyanobacteria that carries out N fixing
Give seven examples of allochthonous nitrogen loading processes
Rainfall, aerial deposition, dust particles, fertiliser application, fossil fuel combustion, N-fixing crops, and waste water disposal
Give two examples of autochthonous nitrogen and phosphorus loading processes
Sediment and nutrient cycling
Why can’t atmospheric nitrogen be used by organisms?
It is unreactive because of its stable covalent bond
What nitrogens are most and least abundant in freshwater?
Nitrate (NO3) is most oxidised by lake and most abundant, nitrite (NO2) is present in small amounts
What type of nitrogen do plant cells use and how is it transferred?
They use a reduced form and it is transferred intercellularly as the amino group NH2.
What does an increase in reactive nitrogen result in?
Higher productivity
What does a shortage of nitrogen for terrestrial plants suggest?
A shortage of nitrogen available for growth in the water
Give three examples of where phosphorus is used in organism growth
Nucleic acids, organelle walls, and energy molecules
What is the relationship between phosphorus and organism growth?
It is a growth-limiting nutrient
Where is phosphorus not found?
In the atmosphere
Give three examples of allochthonous phosphorus loading processes
Weathering of rocks, human activity (inc. detergent pollution, agricultural runoff, runoff from cities (sewage)), and detritus (POM)
Describe the process of eutrophication
Phosphorus is transferred into lakes and it sinks into the sediment. Movement of P from the sediment to the water is mechanical (bioturbation)
Where is excess phosphorus stored?
In algae that later sinks to the substrate
What causes a species shift and how can this challenge the biota?
Can be caused by increased levels of N and P. New, harmful algae can release toxins, leading to a loss or reduction of aquatic life
What causes increased productivity and how can this challenge the biota?
Can be caused by increased levels of N and P. Increased organic matter, which increases respiration, decreasing oxygen availability, leading to a loss or reduction of aquatic life.
A 2013 paper on the consequences of the human modification of the global nitrogen cycle showed what benefits?
Reactive nitrogen emission lead to coastal and terrestrial eutrophication.
A 2013 paper on the consequences of the human modification of the global nitrogen cycle showed what negative consequences?
Freshwater pollution and biodiversity loss. O3 and PM increase in atmosphere.
