Decomposition Flashcards
1
Q
What chemical does the flow of energy follow through a food chain?
A
carbon
2
Q
What is the ultimate fate of the carbon that has been fixed by photosynthesis?
A
3
Q
How do nutrients move through a chain?
A
4
Q
T or F: no essential nutrients are recycled in an ecosystem
A
false, most essential nutrients ARE recycled
5
Q
What happens to nutrients in organic matter during decomposition?
A
they are mineralized
6
Q
What limits plant growth in an ecosystem?
A
the availability of the nutrient that’s in the smallest relative amount
7
Q
What nutrient is usually limiting? Who discovered this?
A
nitrogen
Liebig’s Law of the Minimum
8
Q
T or F: it’s only ever nitrogen that’s limiting to plant growth
A
false, it can be phosphorous in some aquatic ecosystems and iron in some marine ecosystems
9
Q
What form of nitrogen is accessible to plants (organic or inorganic)?
A
inorganic, mineral form
Nitrate (NO3-) usually
10
Q
How do plants use the nitrogen they uptake?
A
plants can incorporate nitrogen into their tissues for growth (ex. amino acids into proteins and nucleic acids)
11
Q
How do plants return nitrogen to the ecosystem?
A
plants will eventually drop their leaves which will become dead organic matter
this dead OM can be decomposed/mineralized into soil nutrients so that other plants and organisms can acquire them
12
Q
How can plants recycle nutrients within themselves?
A
retranslocation
when deciduous plants or trees are ready to drop their leaves, they will cut off the transportation of nutrients into their leaves before they fall off
13
Q
Describe decomposition
A
the breakdown of chemical bonds that make up the organic molecules and tissues of a living organism
14
Q
What 3 things happen when organic matter is decomposed?
A
energy fixed by photosynthesis is released
CO2 and water is released by respiration
organic compounds are mineralized
15
Q
What happens to the energy fixed by photosynthesis during decomposition?
A
it’s released
16
Q
What happens to the organic compounds contained in dead organic matter during decomposition?
A
mineralized
17
Q
What are 5 different ways something can be decomposed?
A
leaching
fragmentation
changes to physical and chemical structure
ingestion
waste excretion
18
Q
How do invertebrate detritivores breakdown dead organic matter?
A
by fragmentation
19
Q
What are the 4 major detritivore groups and how are they classified?
A
by body width:
< 100 micrometers = microfauna and microflora
100 micrometers - 2mm = mesofauna
2-20mm = macrofauna
> 20mm = megafauna
20
Q
What would be considered microfauna and microflora?
A
protists, nematodes
21
Q
what would be considered megafauna?
A
millipedes, earth worms, etc.
22
Q
What is white rot fungus? What’s a local example?
A
a fungi type that breaks down lignin and leaves behind a white colour (cellulose)
ex. Turkey tail, Trametes versicolor
23
Q
How can white rot fungus be used in the paper and pulp industry?
A
it can be used to replace the harmful acids that are used to bleach paper
24
Q
What is brown rot fungi? Give a local example
A
fungus that breaks down cellulose and leaves behind lignin (a brown colour)
red-belt conk, Fomitopsis pinicola
25
What are 2 examples of mesofauna?
mites (larger species) and springtails
26
What body size are microflora and microfauna?
<100 micrometers
27
What body size are mesofauna?
100micrometers - 2mm
28
What body size are macrofauna?
2-20mm
29
What body size are megafauna?
>20mm
30
What are examples of terrestrial macrofauna and megafauna?
millipedes, centipedes, earthworms
31
What are examples of aquatic macrofauna and megafauna?
molluscs (bivalves)
crabs (decapoda)
32
What do microbivores feed on?
bacteria and fungi
33
What organisms are microbivores?
protists (Amoebas)
springtails
nematodes
beetle larvae (grubs)
mites
34
What do small microbivores feed on?
bacteria and fungal hyphae
35
What do larger microbivores eat?
microflora and detritus
36
Describe the steps of mineralization fo organic matter in soil or sediment
complex polymers (e.g., cellulose, polysaccharides, proteins, lipids, nucleic acids) are hydrolyzed by cellulolytic and other polymer-degrading bacteria into monomers (carbohydrates, amino acids, fatty acids)
monomers are fermented into:
H2, CO2 ; acetate ; propionate butyrate succinate alcohols
propionate... is converted into H2 and CO2 and acetate through syntrophy
Acetogens convert H2 and CO2 into acetate via acetogenesis
methanogens convert acetate into CH4 and CO2 via methanogenesis
37
What happens to complex polymers in the first step of mineralization?
cellulose, polysaccharides, proteins, lipids, nucleic acids etc., are hydrolyzed by bacteria that can break down those polymers into monomers
38
What happens to monomers in mineralization?
carbohydrates, amino acids, fatty acids are fermented by primary fermenters
39
What are the products of fermentation of monomers? (mineralization)
H2 and CO2
acetate
propionate butyrate succinate alcohols
40
What happens to H2 and CO2 that are produced by fermentation in the mineralization of OM process?
acetogens convert H2 and CO2 via acetogenesis into acetate
the acetate is then converted into methane (CH4) and CO2 by methanogens (methanogenesis)
41
What happens to acetate that is produced by fermentation in the mineralization of OM process?
methanogens convert acetate into CH4 (methane) and CO2 via methanogenesis
42
What happens to pbs alcohols that are produced by fermentation in the mineralization of OM process?
syntrophy produces both H2 and CO2 and acetate
methanogens convert these into methane and CO2 via methanogenesis
43
What is the last step in mineralization of OM regardless of the type of fermentation product?
methanogenesis by methanogens to produce CO2 and CH4 (methane)
44
How can the fate of OM / decomposition be studied?
litterbags
meshbags made of material that doesn't easily decompose and holes large enough for decomposers, but small enough to keep in leaf litter
these are placed in the range of study and left for a period of time
the fresh dead OM is weighed and then the decomposing OM is weighed over time to understand the rate of decomposition by measuring the % mass remaining of the original mass
45
What did Martin Swift's (Zimbabwe) study do? what were the results?
looked at sawdust decomposition to measure the growth of fungi by measuring the proportion of chitin over time
39% of the sawdust's original weight was lost
58% of the remaining mass = living and dead fungal biomass
46
What is the apparent decomposition rate?
47
What is the actual decomposition rate?
48
How is dead organic matter/decomposition measured in stream ecosystems?
litterbags in leaf packs (areas of deposition and accumulation of leaf litter) and anchored in the area
49
What is used to estimate the rate of decomposition in leaf litterbag experiments?
the mass lost (mass remaining subtracted by the initial mass)
50
what timeline do soil litter bag experiments usually run?
over months or years
51
How are data collected from soil litter bag experiments usually graphed?
using negative exponential regressions (non-linear) and with
x axis: time (weeks, months, years)
y axis: % original mass remaining
52
In the soil litter bag study looking at red maples and virginia pines, which decomposed at a faster rate? explain
the virginia pine decomposed at a faster rate: on the exponential regression graph, % original mass remaining decreased faster than the red maples
less of the original mass remained
53
What 2 major factors influence the rate of decomposition/decay?
quality of plant litter - plant litter is a food source so if it's low quality, less organisms will be able to digest it
the features of the physical environment that effect decomposer populations (ex. pH and texture of soil, temperature and precipitation)
54
What abiotic environmental factors might influence the decomposition rate? Why?
soil pH and texture
temperature and precipitation
these factors will influence the populations of decomposers = influence decomposition rate
55
What pH levels do most forests have? what does this mean for decomposition rates?
usually quite low (acidic) = slow decomposition because it supports less bacteria
56
What is the ideal soil texture for good decomposition? why?
loam = equal parts sand, silt, clay
maximizes retention of water and drainage
57
How do temperature and precipitation influence decomposition rates?
generally
higher temperature, higher decomposition
higher elevation = lower temperature = lower decomposition
if soil is too wet and becomes saturated = anaerobic conditions lead to slow decomposition
58
Describe how the 3 different forest structures on Mount Doug may have varying rates of decomposition
At the base, where it's mostly Western Red Cedar: soil will be more acidic and likely more wet = slower decomposition
in the middle, where it's mostly DF: soil will have adequate drainage and retention = probably optimal decomposition
at the top, where it's mostly Garry Oak: soil will have the least water retention and most drainage = slow decomposition
59
How does the quality of plant litter affect decomposition rates?
quality here means composition basically
higher quality = easier to break down = faster decomposition
60
Describe plant litter quality and provide some examples
higher quality: sources of small molecules and high energy bonds, ex. glucose and simple sugars = easiest to degrade
moderate quality: complex molecular structures like cell wall components, ex. cellulose and hemicellulose
lowest quality: large molecules with complex molecular structures, ex. lignin = hardest to degrade
61
What would high quality plant litter be composed of?
small molecules with high energy bonds that are easy to break
ex. glucose and simple sugars
62
glucose and simple sugars are an example of what quality of plant litter?
high quality
63
What would moderate quality plant litter be composed of?
molecules such as cellulose and hemicellulose which compose cell walls and are structurally more complex and difficult to breakdown
64
Cellulose and hemicellulose are examples of what quality of plant litter?
moderate
65
What would low quality plant litter be composed of?
large molecules that are structurally very complex (3D) and are not easy to break down
very little energy released in these bonds
ex. lignin
66
Lignin is an example of what quality of plant litter?
low quality
67
What makes lignin so hard to decompose?
it's 3D aromatic carbon ring structure is very difficult for enzymes to attack
68
What is the slowest plant tissue to decompose?
lignin
69
T or F: lignin, while difficult to decompose, provides the highest amount of energy when the bonds break
false - it's hard to decompose and it provides little energy for microbes
70
What type of enzymes can degrade lignin? What's an example of a species that can do this?
peroxidase and laccase
found in Trametes versicolor (turkey tail fungi)
71
What species that grows on Mt Doug can digest and decompose lignin?
Trametes versicolor (turkey tail)
a type of white-rot fungi
72
T or F: the slow rate of decomposition for lignin has been seen only in terrestrial ecosystems
false, it's also been observed in aquatic ecosystems
73
List the steps of mineralization of organic matter in soil or sediment
1. complex polymers are hydrolyzed by cellulolytic and polymer-degrading bacteria into monomers
2. monomers are fermented by primary fementers into:
3. H2, CO2
3. acetate
3. propionate, butyrate, succinate alcohols
4. acetogens convert H2 and CO2 via acetogenesis into acetate
4. acetate is directly converted into CH4 and CO2 by methanogens
4. the alcohols are converted into either H2, CO2 or acetate via syntrophy
5. methanogens convert acetate and H2, CO2 via methanogenesis into CH4 and CO2
74
What are complex polymers that can be mineralized from organic matter in soil or sediment?
cellulose
polysaccharides
proteins
lipids
nucleic acids
75
How are complex polymers in organic matter mineralized into monomers?
via hydrolysis by cellulolytic and other polymer-degrading bacteria
76
What are monomers that are mineralized in organic matter?
fatty acids
sugars
amino acids
77
What are monomers in organic matter mineralized into? how does this occur?
H2, CO2
acetate
propionate, butyrate, succinate alcohols
converted by fermentation by primary fermenters
78
How are H2 and CO2, produced by the fermentation of monomers, mineralized further? and into what?
acetogens convert H2 and CO2 into acetate via acetogenesis
79
What happens to the acetate produced by the fermentation of monomers?
it is converted by methanogens via methanogenesis into methane (CH4) and CO2
80
What happens to the proprionate, butyrate, and succinate alcohols produced by fermentation of monomers?
a process called syntrophy converts these alcohols into H2 and CO2 and acetate
81
What happens to acetate produced from any pathway of mineralization of organic matter?
acetate is converted into methane (CH4) and CO2 via methanogenesis by methanogens
82
What is syntrophy?
the process of one organism living off the products of another organism
83
Describe the litter bags used in soil litter bag experiments
mesh bags of synthetic material (not easily degraded) with 1-2mm holes big enough for decomposers to enter, but small enough to stop losing plant material
84
What are leaf packs?
areas of accumulated leaf litter where there's active decomposition
85
What is the primary way to study decomposition?
soil litter bags collected at regular intervals over months or years
86
How is the rate of decomposition calculated from soil litter bag experiments?
remaining mass - initial mass = mass lost
87
In a negative exponential regression model, what is the equation? what is the k?
y = e^(-kx)
-k is the decay function (a constant)
88
In the negative exponential regression model, what does it mean if k is large?
the rate of decay is faster
89
What type of ecosystem can carbon quality of plant litter have a strong influence on decomposition?
coastal marine environments
90
How does the carbon quality in coastal marine environments influence decomposition?
because phytoplankton have low lignin content, decomposition can occur faster
but vascular plants (macrophytes, marsh grasses, reeds) may have some lignin concentrations = slower decomposition
91
T or F: decomposition in aquatic systems is unrelated to oxygen content
false, it's affected by O2 content
92
What factors effect the rate of decomposition in aquatic systems?
carbon quality of plant litter
lignin concentration
oxygen concentration
temperature
moisture
elevation/latitude
93
T or F: bacteria can completely degrade (mineralize) lignin
false, only fungi can completely decompose lignin
94
In anaerobic conditions (ex. mud and sediment), what organism does most of the decomposition?
anaerobic bacteria
95
How does oxygen content affect the decomposition of lignin?
higher O2 content = allows growth of fungi that decompose lignin
lower O2 content = less fungi, less decomposition of lignin
96
How do temperature and moisture effect microbial activity (decomposers)?
generally, low temperatures and dry conditions reduce activity of microbes
97
How does latitude effect microbial activity (decomposers)?
higher latitudes with cooler temperatures have decreased microbial activity
98
How does air temperature and diurnal changes in air temperature affect decomposition? how is this measured?
by measuring CO2 concentration in a temperate deciduous forest
as temperature increases throughout the day and reaches its peak around 12/1pm and then decreases into the evening/night
CO2 release follows this trend
99
How is CO2 concentration in the air above a temperate deciduous forest measured?
static gas chambers and gas chromatography
100
define static gas chamber experiments
put a closed container in the soil that also reaches above the soil surface
use a syringe to extract gas and measure with a gas chromatographer
101
T or F: the nutrient quality of dead organic material does not vary
false, it varies a lot
102
what happens to the nutrients in dead OM after it's consumed? is the pathway the same for all essential nutrients?
103
What is the usual nitrogen content in dead leaf material?
0.5-1.5%
104
What does a higher nitrogen content in dead plant matter mean for decomposers (bacteria and fungi)?
more nitrogen = higher nutrient value for bacteria and fungi
105
define mineralization
the process of converting elements (ex. nitrogen, carbon) from organic compounds into inorganic (mineral) compounds by microbial decomposers
106
Define immobilization
the process of microbial decomposers consuming and assimilating mineral nutrients
107
What is the rhizosphere? what organisms are highly concentrated here?
the region around the roots of plants in which mineralization and immobilization of essential nutrients occurs
there's a high concentration of bacteria and fungi in these regions
108
Describe the cycle that involves carbon, mineralization, and immobilization
dead leaf litter is consumed by fungal and bacterial decomposers as a source of energy and nutrients which respire (release) CO2
bacteria and fungi mineralize organic compounds into mineral nutrients
mineral nutrients are immobilized (assimilated) by fungi and bacteria (decomposers)
109
What is the C:N ratio in plant leaf litter?
50:1 to 100:1
C:N
110
What is the C:N in fungi and bacteria?
10:1 to 15:1
C:N
111
How do you calculate net mineralization rate?
mineralization rate - immobilization rate
112
Why is immobilization a key process for decomposers?
because plant litter has pretty low nitrogen content (~50:1-100:1) so the nitrogen uptake by decomposers needs to be compensated/increased by immobilization
113
Why is there such low nitrogen content in the litter relative to carbon?
nitrogen (in the water soluble form of nitrate) is easily leached out with water
114
What happens to nitrogen content in litter when immobilization is higher than mineralization?
nitrogen % remaining increases
115
What happens to nitrogen content in litter when mineralization is higher than immobilization?
the % nitrogen remaining decreases
116
What makes up the organic material in litter bags?
original dead leaf matter and living and dead microorganisms
117
Is the nitrogen content higher in bacteria and fungi than it is in plant litter?
higher in bacteria and fungi (50:1-100:1) vs plant litter (10:1-15:1)
118
How is the C:N ratio effected by decomposition in a soil litter bag?
as more plant litter is decomposed and more nutrients are mineralized, more nutrients will be immobilized by decomposers and the C:N ratio in plant litter will decrease and C:N in decomposers will increase
119
what happens to carbon quality as decomposition proceeds?
carbon quality declines because lignin proportion increases
120
What happens to nitrogen as decomposition proceeds?
there's a net release of nitrogen into the soil and water
121
Does the same pattern of immobilization and mineralization occur to all essential nutrients?
yes
122
What does the pattern of dynamics of decomposition depend on?
the nutrient content of the litter and the requirements of the microbes
123
What are 3 other nutrients that are key for mineralization and immobilization of soil litter decomposers? how are these effected during decomposition?
sulphur, calcium and manganese
these nutrients are decreased over time of decomposition
124
What does litter eventually become because of decomposition and mineralization?
humus
125
What is humus?
dark homogenous organic matter
126
What component is high in humus?
lignin
127
What happens to humus?
128
How does decomposition affect soil?
129
What is soil organic matter?
humus within the soil matrix
130
How long did the Swedish study on Scots Pine go on for?
5 years
131
What did the 5 year study of long-term decomposition of leaf litter in Scots pine forest in Sweden find in regard to carbon content?
as decomposition of plant litter increases over time, the carbon content in the litter decreases as it becomes assimilated into the decomposers' bodies or is lost as CO2 (respiration)
132
What is the net effect on nitrogen as decomposition continues (ie., mass is lost) found from the Swedish study on Scots pine?
the nitrogen concentration in the leftover organic matter (plant materials and microbial tissues) increases
133
Due to the high C:N ratio in plant litter, what did the Swedish study on Scots pine find in regards to nitrogen content?
a net increase in nitrogen in the litter bags because the C:N ratio was so high in the leaf litter that more nitrogen needed to be immobilized from the soil into the decomposers to support their growth
134
How is the C:N ratio affected overall as decomposition continues over time? (Swedish Scots pine)
as the decrease in carbon and increase in nitrogen content in residual OM continues, the C:N ratio is lowered
this is because decomposition is now proceeding toward humus and soil organic matter
135
Explain the major outcomes of the Swedish Scots pine study
over the course of the study, mass and carbon declined
mass decreased as consumers consumed plant litter
mineral nitrogen increases because organic nitrogen is being mineralized from the plant litter into the soil then decreases as decomposers immobilize nitrogen into their body = increase of nitrogen in biomass (leaf litter bag)
carbon decreases because of release of CO2 from microbial respiration and assimilation by microbes
overall, C:N ratio decreases
136
T or F: the declining C:N ratio and increase in nitrogen concentration in the residual organic matter indicates an overall increase in available nitrogen for microbes
false, it doesn't
as OM is decomposed, the easiest and highest energy compound carbon bonds are broken first, leaving behind more recalcitrant molecules (eg., lignin) and so
as nitrogen concentration increases in residual organic matter, the quality is decreasing because it is binding to lower quality and more recalcitrant carbon molecules
= less available
137
How does decomposition time affect the proportion of lignin? (Swedish scots pine)
as decomposition progresses, the proportion of lignin increases because the easier, higher energy bonds are broken first, and very few organisms can decompose lignin (only fungi)
138
What process converts plant litter into soil organic matter?
fragmentation by soil invertebrates and chemical decomposition by microbes
139
What is chitin?
a complex molecular component of arthropod exoskeletons and fungal cell walls that is very hard to degrade
140
What happens to the proportion of chitin in residual organic matter as microbes die?
the proportion of chitin increases as microbes die
141
What is the result of increasing proportion of chitin in residual organic matter?
as microbes die, the proportion of chitin in the residual organic matter increases and this leads to the production of humus
142
what happens to the quality of soil organic matter over time? what about the C:N ratio?
soil organic matter quality decreases over time and the C:N ratio declines
143
At Mt Douglas park, would you expect chitin to be homogenous?
no, there are many organisms at Mt Doug that would contain chitin
ex. myriad of fungi, insects, and in the aquatic systems, cephalopods
144
What groups of eukaryotes contain chitin?
insects (exoskeletons)
fungi (cell walls)
cephalopods (ex. squid beaks)
145
what does recalcitrant mean?
compounds with reduced quality that are complex and difficult to break down and provide little energy
146
Why does the decrease in C:N ratio not indicate increased nitrogen availability?
as the C:N ratio declines, the carbon that is left over is very low quality (recalcitrant, usually lignin) and nitrogen will bind to this becoming unavailable for decomposers
147
Why is decomposition of residual soil organic matter really slow?
because the carbon that is leftover is very low quality and doesn't provide much energy to decomposers and is also very complex, so only few organisms can break it down (fungi)
also, residual nitrogen will bind to these molecules making them more difficult to obtain
148
T or F: humus degrades quickly because it is so rich in carbon and nitrogen
false, humus degrades really slowly because its carbon components are low quality and hard to degrade
149
How significant (or not) is humus in terms of carbon and other nutrient storage and release?
very significant because it is very abundant
150
What is the rhizosphere?
the region surround plant roots where plant roots function and bacteria and fungi are active decomposers
where the soil microbial loop occurs
151
What is the rate of decomposition in the rhizosphere?
152
What determines the rate of nutrient cycling in the rhizosphere?
the relationship between microbial decomposers and microbivores because this determines the amount of available nutrients (mineral) for plants
153
How do roots affect the chemistry of the rhizosphere?
154
How much photosynthetic energy is used by processes in the rhizosphere?
155
What is the soil microbial loop? where does it occur?
the process of recycling nutrients between plants, microbial decomposers, and microbivores
occurs in the rhizosphere
156
Describe the soil microbial loop
plants provide microbial decomposers carbon in the rhizosphere
provides decomposers with energy to decompose soil organic matter and immobilize nitrogen from the soil (assimilate nitrogen into their biomass)
consumption of microbes by microbivores remobilizes nitrogen from microbial biomass in the form of excreting ammonia, a plant available form of nitrogen
plant roots uptake ammonia
cycle continues
157
How is the nitrogen assimilated in microbial biomass released back into the soil for plant use?
microbivores such as protozoa and nematodes consume bacteria or fungi and remobilize the nitrogen by
because there's not much difference between the C:N ratio of microbes and of microbivores and the low assimilation efficiency, the excess nitrogen is excreted by microbivores as ammonia which is a plant-available form of nitrogen
158
what form of nitrogen is available for plants to take up from the soil organic matter? what organism produces it?
ammonia (NH3)
produced by microbivores consuming microbes and excreting excess nitrogen as ammonia
159
what are two examples of microbivores that consume microbial decomposers?
nematodes and protozoa (protists)
160
MIDTERM: what is retranslocation?
the process of reuptaking nutrients
161
MIDTERM: what constitutes microflora? microfauna?
microflora: <100um (bacteria and fungi)
microfauna: protozoa (protists), nanoflagellates, cilia, nematodes
162
MIDTERM: what is the scientific name of the white rot fungi, what is significant about them?
Trametes versicolor, turkey tail
they can mineralize lignin (leave being cellulose)
163
where is a local example of where you can find white rot fungi (ex. Trametes versicolor)?
Mt Doug
164
MIDTERM: what method is used to study decomposition in terrestrial ecosystems?
soil litter bags
165
MIDTERM: what method is used to study decomposition in aquatic ecosystems?
sediment microcosms
166
Globally, what % of energy fixed by photosynthesis is used by processes in the rhizosphere?
50% - a significant amount
167
Globally, what % do processes in the rhizosphere contribute to atmospheric CO2?
50%
168
What rate does plant litter in aquatic systems decompose in comparison to terrestrial? why?
rapidly in permanently submerged conditions
because the detritivores in aquatic systems are in the water
169
How does decomposition occur in moving bodies of water?
aquatic fungi colonize organic litter
aquatic arthropods fragment (shred) organic particles and consume the bacteria and fungi that are decomposing it
further along, arthropods (filterers and gatherers) filter out fine particles and fecal matter from shredders
grazers and scrappers consume algae (phytoplankton biofilm), bacteria, fungi and OM on rocks
Algae assimilates nutrients and dissolved OM
170
How does decomposition of POM occur in still, open-water systems?
particulate OM (POM) sink toward bottom of lake or ocean and is consumed and mineralized along the way before settling as humus in the sediment
bacteria are decomposing at the bottom in the anaerobic layers of sediment
171
T or F: decomposition of POM in still, open water ecosystems is rapid
false!
anaerobic bacteria are major decomposers in the sediment and this is very slow
172
What are major sources of Dissolved OM in aquatic systems? how does DOM contribute to fixing carbon?
Dissolved OM is a source of carbon for decomposition
free-floating macroalgae, phytoplankton and zooplankton are main sources of DOM because their bodies dissolve rapidly after death
also some phytoplankton and algae can secrete OM during growth and reproduction which can support bacteria
173
How does the microbial loop contribute to the aquatic nutrient cycle?
it recycles carbon (OM)
Bacteria bring DOM back into the food web
Ciliates and zooplankton consume bacteria
174
Where is DOM most commonly found in an aquatic system? why? what effect does this have on the carbon cycle?
near the surface because it's very light
it supports PP
175
What 2 processes are most important to nutrient cycling within an ecosystem?
photosynthesis and decomposition
176
What determines the rate of nutrient uptake in an ecosystem?
primary productivity
177
What determines the net rate of mineralization in an ecosystem?
decomposition
178
How do photosynthesis and decomposition interact to limit internal cycling of nutrients in an ecosystem?
if photosynthesis is low, PP is low, less carbon being transferred through food chain, less DOM entering the detrital food chain = less decomposition
overall less nutrients being cycled
179
How is the rate of photosynthesis influenced by nitrogen cycling?
photosynthesis is strongly correlated with [N] in leaves
Nitrogen is a major component of photosynthetic compounds = influences carbon uptake
180
Give two forest examples that display how nitrogen availability influences the rate of decomposition and photosynthesis
a pine forest has lower N concentration and mineralization and photosynthesis are decreased compared to a maple forest
181
What processes does the quantity and quality of organic matter influence?
organic matter is a food source for decomposers, so the quality and amount of it will influence the rate of decomposition and rate of nitrogen mineralization (nutrient release)
182
What does a lower nutrient concentration in dead OM result in?
more immobilization of nutrients to meet demands of decomposers - reduces overall nutrients available for plants = decreases PP
183
What type of feedback system exists for internal cycling of nutrients in an ecosystem?
positive feedback
when there's less nitrogen available, there's less PP, which results in less nitrogen available
pushing further from set point
184
What does a lower C:N ratio mean for quality of leaf litter?
higher quality of leaf litter with lower C:N
185
What is a direct link between NPP and decomposition?
nutrient cycling
186
How does the link between NPP and decomposition vary between terrestrial and aquatic ecosystems?
there's connections between the zones of PP and decomposing in forests whereas, there's 2 separate zones in oceans/lakes (vertical)
187
What links the production and decomposition zones in a terrestrial environment?
plants
188
How do plants bridge the production and decomposition zones?
they exist and function in both above soil and in soil zones
production in leaves
decomposition in soil - roots absorb nutrients in soil and vascular system sends nutrients to leaves
189
T or F: in every open water ecosystem, there's no bridge between the photic and benthic zones (the production and decomposition)
false, in shallow systems plants can bridge
190
Usually, how are nutrients transferred between the 2 zones in open water systems?
vertically via upwelling
191
What is a major contributor to the low productivity of open oceans and large lakes?
the fact that the decomposition zone and photosynthesis zone are spatially separated
192
What are the 3 distinct zones in vertical water columns?
epilimnion
thermocline (metalimnion)
hypolimnion
193
describe the epilimnion
surface water
warm from sun
high O2
lots of light penetration
= photosynthesis zone
194
describe the thermocline/metalimnion
steep temperature gradient
the zone between the epilimnion and hypolimnion
195
describe the hypolimnion
the deep, cold, dense water
usually low in O2
little/no light penetration
sediment/DOM build up
= zone of decomposition
196
What are the 5 'mixing/upwelling' types of lakes?
monomictic - one mixing
dimictic - 2 mixings seasonally
polymictic - many
amictic - none / permanently frozen
meromictic - infrequent
197
What is an example of dimictic lakes?
in temperate regions
198
What is an example of monomictic lakes?
Elk lake
199
Where would you find polymictic lakes?
tropics
200
Where would you find amimictic lakes?
High Arctic, these are frozen
201
Where would you find meromictic lakes?
ex. Lake Mahoney in Osoyoos
202
Why is mixing in lakes key for the succession of bacteria?
it brings up nutrients, specifically Si which is key for diatoms
203
When wind causes turbulence in open waters, what layers are mixing?
just the epilimnion
204
How does upwelling occur in open-water ecosystems?
in cooler seasons (spring and fall), water temperature of epilimnion drops as sunlight decreases and approaches temperature of hypolimnion
this causes the thermocline to become no different than the epilimnion and the epilimnion and hypolimnion can mix
nutrients from sediments are brought to surface waters to support photosynthesizers
205
At what water temperatures do the epilimnion and hypolimnion mix?
4 deg C
206
What is the succession of algae in open water ecosystems as there's seasonal changes to the thermocline?
diatoms most dominant in spring when upwelling increases Dissolve Si
chrolophyceae replace diatoms in late spring/summer as silica decreases
cyanobacteria replace chlorophyceae in late summer as Nitrogen becomes limiting (they can fix N2)
207
What better represents the cycling of nutrients in a river system? why?
a spiral because nutrients are constantly transported downstream = nutrient spiralling
208
Why is nutrient cycling in river systems called nutrient spiralling?
because nutrients are recycled in different locations along the river - involves time and space
209
what are the 2 types of spiralling?
tight and open
210
Describe tight spiraling
when the river flows more slowly = more similar to nutrient cycling because nutrients remain in place longer
211
describe open spiralling
faster river flow
nutrients moved quickly
212
What affects the speed of organic matter downstream?
rate of water flow (tight or open spiral)
presence of physical features that can block movement (logs, pools, sediments, vegetation)
213
Why are coastal ecosystems so productive?
because water from terrestrial environments (rivers and streams) bring nutrients from terrestrial environments and release into ocean
214
What is an estuary?
region where freshwater from a river or stream meets the ocean
215
what happens to sediments carried by the river when it meets the ocean?
the sediments are deposited into the estuary
216
how do nutrients cycle in coastal ecosystems?
similar to both terrestrial and river systems:
T: plants are rooted in sediment, so the production and decomposition zones are bridged and submerged plants can assimilate nutrients from sediments and water column
R: flow of water brings OM and nutrients into and out of the ecosystem
217
What type of food chain (grazing or detrital) does a salt marsh support? why?
only detrital
very small portion of PP is consumed by grazers
most of the NPP is lost through decomposer respiration
most of the detritus is consumed by bacteria and fungi
because there's very low O2 content = anaerobic bacteria can ferment and respire
218
Where does some of the NPP from salt marshes go?
into nearby estuaries
219
How can nutrient cycling vary in salt marshes?
some salt marshes require tides to bring nutrient inputs and take in more than they release
some export more than they import
220
What brings nutrients and oxygens into estuaries?
tides
221
What is a salt wedge in an estuary? what does this result in?
high density salt water beneath the freshwater
results in a surface flow of freshwater and a lower counterflow of brackish
222
what is the pynocline in estuaries? what is it similar to in lake systems?
the zone in an estuary where there's maximum density differences between fresh and salt water
similar to thermocline
223
How does the pynocline contribute to the transfer of nutrients in estuaries?
OM particles move through the pynocline into the countercurrent of salt water and are carried up the estuary
224
What is a local example of an estuary? how does it exhibit stratification/pynocline?
Saanich Inlet
aerobic conditions are separated from anaerobic
differences in the density of water creates layers that keep phytoplankton in the surface waters
225
How does the pynocline slow down the sedimentation rate?
by establishing a max difference in water density, lightweight phytoplankton can't settle into the brackish layer leaving and nutrients and PP are maintained in the estuary
226
What allows for higher mixing in estuaries?
the regular movement (tides) of saltwater and freshwater and they're usually shallower
227
What influences the global nutrient cycling in oceans?
global ocean surface currents driven by the Coriolis effect
228
How do global surface currents affect upwelling along western coastlines?
surface water currents flow along coastlines towards the equator which are then pushed offshore by the Coriolis effect which leads to mixing
229
How do global surface currents affect upwelling near the equator?
two currents flow west at the equator and are deflected in opposite north and south directions = upwelling
