Ecosystem Energetics Flashcards
What is the basis of a natural ecosystem?
the energy source
Aside from being involved in nutrient cycling themselves, what makes bacteria so critical in energy transformation?
mitochondria and chloroplasts (organelles in eukaryotic organisms involved in energy transformation) evolved from bacteria
What are the major sources of energy for an ecosystem?
sunlight in the form of photons
or
some organisms can intake energy from geothermal or hydrothermal environments (not light related)
What other type of energy can photons be converted into?
heat
chemical energy (ATP)
What effect does the transformation of photons into heat energy have?
the heat energy warms the surface of the earth and the oceans
it drives the water cycle
it causes the wind and water currents
What governs the flow of energy in ecosystems?
the laws of thermodynamics
What is potential energy?
energy that is stored and available for and capable of doing work
ex. the ball at the top of a hill has stored energy
ex. potential energy stored in chemical bonds is released when wood burns
What is kinetic energy?
the energy of motion
it does work and acts as a force on an object to displace it
ex. the energy acting on the ball as it rolls down the hill
ex. kinetic energy is produced as heat and light as wood burns
What is the first law of thermodynamics?
energy is conserved
ie., it is not created or destroyed
it can change from one form to another
move from one place to another
it can act on matter in multiple ways
but there is never a gain or loss in total energy
What is the second law of thermodynamics?
when energy is transferred, entropy (disorder) increases and it’s in a form that can’t do work (loses capacity)
What happens to energy when it is transferred from one organism to another?
some energy will be stored in living tissues
some energy will be lost as heat
entropy will increase
If entropy increases with energy transfer, according to the second law of thermodynamics, how do ecosystems maintain order and energy?
ecosystems are open systems, which the second law of thermodynamics doesn’t apply to
the law only applies to systems within which no energy or matter is exchanged with the environment
the constant input of energy (mainly sunlight) in ecological systems contradicts the effects of entropy and maintains order and conserves energy
What is primary production?
the energy that is fixed in the system during photosynthesis
the rate at which autotrophs transform CO2 from the atmosphere or water into organic compounds
What are the 2 types of autotrophs?
chemoautotrophs
photoautotrophs
What are chemoautotrophs? give an example
primary producers that fix CO2 from their environment using energy from chemical compounds (oxidation of electron-donating molecules)
ex. Nitrosomonas europea use ATP to fix CO2
ex. Thiobacillus hydrothermalis use sulphur
What are photoautotrophs? give an example
primary producers that fix CO2 from their environment using energy from sunlight
ex. trees, herbs, mosses, Lamprocystis purpurea, Gammaproteobacteria, Cyanobacteria, Chloroflexus
What are the 2 measurements of primary productivity in a natural system?
gross primary productivity (GPP)
net primary productivity (NPP)
what is GPP?
Gross Primary Productivity is the TOTAL rate of photosynthesis by autotrophs
this includes energy converted for the organism’s own respiration
What is NPP? what is it’s formula?
Net Primary Productivity is the rate of energy storage in the form of organic molecules AFTER energy is used for cellular respiration (loss of energy)
NPP = GPP - Respiration
units: kcal/m^2/yr or g/m^2/yr
can be calculated from the Standing Crop Biomass accumulation
What is the standing crop biomass accumulation?
scientist makes multiple transects at different elevations and measures the diameter at breast height of the 4 closest trees to the transect as well as notes down the identification
How is NPP measured in aquatic systems?
the light/dark bottle method
Explain the light/dark bottle method that’s used to measure NPP in aquatic systems
used to measure the production and consumption of oxygen
light bottles are used to estimate NPP: they contain an incubated water sample with autotrophs - if photosynthesis surpasses respiration, dissolved oxygen will accumulate
dark bottles are used to estimate respiration: they contain the same sample incubated for the same time - if there’s no photosynthesis, and only respiration, the dissolved oxygen should decline
How can the light/dark bottle method be used to determine the amount of dissolved oxygen produced by photosynthesis?
the light bottle will have both photosynthesis and respiration occurring, whereas the dark bottle will only have respiration
to get the total amount of O2 that was produced by photosynthesis (GPP), you have to subtract the amount of O2 consumed by respiration (the purpose of the dark bottle)
What is the purpose of the dark bottle?
To learn how much O2 is consumed during respiration so it can be subtracted from the value found in the light bottle to determine the amount of O2 produced by photosynthesis
the dark bottle is the control
What is a microcosm?
a small representation of a larger system
ex. the light and dark bottles with samples containing autotrophs
What are the biases of studying microcosms?
they are removing the medium and study organisms from the actual environment, so they are removing natural inputs and contributing factors so it may not be representative of reality
Why do we like microcosm studies?
they are generally less $$
simple
reliable
they could be used for bioremediation and isolation of bacteria
Which bottle is the experimental one and which is the control?
the light bottle is the experimental
dark bottle is control
How do environmental factors effect NPP in terrestrial ecosystems?
Temperature and precipitation are major influencers of NPP
NPP increases with increasing precipitation and temperature (ex. tropical wet forests)
How is solar radiation related to average annual temperature?
How are the effects of temperature and precipitation on primary productivity related?
generally:
as precipitation increases, NPP increases; as temperature increases, NPP increases
ex. Low NPP, more extreme temperatures, lower ppt in Kelowna
higher NPP, moderate temperatures, higher ppt in Victoria
highest NPP, moderate-cold temperatures, highest ppt in Tofino
How does NPP vary across different ecosystems?
It depends on the particular climate
higher ppt tends to increase NPP
elevation will have an effect because temperature and moisture levels will change
Describe the biome diagram by Whittaker
precipitation (cm/yr) on x axis
air temperature (C) on y axis
the diagram shows and relates climates of terrestrial biomes to one another in terms of their ppt and temperature
Where on Whittaker’s biome diagram would Victoria be?
~temperate forest
between 100-230 cm/yr ppt
between 18-2 C
rough ^^^
Where on Whittaker’s biome diagram would Tofino be?
temperate wet forest
between 150-450 cm/yr ppt
between 18- -5C
Where on Whittaker’s biome diagram would Kamloops be?
desert
<50 cm/yr ppt
between 30- -15C
Order the 4 biogeoclimatic zones on Vancouver island in terms of temperature and NPP
alpine mountains: lowest temp (-10-0), lowest NPP
mountain hemlock: lower temp (-10-0), lower NPP
Coastal Western Hemlock: mid temp (~10), mid NPP
Coastal Douglas-fir: mid temp (~10), mid NPP
How does the length of the photosynthetic period per day affect NPP?
In latitudes closer to the equator, the photosynthetic period is longer = higher NPP
as you move up or down latitudes toward either of the poles, the photosynthetic periods become shorter = lower NPP
Describe the basics of photosynthesis
photoautotrophs uptake CO2 and water to convert energy from the sun into chemical energy
stomata in cells open to intake CO2
water is lost while stomata is open (evapotranspiration)
roots uptake water from the environment
How might photosynthesis (NPP) be affected by amount of water in environment?
while stomata are open for intake of CO2 from environment, water vapor molecules are being lost from the photoautotroph
so if there’s less ppt, the plant may have to adjust how long the stomata are open (or what time of day, when it’s less hot etc) = less photosynthesis
if there’s more ppt, the more water can be replaced by the roots of a plant and the stomata can be open for longer = more photosynthesis
What is evapotranspiration?
when water is lost through transpiration via stomata in plant cells
What does the amount of water available in the environment limit?
rate of photosynthesis
the number of leaves that a plant can support
On a global level, what level of NPP do coastal ecosystems have?
intermediate
On a global level, what areas tend to have the lowest NPP?
higher and lower latitude areas as well as higher elevations
On a global level, what areas tend to have the highest NPP?
regions closer to the equator / mid-latitudes
how is world NPP calculated in terms of biomes?
for each biome, the area (10^6km^2) is multiplied by its mean NPP per unit area (g/m^2/yr) = world NPP (10^9 mt/yr)
What is the relative NPP? how is it calculated?
it’s the amount of NPP that is stored in the biomass of a biome type
calculated by:
mean NPP/mean biomass per unit area (g/g/yr)
If a biome type (ex. boreal forest) has a higher relative NPP than another (ex. temperate evergreen forest), what does this suggest?
the boreal forest is more productive per unit of biomass than the temperate evergreen forest
order the 7 ecosystems on VI from lowest to highest relative NPP
temperate evergreen
boreal forest
woodland/shrubland
tundra and alpine meadow
algal beds and reefs
estuaries
lake and stream
Which terrestrial ecosystem found on VI has the highest relative NPP?
lakes and streams
How does the availability of essential plant nutrients affect ecosystem productivity?
essential plant nutrients affect the rate of nutrient uptake, photosynthesis, and plant growth
How is NPP affected by soil nutrient availability?
increase in soil nutrient availability = increase in NPP
What example was provided to show that NPP increases with soil nutrient availability?
forest on Blackhawk Island, Wisconsin
with increasing mineralization of nitrogen (increasing soil nitrogen availability), the number of primary producers increases = increasing NPP
How could we measure the mineralization of Nitrogen in the soil?
create a transect for the primary producers in the area of interest
collect soil samples from each quadrat
create a microcosm with N15 isotope and NH4+
use mass spectroscopy to follow the % of N15 and graph
where the graph plateaus, mineralization is occurring
What theory does the Blackhawk Island, Wisconsin, study provide evidence for? Explain
Liebig’s Law of the Minimum
that nitrogen is the limiting element in soil systems because aboveground productivity increases as nitrogen availability increases
What else increases with increasing soil nitrogen availability?
organic matter
Will a recently burned forest have higher or lower nitrogen mineralization?
lower
What is PAR?
photsynthetically active radiation
In aquatic systems, how is photosynthetically active radiation affected by water depth?
PAR declines exponentially with water depth
How is the rate of photosynthesis and GPP of phytoplankton affected by PAR?
photosynthesis and GPP of phytoplankton are highest when PAR is at an intermediate level
How is respiration affected by water depth?
it’s not really affected, it stays relatively constant regardless of depth
What is the compensation depth?
When GPP is equal to respiration, NPP = 0
Above this depth, phytoplankton are productive and can do photosynthesis, live, grow, reproduce
below this depth, phytoplankton cannot photosynthesize
Of the 3: Nitrogen, iron, and phosphorous, which had the greatest impact (ie., which is most limiting) on marine phytoplankton in terms of growth rate? Which also had a high effect?
nitrogen had the largest effect on growth rate of marine phytoplankton
secondly, iron had a fairly high effect
How can growth rate be measured in marine phytoplankton?
measuring chlorophyll a (related to biomass)
What happens to growth of marine phytoplankton in high nutrient, low chlorophyll areas (HNLC)?
ex. Northeast Pacific
where iron is the limiting nutrient instead of nitrogen, iron can have a larger influence on growth rate
How does the effect of phosphorous on marine phytoplankton growth change when looking at marine environments as a whole vs as individual ecosystems?
When looking as a whole, it appears that phosphorous has no effect on growth rate
when looking individually, phosphorous can be limiting and have a higher effect on growth rate (ex., coastal, oceanic)
but overall, it has little impact
Globally, where is the highest NPP? The lowest? why?
highest = coastal regions because these are areas where nutrients are leaching from the land / terrestrial ecosystems via rivers and streams
lowest = open ocean because there’s a lower input of nutrients
In aquatic ecosystems, what are the major controllers of NPP?
light and nutrient availability
Why do shallow waters have higher NPP than open ocean?
the amount and frequency of nutrients that can be transported from sediments at the bottom to the surface is much greater due to waves and tides
What are 2 constraints on NPP in freshwater ecosystems?
solar radiation = light intensity and temperature are related
nutrient availability = when phosphorous is excessive, there’s high NPP
How does increase in phosphorous effect NPP in lake ecosystems?
increasing phosphorous = increasing NPP
ex. Northern temperate lake study = increase in summer chlorophyll a with increasing phosphorous
How may the NPP of a stream system be effected in the summer months?
when light availability is limited due to the leaf canopy cover of the stream, the light levels are reduced enough to limit production over the summer months
In stream ecosystems, which of the 2 restraints was more limiting of NPP in the summer?
light availability = greater canopy coverage blocks light availability in the stream = lower NPP
In stream ecosystems, which of the 2 restraints was more limiting of NPP in the fall?
canopy is open in the fall and the light levels can increase, so now the limiting factor is the nutrient availability
Under what conditions are the greatest increases of NPP observed in stream ecosystems?
when light and nutrient levels were increased
What is an autochthonous ecosystem?
an aquatic ecosystem that produces its own source of organic carbon
How is organic carbon produced in an autochthnonous ecosystem?
through photosynthesis by photoautotrophs (plants, algae, phytoplankton)
What is an allochthonous ecosystem?
an aquatic ecosystem in which the organic carbon is produced outside the ecosystem
How is organic carbon produced in an allochthonous ecosystem?
inputs of dead organic matter from nearby terrestrial environments (consider the phytochemical landscape of plant secondary metabolites)
What forms of organic matter can be used as organic carbon source in allochthonous ecosystems?
either dissolved (DOM) or particulate (POM
Describe the trend of allochthonous organic matter contribution to smaller streams –> larger rivers
allochthonous OM makes up a large component of the OM in smaller streams and then decreases as the size of the system increases (small contributions to large river)
ex. a small stream will have more canopy cover = leaf drop and more of the surface area will be overlapping with the terrestrial environment
Describe the trend of autochthonous organic matter contribution to smaller streams –> larger rivers
autochothonous OM has much smaller contributions to smaller stream systems than to larger rivers
larger river systems receive less OM from external inputs and more is produced by the organisms within the system
What are contributors of autochthonous organic matter?
phytoplankton
attached algae (periphyton)
macrophytes
Which types of aquatic systems do the contributors of autochthonous OM (phytoplankton, periphyton, macrophytes) contribute most to?
periphyton and macrophytes contribute more to smaller sized stream systems than larger
phytoplankton contribute significantly more to larger river systems than smaller streams
What are periphyton?
algae that grow on rocks and the bacteria that grow with them (biofilm)
What is biofilm?
the bacteria that grows with periphyton (algae that grow on rocks)
what are macrophytes?
plants in aquatic ecosystems that have their roots underwater
usually exist at the edges of terrestrial/aquatic environments
ex. cattail, sagittaria
In a lake ecosystem, what determines the importance of the internal vs external carbon sources?
the size and shape of the lake: the smaller a lake is, or the less smooth the edges are, the higher contribution the external inputs may be
the surrounding terrestrial environment (catchment) - nutrient levels, types and abundance of primary producers
what’s a catchment?
the terrestrial environment that surrounds a lake
What type of feedback system is plant growth?
positive feedback system
How is the net carbon gain and plant growth affected by the allocation of carbon by a plant to photosynthetic vs non-photosynthetic tissues?
If the plant allocates more carbon to photosynthetic tissues such as leaves than the nonphoto tissues, the net carbon gain and plant growth will be higher
Explain how the NPP (measured by average standing biomass) has an inverse relationship with Relative NPP
when NPP is high, RNPP is low and vice versa
this reflects the lifespan of the primary producers and how NPP is measured (annually)
ex. a temperate forest like the CDF will have a very high standing biomass and NPP, but the relative NPP is low because most of the biomass is allocated to longer term structures like branches and stems than leaves
whereas,
in a temperate grassland (ex. bunchgrass in Kelowna), the standing biomass is much lower, but the RNPP is higher than the CDF because grasses have a higher relative growth rate than trees
How does the inverse relationship between NPP and RNPP present in marine ecosystems? How does this compare to terrestrial?
primary producers in terrestrial ecosystems usually have longer lifespans than the time period for measuring NPP (annually) so the RNPP is quite low
whereas, in marine ecosystems, phytoplankton have a lifespan of weeks and multiple generations can contribute to the NPP
generally in marine systems, the standing biomass is low compared to the RNPP
ex. open ocean is 42.3 g/g/yr RNPP vs temperate forest RNPP = 0.04 g/g/yr
T or F: primary production does not vary depending on ecosystem age and the time
false, it varies with both
Why can seasonal variation cause changes to primary productivity?
some regions are cold in the winter and hot in the summer
some have wet and dry seasons
these variations in temperature and moisture will effect the NPP of a system over the year
How do cold and dry conditions affect plants?
the plants can become dormant and conduct very little or no PP
Describe the seasonal variations of a forest ecosystem in terms of productivity
0 PP in the winter months from Jan-April
dramatic increase of PP in May and stays quite high with gradual decrease and sudden drop off in October
0 PP from November-April/May
How can seasonal variations affect the NPP of a system over time (years)?
some years may be hotter/colder or drier/wetter than previous years which will cause annual variations in NPP
Explain decadal NPP and how NPP can change over longer periods of time
decadal NPP graphs show the ecosystem’s NPP production over the course of decades
generally there’s a low NPP > a gradual increase > a peak > a drop off
based on ecosystem succession
ex. there’s a disturbance to a forest ecosystem (clear cutting, fire, etc), so pioneer species like alder begin growing = small NPP
more species move in and maybe outcompete some of the alder and produce higher NPP
eventually the forest may reach its climax stage where there’s high NPP
another disturbance may occur, causing NPP to decrease
What is the longest ongoing experiment in ecology and agriculture?
the grassland study at Rothamsted Experimental Station in England, founded by John Lawes
What did the Rothamsted grassland study show about how seasonal variations in moisture and temperature affect the NPP?
periods of hot and dry weather = low PP
periods of cool, wet weather = high PP
How does the seasonal variation in temperature and moisture affect forest ecosystems differently than grasslands?
forests had low/no NPP in cold, winter months
grasslands had high NPP in cooler, wet months
forests had higher NPP in warmer summer months
grasslands have lower NPP in warm, dry summer months
How can NPP vary with stand age in forest ecosystems?
woody vegetation like trees and shrubs can have long life spans and will allocate carbon and energy to different structures at different life stages
when energy isn’t allocated highly to photosynthetic tissues, there will be less NPP
In a young forest with many saplings, will the NPP be higher or lower than an older forest with more established trees? explain
higher, more of the plant’s energy and biomass will be dedicated to growth which relies on photosynthesis and PP
as a tree grows, less of its biomass is in photosynthetic structures like leaves, more of it is in stemwood for maintaining structure and energy will be put into lignin instead of cellulose
What limits secondary production?
primary productivity
What happens to all the primary productivity in an ecosystem?
herbivores or detritivores will consume almost all of it
What happens to the energy from primary productivity when its consumed by herbivores or detritivores?
some of it is assimilated in the body
- metabolism, heat
- maintenance (getting food, performing work like muscle contractions, repairing organism’s body)
some of it is excreted from the body as waste (feces, urine)
some of it is used for production:
- new tissues
- reproduction of offspring
Why is the excretion of energy via feces and urine by secondary producers important?
key in nutrient cycling
these can be substrates for other organisms to grow on or consume
define secondary production/productivity
the net energy allocated to production in heterotrophs
how is secondary productivity measured?
the heterotroph biomass over a period of time (g/unit area/unit time)
When is secondary production the highest?
when a population’s birthrate and individual growth rate are highest
Describe the relationship between herbivore consumption and NPP in terms of energy transfer
generally, as NPP increases, the herbivore consumption increases as well and at a fairly large rate (1:10 ratio), fairly efficient energy transfer
Describe the relationship between herbivore biomass and NPP in terms of energy allocation. How does this compare to how much herbivores consume? what does this mean?
generally, as NPP increases, herbivore biomass increases but at a smaller scale (1:1000) than how herbivore consumption increased with NPP (1:10)
this means that though herbivores are consuming a lot of PP, not much of it is being assimilated into biomass
Describe the relationship between herbivore SP and NPP in a terrestrial environment. How does this compare to aquatic systems?
In both systems, as NPP increases, the SP also increases but at different scales
in terrestrial systems, the increase in SP requires a significantly larger NPP (1:10000)
in aquatic systems, the increase in SP requires much less NPP input (1:10)
What type of control on energy flow is observed in aquatic and terrestrial ecosystems where the increase of NPP increases SP?
bottom-up control energy flow
Describe bottom-up control of energy flow
When secondary productivity and the heterotroph populations are controlled by primary productivity and the autotroph populations
Describe top-down control of energy flow and the “world is green” hypothesis
predator populations keep herbivore populations in check so the plant biomass increases
Why are top-down controls important in a lot ecosystems?
NPP is influenced by both abiotic conditions and herbivore population control by predators
trophic cascades = control community structure and NPP
What is assimilation efficiency? How is it calculated?
the consumer’s ability to acquire and assimilate energy from the food it consumes
A/I
How much energy is assimilated into the gut divided by the amount of food ingested by the consumer
What is production efficiency? how is it calculated?
how efficiently the energy that the consumer has assimilated is incorporated into secondary production
P/A
assimilated energy used for production / the energy that has been assimilated
Describe the basic flow of energy when a secondary producer consumes food?
food is ingested (I)
ingested food can be assimilated into the gut (A) or
excreted as waste (W)
assimilated energy can then be either
used in respiration (R) or
used for production (P)
How do mammals compare to insects in terms of production efficiency (the amount of assimilated energy used for production / the amount of energy assimilated)?
mammals have significantly lower production efficiency than insects do
What’s a food chain?
the series of steps for how stored energy from autotrophs is transferred through the ecosystem
What are trophic levels?
one trophic level = all the organisms that acquire energy in the same number of steps from autotrophs
the feeding relationships in an ecosystem have different levels
basically who eats what/who
ex.
primary producers > eaten by primary consumers (herbivores) > eaten by secondary consumers (ex. foxes) > eaten by tertiary consumers (apex predators, ex. lions)
How are the grazing food chain (trophic) and the detrital food chain linked?
primary production
the primary producers in the grazing food chain still produce the energy that can become organic matter and eventually detritus or dead organic matter to be used in the detrital food chain
the waste produced by the grazing food chain is consumed in the detrital food chain
what’s the main difference between the grazing food chain and the detrital food chain?
the energy source
grazing uses NPP from living biomass
detrital uses dead organic matter
What type of organism makes food chains more complicated? why?
omnivores because they can occupy more than one trophic level
ex. bears can be primary consumers because they eat plant material, but they are also secondary/tert consumers because they eat other animals
How are the major feeding groups (autotrophs, herbivores, carnivores) in a food chain categorized?
based on their energy source
autotrophs: CO2
herbivores: primary producers (cellulose)
carnivores: herbivores
How are the feeding groups linked to each other in a food chain?
by the flow of energy
Describe the grazing food chain?
based on NPP in the form of living plant biomass as the source of energy for herbivores
Describe the detrital food chain?
based on dead organic matter/detritus as the energy source for the decomposers
ex of organisms: snails, millipedes, earthworms, fungi, bacteria
explain how the grazing food chain is unidirectional
primary producers convert energy from the environment into chemical energy
primary producers are consumed by herbivores or die and become detritus
herbivores either die and become detritus (energy enters detrital food chain) or are consumed by carnivores
carnivores die and become detritus
unidirectional because energy cannot be transferred back to primary producers at any stage of the energy flow, it only moves forward
explain how the detrital food chain is not unidirectional
either primary producers, herbivores, or carnivores die and the organic matter becomes detritus
detritus is consumed by decomposer herbivores
decomposer herbivores either die and become detritus or are consumed by carnivores
carnivores die and become detritus
not unidirectional because at any stage, the energy can be returned as detritus (base of the food chain)
How can the 2 food chains overlap at higher levels?
carnivores from either food chain can consume herbivores from either food chain
What are the major processes involved in secondary production?
consumption
ingestion
assimilation
respiration
production
What happens to the energy assimilated between trophic levels?
some lost to respiration
some goes to production which can be transferred to the next trophic level
What determines the pathway of energy flow through food chains?
consumption efficiency
In open-water aquatic ecosystems that have algae/phytoplankton as dominant PP, what trophic level has the largest influence on energy flow?
grazing herbivores
energy transfer in the form of primary production removed by herbivores is most efficient in ecosystems dominated by algae
Explain how energy transfer efficiency is affected in ecosystems where aquatic macrophytes (ex. cattail) are most dominant
more observations of lower % of primary production being removed by herbivores = energy transfer is less efficient
Explain how energy transfer efficiency is affected in terrestrial ecosystems
more observations of low % of primary production being removed by herbivores = energy transfer is least efficient
How does herbivore consumption efficiency compare in a deciduous forest vs a grasslnad?
deciduous forests may have more biomass but the herbivore consumption efficiency is significantly lower than in grasslands
How does predator consumption efficiency compare in a deciduous forest vs a grassland?
a deciduous forest ecosystem had higher predator consumption efficiency than grasslands, but the difference was not as significant as in herbivore consumption
T or F: energy flow patterns in flowing water ecosystems are very different from those in terrestrial or still water ecosystems
true
Do moving water ecosystems have high or low NPP?
very low
Describe the relative importance of the two food chains in stream and river ecosystems
grazing food has minor impact
detrital food chain is dominant
What is the general ecological rule of thumb for the amount of energy that is transferred between trophic levels?
10% of stored energy in the form of biomass is transferred to the next trophic level and converted to biomass
ex. herbivores eat 1000 kcal of plant energy
~100 kcal converted into herbivore tissue
~10 kcal converted into first-level carnivore tissue
~1 kcal converted to second level carnivore tissue
What is trophic efficiency? how is it calculated?
the transfer of energy between trophic levels
ie., the ratio of the productivity in one trophic level to the trophic level that is beneath it
TE = Pn (productivity of carnivores) / Pn-1 (productivity of herbivores)
How did Daniel Pauly help describe the 10% transfer energy?
he looked at ~140 trophic interactions and found that majority of systems had 10% transfer efficiency
Why is the concept of transfer efficiency important in fisheries?
can be used to inform models of resources to determine for example how much fish will be produced and what’s limiting
What is a key consequence of the decreasing energy transfer from one trophic level to the next?
the standing biomass in the form of individual organisms decreases with each level (biomass pyramid)
ex. there can be a huge number of primary producers and very few high level predators - the amount of energy in the system can only support so many high level predators
Describe a biomass pyramid
each level in the pyramid represents the standing biomass in each trophic level
Generally which end of the pyramid is the largest? why?
usually the base is the largest and the pyramid gets smaller with each successive level
because the 10% energy loss can only support so many organisms in each trophic level
explain why some ecosystems have an inverted biomass pyramid
ex. English channel aquatic system has smaller number of primary producers than consumers
this happens because the pyramid doesn’t include the lifespan of the organisms - primary producers (phytoplankton) have a much shorter lifespan than the zooplankton so zooplankton can have a higher intake of the phytoplankton = supports more consumers
