Eutrophication Flashcards
eutrophication is the process of _____ enrichment, increased production of ____ ____, and subsequent ecosystem ____
nutrient
organic matter
degradation
What is eutrophication?
Excessive plant and ____ growth due to the increased availability of one or more ____ ____ _____ needed for photosynthesis (____ production)
algal
limiting growth factors
primary
what’s the #1 symptom of eutrophication?
primary production (excessive growth)
T/F
eutrophication happens in aquatic systems, not on land
false
can happen on land, although not common (more common in aquatic systems)
What is cultural/ anthropogenic/ artificial eutrophication?
List 3 sources
increases in plant & algal growth due to anthropogenic nutrient inputs
- sewage
- fertilizer runoffs
- phosphorous-containing detergent (pre-1970’s)
Eutrophic = ___ productivity
Oligotrophic= ____ productivity
Mesotrophic= _____ productivity
high
low
moderate (meso=middle)
- nutrients here higher than limiting level
What are the 4 requirements for photosynthesis (primary production)
- light
- nutrients (N, P, etc)
- water
- CO2
- any of these can be the limiting factor in an ecosystem
What term does this describe:
Certain ecological functions are controlled by whichever enviro factor is present in the least supply relative to demand
Liebig’s Law of the Minimum
ie Principle of Limiting Factors
List 5 things that can be limiting factors
- water
- light
- nutrients
- CO2
- biotic factors (predators, competition, etc)
*note #1-4 are the requirements for primary production
the most limiting factor determines the ___ ___
yield potential
what’s the main limiting factor in freshwater?
In terrestrial ecosystems?
freshwater- phosphorous
*majority of P is found in rocks
terrestrial- Nitrogen
The forms of P in surface water strive for chemical _____
Describe P retention by sediments
equilibrium
dissolved P in water –> biomass P (eg in a fish) –> fish dies and releases its P in the bottom sediments (sediment P)
(this is a cycle and it takes a very long time)
a whole-ecosystem experiment in the Antarctic Ocean determined that __ can be a limiting factor in the ocean
iron (Fe)
what were the effects of adding iron to the ocean?
- reducing the availability of atmospheric CO2 (more goes into ocean)
- increases ocean pollution (more dissolved CO2) and little effect on atmospheric CO2
- this happens b/c phytoplankton produce more (removes CO2 from surface water, but that’s constantly replaced by atmospheric CO2)
Research at ELA in 1960s-80s looked into which nutrients are limiting. Which 3 nutrients did they look at?
Why did they do these experiments?
P
C
N
these experiments were in response to eutrophication of lake eerie in 1950s
explain the experiment that occurred at ELA Lake 227
Lake 227 was an oligotrophic (nutrient poor) lake, which they added P to. After the P additions, the lake quickly became nutrient rich (eutrophic)
Using ELA Lake 226, how did they confirm that P was what caused Lake 227 to become eutrophication?
Lake 226 was divided into 2
- in one half, nitrogen and carbon were added
- in the other half, nitrogen, phosphorous, and carbon were added
Only the half that contained P became eutrophic, the other half remained oligotrophic (C and N don’t have an effect)
T/F
experiments in ELA lakes 226 and 227 caused ban P use in detergents
true!
T/F
there is no clear consensus on how to address eutrophication
true :(
explain top-down vs bottom-down controls on primary production
Top-down controls: herbivores are in control of primary production (production of grass for ex)
Bottom down controls: nutrients, light, water, etc are in control of primary production
A lake has the following trophic cascade:
Piscivore (top predator)
Planktivore (predator)
zooplankton (herbivore)
phytoplankton (autotroph- algae)
How does the presence of the top predator decrease eutrophication?
Piscivore (top predator) feeds on the planktivore. So, there are fewer planktivore to feed on zooplankton, causing an increase in zooplankton.
These zooplankton feed on phytoplankton, causing a decrease in phytoplankton, meaning that there is less algae in the lake (no eutrophication!)
The opposite is true without a top predator= more phytoplankton= eutrophication
In a eutrophic lake, the bottom becomes deoxygenated. What would be the effect on a fish species that is undergoing speciation (one species in surface waters, one in deep waters)
They’ll undergo reverse speciation!
The species living in the deep water will move up to access the higher oxygen waters. But, that’s where the other species is, and they will start to interbreed again. Eventually, the speciation is fully reversed and you’re left with just one species again
a natural (____) aquatic system has:
- natural ____
- few ____ and few phytoplankton
- lots of _____
pristine
vegetation
nutrients
predators
A ____ aquatic system has many stressors.
List 5
developed
agriculture
cottages
sport fishing
high nutrients
few predators
T/F
a cyanobacterial bloom limits light penetration, smells bad, and is non-toxic
false
TOXIC!
does smell bad and does limit light penetration
why is eutrophication predominant in the west end of Lake Eerie?
lots of rivers come in on this side- they bring in lots of nutrients from agricultural runoff
T/F
1. the algal bloom of 2015 in Lake Eerie ended in 2018
- the middle of Lake Eerie suffers the most from oxygen depletion because it is the deepest
- false- it’s still happening :(
- true- surface waters have sufficient oxygen
hypoxia occurs when water concentration is less than __ mg/L
2
extreme loss of oxygen
___ ___= hypoxic areas in aquatic ecosystems, typically a consequence of pollution, eutrophication, and high rates of decomposition, that are essentially devoid of life (can’t support most organisms)
dead zones
extreme loss of oxygen :(
anoxic=
0mg/L of oxygen- no oxygen at all!
explain how a hypoxic zone forms
- nutrients enter the lake
- these nutrients cause an algal bloom
- these algae eventually die and sink to the bottom
- bacteria decompose the algae, respiring and consuming oxygen
- the temp. stratified water prevents the cold, dense, oxygen-depleted water at the bottom from mixing with the warmer, oxygenated upper water
explain how a dead zone forms in the gulf of mexico (marine example)
- during the spring, warm, oxygenated freshwater from the Mississippi river pushes the colder saltwater down (cuts off contact with atmospheric oxygen)
- nutrients cause an algal bloom. When they die, they sink to the bottom and use up the oxygen in the deeper water as they decompose
- the deeper water become oxygen-deprived, and doesn’t have contact with any oxygen to replenish= becomes a dead zone (organisms avoid this zone or die in it)
- in the winter, the freshwater is colder, so mixing is possible and this problem doesn’t occur. But it’ll happen again in the spring
There are over ___ dead zones across the world, mostly around ___
400
coasts
The root of the dead zone problem in the gulf of mexico is:
the huge watershed of the Mississippi river
- tons of fertilizers used, agricultural runoff, etc- they end up in the river and then in the gulf
T/F
dead zones can occur in both marine and freshwater
true
HABs=
harmful algal blooms
cyanobacteria=
“blue-green algae”
= a phylum of bacteria that can photosynthesize (not actually algae)
Some cyanobacteria produce toxins called ___
- List 3 different types and what they impact
cyanotoxins
- neurotoxins- damage the brain
- hepatotoxins- cause liver damage
- dermatoxins- cause skin irritations
_____= the most common bloom-causing cyanobacteria. Can produce both neurotoxins and microcystins (a type of ___)
microcystis sp.
hepatotoxins
Nodularia sp. produces potent ____ called nodularins that can greatly harm humans
hepatotoxins
what’s the most likely exposure fof all kinds of microcystins?
digestion (in our water, etc)
