Unit 2 - Food Webs & Trophic Levels, Apex Predators, & Marine Pollution Flashcards
definition: theory that suggests choosing prey that maximize net energy GAIN
optimal foraging theory
What 2 prey of otter have very low, constant frequencies in the habitat, which explains why they are less frequent in sea otters’ diet?
cancer crab & red abalone
When there was a drop of Red Sea urchins making up 8% to 1% of the environment, what happened to the frequency of kelp crab in diet?
went up
Kelp crab are ______ frequent in the habitat compared to Red Sea urchin, cancer crab, and red abalone.
very
Sea otters eat everything at a higher rate than in environment except what?
kelp crabs
Even though they have a high frequency, sea otters tend to ignore ______.
kelp crabs
Urchin frequency in diet and ecosystem _____ significantly.
drops
What two species do otters always prefer, but they are rare? What does this lead to?
abalone and cancer crab; they in turn eat a lot of urchins until they become rare
Once urchin population become rare, who do sea otters have to turn to?
clam & kelp crab
definition: switching to the next best prey item when a preferred item becomes rare (energetically more costly) (ex: cancer crabs > abalone > urchins > kelp crabs
prey switching
What do arrows represent in a food web?
energy flowing through a system
definition: where an organism is in the food chain / how far it is energetically removed from photosynthesis
trophic level
What are the producers in the Kelp forest ecosystem?
kelp, seaweed, and phytoplankton (plant plankton)
Where does the energy in a food web come from to begin with?
the sun–solar energy
Producers are on the _____ level of a food chain.
lowest
Primary consumers eat ______.
producers
What are some unique characteristics of phytoplankton?
-“Plant plankton”
-producers
-photosynthetic microorganisms
-microscopic algae
-contribute 1/2 of the world’s Oxygen
What are some unique characteristics of zooplankton?
-animal plankton or planktonic invertebrates
-eat phytoplankton or other zooplankton
-can be primary or secondary consumers
Energy loss (trophic efficiency):
-each step up in trophic level decreases energy by how much?
90%
Only ____% of energy is conserved as you go up a trophic level.
10
If there is less sun, what is the effect on higher trophic levels?
less upper-level organisms because there will be less energy reaching those upper levels
With more _____ energy at the bottom, we can support a lot more life & biodiversity at the top.
solar
Why is so much of the energy (biomass) lost as you go up trophic levels?
when converting energy forms, some energy is lost as heat/entropy
____ law of thermodynamics: energy can be transferred and transformed, but not created or destroyed
first
_____ law of thermodynamics: every energy transfer or transformation increases the entropy (disorder) of the universe
second
Where does all the biomass (energy stored in bonds) go when a caterpillar eats a leaf?
50% is eliminated in feces
35% is used for cellular respiration
15% is used for growth
Is all the energy incorporated by plants through photosynthesis available to the caterpillar?
No, only 10% of the energy is available to the caterpillar
What % of the plants eaten by a caterpillar would be useful to a bird that eats the caterpillar?
1%
How much % of calories in grain grown for livestock is assimilated by humans?
1%
How much % of crop calories are consumed by humans?
27%
Is eating meat or crops more efficient?
crops
What are two reasons that eating meat is better for the planet?
(1) reduced carbon emissions
(2) less land use
Does a veggie or meat burger require more energy to produce?
meat (animals eat more complex food so they need more energy to synthesize it)
When were otters hunted to near extinction in the West?
in the 1800s
After extinction in the early 1900s, when was the first otter population spotted in Big Sur CA?
1938
With sea otters, what does the ecosystem look like?
kelp forest
Without sea otters, what does the ecosystem look like?
urchin barren
What species on the normal kelp forest food web decreases without sea otters being present? increase?
extinction: abalones, larger crabs, larger fishes and octopus, sessile invertebrates, small herbivorous fishes & invertebrates, smaller predatory fishes and invertebrates
increase: sea urchins
decrease: drift algae & dead animals, kelp, planktonic invertebrates
What was the timeline for the switch from kelp forest to urchin barren?
1800s–> early 1900s
What are some unique characteristics of sea urchins?
-invertebrates
-related to sea stars (echinoderms)
-mostly herbivores
-spines for protection
-kelp is primary food source when available
definition: when changes at ONE trophic level have dramatic effects throughout a food web
trophic cascade
definition: an organism with an outsized influence relative to its abundance
keystone species
What is usually thought of as the “collapse” of an ecosystem?
trophic cascade
What makes sea otters a keystone species?
-its role as a top predator
-maintains healthy kelp forests and seagrass beds
Do keystone species have to also be predators?
no
What are some examples of keystone species?
wolves, bears, starfish, & elephants
In kelp forests, what organism is the keystone species?
sea otters
definition: an organism/predator at the top of the food chain
apex predator
Are sea otters apex predators?
yes
Even though kelp forests are diverse with high stability, what caused them to topple so fast?
removal of a keystone species
Why is a kelp forest preferable to an urchin barren?
-carbon sequestration
-vertical complexity
-biodiversity
-ecosystem stability
-economically important juvenile fish habitat (fish have better protection from predators in Kelp forest)
What is the process called where phytoplankton, which live on the warm, light-filled surface, suck CO2 out of the atmosphere for food?
carbon sequestration
With sea otters, what are the levels of kelp and urchins like?
kelp: very high
urchins: low
Without sea otters, what are the levels of kelp and urchins like?
kelp: very low
urchins: extremely high
Is there a continuum that exists between no kelp and tons of kelp?
not really
Urchin barren and kelp forest are examples of alternative _____ ecosystems?
stable
What concept states that ecosystems can have multiple stable modes that are difficult to transition out of?
alternative stable states
What are examples of alternative stable states?
-savannah and forest
-coral reef and algae
definition: ______ control: producer’s populations are limited by ABIOTIC factors (nutrients, climate disturbance)
bottom-up
definition: _______ control: producer’s populations are kept in check by herbivory & predators control herbivore populations
top-down
What type of control do kelp forests have? Why?
top down because urchins exhibit pressure on kelp (herbivory)
In the Sonoran desert, what type controls plant populations?
bottom-up –> plants are mostly likely dependent on the limiting resource of water in their soil
In what year do otter reintroductions start? And what happens to urchin barren?
1970s; reversal of alternative stable state back to kelp forest
What happens when a top predator is reintroduced like sea otters?
the population will grow and then stabilize at its maximum capacity in the 1980s and 90s along the CA coast
What happened after a century of recovery with sea otters?
they began disappearing again (especially in Alaska)
What was the main reason for otter reduction the 2nd time?
orca/killer whales
What was the main reason for otter reduction the first time?
overhunting
What demonstrated that the otter’s keystone role has been reduced or eliminated?
elevated sea urchin density and consequent deforestation of kelp beds
What are some pieces of evidence that implicate orcas as the reason for the decline in otters?
-decline of great whales from whaling, a common prey of killer whales, forced them to turn to other Marine animals
-sea otters are easy to catch and eat & only a small number of orcas are needed to greatly decreases sea otter populations
-no washed up sea otters
-no relocation of sea otters
-increased orca attack sightings
-only otter loss in the open ocean, not in protected lagoons
What is the preferred prey list for killer whales?
great whales–>harbor seals–>stellar sea lions–>sea otters
Why would orcas all of the sudden start eating more otters?
their preferred prey declined dramatically, so they prey switch
What led from kelp–> urchin barren from pre-19th century–> 19th century?
hunting of otters
When did otters recover after being hunted?
in mid to late 1950s
What led from kelp–> urchin barren again from the 1990s–> 2010s?
killer whales
What shows the structure–>function of ecosystems?
-number of trophic levels (structure) is related to the function of an ecosystem:
-3 trophic levels: kelp
-4 trophic levels (addition of orcas): no kelp
-5 trophic levels (to get rid of orcas): kelp
In an uncolonized habitat, what does the rate of colonization depend on?
mobility
In recently colonized sub-populations, what is the growth rate like?
very high
In long established subpopulations at carrying capacity, what is growth rate like?
population is regulated at local scales
When was direct evidence of orca responsibility released and how?
in 2020; a beached orca was found with 6 recently eaten otters in its stomach
What are the 3 main things involved in non-Carbon pollution?
(1) Heavy metals
(2) persistent organic pollutants (PCBs)
(3) nutrients (N & P)
Which pollutants (heavy metals) tend to accumulate in organisms over time?
Mercury (Hg) and Lead (Pb)
Which pollutants (persistent organic pollutants POP) tend to accumulate in organisms over time?
PFAs, PCBs, DDT
Where are POPs stored in the body? How are they passed on to offspring?
fatty tissue; through blood and breastmilk (particularly a big problem in mammals)
In what two ways can toxin accumulation cause excess mortality?
(1) trophic level
(2) age
definition: toxin build up in an individual as it AGES (only one species involved)
bioaccumulation
definition: toxin concentrations increase as you move up through TROPHIC LEVELS (different species involved)
biomagnification
Why does a young fish have less toxins than an older fish?
it hasn’t had as many chances to accumulate toxins; hasn’t ate as much other organisms yet
Can both bioaccumulation and magnification happen?
yes
Why do top predators of the food chains have more toxins than producers?
because the contaminants increase in concentration up the food chain
What are 3 examples of persistent chemicals that bioaccumulate or magnify?
mercury, lead, and PCBs
What do all of the fish that should be avoided during pregnancy because they have high mercury content have in common?
they are all top predators and higher up on food chain
What has been happening to orcas?
-increased juvenile mortality
-some populations are plummeting
-overfishing
-biomagnification
-whaling
Why do transient killer whales experience more juvenile mortality than resident pods?
they are higher up on food chain; exist at a higher trophic level = more toxins = more harm to offspring
What nutrients and fertilizers runoff from many sources into water? What will this do to an organism in the water?
Nitrogen and phosphorus; cause algal blooms and plant growth
definition: a process that results in EXCESS plant growth and eventually leads to the death & loss of animal life
eutrophication
Steps of eutrophication:
(1) _____ of excess nutrients from yards and farms
(2) _____ of nutrients causes aquatic plants and algae to ____
(3) ____ is released
(4) resources become ______ and algae reach _____ ______
(5) algae begin to ____ and _______
(6) ______ is consumed
(7) hypoxia or ______
(8) animals ____ or ____
runoff
pulse
oxygen
limited; carrying capacity
die; decompose
oxygen
anoxia
leave; die
In the decomposition process, bacteria will use up all the available _______.
Oxygen
What are some eutrophication solutions?
-reduction of fertilizer
-erosion control (no/low till agriculture)
-riparian river buffers–> keeping more vegetation surrounding waterways
What leads to the dead zone in the Gulf of Mexico?
the Mississippi River collecting nutrients and water from farms all over the middle of the US (eutrophication)
What is ocean acidification a result of?
increasing atmospheric CO2 (not climate change directly)
Ocean is a CO2 ______.
sink
What is the evil twin of global warming?
ocean acidification
Carbon dioxide from the atmosphere and water lead to the formation of what?
carbonic acid
What do organisms use to build their shells?
Calcium Carbonate
What do abundant healthy corals, mollusks, and other marine calcifies want?
carbonate ions for their shells
Why does carbonate level decrease with ocean acidification?
more carbonate molecules become bound up to carbonic acid molecules
What happens to the pH of water with ocean acidifcation?
drops
Small reductions in pH levels make it _____ for organisms to form Ca shells (shells become thinner & more brittle).
harder
What will happen to species is we remove plankton?
bottom-up trophic cascade
A collapse in plankton population would echo _____ the food chain.
up
What are the 2 main steps in ocean acidification?
(1) Ocean absorbs CO2 from the atmosphere, creating carbonic acid in waters.
(2) Carbonic acid (steals) carbonate needed by some marine organisms to build their shells.
What are some common shell building organisms?
coral, clams, urchins, mussels
What are 3 main steps in ocean acidification?
(1) CO2 dissolves in water releasing Hydrogen ions (H+)
(2) H+ and Calcium (Ca2+) compete for carbonate
(3) the excess H+ hogs the carbonate
How is it possible to have kelp forests without sea otters?
other keystone species such as sea stars (SUNFLOWER stars specifically)
Intertidal kelp ecosystems maintained by sunflower/sea stars are not able to support what?
otters
What were the main 2 things contributing to sea star wasting syndrome?
(1) climate stress
(2) bacteria
