Marine bio review
1. Compare and contrast the terms ecosystem services and ecosystem
function. Describe 3 ecosystem functions that coral reefs, oyster reefs and
salt marshes have in common. For each function mentioned, list a
corresponding service.
Ecosystem Service: The benefits that ecosystems provide to humans, both directly and indirectly such as food, water, fiber, and fresh air.
Ecosystem Function: The physical, chemical, and biological processes that occur within an ecosystem.
Three functions in common:
Provide habitat structures for other organisms, which is an ecosystem function.
The structures they form help protect shores from storms and erosion, which is an ecosystem service. (shoreline stabilization)
Support multi-trophic level food chains through which nutrients and energy flow.
people can then eat various organisms from these food chains. (nutrient cycling)
Filter the surrounding water
cleaner waters for humans
2. What are the 5 most important biological lessons you learned during the
course and why?
3. Describe how incorporation of positive interactions into restoration design
of mangrove or salt marsh plants could increase yield of those
conservation projects. Give 3 examples for each foundation species.
Incorporating positive interactions into the restoration design of mangrove or salt marsh plants can help
increase the growth and resilience of salt marsh plants and cordgrass
create positive feedback loops that provide increasing benefits to the foundation species over time.
Salt Marsh:
Shellfish: (oysters and mussels)
provide nutrients to marsh grasses
decrease sulfide stress
filter water
increase marsh resistance to drought. Cordgrass in turn provides a habitat for mussels and reduces heat stress.
Blue Crab: Blue crabs
feed on periwinkle snails that graze on marsh grasses - promote the health of salt marsh plants
slow nitrogen depletion in salt marsh communities
provide a habitat for blue crabs and sources of nutrition
Fiddler Crabs and Mycorrhizal Fungi:
fiddler crabs increase oxygen in marsh sediments by burrowing
aerate the soil and allow the flow of oxygen
acilitate the growth of microbes and mycorrhizal fungi
fungi that grow on cord grass roots extend into the soil and promote nutrition absorption
4. Using graphs and words describe alternative stable states and define
hysteresis. Draw and describe 2 graphs of urchin (as stressor) and kelp
abundance showing (1) no hysteresis and then (2) large hysteresis in kelp
decline-recovery dynamics.
Alternative stable states:
An ecosystem can exist in multiple distinct, self-sustaining states under similar environmental conditions, with the ability to transition between these states depending on the intensity of a disturbance or stressor, often with a tipping point separating them
Hysteresis:
phenomenon where an ecosystem does not readily return to its original state even when the stressor is reduced to its previous level, resulting in a "lag" in recovery, requiring a significantly lower stressor level to revert back
Graph 1: No Hysteresis in Kelp-Urchin Dynamics
[Image: A graph with urchin abundance on the x-axis and kelp abundance on the y-axis. The line is a smooth curve, indicating a gradual decline in kelp abundance as urchin density increases, with a relatively smooth transition back to high kelp abundance when urchin density decreases.]
Explanation: As urchin density increases, kelp abundance gradually declines, and when urchin density decreases, kelp abundance smoothly recovers, following the same trajectory in both directions. This indicates no hysteresis; the ecosystem readily reverts to its original state with decreasing stressor levels.
Graph 2: Large Hysteresis in Kelp-Urchin Dynamics
[Image: A graph with urchin abundance on the x-axis and kelp abundance on the y-axis. The line shows a sharp decline in kelp abundance at a critical urchin density threshold, followed by a much lower urchin density threshold required for kelp recovery, creating a large "hysteresis loop".]
Explanation: When urchin density increases past a critical threshold, kelp abundance rapidly declines to a low level. Even when urchin density is reduced, kelp cannot recover to its previous abundance unless urchin density is significantly lower than the initial tipping point, creating a large hysteresis loop. This indicates a distinct alternative stable state where the kelp-dominated system has transitioned to an urchin-dominated one with difficulty returning to the previous state.
5. Describe and name 3 oceanographic processes that drive massive
anchovy fisheries off the west coast of the Americas in the temperate
zone. Describe and name the oceanographic process that can shut those
processes down and lead to fishery collapse.
Upwelling:
water from the deep sea makes its way to the surface.
winds blow North along the West coast
surface water moves away and water from the depths moves upward
nutrient-rich
full of phytoplankton
food for the anchovy fish.
Higher water temperatures:
warmer water naturally holds less dissolved oxygen
which is crucial for aquatic life like anchovies to survive
the southern part of the anchovy range may become uninhabitable
ANOTHER?
El Nino:
climate fluctuation that happens 3-7 years
reduces trade winds and upwelling
warmer waters hold less oxygen which influences whether anchovies are able to live in the environment or not\
lack of oxygen is also known as hypoxia.
6. Define the three types of ecological succession. Which one typifies salt
marsh succession and systems represented by alternative stable states?
Facilitative: Where species A has a positive effect on species B and then species B has a negative effect on species A and out competes it. Ex: Spartina stabilize and make salt marsh more habitable, and then sea lavender comes in as secondary species and then outcompetes spartina.
Tolerance: When species A gets there, changes the environment, and, while having a negative effect on species B, has a greater negative effect on itself. Ex: Pine creates a lot of shade, and neither oak nor pine trees grow better in shade, however oaks are more tolerant of shade than pines are.
Inhibition: Inhibition is where whoever gets there first wins. Ex: In areas where bryozoans are established first, tunicates and sponges cannot grow there.
Facilitative succession typifies salt marsh succession.
7. (A) What is ecological succession? How does this contrast with zonation?
(B) Define and contrast the three types of succession as defined by
Connell and Slayter and describe an example of each. (C) Design a
manipulative experiment to examine the impacts of pioneering plant
species on later plant colonizers during succession in mangrove forests.
What are your independent variables? What is your response or
dependent variables?
8. Define fundamental and realized niche. What role does competition play
in the development of these terms? Now use schematic diagrams and
words to show how positive interactions should modify the original theory
behind the fundamental and realized niches.
fundamental niche:
full range of environmental conditions under which a species can potentially survive and reproduce (assumes no competition)
realized niche:
narrower set of conditions a species actually occupies in a given environment (competition)
#1 [Image: A large oval representing the "fundamental niche" with a smaller oval inside, representing the "realized niche" with a dotted line indicating the boundary.]
#2 [Image: Same as above, but with additional small circles overlapping the realized niche, representing positive interactions like mutualism or commensalism, which expand the realized niche beyond the original boundary.]
Positive Interactions Modifying the Theory:
Mutualism: When two species benefit from each other's presence, it can expand the realized niche of both species by providing access to new resources or protection from predators.
Commensalism: When one species benefits from the presence of another without significantly affecting the other, it can also lead to an expansion of the realized niche. For example, barnacles living on the skin of whales gain access to food and transportation without harming the whale.
9. a) What is the Coriolis effect? b) How is it generated? c) How would the
Coriolis effect impact a giant swarm of krill floating in body of oceanic
water moving 500 miles from East to West vs. one moving 500 miles
South to North in the Northern Hemisphere? Describe an Ekman spiral
and the processes that created it. Why is the Ekman spiral important for
the ability of zooplankton to control their movements?
(a) The Coriolis effect is an apparent deflection of moving objects, like wind or ocean currents, that occurs due to the Earth's rotation, making them curve to the right in the Northern Hemisphere and to the left in the Southern Hemisphere
(b) Because the Earth rotates on its axis, circulating air is deflected toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere.
(c) A swarm of krill moving South to North in the Northern Hemisphere would tend to float to the East, whereas krill moving East to West would float to the North.
(d) An Ekman spiral is a spiraling pattern of water movement in the ocean, where each layer of water moves at a slightly different angle and speed due to the Coriolis force, creating a helical pattern that extends downwards from the surface when wind pushes on the water
Zooplankton because it allows them to
utilize different water layers to access food
avoid predators by moving vertically within the spiral
10. Why do salt marshes dominate the intertidal zone on the East Coast of the
US, while rocky shores dominate the West Coast? How does this impact
the distribution of fiddler crabs?
minimal wave action due to the shallow depths and very far-reaching continental shelf
continental shelf is much closer on the West Coast
wave action is stronger
sediment is not able to accumulate
rocky shores are best equipped to withstand it.
The lack of salt marshes on the west coast limits the geographic range of fiddler crabs compared to east coast range stretching all the way to Massachusetts
11. Compare and contrast how acidification, increased nutrient loading, and
overfishing might impact coral reefs.
Acidification:
hurts both oyster reefs and seagrasses.
Oyster:
dissolving of their calcium shells -> decreased survival;
then release their calcium carbonate—an alkaline salt that buffers against acidity.
Seagrasses:
through their absorption of carbon are able lower the amount that can react with water reducing the amount of carbonic acid produced.
Increased nutrient loading
can be detrimental for seagrasses and oysters
Extra nutrients in the water increases the amount of algae which can outcompete seagrasses for light
As nutrient levels increase so do algae and bacteria who can use up available oxygen
creating a hypoxic environment that oysters can not compete in.
Overfishing
detrimental for seagrasses (trophic cascade)
small fish populations increase
eat more of the mesograzers
can not longer keep algae blooms at bay
declines in spat (juvinile oyster) survival
Blue crabs and toadfish scare mudcrabs and keep them from openly hunting in oyster habitat
By keeping them in cracks and crevices oyster spat have an increased survival.
12. Describe in detail what happens when corals bleach in response to
temperature stress, and how they could recover.
13. Define trophic cascade and food chain length. How can changes in food
chain length affect the outcome of a trophic cascade? Compare and
contrast the mechanisms and end results of the trophic cascade in rocky
shores as described by Bob Paine and in salt marshes as described by
Silliman and Bertness.
Trophic cascade: indirect interactions between species starting with predators and cascading to lower levels.
the decline of the top predator can lead to mesopredator release, resulting in overpredation of the grazers by the mesopredators.
Food chain length: is the number of links from the bottom of the foodweb to the top of the food web.
In longer food chains, the trophic interactions and cascades can be quite complex.
odd numbers of trophic levels lead to higher levels of primary producer biomass with larger populations of top predators (Otters -> Urchins -> kelp)
even numbers of trophic levels lead to lower levels of primary producer biomass with larger top predator biomass (Sharks -> grouper -> reef grazers -> algae).
Paine removed Pisaster (a keystone, predatory sea star) from a section of the rocky intertidal. Pisaster normally preys on mussels and barnacles, but with Pisaster removed, the mussels were able to flourish and out compete the overwhelming majority of other organisms for space, which is one of the key limiting factors in the rocky intertidal. As a result, species diversity without Pisaster declined from 15 to 8. Benthic algae, chiton, and limpets were unable to exist in areas without Pisaster due to lack of appropriate food and lack of space. Removing Pisaster also decreased anemone density and messed up the sponge-nudibranch food chain, demonstrating indirect effects of Pisaster removal. Similarly Silliman and Bertness conducted predator exclusion experiments and also tethered snails by gluing a small piece of fine nylon line to adult Littoraria, allowing them to graze normally, but preventing them from moving up the cordgrass to escape predators in the water. These experiments showed that in the absence of predators (blue crabs in particular), Littoraria can have massive impacts on Spartina by overgrazing and can turn salt marsh to mudflats.
In both studies, a trophic cascade is demonstrated when a top predator is removed from the system. In the saltmarsh, the cascade is simple. Crabs eat snails which graze on Spartina. Less crabs leads to more snails which leads to less Spartina. In the rocky shore study, the food web is more complicated. Basically, starfish prey on mussels which do not prey on other organisms, but instead are effective at competing for space. As a result, removing starfish increases the competitive dominant mussels which decreases the barnacles, algae, chiton, anemones, and limpets that can exist in the space. In both cases diversity is decreased with the removal of the top predator, but in Paine, the impacts affect more species. Also, in the salt marsh, the trophic cascade results in turning the salt marsh to mudflat, leaving large areas of basically uninhabited sections. On the rocky shoreline, the overall biomass or inhabited area remains the same or may actually increase, but the diversity is lost.
14. What is a competitive dominant? Describe 3 forces that can maintain
species co-existence in the presence of a competitive dominant. Why do
these forces have such effects on increasing diversity?
Competitive dominant—organisms that can access the limiting resource; the bullies!
There are associated trade-offs when being a competitive dominant
Three forces that maintain species co-existence in the presence of a competitive dominant
Predation—if energy is invested in competition, it cannot be invested in defense
Disturbance—high levels of disturbance are likely to knock out competitors which are not able to adapt to environmental changes
Stress gradients—in high stress environments, species need to allocate resources to deal with stress in order to survive. If an organism is a competitive dominant, it may not be able to deal with certain stress factors (i.e. low oxygen)
15. In salt marsh plants and mangroves, why are the upper elevation range
limits of plants most often set by competition and their lower elevation
range limits set by physical forces, while the opposite pattern occurs for
rocky intertidal organisms?
salt marsh plants and mangroves:
higher elevations plants have more access to resources (sunlight and nutrients)
increased competition for space
lower elevation range limits are set by physical forces (wave action and sediment deposition) which can
physically displace or drown the plants
rocky intertidal shores:
upper limit typically set by desiccation stress (physical force)
organisms are exposed to air for longer periods at higher elevations
limits the organisms in this zone to only those that are most capable of handling exposure to air and sun
while the lower limit is often determined by competition
stronger more wave-resistant species at lower elevations
organisms in the lower intertidal zone grow faster and larger and will outcompete organisms from the upper intertidal for space
16. (A) What is the range of food chain links typically found in natural food
webs? (B) List three factors that can limit the total number of food chain
links in a food web and discuss why they can limit food chain links. (C)
Construct a biomass pyramid reflecting relative biomass at each trophic
level for the food web of the Serengeti Plains. The opposite/inverse
pattern of that Serengeti Plain biomass pyramid is true for open ocean
systems. Draw this open ocean biomass pyramid as well. Formulate a
hypothesis as to why these biomass pyramids are the inverse of each
Other.
17. Describe three examples of how positive interactions (e.g. mutualisms,
facilitation, indirect and direct, trophic and non-trophic) in the coral reef
community are key to its success and persistence in the face of increasing
human disturbance.
Coral-Zooxanthellae Symbiosis (Mutualism):
coral provides a protected environment for the algae
algae produce oxygen and carbohydrates through photosynthesis
allows corals to thrive in nutrient-poor waters and build the reef structure
Fish-Coral Habitat Provision (Facilitation):
coral reef provides shelter and hiding places for a diverse array of fish species
smaller fish feed and reproduce more readily
contributing to the overall biodiversity and resilience of the reef ecosystem.
Herbivorous Fish Grazing (Trophic Cascade):
(parrtor fish example) grazing on algae that can smother corals
fish indirectly facilitate coral growth
prevents reef from becoming dominated by algae--which can occur under conditions of stress like nutrient pollution.
18. Define density-dependence and density-independence. Using qualitative
graphs and words, compare and contrast the density-dependent impacts
of hurricanes, predation pressure, and foundation species on mortality for
oysters and infaunal clams.
Density-dependent: factors that limit populations differently depending on how dense the population is (i.e. competition for food, nutrients, parasitism)
Density independent: factors that have the same effect on members of a population regardless of density (i.e. wildfires, hurricanes, precip.)
X axis: population density
Y axis: mortality
Hurricanes: density independent influence on oyster mortality (horizontal line)
Predation pressure: density dependent influence on oyster mortality (increasing mortality with increasing density)
Foundation species: density independent influence on oyster mortality (horizontal line)
19. What is the average ocean salinity? What are the eight most abundant
salts in the ocean? Why is the ocean salty, while lakes are fresh?
average ocean salinity: 3.5%,(35 grams/liter of seawater)
most abundant salts: chloride (Cl−), sodium (Na+), sulfate (SO24−), magnesium (Mg2+), calcium (Ca2+), and potassium (K+)
the ocean is salty because rainwater washes minerals from land into the ocean over time
lakes are fresh due to their shorter water retention time and replenishment from freshwater sources like rivers and rain.
20. What is pH and what is the scale on which is measured? How many more
H+ are in solution of a pH 4 vs. pH of 7? What is the average pH of the
ocean and why is it higher than 7? Use words and chemical equations to
describe how increasing C02 in the atmosphere is lowering the pH of the
ocean and how that negatively affects skeleton deposition in corals.
pH: "potential of hydrogen"
how acidic or basic a solution is
scale from 0 to 14
7 is neutral
values below 7 are acidic
and values above 7 are basic
solution with a pH of 4: 1000 times more hydrogen ions (H+) than solution with pH of 7
the average pH of the ocean is slightly basic (8.1)
presence of dissolved minerals like carbonates; increasing atmospheric CO2 leads to more carbonic acid forming in the ocean, lowering the pH (ocean acidification), which disrupts the ability of corals to build their calcium carbonate skeletons, hindering their growth and survival.
21. Describe 4 processes and the mechanism(s) underlying them that
determine effectiveness of MPAs.
22. Defend or refute this comment with data/stats and with at least three
examples: Sewage pollution is isolated in coastal marine systems and has
minimal impacts on marine ecosystems.
23. Compare and contrast how whales facilitate primary production in
phytoplankton communities and grunts facilitate primary production on
coral reefs.
Whales in phytoplankton communities:
recycle nutrients
intake food in highly productive areas
release fecal plumes
releases nutrients for phytoplankton
Grunts on coral reefs:
grunts eat prey in areas outside of reefs but poop on top of corals when they are resting at night; recycles nutrients from outside coral reefs back to the reef (little nutrients in the water around reefs)
compare: recycling nutrients through fecal matter
contrast: whales in open ocean, while coral reefs are within the continental shelf
whales include phytoplankton as part of their food source while grunts do not
24. What is the blue water paradox of coral reefs? Give two major
mechanisms that solve this paradox – i.e., explain how to apparently
counteracting facts can co-exist.
Bluewater paradox:
The fact corals are able to thrive in waters that are low in nutrients and productivity
It is because of symbiosis with sponges and
Symbiosis with algae (zooxanthellae):
corals have a symbiotic relationship with microscopic algae living within their tissues called zooxanthellae
photosynthesize and provide the coral with a significant portion of its nutrition
allows them to "farm" their own food source in nutrient-limited waters.
Nutrient recycling by sponges:
sponges filter large volumes of water
captures dissolved organic matter (DOM) released by other organisms
converts it into nutrients that can be utilized by other reef creatures
creates a "sponge loop" that effectively recycles nutrients within the reef environment
25. Explain convergent and divergent evolution and give three examples of
traits that you’ve learned so far for each type of evolution.
Convergent:
when two organisms that lack a recent common ancestor end up more and more alike as they adapt to a similar ecological niche
Bat wings and insect wings
Shark and dolphin bodies
Vertebrae and cephalopod eyes
Divergent:
when two organisms with a common ancestor end up as different species.
Darwin's finches
Dogs
Humans and apes
Bonus Questions:
1. Draw your favorite marine organism you learned about in class (2 pts)
2. List its common and scientific name (2pts)
3. Describe three interactions your organism has with other marine species
and label them as predation, competition, mutualism, or facilitation (6pts)