Marsci Exam 2 Prep

Terms §

• Stress gradient hypothesis

• Hysteresis

• Alternative Stable States

• Trophic Cascade

• Paradox of the plankton

• Riftia

• Chemosynthesis

• Fringing vs. barrier reef

• Disturbance

• Intermediate Disturbance hypothesis

• Facilitation cascade

• Foundation species

• Keystone species

• Spartina

• Crassostrea

• Zostera

• Acropora

• Macrocystis

• Rhizophora

• Green vs. brown food webs

• Aerenchyma

• Lacuna

• Custom terms

  • Turbid
  • blue water paradox of coral reefs

1. What are the 5 most important biological lessons you learned during the course and why?
2. Explain convergent and divergent evolution and give three examples of traits that you’ve learned so far for each type of evolution.
   1. Convergent Evolution: Different species evolving similar traits independently due to similar environmental pressures.
      • Streamlined body shapes in dolphins and sharks
      • Filter feeding structures in baleen whales and whale sharks
      • Bioluminescence in different deep-sea organisms
   2. Divergent Evolution: Related species evolving different traits as they adapt to different environments.
      • Different beak shapes in Darwin’s finches
      • Varying body forms in coral reef fish from a common ancestor
      • Different feeding strategies in sea stars from the same family

Stressors §

1. 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.
   1. Graph 1 (No Hysteresis): Shows a simple negative relationship between urchin density and kelp abundance. The system responds predictably to changes in urchin density.
   2. Graph 2 (Large Hysteresis): Shows how the same kelp system can exist in two alternative stable states at the same urchin density. The blue line shows kelp decline as urchin density increases, while the dashed red line shows the recovery pathway. The vertical gray line shows where two stable states can exist at the same urchin density.
2. 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.
   1. incorrect for several reasons:
      • Sewage contains nutrients that cause eutrophication, affecting entire food webs
      • Studies show sewage-derived nitrogen can be traced kilometers offshore
      • Examples of widespread impacts:
        • Dead zones in coastal areas due to oxygen depletion
        • Harmful algal blooms affecting entire regions
        • Coral reef degradation from nutrient loading
3. 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.
   1. Hurricanes (Density-Independent Impact):
      • Descriptionon: Hurricanes can cause widespread destruction through strong winds, storm surges, and altered salinity levels.
      • Impact on Mortality: Mortality rates for oysters and infaunal clams increase significantly during hurricanes, regardless of their population densities. The physical forces and environmental changes affect individuals equally, leading to density-independent mortality.
   2. Predation Pressure (Density-Dependent Impact):
      1. Description: Predators such as blue crabs feed on oysters and infaunal clams.
      2. Impact on Mortality: At higher prey densities, predators can locate and consume more individuals, leading to increased mortality rates. This results in a positive correlation between prey density and mortality due to predation.
   3. Foundation Species (Density-Dependent Impact):
      • Description: Foundation species like seagrasses and oysters create habitats that provide shelter and resources for other organisms.
      • Impact on Mortality: The presence and density of foundation species can reduce mortality rates for oysters and infaunal clams by offering protection from predators and stabilizing the environment. As the density of foundation species increases, the protective benefits also increase, leading to lower mortality rates.
4. Describe 4 processes and the mechanism(s) underlying them that determine effectiveness of MPAs.
   1. Size and Spacing:
      • Mechanism: Larger MPAs support viable populations and provide spillover benefits
      • Optimal spacing allows larval connectivity between protected areas
   2. Habitat Quality:
      • Mechanism: Higher quality habitats support greater biodiversity
      • Includes factors like structural complexity and habitat diversity
   3. Enforcement Level:
      • Mechanism: Effective enforcement prevents illegal fishing and habitat destruction
      • Regular monitoring and penalties maintain protection
   4. Connectivity:
      • Mechanism: Networks of MPAs allow species movement and genetic exchange
      • Considers both physical oceanographic connections and species’ life histories

Salt Marsh & Mangrove §

1. 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?
   1. East Coast:
      • Gentle slope, sediment accumulation from glacial deposits
      • Enables marsh plant establishment
      • Suitable habitat for fiddler crabs
   2. West Coast:
      • Steep, rocky terrain from tectonic activity
      • Limited sediment accumulation
      • No habitat for fiddler crabs
2. 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?
   1. Reason:
      1. Salt marsh and mangrove plants can engineer their environment through root systems and canopy development
      • Rocky intertidal organisms are largely at the mercy of existing physical conditions
      • Limited ability to modify environment
   2. Salt marsh/mangroves:
      • Lower limit: Flooding stress/salinity/submergence thus lower oxygenation
      • Upper limit: Competition from terrestrial plants
      • Plants can modify environment to reduce stress
   3. Rocky intertidal:
      • Lower limit: Predation pressure
      • Upper limit: Desiccation stress
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.
   • Salt marsh:
     1. Clumped planting for mutual shading (Reduces soil salinity through shared root oxygen, increases sediment binding)
     2. Adult nurse plants protecting seedlings (Reduced soil temperature, increased humidity, wave protection)
     3. Mixed species assemblages for facilitation (Different root depths reduce competition, increase soil oxygenation)
   • Mangroves:
     1. Density optimization for root stability (Shared prop root structure increases stability)
     2. Pioneer species establishing substrate, i.e. facillitation succession (Plant A. germinans 2 years before L. racemosa)
     3. Plant in patches (Increases seed capture, natural recruitment, sediment trapping, natural expansion)

Food Chain §

1. Define trophic cascade and food chain length.
   • Trophic cascade: Effects of predator changes propagating through food chain
   • Food chain length: Number of feeding links from primary producers to top predators
2. How can changes in food chain length affect the outcome of a trophic cascade?
   • Longer chains dilute top-down effects
   • Intermediate consumers buffer impacts
   • Time lag effects
   • In gneeral, longer chains are:
     • Less stable demographically
     • More vulnerable to perturbation
     • Higher extinction risk
3. 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.
4. What is the range of food chain links typically found in natural food webs? 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.
   1. Naturally 3-5
      1. Energy loss between levels (10% energy transfer rule between levels)
      2. Population stability requirements (Each level needs minimum viable population)
      3. Body size constraints (Size increases up chain by ~10x)
5. 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.
   • Serengeti: Slow plant turnover, large standing biomass
   • Ocean: Rapid phytoplankton turnover, low standing biomass but high productivity supports larger consumer populations

Ecological Interaction & Environment §

1. Compare and contrast how whales facilitate primary production in phytoplankton communities and grunts facilitate primary production on coral reefs.
   • Whales: release nutritious fecal plumes after consuming in high-productivity feeding areas and arriving in low-productivity calving areas, will cause phytoplankton blooms.
   • Grunts: Go to other seagrass beds and sand plains to feed on microorganisms, return to coral reef, shit near coral polyps with nitrogen and phosphorus shit, causes algae blooms near juvenile polyps that suffocate them
2. 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: Organism that is best adapted to the environment, one that will presumably outcompete all other organisms in the habitat
   • 3 forces:
     1. Resource partition: with resource limitations, the competitive dominant species will hit density dependent factors such as lack of resources much faster and be less dominant
     2. Adopting different life cycle (one organism should be more resource efficient in larval stage and one should be less resource efficient in adult stage. These stages must not clash so that they aren’t really competing for resources at any stage.),
     3. Predation on the competitive dominant (mussels and starfish, or keystone species, on rocky shores)
3. 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: niche the organism would occupy without any limiting factors
   • Realized niche: niche the organism actually occupies
   • Ex. Cthalamus and Balanus interactions, cthalamus should occupy everything, but bc of competition Balanus occupies half of intertidal zone
   • Niche theory: Competition traditionally reduces realized niche. Positive interactions can expand realized niche beyond fundamental through stress amelioration/resource enhancement.
4. 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 function: “the ecological processes that control the fluxes of energy, nutrients and organic matter through an environment”
   • Ecosystem service: “the conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfill human life.” Basically the ecosystem functions that are useful to humans
   • Both are active elements of the ecosystem that regulate its biotic factors. The difference lies in the fact that ecosystem services are a subset of ecosystem functions that act on human existence.
   • Common Functions & Services:
     1. Wave Attenuation
        • Function: Energy dissipation
        • Service: Coastal protection
     2. Nutrient Cycling
        • Function: Element transformation/storage
        • Service: Water quality improvement
     3. Habitat Provision
        • Function: Physical structure creation
        • Service: Fishery enhancement

Oceanographic Process/Environment §

1. 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?
   • The Coriolis effect is an apparent deflection of moving objects due to Earth’s rotation. It occurs because Earth rotates underneath moving objects, causing rightward deflection in Northern Hemisphere and leftward in Southern Hemisphere.
   • For krill:
     • East-West movement: Less Coriolis impact since movement is parallel to Earth’s rotation
     • South-North movement: Stronger rightward deflection in Northern Hemisphere
2. 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?
   • Ekman spiral: Wind-driven surface water moves 45° right of wind direction, with each deeper layer moving progressively further right and slower, creating a spiral pattern.
   • Created by balance between Coriolis force and friction.
   • Important for zooplankton as they can move between layers to control their transport direction/distance.
3. 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.
   1. Key processes driving anchovy fisheries:
      1. Coastal upwelling: Wind drives surface water offshore, bringing nutrient-rich deep water up
      2. Thermocline shoaling: Brings nutrient-rich water closer to surface
      3. Tidal mixing: Vertical mixing of nutrients in coastal areas
   • El Niño can shut these down by:
     • Deepening thermocline
     • Weakening upwelling
     • Reducing nutrient availability
4. 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?
   1. Average ocean salinity: 35 PSU (parts per thousand)
   2. Most abundant salts:
      1. Sodium chloride (NaCl)
      2. Magnesium chloride (MgCl₂)
      3. Magnesium sulfate (MgSO₄)
      4. Calcium sulfate (CaSO₄)
      5. Potassium sulfate (K₂SO₄)
      6. Calcium carbonate (CaCO₃)
      7. Magnesium bromide (MgBr₂)
      8. Potassium chloride (KCl)
   3. Oceans are salty due to accumulated mineral weathering from land over millions of years, while lakes flush minerals through outlets.
5. 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.
   1. pH measures hydrogen ion concentration on 0-14 scale. pH 4 has 1000x more H+ than pH 7 (3 pH units = 1000x difference).
   2. Ocean average pH ≈ 8.1, higher than 7 due to carbonate buffering system.
   3. CO₂ impact:
      • CO₂ + H₂O → H₂CO₃ (carbonic acid)
      • H₂CO₃ → H+ + HCO₃- (bicarbonate)
      • More CO₂ = more H+, lowering pH. This affects coral calcification:
      • Ca²+ + CO₃²- → CaCO₃ (coral skeleton)
      • Higher H+ reduces available CO₃²-, making skeleton formation harder.

Ecological Succession §

1. What is ecological succession? How does this contrast with zonation?
   • Ecological succession: Basically, the series of progressive changes in the composition of an environment over time (e.g. after wildfire)
   • Zonation: Gradual change of the distribution of a species across an environmental gradient over space (e.g. shoreline)
2. Define and contrast the three models of succession as defined by Connell and Slayter and describe an example of each.
   1. Facilitation: Early species improve conditions for later species; e.g. Lichens break down rock, creating soil for mosses
   2. Tolerance: Early species neither help nor harm later species; e.g. Different species of sponges colonizing a reef wall, each establishing independently based on available space and water flow conditions
   3. Inhibition: Early species prevent establishment of later species; e.g. Dense mussel beds preventing barnacle settlement through space occupation and filtering of larvae
3. 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?
   • Independent Variables: Presence/absence of pioneer species (treatment plots) & Different pioneer species combinations
   • Dependent Variables: Soil characteristics (salinity, organic matter); Survival rates of later colonizers
   • Experimental Design: Replicated plots with/without pioneer removal; Control for environmental gradients; Measure physical and biological parameters
4. Define the three types of ecological succession. Which one typifies salt marsh succession and systems represented by alternative stable states?
   1. Primary Succession: Succession that happens in lifeless areas, e.g. earth’s creation. Rocks eroded to soil by microorganisms, soil can now sustain plant life
   2. Secondary Succession: When primary succession community gets wiped out. E.g. stuff after wildfire. Recolonizing of previously life-containing area
   3. Cyclic succession: Constant changing of structure of ecosystem, associated with seasonal changes. Some plants are alive at some time, some aren’t. some animals hibernating, some active. Like cicada life cycle
   • Cyclic succession by erosion disturbance. Alternative stable states endpoints develop

Corals §

1. Compare and contrast how acidification, increased nutrient loading, and overfishing might impact coral reefs.
   1. Acidification: Reduces calcium carbonate availability → problems with coral skeleton fomation → weakens & susceptible to physical damage
   2. Nutrient Loading: excessive algal growth → outcompete corals for space; increased turbidity (→ reduced light penetration); increased pathogen growth; distrupts nutrient cycling
   3. Overfishing: Removes key herbivores that control algal growth → phase shift from coral-dom to algal-dom system; trophic cascade
2. Describe in detail what happens when corals bleach in response to temperature stress, and how they could recover.
   1. The bleaching process:
      1. High temperatures cause coral polyps to become stressed
      2. The symbiotic zooxanthellae (algae) begin producing excessive reactive oxygen species (=ROS)
      3. Corals expel their zooxanthellae as a stress response
      4. Without zooxanthellae, corals lose their color and primary energy source
      5. Coral tissue becomes transparent, revealing white skeleton underneath
   2. Recovery pathway:
      1. If conditions improve quickly enough, corals can recruit new zooxanthellae
      2. Different clades of zooxanthellae may colonize, potentially providing better heat tolerance
      3. Corals slowly regain their color as symbiont populations rebuild
      4. Energy reserves must be sufficient to survive the bleached period
      5. Recovery can take weeks to months under optimal conditions
3. 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.
   1. Coral-Zooxanthellae Mutualism
      • Zooxanthellae provide up to 90% of coral energy needs through photosynthesis → rapid calcium carbonate deposition → Creates the physical structure that supports the entire reef community
      • Corals provide protection and nutrients to zooxanthellae
   2. Branching Coral-Damselfish Mutualism
      • Damselfish use coral branches as shelter and nesting sites → they defend their territory against coral predators and algae-eating fish → protects coral from predation and algal overgrowth
      • Fish waste provides nutrients to coral: important when reefs face stress from pollution or warming
   3. Coral-Coralline Algae Facilitation
      • Presence indicates suitable habitat conditions for coral growth
      • release chemical cues that guide coral larval settlement
      • provide stable substrate for coral recruitment
        • Help cement reef structure against storm damage
      • relationship is crucial for reef recovery after disturbance events
4. 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.
   • The Paradox: Coral reefs are highly productive ecosystems existing in nutrient-poor tropical waters
   • Major mechanisms that resolve this paradox:
     1. Efficient Nutrient Recycling: tight coupling (=rapid transfer through trophic levels) between producer & consumer minimize nutrient loss
     2. Physical Processes and Reef Structure
        • Complex reef structure creates eddies and upwelling → Enhances particle capture from passing water; Promotes retention of nutrients within the reef system