Coral Reefs
Explain the symbiotic relationship between corals and zooxanthellae. How does each organism benefit from this interaction?
Benefits to coral:
1) get nutrients from zoox photosynthesis (95% of hosts energy)
2) facilitation of calcification (zoox remove dissolved CO2, increasing pH)
3) zoox sequester toxic compounds
Benefits to zooxanthellae:
1) protection from UV damage
2) have a stable substrate to live on
3) obtain nutrients from cellular byproducts of coral
What is the difference between specialists and generalists?
1. Specialists: species that eat a limited diet and occupy a narrower niche
2. Generalists: species that can survive in a variety of environments and eat a range of foods
How many primary productivity peaks do we observe in the polar oceans? In what season(s) does the peak(s) occur?
1 primary productivity peak that occurs in the summer -- why?
Sunlight! Primary productivity in polar seas is light dependent, and there is a lot of seasonality in polar regions. Therefore, productivity only peaks in the summer because this is the only time light is available at the poles (due to Earth's tilt and rotation).
What is the difference between resilience and resistance?
Resilience: how quickly the ecosystem returns to its original state after the disturbance
Resistance: how well the ecosystem resists disturbance; how little it changes from its original state
2 mg/L
1. What is the difference between hermatypic and ahermatypic corals?
2. What are the 2 types of hermatypic corals?
1. Hermatypic: reef framework builder, have many zooxanthellae, high calcification rates
Ahermatypic: not framework builders, low calcification rates
2. Branching (grow in linear dimension fairly rapidly, 20 cm per year) and massive (produce lots of calcium carbonate but grow more slowly in linear dimensions, about 1 cm per year )
What does the Theory of Island Biogeography state?
A small island that is distant from the mainland will have very few species, while a large island near the mainland will have a greater number of species.
Justification for this claim:
- Larger islands have a lower extinction rate than smaller islands (more space = more resources = more organisms = lower chance of total extinction)
- Islands closer to mainland will have greater immigration rates compared to islands further from the mainland (easier for organisms to migrate to closer islands)
What is pack ice? What is the importance of pack ice for polar communities?
- Pack ice: mixture of ice crystals, brine channels, and brinicles
- Importance: Pack ice provides a variable "substrate" for ice-associated communities to thrive. Diverse organisms interact to create dynamic food webs (ex: diatoms, bacteria, ciliates, and heterotrophic dinoflagellates living in or on the sea ice provide food for larval fish, adult fish, copepods, and krill).
What is the difference between fluctuations and disturbances? Provide at least 2 examples of each.
Fluctuations: Regular, cyclic changes in the environment that can be anticipated. Examples include: tides, day/night, seasons, phenology
Disturbances: discrete events in time that disrupt ecosystem, community, or population structure and change resources, substratum, or the physical environment; they can only be predicted to a degree. Examples include: hurricanes, droughts, oil spills, forest fires
Explain the Greenhouse Effect and list the 3 major greenhouse gases.
- The Greenhouse Effect: The warming of the earth due to light energy being re-radiated into the atmosphere where it is absorbed by a "blanket" of atmospheric gases (as opposed to being reradiated into the space).
- Major gases:
1. Water Vapor (H2O)
2. Carbon Dioxide (CO2)
3. Methane gas (CH4)
List 3 factors that promote reef growth (there were 5 given in lecture).
1. High sea temperatures (high calcification rates in warmer waters)
2. High light (supports endosymbiosis with algae)
3. Basic pH
4. Open marine salinities
5. Low turbidity (minimal suspended sediment to increase light availability)
1. What does the "Diversification rate hypothesis" state?
2. What does the "Species-energy rate" hypothesis state?
1. Populations diversify faster in tropical regions than in polar regions due to increased rates of speciation and/or lower extinction rates in equatorial regions (Higher temperatures increase the spread of genetic diversity)
2. Species richness is higher in habitats that receive more of the energy needed to power metabolism (tropical regions which receive more solar irradiance due to Earth's tilt)
What are the 4 primary disturbances that the polar oceans experience?
1. Waves
2. Ice (both ice scour and anchor ice)
3. Salinity variation (freshening when the sea ice melts and hyper-salinity when sea ice forms)
4. Macrofauna (both digging and bioturbation)
List 3 examples of natural disturbances in the marine environment (we covered 6 examples in lecture).
List 3 examples of anthropogenic disturbances in the marine environment (we covered 5 examples in lecture).
Natural: weather (storm waves, ocean-atmosphere shifts like El Niño and La Niña, hyper-/hyposalinity, extreme hot/cold water events, ice scour), sediment processes (burial or erosion), harmful algal blooms (like red tide), anoxic/hypoxic events, disease outbreaks or species die-off, and variable recruitment leading to extreme high/low abundance of key organisms in the food web.
Anthropogenic: direct physical disturbances to habitats (trawling, dredge/fill operations, coastal construction), overfishing (trophic cascades), climate changes and acidification, pollution/eutrophication (agricultural runoff increases minerals in water), non-native species introductions (lion fish or green crab)
How does skeletal mineralization in response to climate change (ocean acidification) vary between invertebrates and vertebrates, like skates?
Invertebrates: Mineralization decreases with acidification
Vertebrates: Mineralization increases with acidification (acidification increases hydroxyapatite (HA) density, causing skates to produce more phosphate to counteract this)
What is a coral-algal phase shift?
- Significant change in the reef’s composition
- Composition of community is physically changing from a coral-dominated reef system to an algal reef system following a disturbance (this could be the loss of herbivores or coral bleaching events)
- Coral-dominated system becomes algae-dominated system due to: Overfishing, nutrient runoff, sedimentation, disease outbreak, hurricanes
List 3 extrinsic factors that influence speciation rates.
List 3 intrinsic factors that influence speciation rates.
Extrinsic: habitat age (older habitats indicate more time for species to colonize and evolve), habitat area/geographic range (larger area but smaller geographic range leads to more speciation), temperature (higher temperatures lead to greater speciation)
Intrinsic: Body size (r-selected organisms, which are smaller in size, will reproduce faster therefore resulting in more mutations = increased speciation), life history and dispersal ability (organisms that disperse locally will result in isolation from other individuals of the same species, leading to higher speciation rates), resource specialization (specialists have higher speciation because they are more isolated)
List at least 3 differences between the Arctic and Antarctic seas.
Arctic: Semi-enclosed sea, wide continental shelves, central deep water is isolated, significant river input (surrounded by lad which are sources of nutrient runoff), lower salinity, permanent pack ice, very dynamic system (lots of sea ice and lots of currents), soft sediment on seafloor, disturbance dominated (physical, like rivers, and biological)
Antarctic: ocean "ring" around continental land mass, deep water adjacent to narrow shelf, no river input, mostly temporary pack ice, very strong and permanent gyres, hard sediment on seafloor, mostly physical disturbances (like wind and circumpolar currents), high endemism
What does Connell's Intermediate Disturbance Hypothesis state? At what level of disturbance is biodiversity greatest?
- Connell's Hypothesis states: 1) habitats the experience excessive amounts of disturbance will have low levels of diversity because the species do not have enough time to recolonize, 2) habitats that experience infrequent disturbances will have low levels of diversity because the climax community (few species dominating) will be maintained, and 3) habitats that experience intermediate disturbance will have the highest levels of biodiversity because both r- and k-selected species can survive.
Explain 1) what eutrophication is, 2) what causes it, and 3) a prominent example of a "dead zone" discussed in lecture.
1) Eutrophication = excessive plant and algal growth due to the increased availability of one or more limiting growth factors needed for photosynthesis
2) Causes = increase in anthropogenic nutrients (e.g. fertilizer runoff)
3) Example = Mississippi River Delta that connects to Gulf of Mexico
What are the 3 major reef types? Describe each.
1. Fringing Reef: Close to land, develop on the shorelines of continents and islands, little to no intervening lagoon, thrive in well-illuminated, shallow water
2. Barrier Reef: have an island (usually of volcanic descent), a lagoon, and the surrounding reef area; at this reef stage, the volcano has begun to sink so the reef becomes separated from the land by a lagoon via erosion and coastal subsidence
3. Atoll: In this reef, the volcano has sunk a lot which causes the reef to grow overtop of it; predominantly lagoon
What are the differences between allopatric, peripatetic, parametric, and sympatric speciation?
Essentially, provide the "definition" of each.
1. Allopatric speciation: the origin of species as a result of speciation by extrinsic barriers
2. Peripatric speciation: a small group of individuals break off from the original population to form a new species
3. Parapatric speciation: A species is spread out over a large geographical area, resulting in mating with individuals in their immediate vicinity
4. Sympatric speciation: There is no geographic barrier, but gene flow is restricted in another way (within the population) which leads to the isolation of a small portion of individuals within the initial population.
List the 4 hypotheses that explain why gigantism occurs in polar regions. Does gigantism only occur in polar regions?
1. Oxygen availability - high oxygen levels (because oxygen dissolves more readily in colder water) coupled with lower metabolic rates
2. Silica chemistry: high silica abundance in polar seas
3. Carbonate chemistry: CO2 is more soluble in colder waters, leading to more acidified waters which affects calcifying organisms (CaCO3)
4. Biogeographic and ecological: “monsters from the deep” --> invasion of polar seas by giants from the deep sea (abyssal gigantism)
NO! Hypothesis 4 highlights that gigantism also occurs in deep sea environments.
Explain the steps of succession and recovery after a disturbance.
- Immediately after disturbance, scavengers begin feasting on the dead organisms
- Scavengers leave, and opportunistic species colonize, recruit, or immigrate (these species are typically small, fast-growing organisms tolerant of unstable substrate – these are the “r strategists”)
- Recruitment of organisms that require more stable substrate (Growth and dominance of competitively superior species, typically larger, structure-forming organisms - these are the “k-strategists”)
- Climax community (composed of a few dominant species)
Global climate change has significant impacts on many marine organisms. Two of which are topicalization and phenological mismatches. Explain what each of these are.
1. Tropicalization = Process where tropical species and ecosystems expand to temperate zones as a result of warming temperatures and decreasing extreme cold events
2. Phenological mismatches = Species interactions are affected by changes in phenology (seasonal shifts);
Ex: Phytoplankton blooms happening sooner in Spring (when temperatures are warmer), but the fish (that had adapted to use the phytoplankton bloom timing to grow and reproduce) are not spawning soon enough to utilize the phytoplankton bloom for food