marine ecology

Because marine organisms are shaped by physical variables like salinity, temperature, depth, light, and water movement.

Why is understanding the physical environment essential in marine ecology?

Sodium (Na⁺) and chloride (Cl⁻).

What ions primarily determine salinity?

Evaporation.

What increases salinity?

Freshwater input (e.g., rivers, rain).

What decreases salinity?

~35 ppt.

Typical ocean salinity?

~5–30 ppt.

Typical estuarine salinity?

<1 ppt.

Typical river salinity?

Organisms whose internal salinity changes with the environment.

What are osmoconformers?

Organisms that maintain constant internal salinity.

What are osmoregulators?

Osmoregulation is energy costly but allows broader habitat use.

Trade-off of osmoregulation vs. osmoconforming?

Metabolic rate increases with temperature (to a point).

How does temperature affect metabolism?

A curve showing optimal, critical minimum, and maximum temperatures.

What is a thermal performance curve?

Near the equator.

Where is surface water warmest?

Warm surface water sits above cooler deep water with little mixing.

What causes summer stratification?

0–200 meters where photosynthesis can occur.

What is the photic zone?

Blue and green.

Which wavelengths penetrate deepest in water?

No photosynthesis; it's deeper than 200 m.

What happens in the aphotic zone?

Heat, nutrients, and organisms.

What do currents transport?

Rising of cold, nutrient-rich water to the surface—boosts productivity.

What is upwelling?

Alters circulation patterns (e.g., Gulf Stream, ENSO).

How does climate change affect currents?

It's denser and more viscous.

Why is water more challenging to move through than air?

Water is less dense as a solid.

Why does ice float?

4°C.

At what temperature is water densest?

A dimensionless number describing flow conditions (Re = Velocity × Length / Viscosity).

What is Reynolds number?

Inertia and pressure.

What dominates movement at high Re?

Viscosity.

What dominates movement at low Re?

Because movement is reversible and dominated by stickiness.

Why is flapping ineffective at low Re?

Chaotically, in patchy plumes.

How do substances spread in high Re environments?

Smooth gradients via diffusion.

How do substances spread in low Re environments?

Foraging, sensory adaptations, and chemical cue tracking.

What do these differences affect?

Thermoregulation affects speed and fatigue.

How do fiddler crabs adapt to heat?

Because their environment is more stable.

Why do tropical organisms have narrow thermal ranges?

Currents, salinity zones.

What happens at a global scale?

River inputs, upwelling.

What happens at a regional scale?

Tidal creeks, estuaries.

What happens at a local scale?

Turbulent patchiness and feeding zones.

What happens at a micro scale?

~1 atmosphere every 10 meters.

How much pressure increases with depth?

Organisms adapted to high pressure in deep sea.

What are piezophiles?

High temperature, depth, and biological demand.

What factors reduce dissolved oxygen?

Excess nutrients and decomposition (e.g., Gulf of Mexico).

What causes hypoxic zones?

Broadcast spawning.

What reproductive strategy suits strong currents?

Flattened bodies (e.g., skates).

What morphology suits benthic life?

Alters salinity, turbidity, flow, and destroys habitats.

How does coastal development affect marine systems?

Raises temperature, changes currents, expands low-oxygen zones.

How does climate change affect marine environments?

Shell-forming organisms (e.g., corals, mollusks).

What does ocean acidification impact?

A sharp temperature gradient in the water column.

What is a thermocline?

A sharp salinity gradient.

What is a halocline?

A density gradient (often from temp + salinity).

What is a pycnocline?

Sediment mixing by organisms, affecting nutrient cycling.

What is bioturbation?

Conductivity (salinity), Temperature, and Depth.

What does a CTD profiler measure?

Water clarity (light penetration).

What does a Secchi disk measure?

Chlorophyll concentration (phytoplankton proxy).

What does a fluorometer measure?

Measures water current velocity.

What does an ADCP do?

Physiology affects performance (e.g., speed, fatigue), which influences survival and reproduction, ultimately determining species distribution.

How does physiology relate to species distribution?

Uca panacea performs better at high temps → more common in warmer areas than Uca pugilator.

Example of temperature affecting species distribution?

Survival and performance.

What process links individuals to distribution?

Births, deaths, immigration.

What process links populations to growth rate?

Adaptation and evolution.

What process links species to their niche?

Species interactions (e.g., competition, predation).

What determines diversity and trophic structure at the community level?

Energy and nutrient cycling.

What defines productivity in an ecosystem?

When species with overlapping resource needs cannot coexist indefinitely.

What is competitive exclusion?

Nitrogen-fixing bacteria with plants.

Example of a foundational mutualism?

Transfers energy, regulates populations, can cause trophic cascades.

What role does predation play in communities?

It drains resources and can alter host behavior and population structure.

How does parasitism influence hosts?

Fundamental = possible conditions; Realized = actual conditions due to biotic limits.

Difference between fundamental and realized niche?

Gene flow between populations.

What constrains adaptation?

Geographic or reproductive isolation.

What enhances speciation?

Species composition, trophic structure, diversity, and species associations.

What are key metrics of community structure?

Carbon sequestration potential.

What does primary productivity reflect?

Tropical rainforest (high); Desert (low).

Which biomes have highest/lowest productivity?

Blue carbon loss, climate change, altered nutrient cycles.

What are human impacts on ecosystem processes?

Nt = N₀ × e^(rt)

What is the exponential growth equation?

dN/dt = rN × (K − N) / K

What is the logistic growth equation?

Maximum sustainable population.

What does carrying capacity (K) represent?

Exponential = ideal/lab; Logistic = natural, density-limited.

When is exponential vs. logistic growth appropriate?

Birth/death rates change with population density (e.g., competition, predation).

What is density-dependent regulation?

Effects not related to density (e.g., weather, disasters).

What is density-independent regulation?

S-shaped curve.

What does a logistic growth graph look like?

Erratic, no consistent pattern.

What does density-independent growth look like on a graph?

Control and mechanistic insight.

Advantage of lab studies?

Real-world ecological relevance.

Advantage of field studies?

Connell’s barnacle study (competition and zonation).

Example of important field experiment?

Predict patterns but must be validated with real-world data.

Why are models used in ecology?

It reflects confidence in the mean estimate.

Why is standard error important?

<5% probability the result is due to chance.

What does P < 0.05 mean?

Larger sample size and smaller variance.

What increases statistical confidence?

Overconfidence in mean values and misleading conclusions.

What is the danger of ignoring variance?

What's being limited? Is it density-dependent? What evidence supports it?

What questions should you ask when analyzing ecological data?

Clear null hypothesis, mechanistic link, and visualization.

What makes a good hypothesis test?

Because patterns alone don’t prove mechanism—field tests are needed.

Why distinguish correlation vs. causation?

Resource partitioning or niche shifts.

How can species with overlapping niches coexist?

The speed of recovery after disturbance.

What is community resilience?

High diversity and functional redundancy.

What increases ecological resilience?

Benefits like food, climate regulation, nutrient cycling, and recreation.

What are ecosystem services?

Replication, randomization, control, and awareness of scale.

What makes strong experimental design?

Growth curves, predator–prey cycles, species–area curves, trait distributions.

What graphs should you know how to interpret?

Nt = population at time t; N₀ = initial population; r = intrinsic growth rate; t = time.

What does each variable in Nt = N₀ × e^(rt) represent?

Unlimited resources and no competition.

What are the assumptions of exponential growth?

A J-shaped curve.

What curve does exponential growth produce?