Please enable JavaScript.
Coggle requires JavaScript to display documents.
Lecture 6: Life in Marine Environment - Coggle Diagram
Lecture 6: Life in Marine Environment
Major Zones of Marine Ecosystems
Intertidal Habits
Located between high and low tide zones.
Chararacteristics
Smallest ocean zone but biologically rich.
Dominated by marine species adapted to extreme variability (tides, temperature, wave action, salinity).
Organisms face desiccation, temperature fluctuations, and limited feeding during air exposure.
variability in tolerance effects > zonation
Tidal effects >> exposure to air (shaped by the daily rise and fall of tides)
Zonation
Vertical distribution of species based on tolerance to air exposure.
Estuarine Zone > Coastal Zone > Euphotic Zone > Bathyal Zone > Bathyal Zone > Abyssal Zone
Fundamental vs Realized Niche
Fundamental niche
Where a species could live without competition/predation.
Realized niche
Where a species actually lives due to ecological constraints.
Keystone Species
Organisms with disproportionately large impacts on community structure (e.g., predators maintaining biodiversity).
Example
Natural State
Mussel populations are controlled.
Space and resources are freed for other species (barnacles, rockweeds, gooseneck barnacles).
THUS, high biodiversity:
Multiple species coexist in the intertidal zone
Predation pressure:
Sea stars prey on mussels (a dominant competitor).
Sea Star Removal
Loss of predation:
Without sea stars, mussels proliferate unchecked.
Mussels outcompete other species for space and resources.
Barnacles, algae, and other species decline or disappear.
THUS, Ecosystem collapse:
The intertidal zone becomes a monoculture dominated by mussels.
Example
Little gray barnacles
Fundamental niche:
Could occupy mid-to-high intertidal zones.
Realized niche:
Limited to the high intertidal due to:
Desiccation tolerance
: Adapted to survive drying in high zones.
Avoidance of predators
: Dog whelks are less active in high zones.
Rock barnacles
Fundamental niche:
Could occupy mid-to-low intertidal zones.
Realized niche:
Restricted to mid-intertidal due to:
Competition with mussels
: Mussels dominate lower zones.
Predation pressure
: Dog whelks prey on them in lower zones.
Marine Life Classifications
Plankton
Drifters (e.g., phytoplankton, zooplankton)
Unable to swim against currents.
Phytoplankton
Base of oceanic food webs; responsible for ~50% of global primary productivity.
Convert CO₂ to organic material via photosynthesis; major O₂ producers.
Require nutrients (N, P, Fe) for growth; limited by nutrient availability.
Examples: Diatoms, dinoflagellates, coccolithophores.
Nekton
Active swimmers (e.g., fish, squid, marine mammals).
Benthos
Bottom-dwellers (e.g., corals, worms, crustaceans).
May be permanently attached or mobile.
Energy Flow and Productivity
Primary Productivity
Driven by phytoplankton photosynthesis.
phytoplanton feed on mineral elements (N, Fe, P, Si) to covert light energy to organic materials
Upwelling:
Critical for nutrient supply in coastal regions.
surface water cools, becomes denser > sink > drives thermocline circulation
Cooler, deeper water is more nutrient-rich and is driven upward near the equator by winds
High productivity zones
polar waters & coastal upwelling areas
trapped nutrient in ice is released + short food chain in polar ecosystem have quick nutrient cycle rapidly
Food Webs
Longer and more complex in marine vs. terrestrial/freshwater systems.
Advantages
More trophic levels = more niches for species to occupy. > Specialization
Predators at different levels (e.g., squid, tuna, sharks) reduce competition.
Efficient Energy Use in Low-Nutrient Environments (longer chain allow energy to "stretch" across multiple trophic tropic levels)
Complex chains facilitate nutrient recycling > Carbon is transported to the deep ocean > Carbon Sequestration
Plants (terrestrial) and algae (freshwater) dominate primary production (photosynthesis by plant), but fewer trophic levels exist
Less vertical stratification compared to the ocean. > shorter chain
Longer chain for a more complex envir (e.g. Species like lanternfish feed at night near the surface and hide in deep waters by day.)
Why productivity varies among coastal, polar and open ocean waters?
Larval Stages in Marine Invertebrates
70% of marine invertebrates have larval stages.
Earliest life stage distinct from adults (e.g., planktonic larvae of corals, worms) that will undergo metamorphosis
Metamorphosis
: Larvae undergo a high-risk transformation to become juveniles.
Biofouling
: organisms attaching to surfaces (e.g., barnacles on ship hulls)
Biomineralization
:To attach, larvae use carbonate ions (CO₃²⁻) from seawater to build mineralized structures (e.g., shells, tubes).
CO₂ and H₂O convert to bicarbonate (HCO₃⁻) and carbonate ions (CO₃²⁻), which are used to form aragonite (CaCO₃)
High morphological
diversity+ Most larvae bear little resemblance to adults
Why So Many Species Reproduce via Larval Stages?
Larvae drift with currents (mobile)> spread offsprings > avoid overcrowding + colonize new habitats
Larvae occupy different niches (open water) than adults (seafloor), reducing competition for resources.
The ability to build mineralized structures (using carbonate ions) during metamorphosis ensures survival in harsh environments (e.g., wave-exposed rocks).
While metamorphosis is risky (many larvae die), the payoff is huge: adults gain a stable habitat and reproductive success.
Larvae feed on plankton in the water column, while adults filter-feed or scavenge on the seabed > exploiting different resources