Tema 4

Question 1

Consequences of Life in the Deep Sea

Answer 1

Limited Food Availability: Directly affects organisms’ survival.
Reduced Abundance: 5-10 times fewer organisms as depth increases.
Depth-Related Abundance:
5% of surface abundance.
5-10 times fewer organisms at 500 meters.
10 times fewer at 4000 meters.

Question 2

Food Sources in the Deep Sea

Answer 2

Direct Sources:
Carcasses and organic matter from surface organisms.
Migratory mesopelagic species.
Ontogenetic migrations (species moving through different life stages).
Indirect Sources:
Trophic Relay: Particles from the ocean floor moving upwards, increasing bacteria populations.
Increased organism presence near the deep sea floor.
Decreased oxygen in deep waters, raising the importance of Dissolved Organic Matter (DOM).

Question 3

Organisms in the Mesopelagic Zone

Answer 3

Photoautotrophs
Zooplankton
Arrow Worms (Chaetognatha): Most abundant in upper layers.
Gelatinous Plankton: More abundant in upper regions.
- Siphonophores: Most abundant at depths of 200-400 meters.
Cephalopods

Question 4

Food Sources in the Mesopelagic Zone

Answer 4

Direct Sources:
Carcasses and organic matter from surface organisms.
Migratory mesopelagic species.
Ontogenetic migrations.
Indirect Sources:
Trophic Relay: Particles from the ocean floor move to the water column, increasing bacterial populations.
Increased organism presence in deep zones.
Decreased oxygen levels, raising the importance of DOM

Question 5

Photoautotrophs in the mesopelagic zone (trophic strategies)

Answer 5

Likely few due to limited light.
Trophic Strategies:
Adapted for midwater environments.
Limited food sources result in specialized feeding adaptations.

Question 6

Zooplankton in the mesopelagic zone

Answer 6

Zooplankton:
- Ostracods: Example - Gigantocypris (1 cm).
- Krill and Copepods:
Example: Bathycalanus sverdrupi (16 mm).
- Shrimp:
Increased presence of various species.

Question 7

Cephalopods in the mesopelagic zone

Answer 7

Squids (Order: Teuthida).
Vampyromorphids: Vampyrotheuthis infernalis (deep-sea squid).
Octopuses (Order: Octopoda) - some species found in deep waters.

Question 8

DSL characteristics

Answer 8

Depth: Between 300-500 meters, close to the surface.
Non-Migratory Organisms: Small zooplankton (copepods, krill), increase in fish, shrimp, and squid populations.
Migratory Organisms: Majority migrate, with food coming from above via migrations.
Energy Conservation: Many organisms exhibit torpor (reduced metabolic activity) to save energy.

Question 9

Mesopelagic Zone Division

Answer 9

Faunal Distribution (600-700 m)

Superficial Layer (Upper Mesopelagic):
Example species: Oplophorus spinosus (deep-sea shrimp) and Systellaspis debilis.
Deep Sea:
Dominated by specific adaptations due to extreme conditions.

Question 10

Environmental Characteristics of the Deep Sea

Answer 10

Light: Dominant colors are gray or grayish whites. Bright red shrimp (e.g., Acanthephyra) and black fish (some species appear red).
Temperature:
1-2°C near the seafloor.
Hydrothermal vents can reach 400°C, but temperatures drop to 2-4°C at greater depths.
Salinity: Not specified.
Oxygen: Concentration decreases 20 meters above the seafloor.

Question 11

Superficial vs. Deep Layers of the Mesopelagic Zone

Answer 11

Superficial Layer (Upper Mesopelagic)

Organisms are more active and may exhibit bioluminescence (using photophores).
Organisms tend to migrate more frequently.

Deep Layer (Lower Mesopelagic)

Located near the base of the thermocline.
Increased presence of micronecton (small organisms).
Most macroplankton do not migrate and are less active.