Ocean VL 2 Flashcards
What are the main types of substrates in the benthic zone?
1) Hard grounds: Rocks, boulders, and biogenic substrates (e.g., shells).
2) Sediments: Divided into:
* Endopsammon: Living within sand.
* Epipsammon: Living on sand.
* Endopelon: Living within mud.
* Epipelon: Living on mud.
What are the key characteristics of phytobenthos?
- No cormophytes (vascular plants).
- Microphytobenthos: Diatoms and periphyton (epilithic, epiphytic, or epizoic).
- Macrophytes: Include filamentous algae (cyanobacteria, rhodophytes, chlorophytes, and phaeophyceae). They have rhizoids for attachment, but nutrient uptake is not from roots.
What types of organisms are found in zoobenthos on hard grounds?
- Sessile organisms: Like barnacles, which attach to surfaces.
- Creeping organisms: Such as sea urchins that move across the substrate.
- Swimming organisms: Including benthic fish.
- Zoobenthos often have planktonic larvae and are typically heavier than pelagic organisms, with many toxic species.
What are the main types of zoobenthos found in sediments?
- Endobenthic meiofauna: Includes small organisms like Turbellaria (planarians), Nematoda (roundworms), and Harpacticoida (small copepods).
- Endobenthic macrofauna: Larger, burrowing organisms such as Polychaeta (bristle worms), bivalves, and some benthic fish like flatfish and rays.
What are coral reefs and their importance in the benthic zone?
- Coral reefs are the most species-rich marine habitats, formed by Madreporaria (stony corals), and are heavily dependent on symbiosis with zooxanthellae (photosynthetic dinoflagellates).
- They thrive in nutrient-poor environments through nutrient recycling and
- require well-illuminated waters with significant water movement to prevent sedimentation.
What are the two main types of benthic food webs?
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Shell food chains: Less mobile, shielded organisms
e.g. mussels, snails → predatory snails → sea stars → big crustaceans - Escape food chains: Mobile, escaping animals like amphipods, which are preyed on by small fish, which in turn are eaten by larger fish.
What life forms dominate the deep sea benthos?
- Dominated by animals adapted to extreme conditions such as high pressure, cold temperatures, and food scarcity.
- Common organisms include sea cucumbers, sponges, and various types of corals, with occasional hydrothermal vent communities hosting chemosynthetic bacteria.
What adaptations do organisms in Antarctica have for surviving in cold waters?
- Icefish contain glycoprotein antifreezers in their blood to prevent freezing.
- Crabs and lobsters are absent from Antarctic waters due to the effects of magnesium ions on their nervous system, which would cause them to become comatose in cold temperatures.
How does the diversity of benthic organisms change with latitude and salinity?
- Diversity increases toward the tropics and decreases in colder regions.
- Salinity also affects diversity, with species richness declining in brackish waters where salinity is low or fluctuates.
What are the main types of sediments in the deep sea?
1) Silica mud: Found below nutrient-rich regions, formed from diatoms and radiolarians.
2) Lime mud: From coccolithophores and foraminifera, in oligotrophic regions.
3) Red deep sea clay: Found in the deepest parts of the ocean, formed from minerals at depths greater than 4000-5000 meters.
What are the key characteristics of food webs and energy flow in the benthic zone?
Energy Sources:
1) Benthic food webs rely on two primary energy sources:
* Autochthonous production: Local primary production from benthic microalgae and macrophytes.
* Allochthonous inputs: Organic material originating from outside the benthic zone, including dead plankton and terrestrial matter, which is important for filter feeders.
Types of Food Chains:
1) Shell food chains:
* Less mobile organisms such as mussels, snails, and sea stars.
* Energy flows slowly through these chains as organisms are less efficient at capturing food but well-defended (e.g., hard shells).
2) Escape food chains:
* Composed of more mobile organisms, such as amphipods, small fish, and large predatory fish.
* Energy moves faster through these chains as organisms actively capture prey and avoid predators.
Ecological Efficiency:
- Benthic organisms typically have higher ecological efficiency (up to 20%) compared to pelagic organisms. This means a higher proportion of energy is transferred to higher trophic levels.
Energy Flow in Sediments:
- Benthic systems in soft sediments are net importers of organic material, as they rely on sinking organic matter (marine snow) for much of their energy input.
- Filter feeders like bivalves play a significant role in processing this imported material.
What adaptations allow benthic organisms to survive in extreme environments like the deep sea or Antarctica?
Deep Sea:
* High pressure: Organisms have flexible cell membranes and proteins that function at extreme depths.
* Low temperatures: Slow metabolism and enzymes adapted to cold.
* Food scarcity: Reliance on marine snow or chemosynthetic bacteria near hydrothermal vents.
* Example: Sea cucumbers and sponges.
Antarctica:
* Antifreeze proteins: Found in icefish to prevent blood from freezing.
* High tolerance to low temperatures: Glyptonotus antarcticus (isopod) and Trematomus bernachii (fish) thrive in freezing conditions.
* Crabs and lobsters absent due to high magnesium concentrations, which causes paralysis at low temperatures.
Zones of a rief
