The Benthic Realm Flashcards
Phytobenthos
Plants and algae living in seafloor ecosystems
Zoobenthos
Animals living in seafloor ecosystems
Photic zone
<200m
% of primary production contributed by phytobenthos
15-20%
Examples of phytobenthos
Plants, macroalgae(seaweed) , microalgae )diatoms, photosynthetic bacteria
Examples of zoobenthos
Scavengers, filters, deposit feeders, sea sponge
Epibenthic/epifauna
Live on the sediment - 80% of larger benthic species
Endobenthic/infauna
Live in the sediment
Macrozoobenthos
> 1mm
e.g. polychaete worms (endobenthic)
e.g. Mollusca (epi/endobenthic)
e.g. lobster, shrimps atc
Meioizoobenthos
0.032-1mm
e.g nematode worms
e.g. Copepods
e.g. benthic foraminifera
Microzoobenthos
= microscopic benthic organisms <0.032mm e.g. bacteria
Controlling factors of benthic habitat distribution
- Light
- Nutrients and food availability
- Temperature
- Salinity
- Substrate type: rock,sand/mud
- Competition
- Predation
Substrate type- Mud
Home to deposit feeders
Substrate type- Gravel
Home to filter feeders
Macoma Community
- Muddy substrate
- Deposit feeders
- Snails and worms
_ Different types of bivalves
Venus Community
- Sandy substrate
- Filter feeding bivalves
- More bivalves (hard shells )
- Fewer worms
Benefits of bioturbation
Increases sediment surface area- gas and nutrient exchange and supplies oxygen to deeper layers
Benthic intertidal environment
The defining characteristic of the intertidal zone is the daily inundation and exposure by tides. Organisms living here must be able to tolerate periods of submergence and desiccation (drying out). E.g. rocky shores (barnacles, sea urchins), sandy beaches(sand crabs ) , salt marshes (cordgrass, periwinkles)
Continental shelf benthic ecosystem
= transition zone between thick continental crust and thin oceanic crust 200-4000m
= Coral reefs, seamounts and canyons
Corals - Hermatypic
- Corals secrete CaCO3 skeletons
- Reef-building stony corals
- Contain zooxanthellae
Shallow, upper photic zone
Corals- Ahermatypic
- Not reef building- soft corals
- Only a small number have zooxanthellae
More widespread and can occur in cooler, deeper waters below photic zone
Tropical Coral
Thrive in tropical ocean waters >20C- clear waters; low turbidity and nutrient inputs
Structure of coral reef
organic structure constructed by animals and algae that secrete CaCO3
Reef wall/face
Has the highest diversity of corals at 20-40m
Lagoon
Highest species diversity eg. clams, oysters, worms, lobsters and crabs
Buttress zone
Helps to disperse the energy of incoming waves
Hermatypic Corals
- Form compact colonies of many genetically identical polyps
- Colonies secrete a skeleton over many generations
Coral structure
Corals= animals. Polyps= animal parts
Corallite
- CaCO3 exoskeleton
- Corallite builds up and forms reefs, living on top of dead
Coral symbiosis- zooxanthellae
–>Zooxanthellae provide food through photosynthesis and support coral growth
–> Coral provide habitat and nutrients for zooxanthellae
–> 60% of organic matter provided by zooxanthellae is utilised by the coral
Unicellular algae
Dinoflagellates (primary producers, endosymbionts)
Where are zooxanthellae located
Embedded in outer layers of coral polyp tissue
What do coral reefs support?
Symbiotic relationships and efficient nutrient cycling
Cold water corals
Can be hermatypic or ahermatypic
e.g. soft corals, cold water stony corals
–> Cold/deep water corals
(deep species don’t have zooxanthellae)
Ahermatypic Corals
= Soft corals (lacking a hard skeleton)
–> Supporting stem of fleshy tissue reinforced by a matrix of microscopic calcareous particles
Deep water corals
–> highly diverse- hermatypic/ahermatypic
–> Some form reefs but most form mounds/ patches banks ( less diverse)
Global distribution of cold water corals
Widely distributed with large reefs/beds in the N and S Atlantic, N and S Pacific and the tropics/polar regions
Deep Sea benthic ecosystems
- Flux of organic matter from water column
- Marine snow
- Turbidity currents
Highest benthic biomass
Continental shelves
Lowest benthic Biomass
Under mid-ocean gyres
Volcanic hydrothermal vent ecosystems
Occur mostly along ocean spreading ridges at abyssal depths
Substances released from black smokers
Hydrogen, sulphide (H2S), hydrogen ammonia and methane
What processes occur at black smokers?
Chemosynthesis and anaerobic respiration
Hydrothermal vent water
Rich in dissolved minerals which supports large populations of chemosynthetic prokaryotes
Tube worms
Symbiotic relationships with bacteria living in the trophosome of the tube worm, which provides essential nutrients from the plume, as worms have no digestive tract
Chemosynthesis- tube worms
Worm haemoglobin combines with H2S and is transferred to bacteria, which turn O2, H2S CO2 etc. into organic molecules on which their host worms feed
Human impacts on benthic ecosystems
- Acidification
- Tourism
- Wind farms
- Oil and gas exploration (spills)
- Fishing practices
