The Benthic Realm

Question 1

Phytobenthos

Answer 1

Plants and algae living in seafloor ecosystems

Question 2

Zoobenthos

Answer 2

Animals living in seafloor ecosystems

Question 3

Photic zone

Answer 3

<200m

Question 4

% of primary production contributed by phytobenthos

Answer 4

15-20%

Question 5

Examples of phytobenthos

Answer 5

Plants, macroalgae(seaweed) , microalgae )diatoms, photosynthetic bacteria

Question 6

Examples of zoobenthos

Answer 6

Scavengers, filters, deposit feeders, sea sponge

Question 7

Epibenthic/epifauna

Answer 7

Live on the sediment - 80% of larger benthic species

Question 8

Endobenthic/infauna

Answer 8

Live in the sediment

Question 9

Macrozoobenthos

Answer 9

> 1mm
e.g. polychaete worms (endobenthic)
e.g. Mollusca (epi/endobenthic)
e.g. lobster, shrimps atc

Question 10

Meioizoobenthos

Answer 10

0.032-1mm
e.g nematode worms
e.g. Copepods
e.g. benthic foraminifera

Question 11

Microzoobenthos

Answer 11

= microscopic benthic organisms <0.032mm e.g. bacteria

Question 12

Controlling factors of benthic habitat distribution

Answer 12

• Light
• Nutrients and food availability
• Temperature
• Salinity
• Substrate type: rock,sand/mud
• Competition
• Predation

Question 13

Substrate type- Mud

Answer 13

Home to deposit feeders

Question 14

Substrate type- Gravel

Answer 14

Home to filter feeders

Question 15

Macoma Community

Answer 15

• Muddy substrate
• Deposit feeders
• Snails and worms
  _ Different types of bivalves

Question 16

Venus Community

Answer 16

• Sandy substrate
• Filter feeding bivalves
• More bivalves (hard shells )
• Fewer worms

Question 17

Benefits of bioturbation

Answer 17

Increases sediment surface area- gas and nutrient exchange and supplies oxygen to deeper layers

Question 18

Benthic intertidal environment

Answer 18

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)

Question 19

Continental shelf benthic ecosystem

Answer 19

= transition zone between thick continental crust and thin oceanic crust 200-4000m
= Coral reefs, seamounts and canyons

Question 20

Corals - Hermatypic

Answer 20

• Corals secrete CaCO3 skeletons
• Reef-building stony corals
• Contain zooxanthellae
  Shallow, upper photic zone

Question 21

Corals- Ahermatypic

Answer 21

• Not reef building- soft corals
• Only a small number have zooxanthellae
  More widespread and can occur in cooler, deeper waters below photic zone

Question 22

Tropical Coral

Answer 22

Thrive in tropical ocean waters >20C- clear waters; low turbidity and nutrient inputs

Question 23

Structure of coral reef

Answer 23

organic structure constructed by animals and algae that secrete CaCO3

Question 24

Reef wall/face

Answer 24

Has the highest diversity of corals at 20-40m

Question 25

Lagoon

Answer 25

Highest species diversity eg. clams, oysters, worms, lobsters and crabs

Question 26

Buttress zone

Answer 26

Helps to disperse the energy of incoming waves

Question 27

Hermatypic Corals

Answer 27

- Form compact colonies of many genetically identical polyps - Colonies secrete a skeleton over many generations

Question 28

Coral structure

Answer 28

Corals= animals. Polyps= animal parts

Question 29

Corallite

Answer 29

- CaCO3 exoskeleton - Corallite builds up and forms reefs, living on top of dead

Question 30

Coral symbiosis- zooxanthellae

Answer 30

-->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

Question 31

Unicellular algae

Answer 31

Dinoflagellates (primary producers, endosymbionts)

Question 32

Where are zooxanthellae located

Answer 32

Embedded in outer layers of coral polyp tissue

Question 33

What do coral reefs support?

Answer 33

Symbiotic relationships and efficient nutrient cycling

Question 34

Cold water corals

Answer 34

Can be hermatypic or ahermatypic e.g. soft corals, cold water stony corals --> Cold/deep water corals (deep species don't have zooxanthellae)

Question 35

Ahermatypic Corals

Answer 35

= Soft corals (lacking a hard skeleton) --> Supporting stem of fleshy tissue reinforced by a matrix of microscopic calcareous particles

Question 36

Deep water corals

Answer 36

--> highly diverse- hermatypic/ahermatypic --> Some form reefs but most form mounds/ patches banks ( less diverse)

Question 37

Global distribution of cold water corals

Answer 37

Widely distributed with large reefs/beds in the N and S Atlantic, N and S Pacific and the tropics/polar regions

Question 38

Deep Sea benthic ecosystems

Answer 38

- Flux of organic matter from water column - Marine snow - Turbidity currents

Question 39

Highest benthic biomass

Answer 39

Continental shelves

Question 40

Lowest benthic Biomass

Answer 40

Under mid-ocean gyres

Question 41

Volcanic hydrothermal vent ecosystems

Answer 41

Occur mostly along ocean spreading ridges at abyssal depths

Question 42

Substances released from black smokers

Answer 42

Hydrogen, sulphide (H2S), hydrogen ammonia and methane

Question 43

What processes occur at black smokers?

Answer 43

Chemosynthesis and anaerobic respiration

Question 44

Hydrothermal vent water

Answer 44

Rich in dissolved minerals which supports large populations of chemosynthetic prokaryotes

Question 45

Tube worms

Answer 45

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

Question 46

Chemosynthesis- tube worms

Answer 46

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

Question 47

Human impacts on benthic ecosystems

Answer 47

- Acidification - Tourism - Wind farms - Oil and gas exploration (spills) - Fishing practices