benthic ecology

Question 1

what is epibenthic

Answer 1

animals attached to a hard substratum or rooted to a shallow depth below seabed surface

Question 2

what is Infauna

Answer 2

animals in the sediment

Question 3

what do ecologists often use to categorise a habitat or community instead of using phylogeny e.g. polycheates, crustaceans, molluscs

Answer 3

Functional Groups (group them based on similar lifestyles e.g. ecological function: feeding strategy, food, mobility + life history: size, longevity, reproductive technique)

Question 4

what are Suspension / filter feeders

Answer 4

capture particles from water
-Passive = use existing current
-Active = generate own current (most) e.g. using cilia

Question 5

what are deposit feeders

Answer 5

ingest sediment and digest organic content
- Many are also scavengers
- Some can change their behaviour to take advantage of currents e.g. stick up palps into the current to feed

Question 6

what are herbivores

Answer 6

Graze on things like Macroalgae, sea grasses

Question 7

what are carnivores

Answer 7

eat other animals

Question 8

what does the Sediment present in a certain habitat reflect

Answer 8

the local hydrodynamic regime (strength and consistency of currents)

Question 9

what is the Sediment grain size a good indicator of

Answer 9

current speed - also important determinant of the benthic community
Grain size ∝ current strength

Question 10

what do Areas with high currents experience

Answer 10

extensive erosion and transportation of sediment (scour)

Question 11

what will happen to the Density of deposit feeders when the current speed decreases

Answer 11

increase - more organic material

Question 12

what is the Dominant grain size and Sorting of the sediment told by

Answer 12

Dominant grain size = current speed and strength
Sorting of the sediment = current consistency

Question 13

what does a Well sorted sediment (same sizes) indicate

Answer 13

regular current speed – better drainage and O2 penetration

Question 14

what does Poorly sorted sediment (loads of different sizes) indicate

Answer 14

erratic current speed, several sedimentary processes

Question 15

how are Hydrostatic skeletons used to burrow

Answer 15

Can apply pressure to move the water down to generate anchors – can then contract down and use the anchor to pull yourself down into sediment
- Animals with exoskeletons can also burrow into sediment e.g. mole crabs

Question 16

what kind of currents do hard bottom communities face

Answer 16

strong current

Question 17

adaptations to animals in hard bottom communities

Answer 17

• Sessile forms may have adaptations to minimise drag
• Many passive suspension feeders (already have a current)

Question 18

what are the 3 different types of anthozoa

Answer 18

Hexacorallia (stony corals, sea anemones, zoanthids)
Octocorrallia (soft corals, gorgonians, sea pens)
Ceriantharia (tube-living anemones)

Question 19

5 orders within Hexacorallia

Answer 19

Actiniaria (sea anemones)
Antipatharia (black corals)
Corallimorpharia
Scleractinia (stony corals)
Zoantharia

Question 20

Scleractinia characteristics

Answer 20

• Reef-forming (hermatypic) corals
• Mostly contain zooxanthellae
• Non-reef-forming (ahermatypic) corals: do not contain zooxanthellae

Question 21

what are Reef-forming and non-reef forming stony corals called

Answer 21

hermatypic + ahermatypic

Question 22

what are cold water corals

Answer 22

• Azooxanthellate scleractinians
  (Also Octocorallia and Antipatharia)

Question 23

where are cold water corals found

Answer 23

• colder waters (4° - 12°C)
• relatively shallow waters (50 to 1000 m) at high latitudes ∼ and at great depths (up to 4000 m) at low latitudes

Question 24

what determines cold water corals distribution

Answer 24

• primary productivity in surface waters + subsequent food transport to the sea floor - although aragonite (calcium carbonate) in the water also important
• Corals can occur individually as isolated colonies in small patch reefs OR in large reefs and giant carbonate mounds

Question 25

what does the surface of Hermatypic corals contain

Answer 25

• living tissue on a calcium carbonate skeleton
• Symbiotic algae (zooxanthelle)

Question 26

coral reproductive strategies

Answer 26

fragmentation (asexual) + sexual reproduction

Question 27

how is high temperature a threat to Coral reefs

Answer 27

• Zooxanthellae within the coral is overproducing O2 (oxygen toxicity) within the tissues – solution is to expel the zooxanthellae causing the coral to starve – if temp goes down they can take these back from the water then recover – longer than a few weeks and the skeleton will be covered in algae
• More co2 in atmosphere = more co2 in ocean (increase in protons) - increase acidity – can’t make calcium carbonate shells
• Increase in tropical storms

Question 28

how is Crown of thorns starfish (eutrophication) a threat to Coral reefs

Answer 28

• Increase in algae – more food for crown of thorns larvae - can form plagues
• Causes shift from corals to feeding on larvae away from zooplankton – reduction on bottom + top down control

Question 29

what are the 5 Coral reef threats

Answer 29

1. high temp
2. Pollution from human activity
3. Overfishing e.g. herbivorous fish that eat algae
4. Crown of thorns starfish (eutrophication)
5. Physical disturbances e.g. destructive fishing (dynamite + cyanide)

Question 30

how can we use corals to reveal the secrets of climate change

Answer 30

drill them - If coral are thousands years old they will have isotopes near the centre that can reflect past water temperatures