Stresses and Strains on the Seabed

Question 1

Why are oxygen levels relatively high in benthic environments?

Answer 1

O2 conc decreases with increasing water temp

Question 2

Why are burrowers at risk to oxygen deprivation?

Answer 2

O2 conc is low in fine sediments and fine silt restricts water flow and gas exchange

Question 3

3 anatomical solutions to maintain o2 supply

NEED EXAMPLES TOO

Answer 3

1) retain contact with well oxygenated water
eg. geoduck and siphons

2) increase surface area for gas exchange
eg. nereis and SA of parapodia

3) gills that can reach oxygenated water in case you are a burrowing species
eg. Terebella

Question 4

How are scale worms’ gills adapted?

Answer 4

Notopodial gill is expanded into a flat scale called an ELYTRON that is protected under a roof of felt like hairs

Question 5

Physiological solutions to preventing oxygen deprivation

Answer 5

use oxygen binding proteins

Question 6

List the blood pigments used for O2 binding

Answer 6

1) Haemocyanin (blue)
eg. molluscss

2) haemerythrin (pink)
eg. annelids

3) chlororcruonin (iron, pale red)
eg. polychaetes

4) haemoglobin (iron, red)
eg. most vertebrates

Question 7

What is Bohr effect? Where is this seen?

Answer 7

Under high temperature and low pH extreme conditions, the affinity for oxygen binding is reduced, so oxygen affinity curve shifts right (seen in tissues)

Question 8

Behavioural solutions to preventing oxygen deprivation

Answer 8

1) active movement of water to maintain fresh O2 supply
eg. lugworm
2) microhabitat selection, move to areas with higher O2 conc
3) decrease O2 requirements in hypoxic conditions (not many can!

Question 9

Estuaries

Answer 9

Influx of freshwater reduces salinity

Question 10

Tidal regions

Answer 10

Evaporation increases salinity

Question 11

How is osomoregulation performed?

Answer 11

1) regulate salt balance across permeable regions
eg. movement of water or salt around gills

2) regulate conc of organic osmolytes (urea) or amino acids
eg. seen in sharks and cartilaginous fish

3) reduce skin permeability
eg. limit area of exchange to single organ

Question 12

Behavioural adaptations by Laver spire shell (hydrobia ulvae) to salinity changes

Answer 12

1) live in estuarine systems
2) tolerate a wide range of salinity changes
3) burrow into ground during tidal inundations
4) avoid salinity exposure
5) shut shells

Question 13

Two contrasting objectives to combat water movement for benthic filter feeders that don’t seem compatible

Answer 13

• need large SA to capture lots of food

- but large surface increases vulnerability to water force

Question 14

Solution to tackling water movement for benthic animals

Answer 14

• branching structures that still maintain large SA but allow gaps for water flow
• protein skeleton (such as gorgonin in sea fans) which is way more flexible than CaCO3
• internal filter such as those in sea squirts

Question 15

List 3 biological stresses for benthic animals

Answer 15

1) Food supply
2) competition for resources
3) predation

Question 16

How do benthic animals avoid predation?

Answer 16

1) burrow into sediment
eg. lugworm
2) tubes of mucus and grit
eg. sand mason worm
3) calcified tubes or shells
4) toxic defence and warning colouration
5) camouflage using crypsis or mimicry
eg. sea slugs
6) physiological refuge
eg. upper shore away from starfish

Question 17

Metal ions facilitate (a) binding of oxygen. Useful in varying conditions, eg. haemocyanin can be altered by (b) conditions to increase (c) for oxygen.

Answer 17

a) reversible
b) hypoxic
c) affinity

Question 18

What is microhabitat selection?

Answer 18

• moving to areas of higher O2 conc