The Benthos; microbenthos, meiofauna, macrofauna, megafauna

Question 1

why study the benthos?

Answer 1

natural history
fish food
fundamental ecology
human impacts/conservation

Question 2

categories (by size) of the benthos

Answer 2

microbenthos
meiofauna
macrofauna
megafauna

Question 3

what are the benthos?

Answer 3

organisms living in or on the seabed

Question 4

what are the planktonic categories of the benthos?

Answer 4

phytobenthos

zoobenthos

Question 5

what are organisms which occupy the micro-spaces between particles or live in the individual particles?

Answer 5

meiofaunal/interstitial organisms

Question 6

what does interstitial space mean?

Answer 6

the area between particles of sediment

Question 7

size of microbenthos

Answer 7

<50um

Question 8

size of meiofauna

Answer 8

50-500um

Question 9

size of macrofauna

Answer 9

> 500um

Question 10

size of megafauna

Answer 10

> 50mm

not universally agreed

Question 11

epifauna…

Answer 11

spend most of life on seabed

Question 12

infauna…

Answer 12

sped most of life within sediment

Question 13

many of benthos have…

Answer 13

planktonic larvae

Question 14

where are phytobenthos found?

Answer 14

shallow waters - need sunlight

Question 15

what is an important example of phytobenthos?

Answer 15

maerl

Question 16

what can phytobenthos be made out of?

Answer 16

algae

sea grasses

Question 17

what does maerl do?

Answer 17

calcareous alga

grow into Rhodoliths

Question 18

what are rhodoliths?

Answer 18

nodular structure into which phytobenthic algae, such as maerl, grow into

Question 19

what is a biotope?

Answer 19

combination of an abiotic habitat and its associated community of species

Question 20

what adaptive growth forms may algae take depending on habitat? (example)

Answer 20

littoral zone - encrusting

benthos - nodular (Rhodoliths)

Question 21

what is biogenic habitat?

Answer 21

habitat created by organisms

Question 22

what is an example of a biotope?

Answer 22

sublittoral rocky habitats

Question 23

what is a key feature of a sublittoral rocky habitat?

Answer 23

no sediment build-up

just exposed rocks

Question 24

what is the main covering of the bottom the ocean?

Answer 24

muddy bottom

Question 25

why is diatom ooze (seabed sediment) more common in southern hemisphere?

Answer 25

high productivity of phytoplankton (which are mostly diatoms)
silicate

Question 26

what is the wentworth scale?

Answer 26

scale of medium grain size diameter to defining types of sediment

Question 27

how is sediment type defined?

Answer 27

‘Folk triangle’

mix of mud, sand and gravel

Question 28

Permeability of sediment affects…

Answer 28

redox profiles
redox potential discontinuity
(reducing O2)

Question 29

redox potential (mV) is negative when…

Answer 29

there are lower levels of O2

Question 30

redox potential (mV) is positive when…

Answer 30

there are higher levels of O2

Question 31

types of infauna

Answer 31

burrowing and tubicolous

Question 32

example of burrowing infauna

Answer 32

norway lobster

Question 33

sediment, depth benthos relationships

Answer 33

meiofauna, macrofauna, megafauna - decreasing carbon biomass with depth

bacteria - no change in carbon biomass with depth

Question 34

food source for marine benthos

Answer 34

marine snow
greater

accumulation on the continental slope than abyssal plain

Question 35

adaptations of benthic suspension feeders

Answer 35

polychaete worms - crown of tentacles (feather-like) & mucus

bivalve molluscs - e.g. razorshells - short inhalant & exhalant siphons through gills

brittle stars - hold arms up into water (catch food with feet)

Question 36

adaptations of benthic deposit feeders

Answer 36

sub-surface/surface
selective/non-selective -> particle sorting apparatus

bacteria farm from waste - mud shrimp

Question 37

adaptations of benthic predators

Answer 37

e. g. octopuses, lobster, sea stars

- flexible feeding habits

Question 38

adaptations of benthic scavengers

Answer 38

deep-sea amphipods - high portion of body = energy store

rapid detection

good at stripping off material