The Benthos; microbenthos, meiofauna, macrofauna, megafauna Flashcards
why study the benthos?
natural history
fish food
fundamental ecology
human impacts/conservation
categories (by size) of the benthos
microbenthos
meiofauna
macrofauna
megafauna
what are the benthos?
organisms living in or on the seabed
what are the planktonic categories of the benthos?
phytobenthos
zoobenthos
what are organisms which occupy the micro-spaces between particles or live in the individual particles?
meiofaunal/interstitial organisms
what does interstitial space mean?
the area between particles of sediment
size of microbenthos
<50um
size of meiofauna
50-500um
size of macrofauna
> 500um
size of megafauna
> 50mm
not universally agreed
epifauna…
spend most of life on seabed
infauna…
sped most of life within sediment
many of benthos have…
planktonic larvae
where are phytobenthos found?
shallow waters - need sunlight
what is an important example of phytobenthos?
maerl
what can phytobenthos be made out of?
algae
sea grasses
what does maerl do?
calcareous alga
grow into Rhodoliths
what are rhodoliths?
nodular structure into which phytobenthic algae, such as maerl, grow into
what is a biotope?
combination of an abiotic habitat and its associated community of species
what adaptive growth forms may algae take depending on habitat? (example)
littoral zone - encrusting
benthos - nodular (Rhodoliths)
what is biogenic habitat?
habitat created by organisms
what is an example of a biotope?
sublittoral rocky habitats
what is a key feature of a sublittoral rocky habitat?
no sediment build-up
just exposed rocks
what is the main covering of the bottom the ocean?
muddy bottom
why is diatom ooze (seabed sediment) more common in southern hemisphere?
high productivity of phytoplankton (which are mostly diatoms)
silicate
what is the wentworth scale?
scale of medium grain size diameter to defining types of sediment
how is sediment type defined?
‘Folk triangle’
mix of mud, sand and gravel
Permeability of sediment affects…
redox profiles
redox potential discontinuity
(reducing O2)
redox potential (mV) is negative when…
there are lower levels of O2
redox potential (mV) is positive when…
there are higher levels of O2
types of infauna
burrowing and tubicolous
example of burrowing infauna
norway lobster
sediment, depth benthos relationships
meiofauna, macrofauna, megafauna - decreasing carbon biomass with depth
bacteria - no change in carbon biomass with depth
food source for marine benthos
marine snow
greater
accumulation on the continental slope than abyssal plain
adaptations of benthic suspension feeders
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)
adaptations of benthic deposit feeders
sub-surface/surface
selective/non-selective -> particle sorting apparatus
bacteria farm from waste - mud shrimp
adaptations of benthic predators
e. g. octopuses, lobster, sea stars
- flexible feeding habits
adaptations of benthic scavengers
deep-sea amphipods - high portion of body = energy store
rapid detection
good at stripping off material
