mudflats Flashcards
Location
- all over the world
- intertidal
- near freshwater and sediment output(river, stream)
Physical characteristics (substrate elements):
Substrate: MUD = water + sediment + detritus
Sediment has a diameter of 0.07 mm or less (silt,
clay and detritus)
Sand: 0.02 – 2 mm
Silt: 0.002 – 0.02 mm
Clay: < 0.002 mm
Detritus = non-living particulate organic matter
slope
flat
energy
low
the formation of mudflats
Erosion of rocks
Sediment transport by rivers or ocean
Deposition of sediment – occurs mostly at high, slack tide
Accumulation of sediment to make mudflat
Flat, wide & shallow 🡪 encourages further deposition
temperature
stable within sediment
on top of the mudflats it can vary with air temperature and tides
light
none within sediment
chemical characteristics:
salinity
nutrients
Salinity: within sediment is very stable
On top of mudflats at low tide and in burrows, salinity can vary with run-off, precipitation and evaporation
Nutrients: high organic content of sediment (detritus)
Streams / rivers deliver nutrients in fresh water
And photosynthetic bacteria, diatoms, sea lettuce, eel grass fix carbon and add it to ecosystem
oxygen
low in sediment because:
Little space between sediment particles 🡪 no diffusion
No light 🡪 no photosynthesis within sediment
A very thin layer of oxygenated sediment above a
black, anoxic (= no oxygen), sulfide-rich layer
hydrogen sulfide (H2S) why, colour
high within sediment
Anaerobic bacteria decompose organic material and produce toxic H2S
Black colour is due to reaction of H2S with iron
oxides in silt
Toxic / poisonous!!
biological characteristics:
biodiversity
biomass
productivity
biodiversity- low
biomass- high
prod: moderate
meiofauna
‘meio’ = between; ‘fauna’ = animals
Interstitial organisms (spaces between particles)
Size: 62 um to 0.5 mm
Benthic invertebrates (animals from many phyla)
biological adaptations to mudflats for organism living on the surface
Living on the surface (to avoid low O2, high H2S)
avoid predators: Crabs use camouflage, temporary burrows,
autotomy, and running away fast hard shell, camouflage
Ulva & diatoms must live on surface for light
bio adaptations burrowing
Most of the organisms are found within the sediment
Burrowing is an adaptation for feeding, evading
predators and avoiding fluctuations in
environmental conditions
During low tide burrow water becomes stagnant
burrowing species adaptations
eversible proboscis and feeds as it burrows
clams use their foot to borrow
how are the burrowers in mudflats compared to sandy beaches
slower
living in the dark
eyes are reduced (shrimp) or absent (clams)
relly on smell rather than on vision
low oxygen/high sulfide adaption
- Burrows open to surface to get oxygen-rich,
sulphide-poor water e.g. clams, worms, shrimps
-Euryoxic = tolerance to a wide range of oxygen
levels - Clams: long siphons allow for deep burrowing – can still reach surface for oxygen & plankton
Euryoxic
= tolerance to a wide range of oxygen
levels
clams adaptation to low oxygen/high sulfide
Clams can close up at low tide to keep sulfide out
Clams have low metabolic rates 🡪 low oxygen
requirements
adaption at low oxygen/low sulfide for ghost shrimp
Deposit feeders that burrow continuously
Therefore must be tolerant to low O2, high H2S
Have low metabolic rates 🡪 low oxygen
requirements
mud shrimp adaptation to low oxygen/low sulfide
Filter feeders
Make permanent burrows (U- or Y-shaped) which
they line with mucus
Mucus has iron in it which binds H2S 🡪 excludes sulfide from burrow water
worms adaptation to low oxygen/low sulfide
low metabolic rates 🡪 low oxygen requirements
detoxify sulfide by converting it to a non-toxic form or by binding it to iron (hematin)
Lugworm (Abarenicola pacific): Hemoglobin with high O2 affinity (binds O2 at low
levels)
human impact on mudflats
sewage, disturbance, chemical/oil spills, agricultural run-off of fertilizer and pesticides
what is called the tolerance to a wide range of oxygen levels?
euryoxic
what do clams to avoid high H2S low O2
Use their siphons for deep burrowing
what does ghost shrimp have to survive high amount of sulfide
Hepatopancreas = liver-like organ which detoxifies sulfide to sulfate or thiosulfate
how’s h2s produced
by anaerobic bacteria that decompose organic material
bio adaptation to living on the surface, running
autotomy
