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6.2 INTERTIDAL ECOSYSTEMS, Definitions - Coggle Diagram
6.2 INTERTIDAL ECOSYSTEMS
ROCKY SHORE
Rocky intertidal zone
Characteristics
Tides create partly aquatic
& partly aerial enviro
Distribution of organisms in horizontal bands
Caused by differing tolerances of organisms to stresses, both biotic & abiotic
Banding pattern as a result of rise & fall of tides
Pattern is similar worldwide -> intertidal zonation
Physical
Intertidal: exposed to air & covered by water -> twice a day
Temperature: wide variation with interactions with air
Light: lots in air, but in water varies with depth
Energy (variable with location) : amount of waves & wind hitting the ecosystem
ex: Pedder Bay = low
Race Rocks = high
Substrate: rock
Location
Cosmopolitan ecosystem - all over the planet
In all locations where there is bedrock & large boulders that are exposed at low tide (intertidal)
Limits of organisms
LOWER LIMIT : set by BIOTIC factors
Exceptions
Light setting the lower limit of seaweeds
Predation by terrestrial predators from above
UPPER LIMIT : set by ABIOTIC factors
Chemical
Salinity: wide variation in air & in tidepools, precipitation & evaporation influence it
Nutrients: moderate to high due to proximity to land ; run-off & upwelling
Oxygen: variation in tidepools ; not very accessible to most intertidal organisms in air
Stresses
Abiotic
Food & Oxygen availability
Obtain oxygen from water
Organisms in high IT have limited time to feed & oxygen
Most marine organisms get food from water or plankton so can only feed underwater
Adaptations
Low activity levels at low tide
Feed/oxygen the whole time underwater -> mussels, barnacles
Scaleless fish can absorb O2 across body -> Northern clingfish
Modified O2 absorption -> tube feet of blood stars
Temperature
Water temp varies only slightly over year (7~12*)
Air temp can vary drastically (0~30*)
Organisms out of water are subject to more variations of temp
Adaptations
Eurythermal enzymes in barnacles but not in sea urchins or sea stars
Evaporative cooling in mussels & gooseneck barnacles
UV light
Marine organisms can sunburn, especially out of water
Adaptations
Sunscreen - natural compounds that absorbs UV
Protective shells
Under rocks & overhangs
Desiccation
Water loss, drying out,
dehydration
Adaptations
Lose water then rehydrate -> Porphyra
Live in tidepool
Mucus -> anemones, Fucus
Close up or clamp down -> mussels, barnacles, limpets
Conserve water -> aggregating anemone attaching shells & pulling in tentacles ( help keep the water instead)
Some species are more tolerant to being in the air (e.g. periwinkles, limpets) & can live in high IT
Can increase with wind & temperature
Occurs during low tides due to air exposure
Wave exposure
Some rocky IT are very high energy ecosystems
Organisms waves exposed are adapted to hang on
e.g. mussels have byssal threads
e.g. some algae/seaweeds are very flexible
Salinity
Variation (especially at low tides)
Euryhaline
- tolerant to wide variations (e.g. mussels, barnacles)
Stenohaline
- tolerate only a narrow range (e.g. sea stars)
Adaptations
Close up -> barnacles, mussels, anemones
Ion pumps in gills -> crabs
Can increase with evaporation or decrease with fresh water input
Biotic
Predation
Animals eating other animals
SPECIALISTS : eat a single prey type
Adaptations
Camouflage / e.g. tidepool sculpins, gumboot chitons
Chemical defense / nudibranchs
Protective shells / e.g. hermit crabs
Escape responses
Mutualistic adaptations / keyhole limpet, scale worm
GENERALISTS : eat a wide range of food types
Refuges
Height in IT / e.g. mussels interactions -
Pisaster
Size / e.g. some mussels too big to be eaten by
Pisaster
Space / e.g. limpets living on vertical surfaces to avoid predations by birds Black oystercatchers
Herbivory
Animals eating plants/seaweeds
(Similar to predation)
Adaptations/Refuges
Physical defense / e.g. calcium carbonate in coralline algae
Chemical defense / e.g. sulfuric acid in acid algae - dissolves calcium teeth - or bromine in Prionitis
Height in IT (above predators)
Competition
EXPLOITATIVE -> differential use of resource
INTERSPECIFIC -> between species
INTERFERENCE -> direct interaction
INTRASPECIFIC -> between individuals of the same species
barnacles compete for space
hermit crabs compete for shells
anemones compete for space
Use or defense of a resource (food, space, mate) that reduce its availability to other individuals
MUDFLATS
Sediment covered intertidal ecosystem
Characteristics
Physical characteristics
Slope: FLAT -> typically wide with shallow slope
Energy: low-little to no wave action, except from storms & boat wakes
Substrate: MUD = water + sediment + detritus
Sediment: has a diameter of 0.07 mm or less (silt, clay & detritus)
Detritus: dead organic material, non-living particulate organic matter (bodies, parts of organisms or feces)
Formation
erosion from rocks
sediment transport by rivers or ocean
accumulation of sediment to make mudflats up to thousands of years
Flat, wide & shallow -> encourages further deposition
Temperature: within sediment really stable
Stenothermal
enzymes
on top of mudflats, temp can vary with air temperature at low tide
Light: none within sediment, only on top of mudflats
Chemical characteristics
Salinity: within sediment is very stable ->
euryhaline
On top at low tide & in burrows, salinity can vary with run-off, precipitation & evaporation
Nutrients: high organic content of sediment (detritus)
Streams/rivers deliver nutrients in freshwater & photosynthetic bacteria/diatoms/sea lettuce/eel grass fix carbon & add it to ecosystem
Oxygen: low within 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) or
hypoxic
(low oxygen), sulfide-rich layer
Hydrogen sulfide (H2S): high within sediment
anaerobic bacteria decompose organic material & produce toxic H2S
black color is due to reaction of H2S with iron oxides in silt
toxic / poisonous
binds to iron = safe
H2S + O2 = sulfate SO4^-2 or thiosulfate S2O2^-2
toxic non-toxic
Needs
Intertidal
Near freshwater & sediment output
Species observed
Logworm
Bental clam
Ribbon worm
Gaper clam
Heart cockle
Sea lettuce
Blood worm
Spaghetti worm
Location
Distributed all over the Earth (St Lawrence, Yangtze)
Biological characteristics
Meiofauna
"meio" between
"fauna" animals
(Size: 62 um to 0.5 mm)
Benthic invertebrates (animals from many phyla)
Interstitial organisms (spaces between particles)
Indicator species
Define indicator species more precisely: Species whose presence, absence, or abundance reflects specific environmental conditions.
Give more examples: Besides meiofauna, mention polychaete worms or bivalves as indicators of organic pollution or oxygen levels.
Explain response: Changes in abiotic factors like pollution, salinity, or oxygen can cause measurable shifts in indicator species populations.
2) Productivity: moderate (lower than rocky)
3) Biomass: moderate-high (mass of living matter)
1) Biodiversity: low (adaptations needed)
Biological adaptations
4) Low oxygen / high sulfide
burrows open to surface to get O2-rich, sulfide-poor water
e.g. clams, worms, shrimps
euryoxic
-> tolerance to wide range of O2 levels
e.g. ghost shrimps
deposit feeders than burrow continuously
low metabolic rates -> low O2 requirements
hepatopancreas = liver-like organ which detoxifies H2S to SO4^-2/S2O2^-2
e.g. mudshrimps
filter feeder
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
e.g. worms
typically have low metabolic rate -> low O2 requirement
most detoxify sulfide either by converting it to an non-toxic form or by binding it to iron (hematin)
e.g. clams
long siphons allow for deep burrowing - can still reach surface for O2 & plankton
have low metabolic rate -> low O2 requirements
can close up at low tide to keep sulfide out
e.g. lugworm : hemoglobin with high O2 affinity (binds O2 at low levels)
3) Living in the dark
eyes are reduced (e.g. shrimps) or absent (e.g. clams)
rely on smell rather than vision
e.g. ghost shrimps
2) Burrowing
most of the organisms in sediment-covered shore ecosystems are found within the sediment
burrowing for feeding, evading predators & avoiding fluctuations in environmental conditions
during low tide, burrow water becomes stagnant
in the mudflats, no rapid burrowers compared to sandy beaches
e.g.
Nereis
uses its parapodia to burrow
e.g.
Abarenicola
has an eversible proboscis & feeds as burrows
e.g. clams use their foot to burrow
1) Living on the surface (to avoid low O2, high H2S)
But need means of avoiding predators
e.g. crabs use camouflage, temporary burrows, autonomy, running away fast
e.g. cockles have a hard shell, interlocking valves, muscular foot for escape
Human impacts
Disruption of water flow
coastal squeeze & dams
Invasive species
cord grass to stabilize the mud & varnish clam introduced as larvae from ballast water & european green crab
Pollution - chemicals
microplastics, non-point source, fuel/oil, agricultural waste (fertilizers, pesticides, sewage/poop)
Bycatch (birds in fish nets)
Construction & coastal development & harbour expansion
disruption of feeding/resting for migratory birds & killing of species already living there
Aquaculture -> e.g. clam farms
Trampling by scientists, shellfish harvesters,
compaction, burrow destruction, organism death, crushing
Overharvesting or worms & shrimps for bait
SANDY SHORE
Sediment covered intertidal ecosystem
Characteristics
Physical characteristics
Slope: variable over the seasons & varies with location (wave action) *see graph on powerpoint
Energy: moderate
higher energy beaches have a steeper slope & larger sediment particles
dynamic equilibrium
of sandy shores
beach shape & slope fluctuate about an equilibrium (which also changes with time, but much more slowly)
forces of erosion & deposition reach a dynamic equilibrium
waves, tides, currents & wind erode & transport sand
Substrate: sand
sediment particles have a diameter of 0.02 ~ 2 mm
fine sand can retain water, but coarse sand allows water to drain water
not much detritus is retained in sand
source: depends on location
rocks on land
calcium carbonate (CaCO3) skeletons of animals
coralline algae (including parrot fish poop)
star (Okinawa Japan) & singing beaches (Estonia
Temperature: within sand is quite stable
just like mud, sand is a good buffer against temperature & salinity changes
below the first few cm, the temperature in the sand = temperature of the seawater
Light: absorbed or reflected by the surface layer of sand, so no light in sediment below surface - but with some transparent particles & spaces between particles light penetrates deeper than in mud
Chemical characteristics
Nutrients: little to none in the sand as nutrients move through with H2O & are used quickly BUT waves bring algae to the beach
Oxygen: lots due to high wave action/energy, especially at high tide
may be reduced in interstitial water at low tide as O2 is consumed by organisms
fine-grained beaches don't allow O2 to enter as quickly & therefore may become hypoxic at low tide
Salinity: within sable is quite stable
below the first 10/15 cm, same as surrounding H2O
even with run-off & precipitation, more dense saltwater will sink below freshwater
Hydrogen sulfide: little to none
(except at low tide in fine-grained beaches)
Location
Distributed all over the Earth (Weir's beach, Bay of Fundy)
Intertidal
Biological characteristics
2) Productivity: low
(there are benthic diatoms in first mm of sand but producers get shifted around so much & nutrients are low)
3) Biomass: low to moderate
1) Biodiversity: low
(few organisms are adapted to high energy shifting of sand particles) EXCEPT MEIOFAUNA
Zonation: Just like in rocky intertidal, there is a pattern of zonation due to tides at sandy beaches
Challenges
& Biological adaptations
2) Lack of nutirents
Most organisms depend on waves to bring food & nutrients
e.g. sand dollars, mole crab
Wrack lines very rich in nutrients (organic debris deposited at high tide mark)
Beach hoppers / amphipods in wrack
3) Turbulent habitat with
nothing to hang onto / lack
of stable ground
(Living among the shifting
sands is a significant challenge,
particles are always in motion)
Burrowing is rapid & powerful
e.g. razor clam & mole clam
1) Predation, if living on
the surface (less so if
burrowed in the sand)
Camouflage or burrow
Ecosystem services provided
Breakdown of organic materials & pollutions
Water filtration
Dynamic response to sea level rise
Nutrient mineralization & recycling
Wave dissipation & associated buffering VS extreme weather events
Storage water in dune aquifers & groundwater discharge through beaches
Sediment storage & transport
Maintenance of biodiversity & genetic resources
Providing a nursery area for juvenile fishes (e.g. grunion)
Nesting site or rookeries for turtles, shorebirds & pinnipeds
Prey for birds & other terrestrial wildlife
Scenic vistas & recreational opportunities
Functional links between terrestrial & marine environments
Human impacts
Resource exploitation
Clams & crabs for food
Shrimps & worms for bait
Seaweed as compost
Shells & other treasures
Sand mining
Costal development
Pollution - especially plastic
Invasive/alien/introduced species (e.g. European Green Crabs)
Beach grooming - removes wrack
Climate change / sea level rise (erosion)
Disturbance of species & sand
Definitions
Ecosystem: different organisms living together
Marine: in relation to salty water/ocean
Ecology: study of relationship of living organisms and their environment
Species: group of organisms which can interbreed to produce fertile offspring
Population: group of organisms of the same species at the same time in the same place
Community: many species living and interacting with each other in the same place at the same time
Habitat: place in which species live