Soft substrate communities the intertidal and subtidal zones
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Soft Substrate Communities: The intertidal and subtidal zones. Intertidal Habitats. Exposed - sand beaches Protected - sand and mud flats Sand beaches Appear devoid of macroscopic life Virtually all organisms bury themselves Exposed to waves, face open ocean Pronounced slope

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Soft substrate communities the intertidal and subtidal zones

Soft Substrate Communities:The intertidal and subtidal zones



  • Exposed - sand beaches

  • Protected - sand and mud flats

  • Sand beaches

    • Appear devoid of macroscopic life

    • Virtually all organisms bury themselves

    • Exposed to waves, face open ocean

    • Pronounced slope

  • Sand and mud flats

    • Large numbers of visible macroscopic life

    • Facing bay or lagoon

    • Little or no slope


Sandy shores
Sandy shores

  • Defined by three factors

    • Particle size, wave action, and slope

    • Interrelated

  • Particle size

    • Water retention

    • Suitability for burrowing

  • Substrate movement


Slope
Slope

  • Interaction between particle size, wave action, and swash/backswash

  • Swash - water running up a beach

    • Carries particles

    • Accretion

  • Backswash

    • Removes particles


Substrate movement
Substrate movement

  • Particles are not stable

  • Continually moved and sorted

  • Fines settle out in low wave action

  • Coarses settle immediately

  • Results in zonation based on grain size

  • Different beach types


  • Dissipative beach

    • Strong wave action

    • Energy dissipated in broad flat surf zone

    • Gentle swash

    • Gentle slope

  • Reflective beach

    • Strong wave action

    • Energy is not dissipated

    • Strong swash

    • Steep slope


Seasonal changes
Seasonal changes

  • Changes in wave intensity = change in grain size

  • Common seasonal shift in beach profile

  • Fine sand in summer

  • Coarse beach in winter

  • Substrate may be moved a meter or more

  • Few large organisms occupy the surface


  • Smooth uniform profile

  • Lack topographical diversity

  • Uniform action of physical factors

    • Temperature

    • Wave action

    • Dessication


  • Sand is an excellent buffer

    • Temperature changes

    • Salinity

    • Exposure to sunlight

  • Oxygen

    • Not limiting on surface

    • May become limiting in substrate

    • Interchange of surface water with interstitial water

    • Exchange

      • Fine - slow

      • Coarse - fast

    • Tube builders and burrowers may deepen oxygen


Sand flats
Sand flats

  • Consist of finer grained sand and sediment

  • Waves and water currents affect grain size

  • Very low slope

  • Oxygen generally not limited

    • Unless you go deep


Muddy flats
Muddy flats

  • Characteristic of estuaries, salt marshes

  • Restricted to completely protected areas (waves)

  • Slope is flat

  • More stable

  • Conducive to permanent burrows

  • Long retention time of water in sediment

  • Low exchange rate with water above

  • Results in anaerobic conditions below surface


Rpd redox potential discontinuity layer
RPDRedox potential discontinuity layer

  • Rapid change from aerobic to anaerobic layer

  • Characterized by greyish color, below is black

  • Below decomposition by anaerobic bacteria

  • Biologically significant

  • Reduced compounds diffuse upward

  • Oxidized by bacteria in aerobic sediment

  • Incorporated into bacterial biomass

  • Form basis of food chains


Subtidal habitats
Subtidal habitats

  • Turbulence eliminates thermal stratification

  • Waves may affect stability of of substrate

    • May suspend and move particles

    • Determines types of particles present

    • Removes fine particles

  • Salinity is variable

  • Temperature shows seasonal change

  • Light penetration is reduced

    • just a few meters


Topography
Topography

  • Vast monotonous expanses

  • Ripple marks, worm tubes, fecal mounds

  • Substrate grain size and composition only major differences

  • Fewer habitats for animals to occupy

  • # infaunal species < epifaunal species



Physical Characteristics cycle but shallow (contintental shelf)


Organisms

Organisms cycle but shallow (contintental shelf)


Size of infaunal organisms
Size of infaunal organisms cycle but shallow (contintental shelf)

  • Macrofauna: >0.5 mm

  • Meiofauna: 0.5-0.062 mm

  • Microfauna: < 0.062 (mostly protozoans and bacteria)


Community organization
Community organization cycle but shallow (contintental shelf)

  • Patchiness

    • Time and space

    • Horizontal and vertical

    • Cyclical

    • result of physical factors and interactions between organisms


Community organization1
Community Organization cycle but shallow (contintental shelf)

  • Grain size sets limits for organisms

  • Dominated by suspension feeders (filterers) and detritivores

  • Generally separated

  • Detritivores in fine sand

  • Filterers in clean coarse sand

  • Seasonal change


Community structure
Community structure cycle but shallow (contintental shelf)

  • Changes occur through physical or biological factors


Parallel bottom communities
Parallel bottom communities cycle but shallow (contintental shelf)

  • Thorson 1955

    • Similar communities in similar habitats found globally

    • Similar sediments contain similar organisms

    • Similar ecologically and taxonomically

    • Pattern implies associations are not random

    • Represent interacting systems with similar “rules”


Woodin 1983
Woodin 1983 cycle but shallow (contintental shelf)

  • Classification of organisms into limited # assemblages

  • Functional groups


Types of organisms
Types of organisms cycle but shallow (contintental shelf)

  • Sediment stabilizers

    • Organisms that secrete mucous or roots to bind sediment

    • Amphipods, phoronid worms, anemones, polychaetes

  • Sediment destabilizers (bioturbators)

    • motile or sedentary organisms who cause sediments to move

    • Cucumbers, mobile clams, whelks


Community organization2
Community organization cycle but shallow (contintental shelf)

  • Four dominant taxonomic groups of macrofauna:

    • Polychaetes

      • Tube building worms, Burrowing worms

    • Crustaceans

      • Ostracods, Amphipods, isopods, decapods, mysids, tanaids

    • Echinoderms

      • Brittle stars, urchins, sand dollars, sea cucumbers, sea stars

    • Mollusks

      • Bivalves, scaphopods, gastropods


  • Infaunal animals: cycle but shallow (contintental shelf)

    • Deposit feeders

    • Suspension feeders

  • Predators:

    • Worms

    • Crustaceans

    • Mollusks

    • Echinoderms

    • Bottom fishes


Adaptations

Adaptations cycle but shallow (contintental shelf)


Adaptations1
Adaptations cycle but shallow (contintental shelf)

  • Deep Burrowing

    • Get away from sediment affected by waves

    • Heavy shells - anchors

    • Long siphons

    • Severe storm may wash the up on beach

    • Harder to get back into water and burrow quickly

    • Mercenaria, Pismo clam


Adaptations2
Adaptations cycle but shallow (contintental shelf)

  • Fast burrowers

    • More common

    • Burrow as soon as wave removes organism

    • Annelid worms, small clams, crustaceans

    • Short bodies, limbs

    • Donax, Siliqua and Ensis (razor clams)

    • Emerita (mole crabs)


Adaptations3
Adaptations cycle but shallow (contintental shelf)

  • Swash migration

    • Find food

    • Avoid predators


Adaptations4
Adaptations cycle but shallow (contintental shelf)

  • Smooth shells - reduce resistance of sand

  • Ridges - grip sediment, aid in penetration

  • Reduced spines (echinoderms, sand dollars)

  • Weight belts - accumulation of iron compounds - sand dollars


Adaptations muddy shores
Adaptations (muddy shores) cycle but shallow (contintental shelf)

  • Burrow

  • Permanent tubes

  • Anaerobic adaptations

    • Development of oxygen carriers (hemoglobin)

    • Glycogen stores for anaerobic metabolism

    • Bring surface water down


Reproduction
Reproduction cycle but shallow (contintental shelf)

  • Iteroparous > semelparous

  • Coordinate spawning with tides

    • Lunar rhythms

    • Stranding

    • Predation

  • Latitudinal gradient

    • Planktogrophic - tropics

    • Lecitrophic - temperate zone


Types of organisms sand beach
Types of organisms - sand beach cycle but shallow (contintental shelf)

  • Lack of macroscopic plants

  • Primary producers - benthic diatoms, surf-living phytoplankton

    • Vertical migration in sediments, water column

  • Polychaete worms, mollusks, crustaceans


Feeding ecology sand beach
Feeding ecology - sand beach cycle but shallow (contintental shelf)

  • Very little primary production

  • Organisms depend on phytoplankton in water, organic debris

  • Filter feeders, detritus feers, scavengers

  • Few resident carnivores

  • Opportunistic carnivores, scavengers


Types of organisms sand flats
Types of organisms - sand flats cycle but shallow (contintental shelf)

  • Perrenial microscopic plants, seagrasses

  • Ephemeral algae, seasonally abundant

  • Large and diverse array of microflora

    • Benthic diatoms, dinoflagellates, cyanobacteria

  • Polychaete worms, mollusks, crustaceans


Feeding ecology sand flats
Feeding Ecology - sand flats cycle but shallow (contintental shelf)

  • Productivity from microfloral films, seagrasses, macroalgae

  • Not grazed extensively

  • 90-95% broken down into detritus

  • Scavengers, filterfeeders, and deposit feeders


Types of organisms mud flats
Types of organisms - mud flats cycle but shallow (contintental shelf)

  • Substantial plant life

    • Diatoms, macroalgae, seagrasses

  • Bacteria

    • Highly abundant

    • Sulfur bacteria (oxidize sulfur compounds for energy) (Chemolithoautotrophic bacteria)

  • Two separate layers of productivity

  • Macrofauna similar to sandy areas


Feeding ecology mud flats
Feeding Ecology - mud flats cycle but shallow (contintental shelf)

  • More food available than in sand

  • More large organisms

  • Deposit and suspension feeders are dominant

  • Deposit feeders (worms and bivalves)

    • Burrow through substrate (earthworms)

    • Surface feeding


  • Suspension feeders cycle but shallow (contintental shelf)

    • Mostly like others in sandy areas

    • Must deal with fine suspended particles

    • Partially feed on both particles and plankton

  • Predators

    • Fish, birds, moon snails, crabs, worms

  • Few herbivores

  • Trophic structure based:

    • detritus bacteria base

    • Autotrophic base


Types of organisms subtidal
Types of organisms - subtidal cycle but shallow (contintental shelf)

  • Nutrients are rarely limiting

  • Productivity is relatively high

  • Large populations of zooplankon and benthic organisms

  • Macroscopic plants contribute to primary production

  • Runoff from land plays major role

  • Few large grazing animals


Organismal Characteristics cycle but shallow (contintental shelf)


Community organization of soft substrates

Community Organization of Soft Substrates cycle but shallow (contintental shelf)


What governs subtidal communities
What governs subtidal communities? cycle but shallow (contintental shelf)

  • Predation

  • Disturbance

  • Recruitment

  • Recolonization

  • Competition


Community organization sand
Community organization - sand cycle but shallow (contintental shelf)

  • Grain size sets limits for organisms

  • Dominated by suspension feeders (filterers) and detritivores

  • Generally separated

  • Detritivores in fine sand

  • Filterers in clean coarse sand

  • Seasonal change


Community organization sand1
Community organization - sand cycle but shallow (contintental shelf)

  • Zonation present, but fuzzy

    • Habit of animals to migrate up and down beach

    • Lack of studies


Community organization mud
Community organization - mud cycle but shallow (contintental shelf)

  • Intertidal area extensive

  • Supralittoral

    • burrowing crabs

  • Midlittoral

    • clams and polychaetes

  • Infralittoral

    • No sharp boundary

    • Like midlittoral


Distribution
Distribution cycle but shallow (contintental shelf)

  • Gregarious

  • Crustaceans  exposed and tropical shores

  • Bivalves  protected and temperate shores

  • # macrofaunal sp.  decreasing wave exposure

  • Biomass  exposed beaches


Mclachlan 1983
McLachlan 1983 cycle but shallow (contintental shelf)

  • Abundance and diversity correlated with particle size and slope

  • Faunas if beach is dissipative

    • Wave action dissipated in surf zone

    • Flat slopes

    • Less movement

    • High biomass of filter feeders


Community regulation sandy beaches
Community regulation - sandy beaches cycle but shallow (contintental shelf)

  • Sandy beaches - not studied so extensively

  • Competition for space not major contributor to patterns

    • Three dimensional space

    • Extreme patchiness

  • Competition for food

    • Abundant plankton

    • Sparse populations



Community regulation sand and mud flats
Community regulation - sand and mud flats cycle but shallow (contintental shelf)

  • Physical factors important

    • Grain size

  • Trophic group amensalism

    • Exclusion of one trophic group by another

    • Deposit feeders exclude suspension feeders

    • Burial of newly settled suspension feeder larvae by deposit feeders


  • Seasonal weather changes cycle but shallow (contintental shelf)

    • Migration to deep water

    • Sea ice - scouring

  • Prime factors are:

    • Predation

    • Competition

    • Disturbance

  • Predation, predation/disturbance significant


Wiltse 1980
Wiltse 1980 cycle but shallow (contintental shelf)

  • Moon snail (Polinices duplicatus)

    • Active predator of bivalves

  • Soft shell clam (Mya arenaria)


Wiltse 19801
Wiltse 1980 cycle but shallow (contintental shelf)

  • Removed moon snail

  • Increase in Mya

  • Increase in infauna


Virnstein 1977
Virnstein 1977 cycle but shallow (contintental shelf)

  • Green crab (Caenus maenas)

  • Blue crab(Callinectes sapidus)

  • Crabs which dig in sediment for food


Virnstein 19771
Virnstein 1977 cycle but shallow (contintental shelf)

  • Exclusion resulted in an increase in infaunal densities


Woodin 1978
Woodin 1978 cycle but shallow (contintental shelf)

  • Horseshoe crab (Limulus polyphemus)

  • Digs distinctive pits in search of food


Whelks busycon spp
Whelks ( cycle but shallow (contintental shelf)Busycon spp.)

  • Devastating to sand flat clam populations

  • Consume all sizes of clams

  • No size refuge


Refugia woodin 1978
Refugia? Woodin 1978 cycle but shallow (contintental shelf)

  • Tube-forming worm Diopatra cuprea

  • Forms upright tubes

  • Effectively deters both Limulus and Calinectes

  • Infaunal abundances greater around tubes


Peterson and peterson 1979
Peterson and Peterson (1979) cycle but shallow (contintental shelf)

  • Effects of deposit feeders in NC

  • Hemichordate worm (Balanoglossusaurantiacus)

  • Funnel feeder, digs u-shaped burrow

  • Ingests sediment


Peterson and peterson 19791
Peterson and Peterson (1979) cycle but shallow (contintental shelf)

  • Consumes small infaunal organisms

  • Causes death of others it does not ingest

  • Keeps # of infaunal organisms low

  • Compounded by sea cucumber (Leptosynaptatenuis)

  • Also ingests sediment


Adult larval interactions woodin 1976
Adult-larval interactions (Woodin 1976) cycle but shallow (contintental shelf)

  • Predatory interactions


Direct competition
Direct Competition cycle but shallow (contintental shelf)

  • Levinton et al. (1985)

    • Hydobia totteni (Eurpoean), Ilyanassa obsoleta (native mud snail)

    • H. totteni lives in high intertidal

    • Avoids Ilyannasa

    • H. totteni is an inferior competitor


Brenchley and carlton 1983
Brenchley and Carlton (1983) cycle but shallow (contintental shelf)

  • Littorina littorea (European), Ilyanassaobsoleta (native)

  • Spatial segregation

  • Littorina destroys egg capsules of Ilyanassa


Grant 1981
Grant (1981) cycle but shallow (contintental shelf)

  • Two amphipod species

    • Acanthohaustorius - lives in oxidized layer

    • Pseudohaustorius - lives in anoxic layer

  • Both prefer oxidized layer

  • Acanthohaustorius superior competitor


Predators petersen 1991
Predators (Petersen 1991) cycle but shallow (contintental shelf)

  • Rocky intertidal:

    • Starfish, mollusks

    • Slow moving

    • Limited to inundated parts

  • Soft intertidal

    • Dominated by highly mobile predators

    • Crabs, fishes, birds

    • Ranges throughout intertidal


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