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

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Soft substrate communities the intertidal and subtidal zones

Soft Substrate Communities:The intertidal and subtidal zones


Soft substrate communities the intertidal and subtidal zones

Intertidal Habitats


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


Soft substrate communities the intertidal and subtidal zones

  • 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


Soft substrate communities the intertidal and subtidal zones

  • Smooth uniform profile

  • Lack topographical diversity

  • Uniform action of physical factors

    • Temperature

    • Wave action

    • Dessication


Soft substrate communities the intertidal and subtidal zones

  • 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


Soft substrate communities the intertidal and subtidal zones

  • Sublittoral - subtidal zone - area not exposed in tidal cycle but shallow (contintental shelf)

  • Composed of soft sediments (mud, sand, some hard substrates)

  • Communities dominated by infaunal organisms


Soft substrate communities the intertidal and subtidal zones

Physical Characteristics


Organisms

Organisms


Size of infaunal organisms

Size of infaunal organisms

  • Macrofauna: >0.5 mm

  • Meiofauna: 0.5-0.062 mm

  • Microfauna: < 0.062 (mostly protozoans and bacteria)


Community organization

Community organization

  • Patchiness

    • Time and space

    • Horizontal and vertical

    • Cyclical

    • result of physical factors and interactions between organisms


Community organization1

Community Organization

  • 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

  • Changes occur through physical or biological factors


Parallel bottom communities

Parallel bottom communities

  • 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

  • Classification of organisms into limited # assemblages

  • Functional groups


Types of organisms

Types of organisms

  • 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

  • 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


Soft substrate communities the intertidal and subtidal zones

  • Infaunal animals:

    • Deposit feeders

    • Suspension feeders

  • Predators:

    • Worms

    • Crustaceans

    • Mollusks

    • Echinoderms

    • Bottom fishes


Adaptations

Adaptations


Adaptations1

Adaptations

  • 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

  • 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

  • Swash migration

    • Find food

    • Avoid predators


Adaptations4

Adaptations

  • 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)

  • Burrow

  • Permanent tubes

  • Anaerobic adaptations

    • Development of oxygen carriers (hemoglobin)

    • Glycogen stores for anaerobic metabolism

    • Bring surface water down


Reproduction

Reproduction

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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


Soft substrate communities the intertidal and subtidal zones

  • Suspension feeders

    • 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

  • 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


Soft substrate communities the intertidal and subtidal zones

Organismal Characteristics


Community organization of soft substrates

Community Organization of Soft Substrates


What governs subtidal communities

What governs subtidal communities?

  • Predation

  • Disturbance

  • Recruitment

  • Recolonization

  • Competition


Community organization sand

Community organization - sand

  • 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

  • Zonation present, but fuzzy

    • Habit of animals to migrate up and down beach

    • Lack of studies


Community organization mud

Community organization - mud

  • Intertidal area extensive

  • Supralittoral

    • burrowing crabs

  • Midlittoral

    • clams and polychaetes

  • Infralittoral

    • No sharp boundary

    • Like midlittoral


Distribution

Distribution

  • Gregarious

  • Crustaceans  exposed and tropical shores

  • Bivalves  protected and temperate shores

  • # macrofaunal sp.  decreasing wave exposure

  • Biomass  exposed beaches


Mclachlan 1983

McLachlan 1983

  • 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

  • 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


Soft substrate communities the intertidal and subtidal zones

  • Most sand beach animals are opportunistic

  • Few indigenous invertebrate predators

    • Few exclusion experiments, diversity 

  • Filter feeders - ample food


Community regulation sand and mud flats

Community regulation - sand and mud flats

  • 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


Soft substrate communities the intertidal and subtidal zones

  • Seasonal weather changes

    • Migration to deep water

    • Sea ice - scouring

  • Prime factors are:

    • Predation

    • Competition

    • Disturbance

  • Predation, predation/disturbance significant


Wiltse 1980

Wiltse 1980

  • Moon snail (Polinices duplicatus)

    • Active predator of bivalves

  • Soft shell clam (Mya arenaria)


Wiltse 19801

Wiltse 1980

  • Removed moon snail

  • Increase in Mya

  • Increase in infauna


Virnstein 1977

Virnstein 1977

  • Green crab (Caenus maenas)

  • Blue crab(Callinectes sapidus)

  • Crabs which dig in sediment for food


Virnstein 19771

Virnstein 1977

  • Exclusion resulted in an increase in infaunal densities


Woodin 1978

Woodin 1978

  • Horseshoe crab (Limulus polyphemus)

  • Digs distinctive pits in search of food


Whelks busycon spp

Whelks (Busycon spp.)

  • Devastating to sand flat clam populations

  • Consume all sizes of clams

  • No size refuge


Refugia woodin 1978

Refugia? Woodin 1978

  • 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)

  • 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)

  • 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)

  • Predatory interactions


Direct competition

Direct Competition

  • 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)

  • Littorina littorea (European), Ilyanassaobsoleta (native)

  • Spatial segregation

  • Littorina destroys egg capsules of Ilyanassa


Grant 1981

Grant (1981)

  • 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)

  • 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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