1. Soft Substrate Communities soft sediment = substrate of sedimentary particles; uncemented, unconsolidated or loosely consolidated epifauna – on the surface infauna – in the sediment

4. Physical Environment 1. Grain size - particle size high energy = large grain size; sand low energy = small grain size; mud median grain size – sandy silt, silty sand sorting – range of particle sizes, biological sorting

5. Substrate mobility –influenced by animals – burrowing, binding in tubes –cohesiveness – microbes, mucus Interstitial space – space between grains, “pores” –affects water drainage –diffusion of chemicals

6. 2. Organic Matter - % organic matter - substrate for microbial decomposition, detritus feeders 3. Oxidation-reduction state redox potential discontinuity layer (RPD) - measured by electrode (Eh) Above RPD – oxygen present Below RPD – oxygen absent

7. Chemosynthetic bacteria – use H 2 S Sulfate-reducing bacteria – produce H 2 S (fermentation)

8. Organisms affect the depth of the RPD layer Organisms affect the depth of the RPD layer in irrigated tubes, extend RPD into sediments Organisms must adapt to anaerobic conditions Organisms must adapt to anaerobic conditions –Bring oxygenated water down –Tolerate H 2 S

9. 4. Light – when present, plants present - benthic diatoms - macroalgae - seagrasses

10. Size of infaunal organisms Macrofauna: >0.5 mm Macrofauna: >0.5 mm Meiofauna: 0.5-0.062 mm Meiofauna: 0.5-0.062 mm Microfauna: < 0.062 mm Microfauna: < 0.062 mm

20. Clams

21. Snails

49. Suspension feeders

50. Trophic Structure Suspension Feeders (filter feeders) Suspension Feeders (filter feeders) - primary food = plankton - generalists, size selection by filter Deposit Feeders Deposit Feeders -animal that feeds by consuming particles in or on the substrate -“detritivore”

51. Types of deposit feeders Surface deposit feeders Surface deposit feeders Burrowing or deep Burrowing or deep

54. Microbial Stripping Theory – deposit feeders don’t digest detritus, just digest microorganisms on the detritus and sediment particles Fenchel: - low assimilation efficiency detritus (1-10%) - high assimilation efficiency microbes (40-80%)

55. Logical argument for microbial stripping Composition of the detritus Composition of the detritus - sources, age - temporal variation Digestion detritus vs microbes Digestion detritus vs microbes Constancy and quality of microbes Constancy and quality of microbes -microbial colonization - protein

56. Renewal rates - microbes Animal must not ingest again until microbes recolonize Animal must not ingest again until microbes recolonize pelletization pelletization

57. Predators

59. Physical or biological? Soft bottom benthic communities structured by ??? Soft bottom benthic communities structured by ??? Expt evidence Expt evidence

60. Physical – Oliver 1979 Oliver 1979 –Subtidal zoned on gradient of wave energy –< 14m – regular disturbance, small molbile crustaceans –> stable, tube polychaetes

61. Both biological and physical Mills 1969 – sandy area, low biomass, density of IF Mills 1969 – sandy area, low biomass, density of IF Illyanassa – mech disturbance by snails Illyanassa – mech disturbance by snails Low Illyanassa density – colonization by Ampeleisca tube building amphipod – exclude Illyanassa Low Illyanassa density – colonization by Ampeleisca tube building amphipod – exclude Illyanassa Selective deposit feeding produces fine sediments, tubes create topo diversity, promotes colonization by polychaetes Selective deposit feeding produces fine sediments, tubes create topo diversity, promotes colonization by polychaetes Winter storms, destabilize Ampelisca mats Winter storms, destabilize Ampelisca mats Illyanass recruits in spring, Illyanass recruits in spring,

62. Biological factors Competition Competition direct displacement – rare ( no hard surface to push against), no colonials direct displacement – rare ( no hard surface to push against), no colonials Food/space – evidence form regular spacing of individuals Food/space – evidence form regular spacing of individuals interference- Levinton 1977 interference- Levinton 1977 Direct: Active Bivalve Yoldia limulata disrupts burrows of less mobile Solemaya velum; Illyanassa and Ampleisca Direct: Active Bivalve Yoldia limulata disrupts burrows of less mobile Solemaya velum; Illyanassa and Ampleisca

63. Indirect : more common Burrowing DF – muddy sand w/high [OM] Burrowing DF – muddy sand w/high [OM] Where DF present in high no. SF absent Where DF present in high no. SF absent DF burrow, fecal material, create loose surface layers, unstable, easily resuspended DF burrow, fecal material, create loose surface layers, unstable, easily resuspended Clogs SF feeding Clogs SF feeding Buries SF larvae, DF larvae OK Buries SF larvae, DF larvae OK Exclusion of one trophic group by another Exclusion of one trophic group by another

64. Rhoads and Young 1970 Reworked sediments by 3 sp DF clams, Yoldia, Nucula, Macoma – excludes DF Reworked sediments by 3 sp DF clams, Yoldia, Nucula, Macoma – excludes DF Soft sediment animals affect the sediment they live in Soft sediment animals affect the sediment they live in Functional groups – animals that use/affect the environment in the same way Functional groups – animals that use/affect the environment in the same way –Trophic groups –Sediment stabilizers/destabilizers

65. Types of organisms Sediment stabilizers Sediment stabilizers –Organisms that secrete mucous or otherwise bind sediment; roots –Amphipods, phoronid worms, anemones, polychaetes Sediment destabilizers (bioturbators) Sediment destabilizers (bioturbators) –motile or sedentary organisms who cause sediments to move –Sea cucumbers, mobile clams, whelks

68. Deposit feeders produce fluid fecal rich surface Deposit feeders produce fluid fecal rich surface Easily resuspended by low velocity currents Easily resuspended by low velocity currents Instability might interfere with suspension feeders: Instability might interfere with suspension feeders: –Experiments with Mercenaria in trays above bottom –Deposit feeder larvae not affected

69. Trophic Group Amensalism Interaction between two trophic groups in which one group is inhibited while the other is not Interaction between two trophic groups in which one group is inhibited while the other is not –Inhibitors = deposit feeders; exclude suspension feeders –Physical instability of the sediment – clogs filters, buries newly settled suspension feeder larvae/juveniles; can’t maintain life position; disturbed or eaten by deposit feeders

70. Rhodes and Young 1971 Molpadia oolotica – large, high density, sedentary, silt-clay mud, heads down DF Molpadia oolotica – large, high density, sedentary, silt-clay mud, heads down DF Ingest sediment at depth. Deposit loose fecal matter, form mounds Ingest sediment at depth. Deposit loose fecal matter, form mounds Reworking produces loose high water content easily susp. sediment Reworking produces loose high water content easily susp. sediment Areas between – highly unstable Areas between – highly unstable Cones – stable, fecal pellets, bound material Cones – stable, fecal pellets, bound material

71. attracts SF polychaete Euchone, other SF tube builders attracts SF polychaete Euchone, other SF tube builders SF tube builders stabilize sediment, extend downwards into substrate SF tube builders stabilize sediment, extend downwards into substrate Stabilize cones, prevent resuspnsion attract more tube SF Stabilize cones, prevent resuspnsion attract more tube SF High tube density prevent settlement of large DF/ burrowers – can’t penetrate High tube density prevent settlement of large DF/ burrowers – can’t penetrate Indirect restriction – competitive interference Indirect restriction – competitive interference Also filter out and prey on larvae of DF Also filter out and prey on larvae of DF

72. Coexistence is possible SF prefer more sandy areas – firmer, easier to build sfc tubes SF prefer more sandy areas – firmer, easier to build sfc tubes Sand: DF not favored, low [OM], difficult to burrow Sand: DF not favored, low [OM], difficult to burrow Areas where both can live – sharp boundaries but no physical differences Areas where both can live – sharp boundaries but no physical differences Patches – removal of residents (rays, storms) Patches – removal of residents (rays, storms) Little asexual reproduction - colonize by larval recruitment or adult immigration Little asexual reproduction - colonize by larval recruitment or adult immigration

74. Woodin 1976 Suggests there are 3 major functional groups: Mobile (burrowing) deposit feeders Mobile (burrowing) deposit feeders Suspension feeders Suspension feeders Tube builders Tube builders None have overlapping distributions – why?

75. Adult-larval interactions Deposit feeders – change nature of sediment (trophic group amensalism), feed at surface Deposit feeders – change nature of sediment (trophic group amensalism), feed at surface Suspension feeders – consume larvae while filtering Suspension feeders – consume larvae while filtering Tube builders – dense assemblage creates mat that larvae can’t penetrate; feed at surface Tube builders – dense assemblage creates mat that larvae can’t penetrate; feed at surface

76. Leads to: Strong dominance by year classes Strong dominance by year classes Inhibition model of succession – multiple stable states Inhibition model of succession – multiple stable states Ilyanassa (Nassarius) – mud snail, mobile DF Ampelisca – amphipod, tube builder Sand vs Mud

77. Role of Predation and Competition in Soft Sediment Communities

78. Sediments – 3D Sediments – 3D Refuge form non-digging predators Refuge form non-digging predators Ability to divide resource and avoid competition Ability to divide resource and avoid competition

79. Woodin – predator trophic types Surface –, juveniles vulnerable, affect size classes., esp those with refuge in size/depth Surface –, juveniles vulnerable, affect size classes., esp those with refuge in size/depth Browsers – nippers, rob energy Browsers – nippers, rob energy Burrowers – “weasel” predators (nemerteans, Pisaster brevispinis) Burrowers – “weasel” predators (nemerteans, Pisaster brevispinis) Digging – excavate holes, change sediments, indiscriminate Digging – excavate holes, change sediments, indiscriminate Infaunal – burrowing nemerteans, polychaetes Infaunal – burrowing nemerteans, polychaetes

80. Large predator/disturbers

81. Caging Results: Virnstein 1977– crabs/epifaunal or sfc predators: change in numbers but not composition Virnstein 1977– crabs/epifaunal or sfc predators: change in numbers but not composition Ambrose 1991 – infaunal – reduce infaunal populations, eat other predators, multiple layers of predators Ambrose 1991 – infaunal – reduce infaunal populations, eat other predators, multiple layers of predators

82. Cage results overall – removal of predators Increase in total density Increase in total density Increase in species richness Increase in species richness No tendency for competitive exclusion No tendency for competitive exclusion

83. Why No Competitive Exclusion? Reduced opportunity for interference competition Reduced opportunity for interference competition

85. Vertical distribution Competition for food and space SF and DF Competition for food and space SF and DF Subtidal – food abundant – detritus Subtidal – food abundant – detritus SF – partition space by depth, feeding structure (callianassa) SF – partition space by depth, feeding structure (callianassa) DF – feed at different levels DF – feed at different levels Peterson 1977 Peterson 1977 ––removal of some sp from a depth level – increase in abundance of other sp at that strata – competition –Adding sp to a depth level caused emigration by others – vertical spacing and maintain density

86. Why No Competitive Exclusion? Reduced opportunity for interference competition Reduced opportunity for interference competition Extreme importance of adult-larval interactions Extreme importance of adult-larval interactions

88. Why No Competitive Exclusion? Reduced opportunity for interference competition Reduced opportunity for interference competition Extreme importance of adult-larval interactions Extreme importance of adult-larval interactions Developmental plasticity of marine invertebrates Developmental plasticity of marine invertebrates Lack of clear competitive dominant Lack of clear competitive dominant

89. Caging Artifacts How could these change the results? How could these change the results?

91. Wilson 1991 No evidence for both predation and competition affecting benthic community structure No evidence for both predation and competition affecting benthic community structure No evidence for a competitive dominant in any soft bottom system No evidence for a competitive dominant in any soft bottom system Can’t fully predict effects of predation or competition Can’t fully predict effects of predation or competition Lack knowledge of growth, life spans, trophic types, pop dynamics, esp DF Lack knowledge of growth, life spans, trophic types, pop dynamics, esp DF No unifying theroy of community organization for sof bottom envtsd No unifying theroy of community organization for sof bottom envtsd

92. Multiple Stable States Long term stability – eg Molpadia Long term stability – eg Molpadia Cyclic oscillation – Mills – Illynassa – Ampelisca, biological and physical factors Cyclic oscillation – Mills – Illynassa – Ampelisca, biological and physical factors Multi- year long term – Baltic - alternating states affected by variable recruitment Multi- year long term – Baltic - alternating states affected by variable recruitment Pontoporeia affinis – Macoma baltica Pontoporeia affinis – Macoma baltica High Pontoporeia keeps out Macoma, poor year for Pontiporea allows Macoma, keeps out Pontoporea High Pontoporeia keeps out Macoma, poor year for Pontiporea allows Macoma, keeps out Pontoporea Predators affects r selected species Predators affects r selected species

93. END END

94. Recruitment Dynamics Loss of larvae in the water column Loss of larvae in the water column Larvae as passive particles Larvae as passive particles Larval site selection Larval site selection Adult-larval interactions Adult-larval interactions Meiofauna-macrofauna interactions Meiofauna-macrofauna interactions

95. Meiofauna – Macrofauna Interactions (Watzin 1983) Larval/Juvenile macrofauna are the same size meiofauna (temporary meiofauna) Larval/Juvenile macrofauna are the same size meiofauna (temporary meiofauna) Among the meiofauna are potential predators and competitors Among the meiofauna are potential predators and competitors

97. Meiofauna – Macrofauna Interactions (Watzin 1983) Manipulations in small boxes Manipulations in small boxes –Increased densities of turbellarian predators –Increased densities of “other meiofauna” – potential competitors Exposed to recruitment for one week Exposed to recruitment for one week –Macrofauna larvae avoid treatments, or lower survival of juveniles after settlement Must survive the “meiofauna bottleneck” – escape in size Must survive the “meiofauna bottleneck” – escape in size

98. Meiofauna as Food for Bottom- feeding Fishes

99. Other Roles of Meiofauna Meiofauna as food for deposit feeders Meiofauna as food for deposit feeders Meiofauna stimulate bacterial productivity Meiofauna stimulate bacterial productivity –Speed break-down of detritus –Ingest bacteria – turnover –Mucus – release of DOM

100. Conclusions Trophic group amensalism Trophic group amensalism Disturbance Disturbance Predation Predation Competition Competition Recruitment Recruitment