1. Soft Substrate Communities: The intertidal and subtidal zones

2. Intertidal Habitats

3. 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

4. Sandy shores Defined by three factors –Particle size, wave action, and slope –Interrelated Particle size –Water retention –Suitability for burrowing Substrate movement

5. Slope Interaction between particle size, wave action, and swash/backswash Swash - water running up a beach –Carries particles –Accretion Backswash –Removes particles

6. 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

7. 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

8. 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

9. Smooth uniform profile Lack topographical diversity Uniform action of physical factors –Temperature –Wave action –Dessication

10. 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

11. 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

12. 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

13. RPD Redox 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

14. 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

15. 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

16. 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

17. Sand Beach Sand flatsMuddy flats Subtidal Wave energyHighLow Variable Grain sizeLargeMedFineVariable SlopeHighLow StabilityLowMedHighVariable O2 availability High LowVariable Physical Characteristics

18. Organisms

19. Size of infaunal organisms Macrofauna: >0.5 mm Meiofauna: 0.5-0.062 mm Microfauna: < 0.062 (mostly protozoans and bacteria)

20. Community organization Patchiness –Time and space –Horizontal and vertical –Cyclical –result of physical factors and interactions between organisms

21. 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

22. Community structure Changes occur through physical or biological factors

23. 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”

24. Woodin 1983 Classification of organisms into limited # assemblages Functional groups

25. 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

26. 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

27. Infaunal animals: –Deposit feeders –Suspension feeders Predators: –Worms –Crustaceans –Mollusks –Echinoderms –Bottom fishes

28. Adaptations

29. 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

30. 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)

31. Adaptations Swash migration –Find food –Avoid predators

32. 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

33. Adaptations (muddy shores) Burrow Permanent tubes Anaerobic adaptations –Development of oxygen carriers (hemoglobin) –Glycogen stores for anaerobic metabolism –Bring surface water down

34. Reproduction Iteroparous > semelparous Coordinate spawning with tides –Lunar rhythms –Stranding –Predation Latitudinal gradient –Planktogrophic - tropics –Lecitrophic - temperate zone

35. 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

36. 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

37. 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

38. Feeding Ecology - sand flats Productivity from microfloral films, seagrasses, macroalgae Not grazed extensively 90-95% broken down into detritus Scavengers, filterfeeders, and deposit feeders

39. 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

40. 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

41. 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

42. 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

43. Sand Beach Sand flats Muddy flats Subtidal PlantsLowMedHighVariable Primary productivity LowMedHigh Epifaunal predators LowHigh DetritusLowMedHighVariable Organismal Characteristics

44. Community Organization of Soft Substrates

45. What governs subtidal communities? Predation Disturbance Recruitment Recolonization Competition

46. 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

47. Community organization - sand Zonation present, but fuzzy –Habit of animals to migrate up and down beach –Lack of studies

48. Community organization - mud Intertidal area extensive Supralittoral –burrowing crabs Midlittoral –clams and polychaetes Infralittoral –No sharp boundary –Like midlittoral

49. Distribution Gregarious Crustaceans  exposed and tropical shores Bivalves  protected and temperate shores # macrofaunal sp.  decreasing wave exposure Biomass  exposed beaches

50. 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

51. 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

52. Most sand beach animals are opportunistic Few indigenous invertebrate predators –Few exclusion experiments, diversity  Filter feeders - ample food

53. 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

54. Seasonal weather changes –Migration to deep water –Sea ice - scouring Prime factors are: –Predation –Competition –Disturbance Predation, predation/disturbance significant

55. Wiltse 1980 Moon snail (Polinices duplicatus) –Active predator of bivalves Soft shell clam (Mya arenaria)

56. Wiltse 1980 Removed moon snail Increase in Mya Increase in infauna

57. Virnstein 1977 Green crab (Caenus maenas) Blue crab (Callinectes sapidus) Crabs which dig in sediment for food

58. Virnstein 1977 Exclusion resulted in an increase in infaunal densities

59. Woodin 1978 Horseshoe crab (Limulus polyphemus) Digs distinctive pits in search of food

60. Whelks (Busycon spp.) Devastating to sand flat clam populations Consume all sizes of clams No size refuge

61. Refugia? Woodin 1978 Tube-forming worm Diopatra cuprea Forms upright tubes Effectively deters both Limulus and Calinectes Infaunal abundances greater around tubes

62. Peterson and Peterson (1979) Effects of deposit feeders in NC Hemichordate worm (Balanoglossus aurantiacus) Funnel feeder, digs u-shaped burrow Ingests sediment

63. 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 (Leptosynapta tenuis) Also ingests sediment

64. Adult-larval interactions (Woodin 1976) Predatory interactions

65. 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

66. Brenchley and Carlton (1983) Littorina littorea (European), Ilyanassa obsoleta (native) Spatial segregation Littorina destroys egg capsules of Ilyanassa

67. Grant (1981) Two amphipod species –Acanthohaustorius - lives in oxidized layer –Pseudohaustorius - lives in anoxic layer Both prefer oxidized layer Acanthohaustorius superior competitor

68. 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