1. Benthos

2. Benthos: Definitions –Epifauna: live on or are associated with the surface –Infauna: live within the substrate –Microfauna: animals <0.1 mm in size (e.g. protozoa/bacteria) –Meiofauna: animals <0.5 mm in size: “interstitial” (e.g. nematodes, small amphipods) –Macrofauna: animals > 0.5 mm in size: most familiar kinds of animals (crabs, shrimp, starfish and mollusks)

3. Benthic Feeding Modes Deposit feeders: feed on organically enriched sediments: continuous “reworking” of sediments to extract nutrients: analogous to earthworms: can live in very fine sediments Suspension feeders: filtering devices or mucus nets collect detritus or plankton: need coarser sediments or hard bottom Grazers/predators/scavengers

4. Soft Bottom Communities

5. Soft sediments: Modes of feeding

6. Soft- versus hard-bottom benthic communities Soft: little ‘relief’: ripple marks, worm tubes, fecal mounds: some differences in sediment grain size: fewer inds. Fewer infauna and more epifauna in sand: more individuals in mud and most are deposit feeders Hard: more ‘relief” and more habitat diversity: increase in suspension feeders

7. Soft Bottom Benthic Communities

8. Abiotic Factors Affecting Benthos (to 200 m depth) ) Wave action: influence distribution of sediments and physically affect animals Sediments: vary according to wave action (particle size sorting): terrigenous and marine origin (“allochthonous” and “autochthonous”): fine clays go to deeps Salinity and temperature: FW influences; more thermal variability

9. Benthic Biomass in relation to distance from coast and depth

10. The Intertidal: Where the Benthos is Most Abundant Biomass in intertidal= 10X that of 200 m depth and several thousand times that of the abyss! Not without a cost: wave shock; desiccation; cold; osmotic issues; and land predators. But at high tide: plenty of O2; nutrients; light; and wastes washed away. More vertical relief and habitat diversity= more species diversity

11. Reproduction and Dispersal Broadcast spawning vs. brooding- varying amounts of energy invested, and value of dispersal Where to settle? 1) chemical attractants: settle near your own kind 2) bottom types: settle in appropriate substrates

12. Patterns of Diversity with Depth

14. Soft Sediment Communities Community structure Types of soft-bottom habitats Effects of predation, competition and facilitation

15. Four groups of dominant macrofauna in soft bottoms Class Polychaeta: most numerous: tube-building and burrowing Subphylum Crustacea: ostracods, amphipods, isopods, tanaids, mysids, small decapods Phylum Mollusca: burrowing bivalves and scaphopods, gastropods at surface Phylum Echinodermata: brittle stars, heart urchins, sand dollars, sea cukes

16. Submarine canyons Deep seafloor Shallow water/Shelf Latitudinal Diffs. Temp. = sand Tropic. = mud Polar. = Gravel (Arctic w/ riverine mud)

17. Sandy shores/beaches

18. Muddy shores/bays, estuaries, and lagoons

19. Nearshore benthic habitats (0-200 m )

20. Benthic diatoms Foraminiferans Meiofauna (few mm ) Harpacticoid copepods

21. polychaete worms crustaceans Macrofauna (mm-cm )

22. pycnogonids heart urchins brittle starsbivalves Macrofauna (mm-cm)

23. Predators have big effects on community composition grey whales walrus Megafauna (cm-m )

24. Biodiversity varies with depth, sediment type and biotic factors

25. Community patterns and structure Temperate/tropical Polar

26. Benthic Predators

27. Caging Studies

28. Effects of predator exclusion on the abundance of macrofaunal molluscs, worm and crustaceans General results: 1)Caged areas have up to 500 x density 2)more infaunal spp. in cages 3)no dominance by any single species

29. Direct and indirect effects of predation in soft-sediment food webs

30. Life-history groups Capitella captitata SuccessionImportant classification for understanding effects of disturbance

31. Bioturbation BURROWING SHRIMP Callianassa Burrows of Callianassa fecal strands from polychaetes Upogebia- another burrowing shrimp Upogebia BURROW

32. More Bioturbators Burrowing holothurian Harpacticoid copepod Oligochaete: Paranais Polychaete: Nereis

33. The lugworm (Arenicola) and its burrow/fecal castings

34. More Sediment Modifiers Facilitation Amensalism

36. Competition has a big effect on community structure- depth distribution, population distribution, abundance, and dynamics Competition usually for food with big effects on growth, reproduction, and survival. Density-dependence common Competition in a 3-d environment: rarely for space Competition can be important in soft-sediment communities

37. The intermediate disturbance hypothesis

38. Types and scales of disturbances in soft-sediments

39. Disturbance caused by eutrophication

40. Iceberg scour disturbance

41. On frequently scoured seafloor, what functional groups would you expect?

42. Re-colonization Different mechanisms: Vegetative regrowth of survivors Recruitment from propagules (including spore and seed bank) Influence of patch characteristics: Size and shape Substrate characteristics (e.g. rock or sediment types, topographic complexity, biogenic structures) Patch location (environmental conditions and proximity to propagule sources) Timing of patch creation (availability of propagules and differences in conditions)

43. Agent of disturbance Waves and currents Water-borne material (sediment, logs, rocks) Ice Direct impacts on organisms and Substrate Sessile organisms detached or broken Mobile animals displaced, injured, or killed Substrate overturned Sediment eroded Organisms abraded, buried, crushed or detached Organisms abraded, detached Sediment and organisms excavated and displaced Habitat or assemblages affected Most, declines with depth Most Rocky intertidal and subtidal, Soft sediment, Seagrass beds, Salt mashes (high lat) PHYSICAL DISTURBANCES

44. Agent of disturbance Extended aerial exposure Temperature extremes Salinity stress and freshwater flooding Anoxia Direct impacts on organisms and Substrate Organisms injured or killed by desiccation, heat, UV Organisms injured or killed by heat or cold. Bleaching Organisms injured or killed by osmotic stress Organisms injured or killed by metabolic stress Habitat or assemblages effected Rocky intertidal Coral reefs Seagrass beds Tide pools, Kelp forests, Coral reefs Rocky intertidal, Salt marsh, Coral reef, Mangrove, Soft sediment Soft sediment, estuaries, semienclosed seas PHYSICAL DISTURBANCES

45. Agent of disturbance Landslides, tectonic events Lava flow, volcanic ash Fire, lightening strikes, Meteorite impacts Direct impacts on organisms and Substrate Organisms abraded, crushed, displaced, or smothered Organisms injured or killed by lava, smothered by ash Organisms injured or killed by heat Direct impact and climate change Habitat or assemblages effected Rocky intertidal and subtidal, Soft sediment, slope and rise,vents Rocky intertidal and subtidal, Seagrass beds, Coral reefs, vents Salt marsh, Mangrove Global (mass extinctions) PHYSICAL DISTURBANCES

46. Agent of disturbance Accumulation of plant or animal material (wrack and carcasses) Algal whiplash Bioturbation Sediment excavation by predators Direct impacts on organisms and Substrate Organisms smothered, buried and shaded, chemistry Organisms abraded, recruits vulnerable Organisms buried, sediment load interferes with feeding Organisms displaced, uprooted, and buried Accumulation of debris Habitat or assemblages effected Salt marsh, Seagrass beds, Soft sediment Rocky intertidal and subtidal Soft sediment, Seagrass beds Soft sediments Seagrass beds BIOLOGICAL DISTURBANCES

47. Agent of disturbance Haul out, trampling Red tide Direct impacts on organisms and Substrate Organisms smothered, buried, smashed Organisms suffocated and poisoned Habitat or assemblages effected Rocky intertidal Soft sediment, coastal environments BIOLOGICAL DISTURBANCES

48. Infaunal communities: a Summary “Patchiness” is the rule 2. Physical factors: disturbance (biotic, physical, and anthropogenic) 1. Biotic interactions: predation, competition, & facilitation

50. Where the food comes from

51. SOFT-BOTTOM SUBTIDAL COMMUNITIES Made up of : A. Muddy substrate B. Sandy substrate

52. SOFT-BOTTOM SUBTIDAL COMMUNITIES Influenced by: 1. Particle size distribution 2. Sediment stability 3. light 4. salinity 5. temperature

53. CHARACTERISTICS OF SOFT- BOTTOM SUBTIDAL COMMUNITIES Type of dominant substrate ie sand, mud etc. Most infauna, some epifauna and almost no sessile organisms

54. SOFT-BOTTOM SUBTIDAL COMMUNITIES More abundant than soft-bottom intertidal communities Less abiotic problems : 1. No problem with desication 2. Temperature and salinity more stable

55. DISTRIBUTION OF ORGANISMS Particle size influence distribution of infauna (?) Particle size distribution (depending on depth) Easier for organisms to borrow in sand compared to mud (water drainage better in sand) Patchy sediment type – patchy distribution of organisms

56. DISTRIBUTION OF ORGANISMS Some larvae choose substrate before undergoing metamorphosis Some larvae can detect adults and settle close by

57. SOFT-BOTTOM SUBTIDAL ORGANISMS 1. infauna –Benthic organisms that bury themselves in the sediment 2. epifauna –Organisms that inhabit the surface of the bottom sediment No. of subtidal sp. > intertidal (more stable, no dessication) Distribution of organisms influenced by particle size (mud or sand )

58. PRODUCTIVITY Minimum productivity (by diatoms and other microalgae) Most communities based on ditritus

59. DEPOSIT FEEDERS 1. Polychaetes : accumulation using tentacles or by ingestion of sediment 2. Sand dollars : use mucus to bring food to mouth 3. Bent nosed clam : collect sediment using siphon 4. Brittle stars : collect detritus using tube- feet 5. Peanut worms, sea cucumber, ghost shrimp

60. ProboscisGills Tube feeding by polycheate, Arenicola Marina. Black arrows show water flow and open arrows show sediment flow. Sediment brought to anoxic area, digested and deposited at upper region of shaft

61. SUSPENSION/ FILTER FEEDERS Cockles : water intake via siphon Polychaetes and amphipods Brittle star : traps particles using tube feet Sea pens : traps particle from water column

62. Scavenger dan Predator Shrimps and large crustaceans (scavenger) Whelks dan moon snail : feed on other bivalves Sea stars and crabs (can act as scavenger or predator) Rays and skates Flounder, halibut and sole

63. Distribution and biomass of benthos

64. Would you expect the intermediate disturbance hypothesis to explain diversity patterns in soft sediments?