1. BENTHOS

2. Benthos: Definitions
Epifauna: live on or are associated with the benthic 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, sm. amphipods)
Macrofauna: animals > 0.5 mm in size: most familiar kinds of animals (crabs, shrimp, starfish and most mollusks)

3. Feeding strategies
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 3

4. Soft- and hard-bottom benthic communities
Soft: little ‘relief’: ripple marks, worm tubes, fecal mounds: some differences in sediment grain size: fewer inds. And 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 4

5. 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

6. Distribution and biomass of benthos

7. The Intertidal: Where the Benthos is Most Abundant
Biomass in intertidal= 10X that of 200 m depth and several thousand that of 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 relief and habitat diversity= more species diversity

8. 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

9. Patterns of Diversity with Depth

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

11. Where the food comes from

12. Soft Sediment Communities
Types of soft-bottom habitats
Role of disturbance in regulating community structure
Effects of predation, competition and facilitation

13. 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 13

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

15. Sandy shores/beaches

16. Muddy shores/bays, estuaries, and lagoons

17. Nearshore benthic habitats (0-200 m)

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

19. Macrofauna (mm-cm)
polychaete worms
crustaceans

20. Macrofauna (mm-cm)
heart urchins
pycnogonids
brittle stars
bivalves

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

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

23. Community patterns and structure
Temperate/tropical
Polar

24. Megafauna (cm-m) grey whales
walrus
Predators have a big effect on community composition

25. Benthic Predators

26. Caging Studies

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

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

29. Important classification for understanding effects of disturbance
Life-history groups
Capitella captitata
Succession

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

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

32. The lugworm (Arenicola) and its burrow/fecal castings32

33. More Sediment
Modifiers
Amensalism
Facilitation

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

36. The intermediate disturbance
hypothesis

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

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. PHYSICAL DISTURBANCES
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)

44. PHYSICAL DISTURBANCES
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
by heat or cold. Bleaching
by osmotic stress
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

45. PHYSICAL DISTURBANCES
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
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)

46. BIOLOGICAL DISTURBANCES
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

47. BIOLOGICAL DISTURBANCES
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