BENTHOS

1

• BENTHOS
• Substrate determines distribution
• Macro - gt or equal to 0.5 mm
• Meio - lt 0.5 mm (selected for uniform body
  shape)
• Micro - lt 0.1 mm
• Soft-Sed. Parameters-
• grain size analysis
• lt62 mm (silt-clay fraction) clay lt4 mm

2

• Biogenic Sorting
• organisms ingesting sediment prefer to consume
  small particles - transfer to surface
• maldanid polychaete - Clymenella torquata
  ingests lt1 mm (conveyor-belt feeders)
• bioturbation can affect depth of redox potential
  discontinuity (RPD)

3

• Biotic Effects on Chemical Properties
• Rhoads, 1974
• 1) rate of exchange of dissolved or adsorbed
  ions, compounds, and gases across sed/water
  interface
• 2) vertical gradients - pH, Eh, pO2, depth RPD
• 3) cycles of C, N, P, S -Fe
• 4) transfer of reduced compounds from below the
  RPD to surface-oxygenated sediments

4
Aller Yingst, 1975 - burrow walls had
brown-orange oxygenated halo a few mm surrounded
by black (Fe-sulfides) sediment Zobell, 1938 -
pellets enriched in microbiota Hylleberg, 1975 -
irrigation stimulates growth of microorganisms
5

• Biological Influences on Mass Properties of
  Sediments
• pseudofeces
• feces ?both produced in upper 2-5cm
  
• Sediment Water and Oxygen Content
• flocculent zone (Sanders, 1960)
• pelletized layers

6

• Increase of water content alters mass properties
  of the sediment and greatly reduces the effort
  needed for burrowing to penetrate the substratum
• High water content thixotropic - speed of
  burrowing

7

• Properties of the Sed-Water Interface and
  Turbidity of Overlying Water
• Effects of burrowers on laminar flow or
  turbulent flow - and sediment resuspension
• Topography Callianassa spp. burrowing shrimp,
  can go down to 2-3 m.
• Molpadia oolitica - holothurian - permits
  colonization by several spp. of
  suspension- feeding, tube-dwelling polychaetes
  (Rhoads Young, 1971 Rhoads, 1974)

8

• Ingestion rates of individual deposit-feeders -
  pop. effects - reworking of sediments
• Deposit-feeding bivalve Nucula annulata
• rework the annually deposited sediment 1- 5
  times/d-1 - thus, sediments are often pelletized
  
• Suspension-feeders - enrich sediments with
  fecal pellets populations of Cardium edule
  biodeposits 100,000 metric tons of suspended
  matter/yr -1 in Dutch Wadden Sea

9

• Particulate Organic Matter (POM) in sediments
• Detritus - inputs
• In pelagic realm 60-90 of the 1 production is
  consumed by herbivores
• the remaining goes into sediments
• Much of the 1 production of benthic seaweeds,
  kelp forests, sea grasses, mangroves, and marsh
  grasses - is thought to not be consumed recent
  work challenges this theory

10

• The larger majority of benthic primary
  production (5000-1000 gC m-2yr -1) enters the
  food chain as detritus
• N. Atlantic kelp - Laminaria longicruris
• Mann, 1972 - dominant inputs to benthos, much of
  it is consumed
• In contrast Zostera marina decays more slowly
  - not so important as a benthic food source

11

• St. Margarets Bay, Nova Scotia - 15 of the
  seaweed production reaches the sediment as
  deposited organic detritus
• Georgia - 90 of detritus in estuarine creeks is
  of Spartina spp. origin

12
Adaptation of Benthic Organisms Epibenthos -
barnacles, seaweeds, oysters, serpulid
polychaetes 1) Adoption of short squat profile to
minimize exposure to shear stress (i.e.,
anemones) 2) Hiding in holes (cryptic) 3) Stout
rigid support structures (thick byssal threads)
(i.e., Mytilus californianus) 4) extensibility
13

• Metridium senile - tall
• Anthopleura xanthogrammica - short
• Acropora palamata - strong
• Montastrea annularis - weak and massive
• Sea Fans - Gorgonia - prefered orientation to
  the current

14

• Swimmers
• Octopus - compressible mantle cavity
• Pecten
• Polychaetes - sinusoidal waves

15

• Infauna
• In order to penetrate soft sediments, infauna
  must exert a forward thrust within the sediment
  while maintaining points against which force can
  be exerted
• soft-bodied - form a penetration anchor, then a
  terminal anchor
• lugworm - Arenicola - proboscis exerted
• Abarenicola

16

• streamlined bivalves in sand razor clam
• Ensis directus - rapid borrower
• broad-shaped bivalves
• Mya arenaria
• Many bivalves squirt water with siphons to
  facilitate burrowing

17

• Many infaunal animals make permanent burrows
• Maldanid - ice-cream cone worm, Pectinaria -
  even-sized sand grains
• Many find sediment-dwelling infauna do not
  maintain vertical burrows and burrow laterally
• Yoldia limatula Nucula - protobranch bivalves
• Nephthys incisa - polychaetes - responsible for
  fluidized nature of sediments