Organism-Sediment Interactions and Succession

Question 1

What did Pruvot and Southern contribute to the study of benthic ecology?

Answer 1

Classified fauna into zones (or ‘facies’) corresponding to environmental conditions.

Southern divided fauna into microlithic (infauna) and macrolithic (epifauna)

Question 2

What concept did Peterson introduce in 1912?

Answer 2

‘Animal communities’.

Question 3

What is the ‘parallel-level bottom community hypothesis’ proposed by Thorson?

Answer 3

Similar sediment types house analogous communities in different locations.

Question 4

What shift occurred in studies of organism-sediment interactions?

Answer 4

From cataloging species to understanding how species interact physically and biologically with sediment.

Question 5

What did Rhoads and Young (1971) emphasize in their studies?

Answer 5

Physical/biotic modification of environments by organisms.

Question 6

Give an example of a deposit feeder and its impact on sediment.

Answer 6

Molpadia oolitica; modifies sediment structure, creating features like faecal mounds and intercone depressions.

Question 7

What is a key factor in the dynamics of organism-sediment relations?

Answer 7

Sediment type does not directly correspond to infauna presence due to abiotic-biotic interplay.

Question 8

What was observed in Cape Cod Bay regarding sediment types and fauna?

Answer 8

Transition in fauna from sandy zones to deeper clay-rich sediments.

Question 9

What role do faunal activities play in sediment transport and deposition?

Answer 9

Influences mud deposition and resuspension cycles at large scales.

Question 10

How do surface dwellers influence sediment?

Answer 10

Disturb particles.

Question 11

What effect do suspension feeders have on sediments?

Answer 11

Convert suspended solids into deposits.

Question 12

What is the role of burrowers and polychaetes in sediment dynamics?

Answer 12

Aid sediment sorting and water transport.

Question 13

What is an example of a species that vertically reworks intertidal sediments?

Answer 13

Clymenella torquata.

Question 14

What is particle sorting and its effect on sediment properties?

Answer 14

Significantly alters surface sediment properties resulting in finer, well-sorted sediment near the surface.

Question 15

What does burrow construction by Hediste diversicolor enhance?

Answer 15

Oxygen penetration and nutrient fluxes.

Question 16

List the three parameter sets affected by faunal influence on sediment properties.

Answer 16

• Physical: Bed roughness, texture, transport rates, porosity
• Chemical: Organic matter, oxygen, redox potential, nutrients, metals
• Biological: Changes to microbial, meiofaunal, and macrofaunal assemblages.

Question 17

What community structure factors are shaped by sediment?

Answer 17

Heterogeneity: Variation in sediment creates microhabitats, supporting diverse species.

Species composition: Certain sediment types support specific groups of organisms.

Connectivity: Sediment continuity or barriers affect movement and gene flow between populations.

Location: Sediment influences where certain communities can establish and persist.

Question 18

How does Amphiura filiformis adapt its feeding behavior?

Answer 18

Changes feeding behaviour based on sediment flow.

Question 19

What is the activity pattern of Philine aperta and its influence on sediment?

Answer 19

Active nocturnally, influencing sediment when mobile.

Question 20

What does Macoma do in the absence of predators?

Answer 20

Suspension feeds at the surface

Macoma is a bivalve that alters its behavior based on predation pressure.

Question 21

What is the behavior of Macoma when predators are present?

Answer 21

Burrows deeper, altering vertical particle flux

This change in behavior helps Macoma avoid predation.

Question 22

What was Gray’s focus in his 1974 research?

Answer 22

Larval site selection and initial environmental control

He proposed that assemblages are shaped later by interactions between the environment and organisms.

Question 23

What did Rhoads emphasize in his 1974 research?

Answer 23

Post-settlement modification where organisms actively reshape sediment

This includes biogenic modification as a central theme.

Question 24

What is the key difference between Gray’s and Rhoads’ views?

Answer 24

Gray focused on environmental pre-selection while Rhoads emphasized biology reshaping sediment

Rhoads’ view suggests organisms influence their environment through various activities.

Question 25

What processes are involved in organism-sediment coupling?

Answer 25

* Larval and adult site selection * Sediment modification by populations * Influencing succession ## Footnote These processes highlight how organisms interact with their sedimentary environment.

Question 26

What does Protodrilus prefer for settlement?

Answer 26

Medium grain size ## Footnote This preference is based on studies by Gray in 1967.

Question 27

What type of sediment does Polydora ciliata settle on?

Answer 27

Fine particles ## Footnote This specificity highlights the organism's habitat requirements.

Question 28

What does Corophium prefer for settling?

Answer 28

Biofilm-coated sediment ## Footnote This preference underscores the importance of biological factors in sediment selection.

Question 29

What is required for Sabellaria to settle?

Answer 29

Conspecific chemical cues ## Footnote This demonstrates the role of chemical signals in ecological interactions.

Question 30

What does Sediment Profile Imaging (SPI) provide?

Answer 30

* In situ imagery * Preservation of burrows * Sediment layering * Faunal-sediment relationships ## Footnote SPI is crucial for understanding sedimentary environments without destructive sampling.

Question 31

What ecological aspects does OSI influence?

Answer 31

* Nutrient cycling * Sediment stability * Patchiness (microhabitats) * Particle diversity (food availability) ## Footnote These factors are essential for maintaining ecosystem health.

Question 32

Which type of feeders dominate unstable muds?

Answer 32

Deposit feeders ## Footnote This dominance is linked to the specific conditions of unstable environments.

Question 33

Which type of feeders dominate muddy sands?

Answer 33

Suspension feeders ## Footnote Their prevalence indicates adaptations to sedimentary conditions.

Question 34

What was the main finding of Bagge's 1969 study on pollution?

Answer 34

Shift from Amphiura-dominated to Capitella-dominated communities under pollution ## Footnote This highlights the impact of pollution on community structure over time.

Question 35

What do organic enrichment gradients lead to?

Answer 35

Predictable, sequential species shifts ## Footnote This pattern was observed at key sites affected by pollution.

Question 36

What are the characteristics of SAB curves?

Answer 36

* Low richness near pollution sources * Increasing diversity further away * Approaching reference community ## Footnote These patterns are consistent across various geographic locations.

Question 37

True or False: Tolerance limits drive succession.

Answer 37

True ## Footnote This suggests a predictable relationship between species and enrichment gradients.

Question 38

How does recovery after pollution cessation vary by distance?

Answer 38

* Near-field = slowest recovery * Far-field = fastest recovery ## Footnote Bagge’s study indicated that recovery can take years, especially in heavily impacted areas.

Question 39

What species are found in pristine zones according to the Pearson-Rosenberg Succession Model?

Answer 39

* Nucula * Amphiura ## Footnote These species indicate healthy, undisturbed environments.

Question 40

What is observed in heavily enriched zones according to the Pearson-Rosenberg Succession Model?

Answer 40

Beggiotoa mats (no macrofauna) ## Footnote This indicates extreme environmental stress and loss of biodiversity.

Question 41

What parallels did Rhoads et al. (1978) note?

Answer 41

* Succession after organic enrichment * Succession after physical disturbance (e.g., dredging) ## Footnote This highlights common patterns in ecological recovery.

Question 42

What model did Rumohr et al. (1996) adapt for the Baltic Sea?

Answer 42

Five-stage succession model Stage 1 - long term hypoxia Stage 0- bacterial mats Stage 2 - further colonisation macrofauna Stage 3- more complex larger bodies ## Footnote This model accounts for low salinity and seasonal hypoxia effects.

Question 43

What did Rosenberg et al. (2001) document regarding hypoxia succession?

Answer 43

* Loss of macrofauna * Bacterial mats dominate * Complex recovery pathway post-hypoxia ## Footnote This illustrates the severe impact of hypoxia on benthic communities.

Question 44

What succession was observed in dredge-impacted areas by Cranfield et al. (2004)?

Answer 44

* Bare sediment → bryozoans → mussels → tunicates/sponges → complex reef ## Footnote This shows the potential for recovery and regeneration of biogenic reefs.

Question 45

What did Soster & McCall find about freshwater succession?

Answer 45

Mirrors marine processes ## Footnote This indicates fundamental ecological similarities across aquatic environments.

Question 46

What critique did Snelgrove & Butman (1994) make regarding OSI models?

Answer 46

Oversimplified models that do not account for multiple co-varying factors ## Footnote They emphasized the complexity of predicting sediment type and community structure.

Question 47

What concept did Johnson (1972) introduce regarding tidal flats succession?

Answer 47

Temporal mosaics ## Footnote This concept suggests different areas may be at different stages of succession simultaneously.

Question 48

What did Zajac's reanalysis of Long Island Sound data reveal?

Answer 48

* Different locations follow different paths * Communities co-exist at mixed stages * Succession is non-linear with multiple stable endpoints ## Footnote This indicates the variability of ecological responses based on local conditions and histories.

Question 49

What is Bioirrigation in Non-Cohesive Sediments Driven by

Answer 49

Advection: The physical process where water (and solutes) is transported through sediment by bulk flow or pressure differences, enhancing the exchange between sediment and overlying water. Other processes: Molecular diffusion is slow movement of particles from high to low concentration. Turbulent flow occurs mainly in open water, not within sediments. Deposition refers to settling of particles, not fluid movement.