7 ORGANISM-SEDIMENT INTERACTIONS & BENTHIC SUCCESSION

Question 1

Similar papers but weighting towards importance of environment vs biogenic modification as structural factor differed.

Whereas Gray focussed on … … strategies and argued that the … modifies the assemblage through post … mechanisms, Rhoads focussed on the modification of … properties by organisms through differences in … modes and species …

Answer 1

substratum selection
environment
survival
sediment
feeding
behaviour

Question 2

What was the significance of Rhoads’ view/work?

Answer 2

• emphasised post-settlement processes and species-sediment interactions
• assemblages weren’t just a product of their wider environment, but actively modify their own local environment
• heterogenous communities modified by biology
• ecological significance of biogenic modification
• org-sed interactions important in influencing seafloor stability, substratum patchiness and particle size, ultimately affecting species diversity

Question 3

What is ecological succession?

Answer 3

How biological communities re-assemble following natural or anthropogenic disturbance.

Question 4

What did pearson and rosenberg’s study of organic enrichment produce the suggestion of?

Answer 4

that benthic enrichment caused a predictable and sequential change in the characteristics of the resident macrofauna and associated sedimentary environment.

Question 5

Explain species-abundance-biomass curves.

Answer 5

• first species encountered tend to be small and few
• short distance away, community abundances rise and fall dramatically - peak of opportunists
• species richness and abundance begin to increase towards ecotone point
• ecotone point = transitional zone poor in abundance, species and biomass
• after ecotone point, environment becomes less polluted and community transitions towards composition of unpolluted environment

Question 6

What is the redox potential discontinuity?

Answer 6

the transition zone separating the surficial aerobic sediment from the underlying anaerobic basement.

position of the RPD in sediment profile is known to alter as a function of net redox condition.

at high levels of impact, the consumption of electron acceptors is sufficient to cause an encroachment of the RPD towards the sediment surface.