Week 4 - Faunal Mediation Flashcards
What is benthic-pelagic coupling?
A process involving dynamic exchanges of energy, mass, and nutrients at the sediment-water interface.
What role do fluxes of materials across the sediment-water interface play?
They are crucial for functions such as nutrient cycling and energy transfer in food webs globally.
What are the three stages of benthic-pelagic coupling?
- Deposition of non-living organic matter to the seabed
- Mineralisation of material within the sediment
- Release of nutrients back into the overlying water column
How does seasonal productivity affect faunal activity in temperate latitudes?
It elicits a seasonal pattern of faunal activity in both shallow and deep sea environments.
What types of migrations link organisms on the seafloor with those at the surface?
- Active movement without life form shift
- Active with a life form shift
- Passive events
What is an example of active movement without a life form shift?
Regular diel vertical migrations seen in many plankton species.
What is meant by active movement with a life form shift?
Ontogenetic movement includes egg and larval release where organisms broadcast spawn their gametes into the water column.
What can exacerbate benthic-pelagic exchange?
Extreme events like submarine landslides or human activities such as fishing.
How do species interact with materials as they transit the water column?
They repackage, transform, and redistribute materials.
Is pelagic-benthic coupling an important ecological driver?
Yes, it influences feeding and reproduction in ecosystems.
What drives seasonal feeding in marine environments?
Export flux.
What is the consequence of zooplankton grazing on phytoplankton blooms?
It leads to a food-poor water column after four to eight weeks.
What are the patterns of reproduction timing in deep-sea invertebrates related to?
Seasonal fluxes of organic material from surface phytoplankton blooms.
List the different reproductive responses of deep-sea invertebrates to organic input.
- Fast response, reproducing quickly after bloom
- Slow response, spawning larvae when conditions are favorable
- Slow response, synchronizing egg and sperm development with flux
- No relationship, buffered from bloom dynamics
What is bioturbation?
The modification of sediment habitat by organisms that obscure primary stratigraphic features.
Who calculated the sediment brought up by lugworms, and what was the amount?
Davidson (1891) calculated that lugworms brought 1911 tons sediment acre-1 year-1.
What are the two main transport processes in bioturbation?
- Particle reworking
- Ventilation
What is bioirrigation?
When burrow ventilation has geochemical consequences.
What does burrow ventilation help regulate?
It helps regulate the burrow environment, including removing metabolites and temperature.
What types of burrows do mud and sand fauna typically form?
- Mud fauna form U-shaped burrows
- Sand fauna can form I or J burrows
What are the two processes through which particle reworking and ventilation can occur?
- Biodiffusion
- Bioadvection
What factors can determine burrowing success?
Mechanical properties of sediment and variation in species morphology and behaviour
These factors influence how effectively a species can burrow through sediment.
How do species facilitate burrowing?
Through the production of mucus and contraction/expansion of the body or hydrostatic skeleton
These mechanisms assist in the physical movement through sediment.
What was the primary mechanism of burrowing thought to be until recently?
Peristalsis
A process where a polychaete expands and contracts its body to push sediment away.
