Deposit feeder

Question 1

What animal dominates the soft sediment at the muddy shores in Germanies North Sea and how does it influence the ecosystem?

Answer 1

Arenicola marina (head down deposit feeding worm)

-Sedmient to a depth of 5cm passes through guts of Arenicola 3-7 times/year

Question 2

What phyla dominate the muddy sediments?

Answer 2

• Annelids (primarily polychaetes)
• Molluscs (bivalves & gastropods)
• Arthropods (crustaceans)
• Echinoderms

Question 3

What food do deposit feeders feed on?

Answer 3

• Plant and macroalgae detriturs (coastal/shelf only)
• Benthic microalgae (coastal only)
• Organic detrituts (dead phytoplankton & animals, faeceal pellets)
• Bacteria
• In deeper environments quality and quantity of food available to deposit feeders is low*

Question 4

How can deposit-feeders grow rapidly on a poor food source such as sediment?

Answer 4

1. Microbial stripping -> For POM to be nutritional for deposit-feeders it must be decomposed by microbes and converted into microbial tissue
   - Decomposition

_fragmentation increases surface area:colume ratios

_leaching

_microbial decay

2. Microbial gardening (e.g. Hydrobia ulvae)
3. Feeding strategies

Form of stripping

Deposite-feeders activities enhance microbial productivity (reduce competition, free up resources)

N absorbed by bacteria from water is made available to deposit-feeders

Question 5

Briefly describe four feeding strategies of deposit feeders in the soft sediment?

Answer 5

1. Process large volumes of sediment- typically one body weight/day
   - even at low nutritional value if you consume enough you will survive
2. Particle selection
   - Many species will select smaller particles (higher surface area : volume ratio) which are associated with higher food quality (i.e. more bacteria) especially tentaculate feeders
   - fluidising sediment sorts particles
   - Many particles are rejected for ingestion
3. Modify gut retention times depending on particle quality
   - intracellular digestoin retains nutritious particles
4. Specialist enzyemes to detach microbes from sediments

Question 6

What increases the efficiency of decomposing and breacking down of organic matter in the soft sediment?

Answer 6

Increased oxygen levels

increasesd surface area

Question 7

Why do most deposit feeders live in borrows?

Answer 7

• oxygination of sedimients
• altering surface area (more rapid break down of organic matter)
• increase of interface needed for denitrification (ciritical for resiliance to utrification)

Question 8

Why do a lot of deposit feeders feed with the head down and tail up? (e.g. Arenicola marina)

Answer 8

to avoid predation

Question 9

what two factors make it possible for macrofaunal benthos to live at the sediment water interface?

Answer 9

light and nutrients

Question 10

How do deposit feeders increase stability and reduce erosion in the soft sediments?

Answer 10

mucus -> Bind particles together by producing carbohydrates (extracellular polysaccharites)

Question 11

what anmial is a common bulldozing animal that feeds on bacteria in the soft sediment around continental shelfs?

Answer 11

Echinardium - heart urchin

Question 12

Describe the significance of primary production in the soft sediment ecosystem

Answer 12

Question 13

how do deposit-feeders destabilise sedmient and what are the effects on supension-feeders?

Answer 13

reworking destabilises the sediment and the suspended sediment stresses suspension - feeders (clogs gills, reduces food quality)