L5 - Suspension Feeders

Question 1

Bivalve suspension-feeders

Answer 1

Overview:

• Taxonomy
• Process of suspension-feeding in bivalves
• Ecological significance
• Regulation of food supply
• Community structure
• Nutrient regeneration & primary production
• Water quality

Question 2

Introduction

• Active suspension-feeders - filter living and dead organic matter from the water column
• Can exist in dense aggregations (100-1000s m-2)

Importance?

Answer 2

• Experimental and monitoring animals (mussel watch program)
• Critical food source (other animals & humans)
• Aquaculture
• Key role in benthic-pelagic coupling (transfer of organic matter to the sediments & remineralisation back to the water column)

Bucket of water over the gills p hour

Question 3

Taxonomy

• Phylum: Mollusca
• Class: Bivalvia (two symmetrical shells)
• Order: Lamellibranchia (feed via trapping particles on a gill)
• Families:
• Mytilidae (mussels)
• Pectinidae (scallops)
• Pinnidae (horse mussels)
• Veneridae (cockles)
• Mactridae (surf clams)
• Amphidesmatidae (surf clams)
• Tellinidae (wedge shells, deposit-feeders)

Answer 3

Question 4

Feeding – particle sorting

• Quality and quantity of natural diets vary due to resuspension, phytoplankton blooms etc.
• Bivalves can select higher for quality particles

• A bi-product of suspension-feeding is a greater flux of organic matter to the benthos via biodeposition

Answer 4

High quality faeces.. rejecting as sudo faeces

• Style releases enzymes that aid digestion
• Digestive gland is a site of further digestion

Question 5

Flow, feeding & food supply

• When water moves over muscle bed
• Phytopankton removed from water collumn
• Animals downstream see less and less food
• Increase in ch-a the higer you are from the benthos
• Flow rate/conditions affect absorption rate
• Optimise your growth inaqua culture when you understand flow condition

Answer 5

Flow, feeding & food supply

• In the centre of large patches of suspension-feeders growth maybe limited
• Feeding may deplete the boundary layer of seston influencing growth
• Depletion is a function of, flow speed, distance, feeding rate

3m patches most economic for growth rate of muscles in this example

Question 6

• Adult suspension-feeders may prevent the recruitment of other species (adult-larval interactions)
• Post-settlement processes (transport, predation) are also important

Answer 6

• Faeces and pseudofaeces increase organic flux to the sediments (produce particles with higher settling velocities)
• In culture environments may lead shifts in benthic community composition

Increase food quality to sediments

Without filter feeders inorganic crappy nutrition falls to sediments

Because of filter feeders and their ‘waste’ there is more primary productivity

Question 7

Summary of material processing roles

Question 8

Nutrient regeneration and primary production

• Experiments by MSc student Dean Sandwell

(Sandwell et al. 2009, JEMBE)

• Manipulated cockle density in situ
• Measure dissolved oxygen and nutrient fluxes
• Set up beds at different densities
• Light chambers allowed photosynthesis = algae
• Dark chamber = No photosynthetic activity

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Answer 8

More biomass in dark chamber:

In light chamber:

Higher densities = less ammonium

*Ammonium fuels primary production

Availability of nutrience

Cockles increase availability of nutrience

More ammonia in sediments

Removing animals from system removes quality source of nutrition

Cockles play an important role as they consume primary production materials and also creat fuel for primary production feeders

Question 9

•Pre- 1987

–Low river flow during summer results in long residence times & accumulation of algal biomass

–High river flow in spring & winter flushes algae into the lower estuary

•Post-1987

–Low river flow but no algal bloom

Answer 9

Water collumn stratifies in summer? which keeps phytoplankton away from the benthos where the filter feeders are

Benthic grazers controls eutrophication

Do you want clean water - suspension filter feeders

TOP DOWN CONTROL

Question 10

• Bivalves are likely to regulate phytoplankton biomass when the residence time of the water body is greater than clearance time

(i.e. number of days required for the bivalves to filter all the water)

Water residence time = time water spent in a body..

e.g. tauranga harbour - 1 day

Clearance time = How long it takes for bivalve to process water over the gill

Answer 10

San Fran clearance time = 10/11 days

-Introduce bivalve filter feeders changed clearance time to 1 day

quick turn over of filtration didn’t allow a chance for biomass of algae/phytoplankton to build

Shellfish great assest in water restoration due to water filtering and nutrience enhancing qualities

Question 11