Module 14 Flashcards
Bivalves
Filter feeders
Whether the bivalve is producing faeces or pseudofaeces, the result for the ecosystem is the same – particles in suspension are captured, and after processing, gravity takes them to participate in benthic detrital food webs
By removing particles from the water column, bivalves improve light penetration and therefore, benthic primary productivity by microalgae, macroalgae, corals and sea grasses, as well as fisheries productivity
Shellfish reefs
A reef structure dominated by bivalve molluscs
Provide habitats for other sessile organisms such as sponges, tube worms, and ascidians
Also provide a hiding spot for mobile invertebrates such as crabs, snails, prawns, and fishes
As shellfish reefs grow, they lock up carbon through calcium carbonate in their shells
Also sequester nutrients such as nitrogen and phosphate
Moreton Bay
Naturally oligotrophic, where benthic primary productivity should be roughly an order of magnitude greater than water column primary productivity
Suspended and resuspended sediments block light from reaching the seabed, as do the phytoplankton populations that flourish due to the higher nutrient concentrations
Clearing the water column is an activity at which shellfish reefs excel
Ecosystem benefits provided by oysters
Shore protection services in future seas
Nutrient, carbon, and sediment sequestration services
Shore protection services in future seas
Waves break on shellfish reefs rather than on the shore, so they protect the coastline from wave action
Nutrient, carbon, and sediment sequestration services
Many of our coastal streams have elevated concentration of soluble phosphates and nitrates due to sewage treatment, and urban and agricultural runoff
Such nutrients will fund phytoplankton communities that will then be filtered out by shellfish along with other particulate organic matter
Shellfish reefs reduce wave action, reduce sediment re-suspension and generally make us much happier people
They offer triple bottom line (TBL) outcomes; those in which there are environmental benefits, economic benefits and social benefits
Shellfish reef restoration
Shellfish populations at high densities can possibly protect themselves from waterborne pathogens
They can do this by efficiently filtering them out of seawater or digesting them or coping with parasites using an immune system that is not overloaded
QX Disease
Shellfish populations at high densities can possibly protect themselves from waterborne pathogens
They can do this by efficiently filtering them out of seawater or digesting them or coping with parasites using an immune system that is not overloaded
Traditional restoration practises
Walk along shores and drop oysters over the shore so that the oysters can become homes for young oysters
These would then form clumps which are split and scattered to form even more oyster clumps
Another practise is the placement of wooden stakes on shore
Oysters settle on these and then at a certain point the clump is removed, and the stake is left to continue the restoration
Regulatory challenges
Government applications - costly and lengthy process
Restoration project must be removed once completed
Moreton Bay restoration
Once restored, perhaps shellfish reefs can improve water quality so that corals might once again grow on the Redcliffe Peninsula
Other environmental benefits include increased biodiversity, higher benthic primary productivity, healthy habitats in which fish can recruit and grow, nutrient and carbon sequestration, and the water is nicer for recreational activities
There are clear environmental benefits, and aesthetic enhancements that flow to both human wellbeing (social benefits) and growth in tourism (economic benefits)- meaning Redcliffe gets TBL outcomes
An additional and perhaps increasingly important service is their potential to remove microplastics, but that is subject to debate, so we will not deal with that in detail here but you can explore this further in the additional resources
