Oysters and mussels can create, modify and maintain habitat for a range of other species. Shellfish ecosystems provide a range of ecosystem services such as food provision, habitat for fish and invertebrates, water filtration, fish production and shoreline protection. They once occupied large areas of coastal waters in both temperate and tropical regions, but have been lost or severely diminished by over 85% globally by overfishing, dredging, water pollution and disease.
In Australia, shellfish reefs were formerly abundant in most estuaries along the southern and eastern coastlines prior to European settlement, but today they are rare in many locations (Diggles 2017).
Shellfish reefs can be designed to treat and improve water quality. The shellfish reef treatment systems usually use oysters or mussels and can improve water quality in two ways:
As filter-feeders the shellfish draw in suspended sediment along with their planktonic food and lay this down on the substrate as bio-deposits.
They can armour substrates to reduce the re-suspension of fine sediment and protect shorelines from erosion by dampening wave energy.
Oysters and mussels are suspension feeders, consuming plankton and non-living material from the water column down to a size fraction of ~3μm.
The filtration of suspended matter in the water column by shellfish can cause a reduction in turbidity, improving light penetration and growing conditions for submerged vegetation, whilst the consumption of phytoplankton releases ammonium as a waste product supporting aquatic vegetation growth.
Oyster reefs are also likely to reduce eutrophication through the reduction in phytoplankton and cycling of nutrients, particularly the removal of nitrogen through denitrification and burial via biodeposition, and also uptake in oyster shells and flesh if harvested (for recreational use or by commercial oyster farms).
Restoration of oyster reefs has been trialled overseas and in South East Queensland. Guidelines are available to assist in assessing restoration success.
Some studies suggest establishment of shellfish refs may be a cost effective method to improve water quality and other ecosystem services.
The actual cost-effectiveness of shellfsh reefs will depend on the specific site conditions and project objectives and needs to be considered relative to other treatment systems or management intervention options. Refer to cost considerations for more information.
Services and benefits:
Reduced erosion/shoreline protection
Recreation (collection for eating if safe)
Food source for crabs, fish and other aquatic animals
In addition to the standard disclaimer located at the bottom of the page, please note the content presented is based on published knowledge of treatment systems. Many of the treatment systems described have not been trialled in different regions or land uses in Queensland. The information will be updated as new trials are conducted and monitored. If you have any additional information on treatment systems or suggestions for additional technologies please contact us using the feedback link at the bottom of this page.
^ Baggett, LP, Powers, SP, Brumbaugh, RD, Coen, LD, DeAngelis, BM, Greene, JK, Hancock, BT, Morlock, SM, Allen, BL, Breitburg, DL, Bushek, D, Grabowski, JH, Grizzle, RE, Grosholz, ED, La Peyre, MK, Luckenbach, MW, McGraw, KA, Piehler, MF, Westby, SR & zu Ermgassen, PSE (November 2015), 'Guidelines for evaluating performance of oyster habitat restoration: Evaluating performance of oyster restoration', Restoration Ecology. [online], vol. 23, no. 6, pp. 737-745. Available at: https://onlinelibrary.wiley.com/doi/10.1111/rec.12262 [Accessed 21 April 2022].
^ Elliott, M, Mander, L, Mazik, K, Simenstad, C, Valesini, F, Whitfield, A & Wolanski, E (July 2016), 'Ecoengineering with Ecohydrology: Successes and failures in estuarine restoration', Estuarine, Coastal and Shelf Science. [online], vol. 176, pp. 12-35. Available at: https://linkinghub.elsevier.com/retrieve/pii/S0272771416301044 [Accessed 21 April 2022].
^ Gillies, CL, Creighton, C & McLeod, IM (2016), Shellfish reef habitats: a synopsis to underpin the repair and conservation of Australias environmental, social and economically important bays and estuaries. [online], vol. TropWATER Report No. 15/60. Available at: https://www.nespmarine.edu.au/node/2520.
^ Gillies, CL, McLeod, IM, Alleway, HK, Cook, P, Crawford, C, Creighton, C, Diggles, B, Ford, J, Hamer, P, Heller-Wagner, G, Lebrault, E, Le Port, A, Russell, K, Sheaves, M & Warnock, B (14 February 2018), 'Australian shellfish ecosystems: Past distribution, current status and future direction', PLOS ONE. [online], vol. 13, no. 2, p. e0190914, ed. L D Coen. Available at: https://dx.plos.org/10.1371/journal.pone.0190914 [Accessed 25 March 2019].
^ Humphries, AT, Ayvazian, SG, Carey, JC, Hancock, BT, Grabbert, S, Cobb, D, Strobel, CJ & Fulweiler, RW (12 May 2016), 'Directly Measured Denitrification Reveals Oyster Aquaculture and Restored Oyster Reefs Remove Nitrogen at Comparable High Rates', Frontiers in Marine Science. [online], vol. 3. Available at: http://journal.frontiersin.org/Article/10.3389/fmars.2016.00074/abstract [Accessed 21 April 2022].
^ Lindahl, O, Hart, R, Hernroth, B, Kollberg, S, Loo, LO, Olrog, L, Rehnstam-Holm, AS, Svensson, J, Svensson, S & Syversen, U (March 2005), 'Improving Marine Water Quality by Mussel Farming: A Profitable Solution for Swedish Society', AMBIO: A Journal of the Human Environment. [online], vol. 34, no. 2, pp. 131-138. Available at: http://www.bioone.org/doi/abs/10.1579/0044-7447-34.2.131 [Accessed 21 April 2022].
^ Newell, RIE & Koch, EW (October 2004), 'Modeling seagrass density and distribution in response to changes in turbidity stemming from bivalve filtration and seagrass sediment stabilization', Estuaries. [online], vol. 27, no. 5, pp. 793-806. Available at: http://link.springer.com/10.1007/BF02912041 [Accessed 21 April 2022].
^ab Newell, RIE, Fisher, TR, Holyoke, RR & Cornwell, JC (October 2005), 'Influence of Eastern oysters on nitrogen and phosporus regeneration in Chesapeake Bay, USA. In: The Comparative Roles of Suspension Feeders in Ecosystems', Proceedings of the NATO Advanced Research Workshop on The Comparative Roles of Suspension-Feeders in Ecosystems, pp. 93-120.
Department of Environment and Science, Queensland (2022) Shellfish reefs, WetlandInfo website, accessed 27 October 2023. Available at: https://wetlandinfo.des.qld.gov.au/wetlands/management/treatment-systems/for-agriculture/treatment-sys-nav-page/shellfish-reefs/