Increased Biodiversity Associated With Abandoned Benthic Oyster Farms Highlight Ecosystem Benefits of Both Oyster Reefs and Traditional Aquaculture

Abstract

Oyster reefs are structurally complex habitats which are increasingly recognized for their importance in estuarine systems. With over 85% of oyster reefs lost to human activities globally, there is increasing interest in aquaculture to not only meet the growing need for food worldwide, but also enhance ecological functions and services. Prime among these services is the provision of habitat for marine biodiversity. We assessed the biodiversity associated with an abandoned benthic oyster farm to investigate the potential ecological benefits of benthic farming techniques used in traditional oyster farms. In addition, we made note of any invasive species which may use these abandoned structures as habitat. The macrobenthic assemblage in the oyster habitat formed by the farm was different from the surrounding mudflats, containing 61 and 26 species, respectively. Density of invertebrates was similar in both habitats (~ 5,777 ± 981 indiv·m−2), but biomass in the oyster farm over ten times greater than the mudflat substrate, which had a fauna dominated by small polychaetes (<5 mm long). Molluscs and crustaceans were especially abundant in the oyster habitat and contributed to 90% of the enhanced biomass associated with oyster habitat (excluding oyster biomass). Only one invasive species was documented, the mussel Xenostrobus secures, but at densities lower than nearby artificial substrates (e.g., concrete shorelines). Oyster development on this abandoned farm appears to be self-sustaining, provide habitat and trophic support for associated benthic macrofauna. In addition to supporting higher biodiversity and biomass of associated species, traditional oyster aquaculture could improve the restoration potential of oyster reefs by supporting broodstock of native oysters, thus maintaining larval supply.

Millennial-scale societal shifts drive the widespread loss of a marine ecosystem

“…These areas lack the hard substrate required for the active growth of reefs (Hemraj et al, 2022), combined with ongoing coastal development and pollution (Hong et al, 2021), natural oyster reefs have not re-established since industrial-scale harvesting stopped in the 19 th century. Without these reefs, we hypothesise that the source of oyster larvae is likely to be the relatively extensive traditional benthic oyster farms, which have been abandoned for decades (Chan et al, 2022). In contrast to modern oyster raft techniques that often selectively culture triploid oysters in the PRD aquaculture zones, these abandoned farms relied on natural recruitment to farm structures.…”

“…In contrast to modern oyster raft techniques that often selectively culture triploid oysters in the PRD aquaculture zones, these abandoned farms relied on natural recruitment to farm structures. Left unmanaged for decades, these structures now support mature oyster clumps that can act as not only brood stock, but also some of the functions and services of natural reefs (Chan et al, 2022).…”

“…Morton & Wong, 1975). Today, the local perception of oysters in the PRD is mostly restricted to a declining aquaculture industry (Caswell et al, 2020), which is reliant on artificial substrates (Chan et al, 2022). The long history of human activities and ecosystem degradation alongside societal change and economic expansion is not unique to PRD; it is also common in other coastal areas in East and Southeast Asia that are habitable to oysters and other types of ecosystem engineers (Swerts & Denis, 2015).…”

Some Like it Hot: The Ecology, Ecosystem Benefits and Restoration Potential of Oyster Reefs in Tropical Waters

“…Tropical oyster reefs provide habitat for invertebrate communities (Al-Khayat and Al-Ansi, 2008;Aslam et al, 2020), which can be greater in diversity, abundance and biomass compared to adjacent soft sediment habitats (Chan et al, 2022). The effects of oyster reef habitats on invertebrate communities, however, may vary depending on oyster traits and environmental settings (Bateman and Bishop, 2017).…”

A scientometric analysis of international publication trends in oyster research

“…Meanwhile, the Higgins (1980) study about the effect of algal food availability on the oyster's valve movements at different seawater and fed conditions. Both earlier studies in 80's era are importance in order to understand the basic biology of the oyster for future potential of aquaculture industry or ecosystem benefits (Chan et al, 2022).…”