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

Abstract

Oysters are ecosystem engineers that form biogenic reef habitats in shallow coastal and estuarine waters and provide important ecosystem services. Widespread global declines have triggered a world-wide restoration movement, however a paucity of information on tropical oyster reefs has resulted in their exclusion from existing global assessments and, consequently, restoration. In this review we quantified the known global diversity of native reef-building oysters to compare diversity between temperate and tropical regions and assessed historic oyster reef presence and declines using two tropical case studies. We then summarised the biology, ecology, and benefits of tropical oyster reefs, which have four functional differences to temperate reefs: 1) the diversity of reef-building oysters is over four times higher in tropical than in temperate regions; 2) tropical reef-building oysters can have continuous spatfall throughout the year whereas temperate species have a defined season; 3) tropical reef-building oysters are generally faster growing than temperate reef-building oysters; and 4) tropical oysters commonly create mixed-species oyster reefs whereas temperate oyster reefs are generally formed by a single oyster species. There is evidence of unsustainable and destructive harvesting that has resulted in the decline of tropical oyster reefs, and these reefs should therefore be included in restoration efforts. We highlight knowledge gaps that can guide future research to develop important foundational information that will remove barriers to tropical oyster reef restoration.

Meta-analysis reveals controls on oyster predation

“…Given the global extent of oysters, we were surprised to find few suitable predation studies for species other than C. virginica. More research is needed to determine the global applicability of our findings, particularly for oyster reefs beyond North America and in the tropics (Richardson et al, 2022). Additionally, due to low sample sizes or multi-collinearity, we were unable to examine the effects of several factors that have been suggested to affect oyster predation rates, such as abiotic conditions (dissolved oxygen, elevation, flow velocity, inundation period, salinity; Ruesink, 2007;Knights et al, 2012), biotic factors (parasites, pathogens, and competitors;Carroll et al, 2021), and landscape characteristics (reef size and shape, distance to other habitats; Micheli and Peterson, 1999;Carroll et al, 2015).…”

An assessment of the utility of green gravel as a kelp restoration tool in wave-exposed intertidal habitats

“…Consequently, interest in restoration as a tool to initiate or accelerate the recovery of habitats that have been degraded or lost is growing. In the marine realm, restoration has somewhat lagged behind terrestrial systems, although advances have been made in multiple habitat types including mangrove forests (Kamali and Hashim, 2011), seagrass meadows (Bull et al, 2004;Marion and Orth, 2010;van Katwijk et al, 2016;Unsworth et al, 2019), coral reefs (Rinkevich, 2005;Young et al, 2012;Boström-Einarsson et al, 2020), oyster reefs (Brumbaugh and Coen, 2009;Richardson et al, 2022), and more recently kelp forests (Westermeier et al, 2016;Fredriksen et al, 2020;Graham et al, 2021;Earp et al, 2022;Miller and Shears, 2022;Eger et al, 2022a).…”

The development of multiplex PCR assays for the rapid identification of multiple Saccostrea species, and their practical applications in restoration and aquaculture

“…Globally, tropical regions contain over four times more reef-building species of oysters than temperate regions [ 6 ]. Molecular techniques are required for accurate identification, however, as shell morphology is highly variable which has resulted in species being visually misidentified [ 7 , 8 ].…”