Oyster Reefs Research Articles

Oyster reefs' control of carbonate chemistry-Implications for oyster reef restoration in estuaries subject to coastal ocean acidification.

Globally, oyster reef restoration is one of the most widely applied coastal restoration interventions. While reefs are focal points of processes tightly linked to the carbonate system such as shell formation and respiration, how these processes alter reef carbonate chemistry relative to the surrounding seawater is unclear. Moreover, coastal systems are increasingly impacted by coastal acidification, which may affect reef carbonate chemistry. Here, we characterized the growth of multiple constructed reefs as well as summer variations in pH and carbonate chemistry of reef-influenced seawater (in the middle of reefs) and ambient seawater (at locations ~50 m outside of reefs) to determine how reef chemistry was altered by the reef community and, in turn, impacts resident oysters. High frequency monitoring across three subtidal constructed reefs revealed reductions of daily mean and minimum pH (by 0.05-0.07 and 0.07-0.12 units, respectively) in seawater overlying reefs relative to ambient seawater (p < .0001). The proportion of pH measurements below 7.5, a threshold shown to negatively impact post-larval oysters, were 1.8×-5.2× higher in reef seawater relative to ambient seawater. Most reef seawater samples (83%) were reduced in total alkalinity relative to ambient seawater samples, suggesting community calcification was a key driver of modified carbonate chemistry. The net metabolic influence of the reef community resulted in reductions of CaCO3 saturation state in 78% of discrete samples, and juvenile oysters placed on reefs exhibited slower shell growth (p < .05) compared to oysters placed outside of reefs. While differences in survival were not detected, reef oysters may benefit from enhanced survival or recruitment at the cost of slowed growth rates. Nevertheless, subtidal restored reef communities modified seawater carbonate chemistry in ways that likely increased oyster vulnerability to acidification, suggesting that carbonate chemistry dynamics warrant consideration when determining site suitability for oyster restoration, particularly under continued climate change.

Performance of European oysters (Ostrea edulis L.) in the Dutch North Sea, across five restoration pilots

IntroductionThe European flat oyster (Ostrea edulis) is a biogenic reef former, internationally recognised as threatened and declining in the NE Atlantic by OSPAR and one of the focal species in nature inclusive designs in offshore windfarms in The Netherlands. Oyster reefs offer habitat to many other benthic hard substrate and fish species and provide ecosystem functions such as shelter and feeding grounds. European flat oyster reefs have disappeared from the Dutch North Sea in the early 1900s due to overfishing and diseases but are now subject of nature restoration under the Dutch Marine Strategy.MethodSince 2018, pilot projects have started in the Dutch North Sea to restore European flat oysters at suitable locations, such as offshore windfarms or natural reefs, which are protected from bottom trawling. We compared European flat oyster performance in five pilot projects, using translocated adult oysters sourced from Ireland, Norway, and the Netherlands. The aim of this research was to assess the performance of translocated oysters between pilots, to assess the installation and monitoring techniques, and to come forward with recommendations for future pilot projects.ResultsWe found that translocation of both foreign sourced flat oyster populations (Ireland and Norway in nearshore and offshore areas) and local oysters (in nearshore areas) result in good oyster performance. Oysters were able to grow (max 3.67 mm/month) and reproduce (larvae present) in their new environment. We found that growth rate was explained by origin and average water temperature, to a lesser extent by number of months, location and salinity and not to other environmental factors such as pH and O2. Correlations between growth and environmental conditions need to be considered with caution, since not all pilots were sampled just before and after the growing season. Oysters were Bonamia-negative at the start and end of the pilots, indicating that the offshore Dutch North Sea is still Bonamia-free.Discussion, conclusions, recommendationsBy the year 2050 more than ten new offshore farms will be constructed in the Dutch North Sea and some sites will be suitable for oyster restoration. We conclude that local and foreign sourced oysters performed well at all locations. Based on the success and failure of the different outplacement and monitoring techniques, we provide recommendations on good practice for the future, including developing standardized monitoring protocols. This will enable better inter-site comparisons in upcoming oyster restoration pilots.

Age variability and decadal time-averaging in oyster reef death assemblages

Abstract Using paleoecological data to inform resource management decisions is challenging without an understanding of the ages and degrees of time-averaging in molluscan death assemblage (DA) samples. We illustrate this challenge by documenting the spatial and stratigraphic variability in age and time-averaging of oyster reef DAs. By radiocarbon dating a total of 630 oyster shells from samples at two burial depths on 31 oyster reefs around Florida, southeastern United States, we found that (1) spatial and stratigraphic variability in DA sample ages and time-averaging is of similar magnitude, and (2) the shallow oyster reef DAs are among the youngest and highest-resolution molluscan DAs documented to date, with most having decadal-scale time-averaging estimates, and sometimes less. This information increases the potential utility of the DAs for habitat management because DA data can be placed in a more specific temporal context relative to real-time monitoring data. More broadly, the results highlight the potential to obtain decadal-scale resolution from oyster bioherms in the fossil record.

Extending conservation of coastal and oyster reef restoration for First Nations cultural revitalization.

Extending conservation of coastal and oyster reef restoration for First Nations cultural revitalization.

Facilitation between two dominant ecosystem engineers extends their footprints and degree of overlap

Ecosystem engineers influence the habitat, diversity, and productivity of ecosystems. However, multiple ecosystem engineers may coexist, and because of their dominant influence, how they interact can affect the entire system. In the southeastern US, the eastern oyster, Crassostrea virginica (Gmelin) and coarse cordgrass, Spartina alterniflora (Loisel) are two prominent ecosystem engineers that affect estuarine ecosystem functioning. Despite both species' importance and their proximity to one-another, few studies have focused on bidirectional interactions between these two species. First, we assessed the potential effect of fringing oyster reefs on adjacent cordgrass stands. We found that when tidal creek banks are occupied by oysters, cordgrass horizontally extends towards the water 5.25 m more (often overlapping with the oysters) than adjacent bank areas that were lacking oysters. Ostensibly, the positive effect of oysters to increase cordgrass occupancy is due to known abilities of oysters to stabilize shoreline, baffle hydrodynamic energy, and accrete sediment. Second, we experimentally examined the effects of cordgrass on oysters using the presence and absence of cordgrass and cordgrass-mimic treatments to parse the mechanistic effects of structure and shade provided by cordgrass. We found that oysters recruited 2.4 times more and increased biomass 3.2 times more underneath natural cordgrass and shade mimics compared to plots with cordgrass removal and structure-only mimics. Thus, cordgrass shade is an important mechanism of facilitation, especially on small recruiting oysters that are vulnerable to desiccation. Collectively, the mutualism between these two engineers expands their footprints and amount of overlap, strengthening their presence and thus their ecosystem services to the estuary.

Oyster reef restoration - aquaculture interactions: maximizing positive synergies

Globally, oyster reef restoration is on the rise. In many instances, restoration is occurring alongside established oyster aquaculture industries that grew to prominence following oyster reef demise. This paper examines the potential positive and negative interactions between the two industries and identifies key factors that may promote positive interactions. Interactions between the two industries result from shared resource requirements (e.g., space, clean water, brood-stock, breeding programs), shared knowledge requirements (e.g. around threats and their mitigation, factors optimizing growth/survival) and biological interactions (e.g. over-catch, disease spill-over, competition for resources). Many of these interactions are reciprocated, and can shift from positive to negative depending on environmental, biological and socio-economic conditions. From our examination, three key factors emerge as shaping the strength and direction (positive or negative) of interactions: (1) whether the focal species is common or different between the two industries; (2) the physicochemical and socio-economic environment in which the two industries are occurring; and (3) whether there is open dialogue and consultation between the two industries and relevant stakeholders. Positive interactions can be maximized where the two industries are able to co-invest in and share infrastructure (e.g. hatcheries, breeding programs), resources (e.g. spat, broodstock, shell) and knowledge (e.g. optimal conditions of growth) – an easier task where the target oyster species is in common. Positive interactions may also be maximized by utilizing marine spatial planning tools, such as suitability modelling, to inform optimal siting of the two industries. As the two industries continue to grow, open and inclusive dialogue between these and key stakeholders will be essential for mitigating risk and maximising positive synergies.

The common predator, Sheepshead (Archosargus probatocephalus), enhances survival of the Eastern oyster (Crassostrea virginica) in an experimental setting

Oyster reefs are a vital but declining component of nearshore, estuarine ecosystems. Global efforts to restore this important habitat are ongoing but have had varied success. The potential for biotic factors such as predation to influence restoration trajectories is rarely considered; however, there is mounting evidence that a better understanding of trophic relationships could aid in the restoration of the ecologically critical Eastern oyster (Crassostrea virginica). A common predator-prey interaction within the oyster reef community was examined through manipulative experiments to determine what effect predator presence had on early survivorship of oyster spat – a factor known to influence the success of oyster reef restoration. The juvenile stone crab (Menippe spp.) is a known predator of spat (<30 mm) sized Eastern oysters but also serves as prey for mobile predatory fish. Sheepshead (Archosargus probatocephalus), a fish with a diet high in structure-associated invertebrates, are one of many predatory fishes that utilize oyster reefs. Adult Sheepshead presence was found to significantly increase oyster spat survival. Oyster spat survival can be attributed to both trait and density-mediated indirect interactions. These results suggest that changes in the presence of an exploited finfish species can influence oyster spat survivorship.

Intestinal microbiota of the four omnivorous fishes revealed by 16S rRNA metabarcoding from the habitats of oyster reefs

The habitats of oyster reefs had played various ecological services functions, as an important means of marine ecological restoration and fishery resources conservation, which had been widely used worldwide. And the characteristics of microbial communities would be inevitably affected by habitat of oyster reefs. The aim of this study was to reveal the relationship between oyster reefs and the intestinal microbiota of fish (Takifugu ocellatus, Acanthopagrus latus, Clupanodon thrissa, and Mugil cephalus). Here, based on 16S rRNA sequencing, this research analyzed the microbial communities of fishes gut in the oyster reefs from the most crucial estuary economic zone in Southern China. It was significantly lower that the bacterial alpha-diversity in the fish intestines than in the sediments of oyster reefs. The non-metric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM) results showed that intestines microbiota of T. ocellatus and A. latus were more homologous to sediments microbiota, but intestines microbiota of C. thrissa and M. cephalus were more similar to the water microbiota. There were obvious differences in the contribution of oyster reefs habitat to intestinal microorganisms of four fishes. Source tracking analysis as well reached the similar conclusion. For instance, contribution of water to T. ocellatus and A. latus was lesser than sediments, which was related to their benthic habits. Based on the differences in microbial community compositions, the functional prediction analysis had demonstrated that special functional pathways and independent core indicators had been formed separately from oyster reefs and fish intestines. Overall, these findings highlighted the characteristics of microbial diversity and functions from the omnivorous fish living in oyster reefs habitats. This research proposed new insights into the function of oyster reefs habitats, which have enriched the ecological service value of oyster reefs from microbial ecology and provided a reference for the application of oyster reefs habitats in other estuaries.

STORM MORPHODYNAMICS AND DECADAL EVOLUTION OF BEACHES IN MODIFIED ESTUARIES AND BAYS

Estuaries and bays have a long history as important locations for humanity, where societies and civilizations have thrived. The many sandy beaches within estuaries and bays (BEBs), often in urban environments, provide critical habitats and shoreline protection, as well as being important for recreation, often in urban environments. Due to their historic importance, many estuaries are subject to anthropogenic modification including: (1) dredging; (2) construction of ports and other infrastructure leading to “hard shorelines”; (3) urban sprawl causing encroachment of natural shorelines including BEBs, and wetlands such as mangroves or saltmarshes; (4) contamination and overfishing, leading for example to the ecosystem collapse of oyster reefs and loss of their shoreline protection, although there are efforts internationally at restoration to improve water quality and shoreline protection. Here we present selected examples of BEBs located in modified estuaries and bays, highlighting their morphological diversity.

The influence of oyster reefs and surrounding sediments on nitrogen removal – An in-situ study along the East coast of Australia

Oyster reefs play a crucial role in the removal of nitrogen (N) from aquatic systems by facilitating nutrient regeneration and denitrification, both in their tissues and shells and surrounding sediments. However, we still have a limited understanding about the contribution of each component of the reefs (e.g. oysters vs sediments) to N processes, and whether rates are dependent on site-specific characteristics. To address these knowledge gaps, we conducted an experiment across six oyster reefs along 1080 km of the Eastern Australian coast with different sediment characteristics. By using in-situ clear and dark incubation chambers, we assessed how benthic metabolism, nutrient and dinitrogen gas (N2) fluxes varied among the following treatments: ‘oysters’, ‘sediments’, and ‘sediments + oysters’ that were used to represent components of the whole reef habitat (i.e. reef matrix vs surrounding sediments vs the interaction among them, respectively), and sites. We found that during dark conditions and at siltier sites, N2 effluxes from oysters can be up to 23 times higher than sediments, while N2 effluxes from chambers with both sediments and oysters were similar to sediment treatments, and lower than oyster treatments. These results can be explained by sediment processes including nutrient assimilation by benthic microalgae and/or lower nutrient diffusion into interstitial space. Additionally, oyster treatments showed an uptake of nitrate (NO3-) that was likely converted into N2, whereas sediment treatments showed an overall release of NO3-. In dark conditions, ammonium (NH4+) fluxes remained consistent across treatments and sites, indicating that any exports from oyster excretion (in those treatments including oysters) were either counterbalanced by or comparable to exports from sediments. This study provides evidence that the crucial contribution of oyster reefs to N removal is dependent on interactions between reef components and environmental factors.

Controls on Surface and Downcore Sedimentary Organic Matter in a Constructed Oyster Reef

Oysters provide a suite of important ecosystem services, and recent research shows that oyster restoration rapidly enhances sedimentary organic carbon deposition. In 2012, an oyster reef enhancement project began in the GTM National Estuarine Research Reserve in Northeast FL, USA. We analyzed the spatial and downcore variability in sedimentary organic matter (OM) and particle sizes in the intertidal zone between the reefs and the marsh, along with oyster reef characteristics, to better understand physical and/or biological influences on sediment. Our data indicate that OM in the top 20 cm of sediment cores was negatively correlated with reef age. Similar decreases in particles &lt;63 μm suggest remobilization of sediment, likely driven by the degradation of the reef structure over its approximately 9-year lifetime. Likewise, a survey of surface sediments showed that adjacent reef structural metrics were the best predictor of sediment OM and particle size. These results highlight the importance of reef structure as a control on sedimentary organic carbon deposition and stability in areas where physical energy is relatively high. This result is discussed in the context of implications for carbon budgets and biogeochemical ecosystem services of oysters as a part of living shorelines.

Study on the Wave-Dissipation Effect of Oyster Reefs Based on the SWAN Numerical Model

In the “Blue Bay Remediation Action” project, the oyster reef plays the dual role of ecological restoration and wave suppression, and the study of the effect of oyster reef wave dissipation forms the basis of relevant projects. Taking the Binzhou oyster reef ecological restoration project as its object, this paper studied the wave-dissipating effect of the oyster reef, using the SWAN model. The simulation results showed that after the deployment of oyster reefs in extreme high-water-level conditions, they could produce a wave-dissipation effect, with a wave-dissipation rate between 8% and 21%. Significant wave-dissipation effects can be produced under the designed high-water-level conditions, with a wave-height dissipation rate of 42% to 65%. Among them, the wave-dissipation effect of oyster reefs was more significant for waves coming from the ENE, NE, N, and NNE directions. This study could provide a scientific reference for the design and layout of oyster reefs.

Submarine groundwater discharge interacts with creek geomorphology to affect eastern oyster Crassostrea virginica growth rates in a coastal Georgia creek.

Eastern oysters, Crassostrea virginica, are commercially important coastal species that provide many ecosystem services for coastal communities. Unfortunately, 85% of oyster reefs have been lost globally, prompting investments in restoration efforts to rebuild populations. Managers often consider several well-studied environmental and water quality parameters when making restoration site decisions. However, recent research suggests that submarine groundwater discharge (SGD) may play a role in driving the distribution of oysters in some estuaries. Specifically, SGD may result in localized areas of low dissolved oxygen and low pH that could inhibit oyster recruitment and survival. However, SGD may interact with other potential oyster stressors, including creek geomorphology. On point bars, sediment accumulation could alter growth rates of oysters and physiology, and it is possible that the two factors, SGD and creek geomorphology, could interact to impact oyster growth. We conducted a field experiment to examine the effects of SGD and creek geomorphology on oyster growth rates in a marsh-lined tidal creek in Georgia, USA. High and low SGD sites were paired within point bars and cut banks. Oysters were deployed in cages for 72 days and growth rates were determined. We found a significant interaction between SGD and creek geomorphology on oyster growth rates. Oysters grew at significantly faster rates at locations on accretionary point bars regardless of SGD flux, whereas, on erosional cut banks, high SGD flux significantly reduced oyster growth rate relative to low SGD flux. It appears that SGD may negatively influence oyster growth at specific creek locations, likely due to the presence of other stressors. Therefore, it is important to consider potential interacting and confounding stressors when managing oyster populations. As SGD is still a relatively understudied potential stressor for oysters, it is critical to continue to examine how groundwater might influence oysters in other locations and in combination with other stressors. Regardless, this study provides further evidence that SGD should be considered in future management efforts.

Assessment of benthic habitats of highly threatened oyster reefs of Pulicat Lake, India

The present study was aimed at demarcating the distribution of oyster habitats along the Pulicat Lake, the second largest brackish water lagoon in India, and investigating their benthic faunal assemblages and functional feeding groups. This study delineated three major reefs (6.70 ha, 5.50 ha, and 2.39 ha areas), and two minor beds (1.10 ha and 0.68 ha areas). Four species of oysters, namely, Magallana bilineata, Saccostrea cuccullata, Isognomon ephippium and Pinctada imbricata fucata were found in the oyster habitats, with M. bilineata being a major reef-forming/ecosystem forming species. Macrofaunal assemblages in the oyster habitats comprised 71 species representing five major phyla belonging to 66 genera under 48 families. Macrofauna were grouped into five Functional Feeding Groups (FFG) considering oyster habitats as a primary food provider. The FFG analysis revealed that the oyster reef/bed in Pulicat Lake is in moderate Ecological Quality Status (EQS). This study is considered very important to know the current extent of oyster reefs and gain a better understanding of the community interactions within oyster habitats and their ecological value to the dwelling species.

Documenting Loss and Fragmentation of Intertidal Oyster (Crassostrea virginica) Reefs in a Subtropical Estuary

Intertidal reefs of Crassostrea virginica (eastern oyster) provide ecologically valuable habitat in estuaries along the Atlantic coast of North America. In Mosquito Lagoon, a shallow-water estuary on the east coast of central Florida, USA, historical aerial imagery was used to document a 24% decline in the live C. virginica reef area between 1943 and 2009. Using 2021 imagery, every living and dead reef in the same region was manually digitized to identify changes during the intervening 12 years. Positive impacts of C. virginica reef restoration that took place between 2007 and 2021 were also digitized to quantify long-term restoration impact. Natural, live C. virginica reef coverage throughout the system was found to have decreased by 50.6% between 2009 and 2021 and, thus, 62.6% between 1943 and 2021. This was attributed to reef fragmentation, reef footprint loss, boating activity, and mangrove expansion. Of the 2542 live reefs identified using 2009 imagery, 219 reefs fragmented, 988 reefs no longer had an identifiable footprint, and 598 reefs contained visible mangroves with non-continuous canopies. Conservatively, 63.6% of directly restored reef area was classified as living reef in 2021, and 74.5% of restoration projects were more than 50% live reef. Dead reef area decreased by 57.9% throughout the system. Understanding changes in C. virginica reef acreage, reef numbers, and mangrove expansion is essential for resource management, restoration practices, and tracking climate change impacts on publicly protected estuaries.

Common fear molecules induce defensive responses in marine prey across trophic levels.

Predator-prey interactions are a key feature of ecosystems and often chemically mediated, whereby individuals detect molecules in their environment that inform whether they should attack or defend. These molecules are largely unidentified, and their discovery is important for determining their ecological role in complex trophic systems. Homarine and trigonelline are two previously identified blue crab (Callinectes sapidus) urinary metabolites that cause mud crabs (Panopeus herbstii) to seek refuge, but it was unknown whether these molecules influence other species within this oyster reef system. In the current study, homarine, trigonelline, and blue crab urine were tested on juvenile oysters (Crassostrea virginica) to ascertain if the same molecules known to alter mud crab behavior also affect juvenile oyster morphology, thus mediating interactions between a generalist predator, a mesopredator, and a basal prey species. Oyster juveniles strengthened their shells in response to blue crab urine and when exposed to homarine and trigonelline in combination, especially at higher concentrations. This study builds upon previous work to pinpoint specific molecules from a generalist predator's urine that induce defensive responses in two marine prey from different taxa and trophic levels, supporting the hypothesis that common fear molecules exist in ecological systems.

Characterizing canopy complexity of natural and restored intertidal oyster reefs (Crassostrea virginica) with a novel laser‐scanning method

The structural complexity of oyster reef canopy plays a major role in promoting biodiversity, balancing the sediment budget, and modulating hydrodynamics in estuarine systems. Although oyster canopy structure is both spatially and temporally heterogeneous, oyster canopies are generally characterized using simple first‐order quantities, like oyster density, which may lack the ability to sufficiently parameterize reef roughness. In this study, a novel laser‐scan approach was used to map the surface of intact reference and restored reefs (restoration age: 1–4 years) during low tide, when the oyster canopy was fully exposed. Measurements were used to estimate hydrodynamically relevant roughness characteristics over the entire reef surface (&gt;140 m2; 0.50 m resolution), providing estimates of the canopy height (hc), standard deviation (), rugosity index (R), and fractal dimension (D). Average canopy heights ranged from 3.6 to 4.9 cm, with canopy height standard deviations between 1.4 and 2.0 cm. Mean rugosity indices and fractal dimensions were relatively low on the youngest (1 year) restored reef (R = 1.28;D = 2.67), with substantial increases observed for more mature reef canopies (4 years:R = 1.56;D = 2.71). Structural complexity was consistently greater on reef margins than in reef interiors. Increases in complexity were linked to restoration age, with older reefs exhibiting more complex oyster canopies. The highest fractal dimension was observed on the intact reference reef, highlighting the importance of sustained reef growth for maintaining higher‐order structural complexity. Results provide spatially explicit surface roughness characterizations for healthy, intertidal oyster reefs, with applications in both restoration science and natural and nature‐based feature design.

Climatic effect from oyster reef restoration in Spartina alterniflora invaded intertidal mudflat: From the perspective of CH4 and N2O production

Spartina alterniflora is a dominant invasive species along the coast of China. A surprising phenomenon that the oyster reef formation is substituting the S. alterniflora invasion, was recently observed in the west coast of Bohai Bay, North China. As the intertidal mudflat ecosystem is critical for coastal blue carbon, this paper aims to evaluate the climatic effect of the alternation from the perspective of potential CH4 and N2O production. The sediment geochemical properties and potential CH4 and N2O productions were therefore measured in sediments dominated by Spartina alterniflora (SA), oyster reef (OR), mixture of S. alterniflora and oyster reef (SA-OR) and bare mudflat (BM) at an intertidal mudflat. Meanwhile, sediment microbial community structure and function genes were also determined utilizing metagenome high-throughput sequencing technology. Our results indicated that the formation of oyster reef in S. alterniflora invaded intertidal mudflat might slightly reduce the sediment potential CH4 production and enhance the sediment potential N2O production. The oyster reef formation could alter the community composition of methanogens and the abundance of functional genes in methanogenesis, and transform the main pathway from methylotrophic to hydrogenotrophic methanogenesis in surface sediments. Metagenome sequencing revealed that the oyster reef formation may promote nitrification, inhibit dissimilatory nitrate reduction (DNRA) and nitrate assimilation functions, and reduce the abundance of nosZ genes. Mantel analysis showed that pH, soluble salt and dissolved carbon (DC) were the most important factors influencing the composition of microbial community. In general, our results imply that the growth of oyster reef in the S. alterniflora invaded area has opposing effects from the prospective of the potential CH4 and N2O production.

Maastrichtian-Danian Northpatagonian rocky shore, Argentina

The Atlantic Maastrichtian-Danian (K/P) transgression over northern-central extra-Andean Patagonia (Argentina) covered both Mesozoic sedimentary basins and the Northpatagonian Massif (NPM). The flooding of the NPM resulted in a regional unconformity/nonconformity (70.000 km2) between the pre-Cretaceous basement (Jurassic Chon Aike Silicic Large Igneous Province and igneous-metamorphic Paleozoic basement) and the K/P marine transgressive record, constituting the widest known ancient rocky shore of South America (Northpatagonian rocky shore).The transgressive stratigraphic record over the basement is mainly composed of isolated carbonate bioclastic deposits up to 40 m thick with predomination of bivalves, echinoderms, bryozoan, coralline red algae, and foraminifera skeletal remains; we interpreted these bioclastic near-shore deposits as rocky shore associations. The hard substrate, irregular seacoast and low accommodation space over the NPM provided a preferential ecological niche for encrusting biota (i.e., Oyster reefs) during the K/P epicontinental flooding. The colonization of “engineer ecosystems” organisms over thousands of square kilometers probably enhanced the coastal biodiversity. The K/P Northpatagonian rocky shore favored the conformation of a short-lived, transgressive, cool-water carbonate factory in the south-eastern extreme of South America.

Combining ecology and technology to kick‐start oyster reef restoration

Techniques that enhance the recruitment of foundation species to restoration sites can inform the ecological development of the restored habitat. However, techniques are often considered in isolation, potentially overlooking synergies from combining them. Native oyster reefs have been lost worldwide, resulting in restoration efforts in systems that are often recruitment limited, or where recruiting oysters must spatially compete with opportunistic species. Here, we present a field‐based study that combines ecological knowledge on positive species interactions with novel acoustic technology, both of which are demonstrated to boost oyster recruitment in isolation, to test whether their interaction synergistically enhances the early larval recruitment that drives oyster reef development. At three sites across a 20 ha oyster reef restoration in southern Australia, we used self‐made speakers to broadcast healthy reef soundscapes that attract oysters and combine this with artificial kelp that facilitates oyster recruitment by suppressing competitive species (turfing algae). The combination of acoustic enrichment and artificial kelp increased oyster recruitment to the topside of substrate (326.98% increase), whereas only acoustic enrichment increased recruitment to the underside of substrate (126.95% increase). Our findings suggest that the combination of multiple techniques and their interactive effects might boost the early stages of reef development, providing proof‐of‐concept that these approaches can help oysters to build and bind reefs (i.e. recruit to the topside and underside, respectively). By combining ecology with technology during the first stages of a developing reef restoration, we show the potential value of these novel approaches to kick‐start the recovery of lost oyster reefs.