Recruitment of a threatened foundation oyster species varies with large and small spatial scales.

Understanding how habitat attributes (e.g., patch area and sizes, connectivity) control recruitment and how this is modified by processes operating at larger spatial scales is fundamental to understanding population sustainability and developing successful long-term restoration strategies for marine foundation species-including for globally threatened reef-forming oysters. In two experiments, we assessed the recruitment and energy reserves of oyster recruits onto remnant reefs of the oyster Saccostrea glomerata in estuaries spanning 550 km of coastline in southeastern Australia. In the first experiment, we determined whether recruitment of oysters to settlement plates in three estuaries was correlated with reef attributes within patches (distances to patch edges and surface elevation), whole-patch attributes (shape and size of patches), and landscape attributes (connectivity). We also determined whether environmental factors (e.g., sedimentation and water temperature) explained the differences among recruitment plates. We also tested whether differences in energy reserves of recruits could explain the differences between two of the estuaries (one high- and one low-sedimentation estuary). In the second experiment, across six estuaries (three with nominally high and three with nominally low sedimentation rates), we tested the hypothesis that, at the estuary scale, recruitment and survival were negatively correlated to sedimentation. Overall, total oyster recruitment varied mostly at the scale of estuaries rather than with reef attributes and was negatively correlated with sedimentation. Percentage recruit survival was, however, similar among estuaries, although energy reserves and condition of recruits were lower at a high- compared to a low-sediment estuary. Within each estuary, total oyster recruitment increased with patch area and decreased with increasing tidal height. Our results showed that differences among estuaries have the largest influence on oyster recruitment and recruit health and this may be explained by environmental processes operating at the same scale. While survival was high across all estuaries, growth and reproduction of oysters on remnant reefs may be affected by sublethal effects on the health of recruits in high-sediment estuaries. Thus, restoration programs should consider lethal and sublethal effects of whole-estuary environmental processes when selecting sites and include environmental mitigation actions to maximize recruitment success.

Transgenerational plasticity responses of oysters to ocean acidification differ with habitat.

Transgenerational plasticity (TGP) has been identified as a critical mechanism of acclimation that may buffer marine organisms against climate change, yet whether the TGP response of marine organisms is altered depending on their habitat is unknown. Many marine organisms are found in intertidal zones where they experience episodes of emersion (air exposure) daily as the tide rises and recedes. During episodes of emersion, the accumulation of metabolic carbon dioxide (CO2) leads to hypercapnia for many species. How this metabolic hypercapnia impacts the TGP response of marine organisms to climate change is unknown as all previous transgenerational studies have been done under subtidal conditions, where parents are constantly immersed. Here, we assess the capacity of the ecologically and economically important oyster, Saccostrea glomerata, to acclimate to elevated CO2 dependent on habitat, across its vertical distribution, from the subtidal to intertidal zone. Tidal habitat altered both the existing tolerance and transgenerational response of S. glomerata to elevated CO2. Overall, larvae from parents conditioned in an intertidal habitat had a greater existing tolerance to elevated CO2 than larvae from parents conditioned in a subtidal habitat, but had a lower capacity for beneficial TGP following parental exposure to elevated CO2. Our results suggest that the TGP responses of marine species will not be uniform across their distribution and highlights the need to consider the habitat of a species when assessing TGP responses to climate change stressors.

Limitations of cross- and multigenerational plasticity for marine invertebrates faced with global climate change.

Although cross generation (CGP) and multigenerational (MGP) plasticity have been identified as mechanisms of acclimation to global change, the weight of evidence indicates that parental conditioning over generations is not a panacea to rescue stress sensitivity in offspring. For many species, there were no benefits of parental conditioning. Even when improved performance was observed, this waned over time within a generation or across generations and fitness declined. CGP and MGP studies identified resilient species with stress tolerant genotypes in wild populations and selected family lines. Several bivalves possess favourable stress tolerance and phenotypically plastic traits potentially associated with genetic adaptation to life in habitats where they routinely experience temperature and/or acidification stress. These traits will be important to help 'climate proof' shellfish ventures. Species that are naturally stress tolerant and those that naturally experience a broad range of environmental conditions are good candidates to provide insights into the physiological and molecular mechanisms involved in CGP and MGP. It is challenging to conduct ecologically relevant global change experiments over the long times commensurate with the pace of changing climate. As a result, many studies present stressors in a shock-type exposure at rates much faster than projected scenarios. With more gradual stressor introduction over longer experimental durations and in context with conditions species are currently acclimatized and/or adapted to, the outcomes for sensitive species might differ. We highlight the importance to understand primordial germ cell development and the timing of gametogenesis with respect to stressor exposure. Although multigenerational exposure to global change stressors currently appears limited as a universal tool to rescue species in the face of changing climate, natural proxies of future conditions (upwelling zones, CO2 vents, naturally warm habitats) show that phenotypic adjustment and/or beneficial genetic selection is possible for some species, indicating complex plasticity-adaptation interactions.

Ocean acidification but not warming alters sex determination in the Sydney rock oyster, Saccostrea glomerata.

Whether sex determination of marine organisms can be altered by ocean acidification and warming during this century remains a significant, unanswered question. Here, we show that exposure of the protandric hermaphrodite oyster, Saccostrea glomerata to ocean acidification, but not warming, alters sex determination resulting in changes in sex ratios. After just one reproductive cycle there were 16% more females than males. The rate of gametogenesis, gonad area, fecundity, shell length, extracellular pH and survival decreased in response to ocean acidification. Warming as a sole stressor slightly increased the rate of gametogenesis, gonad area and fecundity, but this increase was masked by the impact of ocean acidification at a level predicted for this century. Alterations to sex determination, sex ratios and reproductive capacity will have flow on effects to reduce larval supply and population size of oysters and potentially other marine organisms.

Transcriptomic profiling of adaptive responses to ocean acidification.

Some populations of marine organisms appear to have inherent tolerance or the capacity for acclimation to stressful environmental conditions, including those associated with climate change. Sydney rock oysters from the B2 breeding line exhibit resilience to ocean acidification (OA) at the physiological level. To understand the molecular basis of this physiological resilience, we analysed the gill transcriptome of B2 oysters that had been exposed to near-future projected ocean pH over two consecutive generations. Our results suggest that the distinctive performance of B2 oysters in the face of OA is mediated by the selective expression of genes involved in multiple cellular processes. Subsequent high-throughput qPCR revealed that some of these transcriptional changes are exclusive to B2 oysters and so may be associated with their resilience to OA. The intracellular processes mediated by the differentially abundant genes primarily involve control of the cell cycle and maintenance of cellular homeostasis. These changes may enable B2 oysters to prevent apoptosis resulting from oxidative damage or to alleviate the effects of apoptosis through regulation of the cell cycle. Comparative analysis of the OA conditioning effects across sequential generations supported the contention that B2 and wild-type oysters have different trajectories of changing gene expression and responding to OA. Our findings reveal the broad set of molecular processes underlying transgenerational conditioning and potential resilience to OA in a marine calcifier. Identifying the mechanisms of stress resilience can uncover the intracellular basis for these organisms to survive and thrive in a rapidly changing ocean.

Intertidal oysters reach their physiological limit in a future high-CO2 world.

Sessile marine molluscs living in the intertidal zone experience periods of internal acidosis when exposed to air (emersion) during low tide. Relative to other marine organisms, molluscs have been identified as vulnerable to future ocean acidification; however, paradoxically it has also been shown that molluscs exposed to high CO2 environments are more resilient compared with those molluscs naive to CO2 exposure. Two competing hypotheses were tested using a novel experimental design incorporating tidal simulations to predict the future intertidal limit of oysters in a high-CO2 world; either high-shore oysters will be more tolerant of elevated PCO2 because of their regular acidosis, or elevated PCO2  will cause high-shore oysters to reach their limit. Sydney rock oysters, Saccostrea glomerata, were collected from the high-intertidal and subtidal areas of the shore and exposed in an orthogonal design to either an intertidal or a subtidal treatment at ambient or elevated PCO2 , and physiological variables were measured. The combined treatment of tidal emersion and elevated PCO2  interacted synergistically to reduce the haemolymph pH (pHe) of oysters, and increase the PCO2  in the haemolymph (Pe,CO2 ) and standard metabolic rate. Oysters in the intertidal treatment also had lower condition and growth. Oysters showed a high degree of plasticity, and little evidence was found that intertidal oysters were more resilient than subtidal oysters. It is concluded that in a high-CO2 world the upper vertical limit of oyster distribution on the shore may be reduced. These results suggest that previous studies on intertidal organisms that lacked tidal simulations may have underestimated the effects of elevated PCO2.

Adult exposure to ocean acidification is maladaptive for larvae of the Sydney rock oyster Saccostrea glomerata in the presence of multiple stressors.

Parental effects passed from adults to their offspring have been identified as a source of rapid acclimation that may allow marine populations to persist as our surface oceans continue to decrease in pH. Little is known, however, whether parental effects are beneficial for offspring in the presence of multiple stressors. We exposed adults of the oyster Saccostrea glomerata to elevated CO2 and examined the impacts of elevated CO2 (control = 392; 856 µatm) combined with elevated temperature (control = 24; 28°C), reduced salinity (control = 35; 25) and reduced food concentration (control = full; half diet) on their larvae. Adult exposure to elevated CO2 had a positive impact on larvae reared at elevated CO2 as a sole stressor, which were 8% larger and developed faster at elevated CO2 compared with larvae from adults exposed to ambient CO2 These larvae, however, had significantly reduced survival in all multistressor treatments. This was particularly evident for larvae reared at elevated CO2 combined with elevated temperature or reduced food concentration, with no larvae surviving in some treatment combinations. Larvae from CO2-exposed adults had a higher standard metabolic rate. Our results provide evidence that parental exposure to ocean acidification may be maladaptive when larvae experience multiple stressors.

Rapid transcriptional acclimation following transgenerational exposure of oysters to ocean acidification.

Marine organisms need to adapt in order to cope with the adverse effects of ocean acidification and warming. Transgenerational exposure to CO2 stress has been shown to enhance resilience to ocean acidification in offspring from a number of species. However, the molecular basis underlying such adaptive responses is currently unknown. Here, we compared the transcriptional profiles of two genetically distinct oyster breeding lines following transgenerational exposure to elevated CO2 in order to explore the molecular basis of acclimation or adaptation to ocean acidification in these organisms. The expression of key target genes associated with antioxidant defence, metabolism and the cytoskeleton was assessed in oysters exposed to elevated CO2 over three consecutive generations. This set of target genes was chosen specifically to test whether altered responsiveness of intracellular stress mechanisms contributes to the differential acclimation of oyster populations to climate stressors. Transgenerational exposure to elevated CO2 resulted in changes to both basal and inducible expression of those key target genes (e.g. ecSOD, catalase and peroxiredoxin 6), particularly in oysters derived from the disease-resistant, fast-growing B2 line. Exposure to CO2 stress over consecutive generations produced opposite and less evident effects on transcription in a second population that was derived from wild-type (nonselected) oysters. The analysis of key target genes revealed that the acute responses of oysters to CO2 stress appear to be affected by population-specific genetic and/or phenotypic traits and by the CO2 conditions to which their parents had been exposed. This supports the contention that the capacity for heritable change in response to ocean acidification varies between oyster breeding lines and is mediated by parental conditioning.

Adult exposure to the synthetic hormone 17α-ethynylestradiol affects offspring of the gastropods Nassarius burchardi and Nassarius jonasii.

The aim of this study was to determine whether adult exposure to endocrine disrupting compounds affects offspring using trans-generational testing. Adult estuarine dwelling gastropods Nassarius burchardi and Nassarius jonasii were exposed to the synthetic estrogen 17α-ethynylestradiol (EE2) to determine the effects on the development and survival of their offspring. Adults were maintained in synthetic seawater controls and EE2 treatments (0.005, 0.05, 0.5, 50µg/L) over a sixteen week period. Egg capsules were collected from the adults following four, ten and sixteen weeks of adult exposure and transferred to different EE2 exposure scenarios. Treatment concentrations were selected to represent changes in EE2 exposure that could occur over different periods in an organism's lifecycle. Egg capsules laid by adults were therefore transferred to control or EE2 treatments (0.005, 0.05, 0.5, 5, 50, 500µg/L) to develop until hatching. The percentage of egg capsules with unviable eggs and abnormalities, number of days for hatching to occur and hatching success were measured. The veliger larvae that hatched from egg capsules following two, eight and fourteen weeks of adult exposure to EE2 and controls were used in 96h acute toxicity tests with controls and EE2 treatments at concentrations of 0.5, 5, 50, 500, 1250, 2500, 4000µg/L. Exposure of adult N. burchardi and N. jonasii to EE2 affected the percentage of egg capsules with unviable eggs, the development and hatching success of embryos and survival of veligers. These toxicity tests produced a complex set of results with different responses in developing eggs and veliger larvae to the adult EE2 treatments and length of adult exposure. This study demonstrates the importance of trans-generational testing and adult exposure scenarios in toxicity investigations.

Ocean warming and Marine Heatwaves unequally impact juvenile introduced and native oysters with implications for their coexistence and future distribution.

Climate change is causing ocean warming (OW) and increasing the frequency, intensity, and duration of extreme weather events, including Marine Heat Waves (MHWs). Both OW and MHWs pose a significant threat to marine ecosystems and marine organisms, including oysters, oyster reefs and farmed oysters. We investigated the survival and growth of juveniles of two commercial species of oyster, the Sydney rock oyster, Saccostrea glomerata, and the Pacific oyster, Crassostrea gigas, to elevated seawater temperatures reflecting a moderate and an extreme MHW in context with recent MHWs and beyond. The survival and size of Pacific oysters to moderate MHWs (22-32 °C; 14 days) was greater than that for Sydney rock oysters (24-32 °C; 15 days). While survival and growth of both species was significantly impacted by extreme MHWs (29-38 °C; 5-6 days), Sydney rock oysters were found to survive greater temperatures compared to the Pacific oyster. Overall, this study found that Pacific oyster juveniles were more tolerant of a moderate MHW, while Sydney rock oyster juveniles were more resilient to extreme MHWs. These differences in thermal tolerance may have consequences for aquaculture and coexistence of both species in their intertidal and latitudinal distributions along the south-eastern Australian coastline.

The 2024 roadmap for understanding marine species' resilience in a changing ocean.

Written to serve as a guideline for future research in this field, this roadmap provides some perspectives on the main developments and remaining challenges in the field of marine animal acclimatisation, adaptive potential and resilience to climate change. There has been extensive research conducted on the impact of climate change stress on marine animals, with studies recognising the potential for cross- and multi- generational impacts. Parents can potentially pass on resilience to offspring. The response of marine animals to climate change stressors is complex where utilising marginal and extreme systems as natural laboratories can help to address key research gaps and provide an understanding of the plastic and adaptive changes necessary for survival under stress.

The long-lived deep-sea bivalve Acesta excavata is sensitive to the dual stressors of sediment and warming.

Human influence in the deep-sea is increasing as mining and drilling operations expand, and waters warm because of climate change. Here, we investigate how the long-lived deep-sea bivalve, Acesta excavata responds to sediment pollution and/or acute elevated temperatures. A. excavata were exposed to suspended sediment, acute warming, and a combination of the two treatments for 40 days. We measured O2 consumption, NH4+ release, Total Organic Carbon (TOC), and lysosomal membrane stability (LMS). We found suspended sediment and warming interacted to decrease O:N ratios, while sediment as a single stressor increased the release of TOC and warming increased NH4+ release in A. excavata. Warming also increased levels of LMS. We found A. excavata used protein catabolism to meet elevated energetic demands indicating a low tolerance to stress. A. excavata has limited capacity for physiological responses to the stressors of warming and sediment which may lead to decreased fitness of A. excavata.

Resilience against the impacts of climate change in an ecologically and economically significant native oyster.

Climate change is acidifying and warming our oceans, at an unprecedented rate posing a challenge for marine invertebrates vital across the globe for ecological services and food security. Here we show it is possible for resilience to climate change in an ecologically and economically significant oyster without detrimental effects to the energy budget. We exposed 24 pair-mated genetically distinct families of the Sydney rock oyster, Saccostrea glomerata to ocean acidification and warming for 4w and measured their resilience. Resilience was identified as the capacity to defend their acid-base balance without a loss of energy available for Scope for Growth (SFG). Of the 24 families, 13 were better able to defend their acid-base balance while eight had no loss of energy availability with a positive SFG. This study has found oyster families with reslience against climate change without a loss of SFG, is an essential mitigation strategy, in a critical mollusc.

Student responses to creative coding in biomedical science education.

Biomedical science students need to learn to code. Graduates face a future where they will be better prepared for research higher degrees and the workforce if they can code. Embedding coding in a biomedical curriculum comes with challenges. First, biomedical science students often experience anxiety learning quantitative and computational thinking skills and second biomedical faculty often lack expertise required to teach coding. In this study, we describe a creative coding approach to building coding skills in students using the packages of Processing and Arduino. Biomedical science students were taught by an interdisciplinary faculty team from Medicine and Health, Science and Architecture, Design and Planning. We describe quantitative and qualitative responses of students to this approach. Cluster analysis revealed a diversity of student responses, with a large majority of students who supported creative coding in the curriculum, a smaller but vocal cluster, who did not support creative coding because either the exercises were not sufficiently challenging or were too challenging and believed coding should not be in a Biomedical Science curriculum. We describe how two creative coding platforms, Processing and Arduino, embedded and used to visualize human physiological data, and provide responses to students, including those minority of students, who are opposed to coding in the curriculum This study found a variety of students responses in a final year capstone course of an undergraduate Biomedical Science degree where future pathways for students are either in research higher degrees or to the workforce with a future which will be increasingly data driven.

Global perspectives of the impact of the COVID-19 pandemic on learning science in higher education.

The COVID-19 pandemic required higher education institutions to rapidly transition to Emergency Remote Instruction (ERI) with little preparation. Discussions are now underway globally to learn the lessons of COVID-19 and to use this knowledge to shape the future of learning science in higher education. In this study, we examined the experiences of instructors and students to ERI in three universities across three continents-America, Europe, and Australia. We measured the instructional strategies used by instructors including assessment types, and interaction opportunities during and outside class schedules. We also measured the learning challenges experienced by students including planning, distractions, technology, learning resources, their views on educational quality and what characterized quality interactions during ERI. Our findings suggest that most instructional strategies used by instructors changed little during ERI, although the nature of instructor and student interactions during class relied more heavily on technology. Students reported significant learning challenges which included distractions from their physical and social media environments and access to technology. Both instructors and students reported that interactions with each other and their peers were concerningly low, albeit similar to pre COVID-19 pandemic levels. There were differences in the perceptions of instructors and students on whether instructor-student interactions were better or worse online. Common among all universities, there was a large proportion of students reporting mental health and work-related stress. Lessons to be learned from the COVID-19 pandemic include ensuring more support for instructors to implement effective and equitable pedagogies and an increased recognition of the importance of practicals, and the social, interactive and hands-on aspects of learning science in higher education. We predict that the incorporation of active learning pedagogies and strategies which increase student engagement and foster a sense of belonging will be ongoing global challenges for learning science in a post COVID-19 campus.

An idea to explore: Interdisciplinary capstone courses in biomedical and life science education.

While biomedical and life science research have embraced interdisciplinarity as the means to solving pressing 21st century complex challenges, interdisciplinarity in undergraduate education has been more difficult to implement. As a consequence, disciplinary rather than interdisciplinary capstones have become ubiquitous. Disciplinary capstones are valuable for students because they enable them to integrate knowledge and skills within the discipline, but they are also limiting because the integration is within rather than across disciplines. In contrast to a capstone, which involves a single discipline, interdisciplinary capstones require two or more disciplines to combine and integrate across disciplinary boundaries. Interdisciplinarity, where two of more disciplines come together, is difficult to implement in the biomedical and life science curricula because student majors and finances are administered in ways, which reinforce institutional organization of schools and faculties and prevent collaboration. Here in this "idea to explore" we provide an interdisciplinary capstone model where students enroll in disciplinary courses, but then these disciplinary courses and students collaborate on interdisciplinary real-world problems. This interdisciplinary capstone model was implemented across two diverse and large biomedical and life science schools within two faculties in a research intensive, metropolitan university. This approach allows for integration of the biomedical, social and ethical perspectives required when solving problems in the real world, such as COVID-19. Interdisciplinary learning also better prepares students for higher degree research and future careers. Overcoming disciplinary curriculum silos and faculty barriers is critical if we are to meet expectations of acquiring interdisciplinarity as a key competency.

Can seagrass modify the effects of ocean acidification on oysters?

Solutions are being sought to ameliorate the impacts of anthropogenic climate change. Seagrass may be a solution to provide refugia from climate change for marine organisms. This study aimed to determine if the seagrass Zostera muelleri sub spp. capricorni benefits the Sydney rock oyster Saccostrea glomerata, and if these benefits can modify any anticipated negative impacts of ocean acidification. Future and ambient ocean acidification conditions were simulated in 52 L mesocosms at control (381 µatm) and elevated (848 µatm) CO2 with and without Z. muelleri. Oyster growth, physiology and microbiomes of oysters and seagrass were measured. Seagrass was beneficial to oyster growth at ambient pCO2, but did not positively modify the impacts of ocean acidification on oysters at elevated pCO2. Oyster microbiomes were altered by the presence of seagrass but not by elevated pCO2. Our results indicate seagrasses may not be a panacea for the impacts of climate change.

Microbiomes of the Sydney Rock Oyster are acquired through both vertical and horizontal transmission.

BACKGROUND: The term holobiont is widely accepted to describe animal hosts and their associated microorganisms. The genomes of all that the holobiont encompasses, are termed the hologenome and it has been proposed as a unit of selection in evolution. To demonstrate that natural selection acts on the hologenome, a significant portion of the associated microbial genomes should be transferred between generations. Using the Sydney Rock Oyster (Saccostrea glomerata) as a model, we tested if the microbes of this broadcast spawning species could be passed down to the next generation by conducting single parent crosses and tracking the microbiome from parent to offspring and throughout early larval stages using 16S rRNA gene amplicon sequencing. From each cross, we sampled adult tissues (mantle, gill, stomach, gonad, eggs or sperm), larvae (D-veliger, umbo, eyed pediveliger, and spat), and the surrounding environment (water and algae feed) for microbial community analysis. RESULTS: We found that each larval stage has a distinct microbiome that is partially influenced by their parental microbiome, particularly the maternal egg microbiome. We also demonstrate the presence of core microbes that are consistent across all families, persist throughout early life stages (from eggs to spat), and are not detected in the microbiomes of the surrounding environment. In addition to the core microbiomes that span all life cycle stages, there is also evidence of environmentally acquired microbial communities, with earlier larval stages (D-veliger and umbo), more influenced by seawater microbiomes, and later larval stages (eyed pediveliger and spat) dominated by microbial members that are specific to oysters and not detected in the surrounding environment. CONCLUSION: Our study characterized the succession of oyster larvae microbiomes from gametes to spat and tracked selected members that persisted across multiple life stages. Overall our findings suggest that both horizontal and vertical transmission routes are possible for the complex microbial communities associated with a broadcast spawning marine invertebrate. We demonstrate that not all members of oyster-associated microbiomes are governed by the same ecological dynamics, which is critical for determining what constitutes a hologenome.

Biotic habitats as refugia under ocean acidification.

Habitat-forming organisms have an important role in ameliorating stressful conditions and may be of particular relevance under a changing climate. Increasing CO2 emissions are driving a range of environmental changes, and one of the key concerns is the rapid acceleration of ocean acidification and associated reduction in pH. Such changes in seawater chemistry are anticipated to have direct negative effects on calcifying organisms, which could, in turn, have negative ecological, economic and human health impacts. However, these calcifying organisms do not exist in isolation, but rather are part of complex ecosystems. Here, we use a qualitative narrative synthesis framework to explore (i) how habitat-forming organisms can act to restrict environmental stress, both now and in the future; (ii) the ways their capacity to do so is modified by local context; and (iii) their potential to buffer the effects of future change through physiological processes and how this can be influenced by management adopted. Specifically, we highlight examples that consider the ability of macroalgae and seagrasses to alter water carbonate chemistry, influence resident organisms under current conditions and their capacity to do so under future conditions, while also recognizing the potential role of other habitats such as adjacent mangroves and saltmarshes. Importantly, we note that the outcome of interactions between these functional groups will be context dependent, influenced by the local abiotic and biotic characteristics. This dependence provides local managers with opportunities to create conditions that enhance the likelihood of successful amelioration. Where individuals and populations are managed effectively, habitat formers could provide local refugia for resident organisms of ecological and economic importance under an acidifying ocean.

Climate change alters shellfish reef communities: A temperate mesocosm experiment.

Climate change is expected to cause significant changes to rocky shore diversity. This study used outdoor mesocosms to test the predictions that warming and ocean acidification will alter the responses of native Trichomya hirsuta and introduced Mytilus galloprovincialis mussels, and their associated communities of infauna. Experiments consisted of orthogonal combinations of temperature (ambient 22 °C or elevated 25 °C), pCO2 (ambient 400 µatm or elevated 1000 µatm), mussel species (T. hirsuta or M. galloprovincialis), and mussel configuration (native, introduced, or both), with n = 3 replicates. Elevated pCO2 reduced the growth of T. hirsuta but not that of M. galloprovincialis, and warming and pCO2 influenced the infauna that colonised both species of mussels. There was a reduction in infaunal molluscs and an increase in polychaetes; there was, however, no effect on crustaceans. Results from this study suggest that climate-driven changes from one mussel species to another can significantly influence infaunal communities.