Ocean acidification alters foraging behaviour in Dungeness crab through impairment of the olfactory pathway

Impact of Microplastic Exposure on Sand Crab Scopimera globosa Behavior: Implications for Microplastic Transport and Sulfur Cycling through Bioturbation

The accumulation of microplastics (MPs) in estuarine regions and their ecological consequences have become global environmental concerns. Estuarine sediments function as major sinks for MPs and hotspots for critical biogeochemical processes, which are significantly influenced by benthic bioturbation. However, the impacts of MPs on the behavior of highly mobile benthic organisms and the ecological effects of bioturbation activities remain poorly understood. This study utilized laboratory simulation experiments, AI-based behavioral tracking, and metagenomic sequencing to systematically examine the effects of sand crab bioturbation on MPs migration, sediment physicochemical properties and sulfur cycling processes. Results demonstrated that sand crab bioturbation substantially enhanced the vertical migration of MPs, with fluxes to surface layers and the overlying water increasing by 27-fold compared to undisturbed conditions. Exposure to PE-MPs reduced sand crabs' surface foraging intensity and induced behavioral abnormalities. The crabs actively avoided MPs, exhibiting a preference for burrowing and residing in deeper sediment layers. This behavioral shift significantly altered microbial community distributions, with an increase of Pseudomonadota abundance and a decline of sulfate-reducing bacteria Thermodesulfobacteriota abundance. Furthermore, bioturbation accelerated sulfate oxidation in deeper sediments while inhibited dissimilatory sulfate reduction. This study is the first to identify the role of bioturbation in promoting the upward migration of MPs in sediments. Altered sand crab bioturbation will impact sediment biogeochemistry, estuarine function, and coastal resilience.

Assessing benthic invertebrate vulnerability to ocean acidification and de-oxygenation in California: The importance of effective oceanographic monitoring networks

Greenhouse gas emissions from land-use change, fossil fuel, agriculture, transportation, and electricity sectors expose marine ecosystems to overlapping environmental stressors. Existing climate vulnerability assessment methods analyze the frequency of extreme conditions but often minimally consider how environmental data gaps hinder assessments. Here, we show an approach that assesses vulnerability and the uncertainty introduced by monitoring data gaps, using a case study of ocean acidification and deoxygenation in coastal California. We employ 5 million publicly available oceanographic observations and existing studies on species responses to low pH, low oxygen conditions to calculate vulnerability for six ecologically and economically valuable benthic invertebrate species: red sea urchin (Mesocentrotus franciscanus), purple sea urchin (Strongylocentrotus purpurpatus), warty sea cucumber (Apostichopus parvimensis), pink shrimp (Pandalus jordani), California spiny lobster (Panulirus interruptus), and Dungeness crab (Metacarncinus magister). Further, we evaluate the efficacy of current monitoring programs by examining how data gaps heighten associated uncertainty. We find that most organisms experience low oxygen (<35% saturation) conditions less frequently than low pH ( < 7.6) conditions. It is only deeper dwelling (>75 m depth) life stages such as Dungeness crab adults and pink shrimp embryos, juveniles, and adults that experience more frequent exposure to low oxygen conditions. Adult Dungeness crabs experience the strongest seasonal variation in exposure. Though these trends are intriguing, exposure remains low for most species despite well-documented pH and oxygen declines and strengthening upwelling in the central portions of the California Current. Seasonal biases of data collection and sparse observations near the benthos and at depths where organisms most frequently experience stressful conditions undermine exposure estimates. Herein we provide concrete examples of how pink shrimp and Dungeness crab fisheries may be impacted by our findings, and provide suggestions for incorporating oceanographic data into management plans. By limiting our scope to California waters and assessing the limitations presented by current monitoring coverage, this study aims to provide a granular, actionable framework that policymakers and managers can build from to prioritize targeted enhancements and sustained funding of oceanographic monitoring recommendations.

Commentary: Best practices for performing olfactory behavioral assays on aquatic animals: A guide for comparative physiologists

As more physiologists start to incorporate animal behavior into their experiments, especially in the olfactory behavior research field, some considerations are often overlooked, partly due to the inherited way that physiological experiments are traditionally designed and performed. Here we highlight some of these subtle but important considerations and make a case for why these might affect the results collected from behavioral assays. Our aim is to provide useful suggestions for increased standardization of methods so they can be more easily replicated among different experiments and laboratories. We have focused on areas that are less likely to be mentioned in the materials and methods section of a manuscript such as starvation, preliminary experiments, appropriate sample sizes and considerations when choosing an odorant for an assay. Additionally, we are strongly cautioning against the use of alarm cue to generate behavioral responses due to its highly unstable chemical properties/potency. Instead, we suggest using pure chemicals (made up of one known molecule) such as amino acids, bile acids, or polyamines that are commercially available and easier to make up in known concentrations. Lastly, we strongly suggest using environmentally relevant concentrations of these odorants. We believe these guidelines will help standardize these assays and improve replication of experiments within and between laboratories.

Resilience of circuits to environmental challenge

Animals of all kinds evolved to deal with anticipated and unanticipated changes in a variety of features in their environments. Consequently, all environmental perturbations, adaptations, and acclimation involve a myriad of factors that, together, contribute to environmental resilience. New work highlights the importance of neuromodulation in the control of environmental resilience, and illustrates that different components of the nervous system may be differentially resilient to environmental perturbations. Climate change is today pushing animals to deal with previously unanticipated environmental challenges, and therefore understanding the complex biology of adaptation and acclimation to various environmental conditions takes on new urgency.

Transcriptomic responses in the nervous system and correlated behavioural changes of a cephalopod exposed to ocean acidification

BACKGROUND

The nervous system is central to coordinating behavioural responses to environmental change, likely including ocean acidification (OA). However, a clear understanding of neurobiological responses to OA is lacking, especially for marine invertebrates.

RESULTS

We evaluated the transcriptomic response of the central nervous system (CNS) and eyes of the two-toned pygmy squid (Idiosepius pygmaeus) to OA conditions, using a de novo transcriptome assembly created with long read PacBio ISO-sequencing data. We then correlated patterns of gene expression with CO2 treatment levels and OA-affected behaviours in the same individuals. OA induced transcriptomic responses within the nervous system related to various different types of neurotransmission, neuroplasticity, immune function and oxidative stress. These molecular changes may contribute to OA-induced behavioural changes, as suggested by correlations among gene expression profiles, CO2 treatment and OA-affected behaviours.

CONCLUSIONS

This study provides the first molecular insights into the neurobiological effects of OA on a cephalopod and correlates molecular changes with whole animal behavioural responses, helping to bridge the gaps in our knowledge between environmental change and animal responses.

Biological and physiological responses of marine crabs to ocean acidification: A review

Marine crabs play an integral role in the food chain and scavenge the debris in the ecosystem. Gradual increases in global atmospheric carbon dioxide cause ocean acidification (OA) and global warming that leads to severe consequences for marine organisms including crabs. Also, OA combined with other stressors like temperature, hypoxia, and heavy metals causes more severe adverse effects in marine crabs. The present review was made holistic discussion of information from 111 articles, of which 37 peer-reviewed original research papers reported on the effect of OA experiments and its combination with other stressors like heavy metals, temperature, and hypoxia on growth, survival, molting, chitin quality, food indices, tissue biochemical constituents, hemocytes population, and biomarker enzymes of marine crabs. Nevertheless, the available reports are still in the infancy of marine crabs, hence, this review depicts the possible gaps and future research needs on the impact of OA on marine crabs.

The impact of ocean acidification and cadmium toxicity in the marine crab Scylla serrata: Biological indices and oxidative stress responses

Ocean acidification (OA) and heavy metal pollution in marine environments are potentially threatening marine life. The interactive effect of OA and heavy metals could be more vulnerable to marine organisms than individual exposures. In the current study, the effect of OA on the toxicity of cadmium (Cd) in the crab Scylla serrata was evaluated. Crab instars (0.07 cm length and 0.1 g weight) were subjected to pH 8.2, 7.8, 7.6, 7.4, 7.2, and 7.0 with and without 0.01 mg l-1 of Cd for 60 days. We noticed a significant decrease in growth, molting, protein, carbohydrate, amino acid, lipid, alkaline phosphatase, and haemocytes of crabs under OA + Cd compared to OA treatment. In contrast, the growth, protein, amino acid, and haemocyte levels were significantly affected by OA, Cd, and its interactions (OA + Cd). However, superoxide dismutase, catalase, lipid peroxidation, glutamic oxaloacetate transaminase, glutamic pyruvate transaminase, and accumulation of Cd in crabs were considerably elevated in OA + Cd treatments compared to OA alone treatments. The present investigation showed that the effect of Cd toxicity might be raised under OA on S. serrata. Our study demonstrated that OA significantly affects the biological indices and oxidative stress responses of S. serrata exposed to Cd toxicity.