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Abstract Essential to life on Earth, assessment of marine photosynthesis is of paramount importance. Photosynthesis occurs in spatially discrete microscopic entities at various levels of biological organization, from subcellular chloroplasts to symbiotic microalgae and macroalgae, and is influenced by the surrounding conditions.As such, in situ photosynthetic efficiency mapping on appropriate scales holds great promise for learning about these processes.To achieve this goal, we designed, fabricated, and tested an underwater microscope that incorporates standard colour, epifluorescence, and variable chlorophyllafluorescence imaging with nearly micron spatial resolution that resolves the structure and photosynthetic efficiency of benthic organisms.Our results highlight coral observations with high‐resolution photosynthetic spatial variability and detailed morphology. Our imaging system therefore enables research never before possible on the health and physiology of benthic aquatic organisms in situ, placing it in the context of their physical and biological environment. 

Social learning, information transmission and culture play vital roles in the lives of social animals, influencing their survival, reproduction and ability to adapt to changing environments. However, the effect of anthropogenic disturbances on these processes is poorly understood in free-living animals. To investigate the impact of anthropogenic disturbance on social learning and information transmission, we simulated individual removal from contact networks derived from long-term behavioural datasets. We simulate the effects of individual removal on network efficiency and social learning for three group-living species—yellow baboons (Papio cynocephalus), African savanna elephants (Loxodonta africana) and Indo-Pacific bottlenose dolphins (Tursiops aduncus). We reveal how removals of key network positions reduce network efficiency. However, groups with high levels of innovation may cope with changing social network structures. These findings highlight the importance of protecting key individuals to preserve group structure and the role of innovation in possibly mitigating the fitness costs of removals. Identifying and safeguarding individuals that drive innovation can reduce a group’s susceptibility to anthropogenic threats and promote cultural resilience in social animals in a changing world. These emerging trends contribute to a growing understanding of the role of conservation interventions in protecting critical individuals in group-living animals. This article is part of the theme issue ‘Animal culture: conservation in a changing world’. 

Abstract The red algaAsparagopsis taxiformishas recently been recognized for its unique ability to significantly reduce methane emissions from ruminant animals when fed in small quantities. The main obstacle in using this seaweed as a methane‐mitigating feed supplement is the lack of commercially available biomass. Little is known about how best to grow this red alga on a commercial scale, as there are few published studies that have investigated the factors that influence growth, physiology, and overall performance. This study examined the effects of temperature and CO₂enrichment on the growth, photophysiology, and concentration of bromoform, the secondary metabolite largely responsible for methane reduction inA. taxiformis. A series of single and multifactor closed culture experiments were conducted onA. taxiformiscollected, isolated, and cultured from populations in Southern California. We identified the optimal temperature range to be between 22 and 26°C, with significant short‐term stress observed below 15°C and above 26°C. Carbon dioxide addition resulted in increased performance, when accounting for growth per CO₂use. In general, we observed the highest bromoform concentrations in algae with the highest growth rates, but these results varied among experiments. These findings indicate that through environmental control and by addressing limiting resources, significant increases in biomass production and quality can be achieved. 

The inclusion Asparagopsis spp. into the diet of ruminant animals has produced compelling data regarding the mitigation of agricultural methane emissions. This reduction is achieved via the action of brominated halogenated compounds, predominantly bromoform, which act to inhibit methanogenic enzymes in ruminant digestion. As such, there is great interest in the mass cultivation of Asparagopsis for use as a dietary supplement for livestock. However, data are still lacking on the basic biology of Asparagopsis relating to factors that influence the synthesis of bromoform, the key bioactive compound of interest. One of the two precursors for bromoform biosynthesis is hydrogen peroxide, while the other is bromide, a naturally occurring ion in seawater. Hydrogen peroxide is generated internally within the alga and can be stimulated by abiotic stress. Currently, the influence of temperature and external hydrogen peroxide addition on bromoform dynamics have been explored. The aim of this study is to explore how the stimulation of hydrogen peroxide by the application of light stress influences the dynamics of bromoform precursor uptake and production, as well as how this may drive changes in bromoform concentration and the persistence of gland cells, the cellular structures where bromoform is stored. While provision of light stress significantly stimulated an increase in hydrogen peroxide production, bromide dynamics were also significantly influenced, resulting in net bromide release, rather than uptake. Further, bromoform concentrations in algal tissue immediately declined after exposure to high light, from 4.5% to 2% (dry weight), while gland cell abundance declined from 95% to around 60%. Here we present data for dramatic alterations in bromoform dynamics after exposure to moderate increases in light intensity. These findings are strongly applicable to commercial Asparagopsis cultivation and will contribute to optimising algal quality during cultivation and harvest. 

Seaweeds, particularly the red seaweed Asparagopsis taxiformis, produce and sequester bromomethanes, which are known for mitigating methane emissions in ruminants when used as a feed supplement. Bromomethane synthesis requires hydrogen peroxide (H₂O₂). We developed a staining assay utilizing 3,3′-diaminobenzidine (DAB) for identifying H₂O₂ in three groups of seaweeds (red, brown, and green), including intensely pigmented species. Our findings indicate the previously identified "gland cell" in Asparagopsis taxiformis, responsible for bromoform synthesis and retention, is a specialized large organelle rich in H₂O₂. Our study introduces an effective survey tool to identify promising seaweed species abundant in bromoform from diverse marine habitats. 

Marine heatwaves are triggering coral bleaching events and devastating coral populations globally, highlighting the need to identify processes promoting coral survival. Here, we show that acceleration of a major ocean current and shallowing of the surface mixed layer enhanced localized upwelling on a central Pacific coral reef during the three strongest El Niño–associated marine heatwaves of the past half century. These conditions mitigated regional declines in primary production and bolstered local supply of nutritional resources to corals during a bleaching event. The reefs subsequently suffered limited post-bleaching coral mortality. Our results reveal how large-scale ocean-climate interactions affect reef ecosystems thousands of kilometers away and provide a valuable framework for identifying reefs that may benefit from such biophysical linkages during future bleaching events. 

Synopsis Anthropogenic change has well-documented impacts on stress physiology and behavior across diverse taxonomic groups. Within individual organisms, physiological and behavioral traits often covary at proximate and ultimate timescales. In the context of global change, this means that impacts on physiology can have downstream impacts on behavior, and vice versa. Because all organisms interact with members of their own species and other species within their communities, the effects of humans on one organism can impose indirect effects on one or more other organisms, resulting in cascading effects across interaction networks. Human-induced changes in the stress physiology of one species and the downstream impacts on behavior can therefore interact with the physiological and behavioral responses of other organisms to alter emergent ecological phenomena. Here, we highlight three scenarios in which the stress physiology and behavior of individuals on different sides of an ecological relationship are interactively impacted by anthropogenic change. We discuss host–parasite/pathogen dynamics, predator–prey relationships, and beneficial partnerships (mutualisms and cooperation) in this framework, considering cases in which the effect of stressors on each type of network may be attenuated or enhanced by interactive changes in behavior and physiology. These examples shed light on the ways that stressors imposed at the level of one individual can impact ecological relationships to trigger downstream consequences for behavioral and ecological dynamics. Ultimately, changes in stress physiology on one or both sides of an ecological interaction can mediate higher-level population and community changes due in part to their cascading impacts on behavior. This framework may prove useful for anticipating and potentially mitigating previously underappreciated ecological responses to anthropogenic perturbations in a rapidly changing world. 

Abstract As humans continue to alter natural habitats, many wild animals are facing novel suites of environmental stimuli. These changes, including increased human–wildlife interactions, may exert sublethal impacts on wildlife such as alterations in stress physiology and behavior. California ground squirrels (Otospermophilus beecheyi) occur in human-modified as well as more pristine environments, where they face a variety of anthropogenic and naturally occurring threats. This makes this species a valuable model for examining the effects of diverse challenges on the physiology and behavior of free-living mammals. To explore potential sublethal effects of habitat modification on O. beecheyi, we compared body masses, behaviors, and fecal glucocorticoid metabolite (FGM) levels for free-living squirrels in human-disturbed versus undisturbed habitats. Prior to these analyses, we validated the use of FGMs in this species by exposing captive O. beecheyi to pharmacological and handling challenges; both challenges produced significant increases in FGMs in the study animals. While FGM responses were repeatable within captive individuals, responses by free-living animals were more variable, perhaps reflecting a greater range of life-history traits and environmental conditions within natural populations of squirrels. Animals from our human-disturbed study site had significantly higher FGMs, significantly lower body masses, and were significantly less behaviorally reactive to humans than those from our more pristine study site. Thus, despite frequent exposure of California ground squirrels to human impacts, anthropogenic stressors appear to influence stress physiology and other phenotypic traits in this species. These findings suggest that even human-tolerant mammalian species may experience important sublethal consequences due to human modifications of natural habitats.