Recently, the effects of ocean acidification (OA) on marine animal behaviour have garnered considerable attention, as they can impact biological interactions and, in turn, eco system structure and functioning. We reviewed current published literature on OA and marine behaviour and synthesize current understanding of how a high CO 2 ocean may impact animal behaviour, elucidate critical unknowns, and provide suggestions for future research. Although studies have focused equally on vertebrates and invertebrates, vertebrate studies have primarily focused on coral reef fishes, in contrast to the broader diversity of invertebrate taxa studied. A quantitative synthesis of the direction and magnitude of change in behaviours from current conditions under OA scenarios suggests primarily negative impacts that vary depending on species, ecosystem, and behaviour. The interactive effects of co-occurring environmental parameters with increasing CO 2 elicit effects different from those observed under elevated CO 2 alone. Although 12% of studies have incorporated multiple factors, only one study has examined the effects of carbonate system variability on the behaviour of a marine animal. Altered GABA A receptor functioning under elevated CO 2 appears responsible for many behavioural responses; however, this mechanism is unlikely to be universal. We recommend a new focus on determining the effects of elevated CO 2 on marine animal behaviour in the context of multiple environmental drivers and future carbonate system variability, and the mechanisms governing the association between acid-base regulation and GABA A receptor functioning. This knowledge could explain observed species-specificity in behavioural responses to OA and lend to a unifying theory of OA effects on marine animal behaviour.

The fossil record is the primary source of data used to study predator-prey interactions in deep time and to evaluate key questions regarding the evolutionary and ecological importance of predation. Here, we review the types of paleontological data used to infer predation in the marine fossil record, discuss strengths and limitations of paleontological lines of evidence used to recognize and evaluate predatory activity, assess the influence of environmental gradients on predation patterns, and review fossil evidence for predator behavior and prey defense. We assembled a predation database from the literature that documents a steady increase in the number of papers on predation since the 1960s. These studies have become increasingly quantitative and have expanded in focus from reporting cases of predation documented by fossils to using the fossil record of predation to test ecological and evolutionary hypotheses. The data on the fossil record of predation amassed so far in the literature primarily come from trace fossils, mostly drill holes and, to a lesser extent, repair scars, derived predominantly from the Cenozoic of Europe and North America. Mollusks are the clade most often studied as prey and inferred predators. We discuss how to distinguish biotic from abiotic damage and predatory from parasitic traces, and how to recognize failed predation. Our data show that identifying the predator is easiest when predator and prey are preserved in the act of predation or when predators were fossilized with their gut contents preserved. However, determining the culprits responsible for bite traces, drill holes, and other types of predation traces can be more problematic.Taphonomic and other factors can distort patterns of predation, but their potential effects can be minimized by careful study design. With the correct identification and quantification of fossilized traces of predation, ecological trends in predator-prey interactions may be discerned along environmental gradients in water depth, habitat, and oxygen and nutrient availability.However, so far, these trends have not been explored adequately for the fossil record. We also

Shifting environmental conditions resulting from anthropogenic climate change have recently garnered much attention in the aquaculture industry; however, ocean acidification has received relatively little attention. Here, we provide an overview of ocean acidification in the context of North American aquaculture with respect to potential impacts and mitigation strategies. North American shellfish farms should make ocean acidification an immediate priority, as shellfish and other calcifying organisms are of highest concern in an increasingly acidifying ocean and negative effects have already been felt on the Pacific coast. While implications for various finfish have been documented, our current understanding of how acidification will impact North American finfish aquaculture is limited and requires more research. Although likely to benefit from increases in seawater CO 2 , some seaweeds may also be at risk under more acidic conditions, particularly calcifying species, as well as non-calcifying ones residing in areas where CO 2 is not the primary driver of acidification. Strategies to mitigate and adapt to the effects of acidification exist on the regional scale and can aid in identifying areas of concern, detecting changes in seawater carbonate chemistry early enough to avoid catastrophic outcomes, and adapting to long-term shifts in oceanic pH. Ultimately, ocean acidification has already imposed negative impacts on the aquaculture industry, but can be addressed with sufficient monitoring and the establishment of regional mitigation plans.

Ocean acidification—decreasing oceanic pH resulting from the uptake of excess atmospheric CO2—has the potential to affect marine life in the future. Among the possible consequences, a series of studies on coral reef fish suggested that the direct effects of acidification on fish behavior may be extreme and have broad ecological ramifications. Recent studies documenting a lack of effect of experimental ocean acidification on fish behavior, however, call this prediction into question. Indeed, the phenomenon of decreasing effect sizes over time is not uncommon and is typically referred to as the “decline effect.” Here, we explore the consistency and robustness of scientific evidence over the past decade regarding direct effects of ocean acidification on fish behavior. Using a systematic review and meta-analysis of 91 studies empirically testing effects of ocean acidification on fish behavior, we provide quantitative evidence that the research to date on this topic is characterized by a decline effect, where large effects in initial studies have all but disappeared in subsequent studies over a decade. The decline effect in this field cannot be explained by 3 likely biological explanations, including increasing proportions of studies examining (1) cold-water species; (2) nonolfactory-associated behaviors; and (3) nonlarval life stages. Furthermore, the vast majority of studies with large effect sizes in this field tend to be characterized by low sample sizes, yet are published in high-impact journals and have a disproportionate influence on the field in terms of citations. We contend that ocean acidification has a negligible direct impact on fish behavior, and we advocate for improved approaches to minimize the potential for a decline effect in future avenues of research.