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Ocean acidification, chemical changes to the carbonate system of seawater, is emerging as a key environmental challenge accompanying global warming and other human-induced perturbations. Considerable research seeks to define the scope and character of potential outcomes from this phenomenon, but a crucial impediment persists. Ecological theory, despite its power and utility, has been only peripherally applied to the problem. Here we sketch in broad strokes several areas where fundamental principles of ecology have the capacity to generate insight into ocean acidification's consequences. We focus on conceptual models that, when considered in the context of acidification, yield explicit predictions regarding a spectrum of population- and community-level effects, from narrowing of species ranges and shifts in patterns of demographic connectivity, to modified consumer-resource relationships, to ascendance of weedy taxa and loss of species diversity. Although our coverage represents only a small fraction of the breadth of possible insights achievable from the application of theory, our hope is that this initial foray will spur expanded efforts to blend experiments with theoretical approaches. The result promises to be a deeper and more nuanced understanding of ocean acidification and the ecological changes it portends.

Organism-level effects of ocean acidification (OA) are well recognized. Less understood are OA's consequences for ecological species interactions. Here, we examine a behaviourally mediated predator–prey interaction within the rocky intertidal zone of the temperate eastern Pacific Ocean, using it as a model system to explore OA's capacity to impair invertebrate anti-predator behaviours more broadly. Our system involves the iconic sea star predator, Pisaster ochraceus, that elicits flee responses in numerous gastropod prey. We examine, in particular, the capacity for OA-associated reductions in pH to alter flight behaviours of the black turban snail, Tegula funebralis, an often-abundant and well-studied grazer in the system. We assess interactions between these species at 16 discrete levels of pH, quantifying the full functional response of Tegula under present and near-future OA conditions. Results demonstrate the disruption of snail anti-predator behaviours at low pH, with decreases in the time individuals spend in refuge locations. We also show that fluctuations in pH, including those typical of rock pools inhabited by snails, do not materially change outcomes, implying little capacity for episodically benign pH conditions to aid behavioural recovery. Together, these findings suggest a strong potential for OA to induce cascading community-level shifts within this long-studied ecosystem.

1. Vessels can have acute and chronic impacts on marine species. The rate of increase in commercial shipping is accelerating, and there is a need to quantify and potentially manage the risk of these impacts. 2. Usage maps characterising densities of grey and harbour seals and ships around the British Isles were used to produce risk maps of seal co-occurrence with shipping traffic. Acoustic exposure to individual harbour seals was modelled in a study area using contemporaneous movement data from 28 animals fitted with UHF global positioning satellite telemetry tags and automatic identification system data from all ships during 2014 and 2015. Data from four acoustic recorders were used to validate sound exposure predictions. 3. Across the British Isles, rates of co-occurrence were highest within 50 km of the coast, close to seal haul-outs. Areas identified with high risk of exposure included 11 Special Areas of Conservation (SAC; from a possible 25). Risk to harbour seal populations was highest, affecting half of all SACs associated with the species. 4. Predicted cumulative sound exposure level, cSELs(Mpw), over all seals was 176-8 dB re 1 µPa²s (95% CI 163·3-190·4), ranging from 170·2 dB re 1µPa² s (95% CI 168·4–171·9) to 189·3 dB re 1 µPa²s (95% CI 172·6–206·0) for individuals. This represented an increase in 28·3 dB re 1 µPa² s over measured ambient noise. For 20 of 28 animals in the study, 95% CI for cSELs(Mpw) had upper bounds above levels known to induce temporary threshold shift. Predictions of broadband received sound pressure levels were underestimated on average by 0·7 dB re 1 µPa (±3·3). 5. Synthesis and applications. We present a framework to allow shipping noise, an important marine anthropogenic Stressor, to be explicitly incorporated into spatial planning. Potentially sensitive areas are identified through quantifying risk to marine species of exposure to shipping traffic, and individual noise exposure is predicted with associated uncertainty in an area with varying rates of co-occurrence. The detailed approach taken here facilitates spatial planning with regard to underwater noise within areas protected through the Habitats Directive, and could be used to provide evidence for further designations. This framework may have utility in assessing whether underwater noise levels are at Good Environmental Status under the Marine Strategy Framework Directive.

Anthropogenic carbon emissions and associated climate change are driving rapid warming, acidification, and deoxygenation in the ocean, which increasingly stress marine ecosystems. On top of long‐term trends, short term variability of marine stressors can have major implications for marine ecosystems and their management. As such, there is a growing need for predictions of marine ecosystem stressors on monthly, seasonal, and multi‐month timescales. Previous studies have demonstrated the ability to make reliable predictions of the surface ocean physical and biogeochemical state months to years in advance, but few studies have investigated forecast skill of multiple stressors simultaneously or assessed the forecast skill below the surface. Here, we use the Community Earth System Model (CESM) Seasonal to Multiyear Large Ensemble (SMYLE) along with novel observation‐based biogeochemical and physical products to quantify the predictive skill of dissolved inorganic carbon (DIC), dissolved oxygen, and temperature in the surface and subsurface ocean. CESM SMYLE demonstrates high physical and biogeochemical predictive skill multiple months in advance in key oceanic regions and frequently outperforms persistence forecasts. We find up to 10 months of skillful forecasts, with particularly high skill in the Northeast Pacific (Gulf of Alaska and California Current Large Marine Ecosystems) for temperature, surface DIC, and subsurface oxygen. Our findings suggest that dynamical marine ecosystem prediction could support actionable advice for decision making. Plain Language Summary Human‐driven climate change is rapidly altering the global ocean, with strong warming, increasing acidity, and declining oxygen trends. On top of long‐term trends, short term variations can lead to rapid changes that can have major effects on marine ecosystems. There is a growing need to predict these short‐term changes in order to better inform marine fisheries managers. In this study, we use a climate model designed to predict changes in the real world months‐to‐years in advance to better determine our ability to forecast changes. Previous studies with similar goals have been limited by sparse observations of acidity and oxygen. We utilize brand new observational products that estimate acidity and oxygen levels in the subsurface ocean for the first time to analyze subsurface forecasts. Our results demonstrate a high potential to predict warming, acidity, and oxygen levels in key marine ecosystems with this climate model. These results suggest that there is potential for eventual operational forecasts of marine ecosystems to better inform marine managers. Key Points Community Earth System Model Seasonal to Multiyear Large Ensemble (SMYLE) forecasts variations in multiple marine stressors up to a year in advance and outperforms statistical persistence Novel observation‐based products allow for the first skill analysis of subsurface carbon and oxygen Analysis of predictability from the SMYLE reconstruction reveals high potential to gain additional temperature and oxygen forecast skill

Global Earth system models are often enlisted to assess the impacts of climate variability and change on marine ecosystems. In this study, we compare high frequency (daily) outputs of potential ecosystem stressors, such as sea surface temperature and surface pH, and associated variables from an Earth system model (GFDL ESM4.1) with high frequency time series from a global network of moorings to directly assess the capacity of the model to resolve local biogeochemical variability on time scales from daily to interannual. Our analysis indicates variability in surface temperature is most consistent between ESM4.1 and observations, with a Pearson correlation coefficient of 0.93 and bias of 0.40°C, followed by variability in surface salinity. Physical variability is reproduced with greater accuracy than biogeochemical variability, and variability on seasonal and longer time scales is more consistent between the model and observations than higher frequency variability. At the same time, the well‐resolved seasonal and longer timescale variability is a reasonably good predictor, in many cases, of the likelihood of extreme events. Despite limited model representation of high frequency variability, model and observation‐based assessments of the fraction of days experiencing surface T‐pH and T‐Ωarag multistressor conditions show reasonable agreement, depending on the stressor combination and threshold definition. We also identify circumstances in which some errors could be reduced by accounting for model biases. Plain Language Summary Ocean ecosystems are under stress from changing temperature and acidity due to the human‐driven increase in global atmospheric carbon dioxide. Global Earth system models (ESMs) are used to study the effects of climate variability and change on marine ecosystems. However, computing power and storage constraints limit the level of detail represented by these simulations. Some short timescale variability present in the real world is missing from ESM output. Despite this inconsistency, we show that at an array of sites where daily observation data from ocean moorings is available, models accurately capture observed spatial patterns in estimates of the amount of time the locations experience combined temperature and acidification stress. We also demonstrate circumstances in which some model errors can be reduced through bias correction. Key Points Physical and biogeochemical variability from moorings and GFDL ESM4.1 output is most consistent on seasonal and longer time scales More high frequency (daily to monthly) variability is present in observations than in ESM output Despite missing high frequency variability, ESM output can be applied to accurately quantify multiple stressor events

Plastics and other artificial materials pose new risks to health of the ocean. Anthropogenic debris travels across large distances and is ubiquitous in the water and on the shorelines, yet, observations of its sources, composition, pathways and distributions in the ocean are very sparse and inaccurate. Total amounts of plastics and other man-made debris in the ocean and on the shore, temporal trends in these amounts under exponentially increasing production, as well as degradation processes, vertical fluxes and time scales are largely unknown. Present ocean circulation models are not able to accurately simulate drift of debris because of its complex hydrodynamics. In this paper we discuss the structure of the future integrated marine debris observing system (IMDOS) that is required to provide long-term monitoring of the state of the anthropogenic pollution and support operational activities to mitigate impacts on the ecosystem and safety of maritime activity. The proposed observing system integrates remote sensing and in situ observations. Also, models are used to optimize the design of the system and, in turn, they will be gradually improved using the products of the system. Remote sensing technologies will provide spatially coherent coverage and consistent surveying time series at local to global scale. Optical sensors, including high-resolution imaging, multi- and hyperspectral, fluorescence, and Raman technologies, as well as SAR will be used to measure different types of debris. They will be implemented in a variety of platforms, from hand-held tools to ship-, buoy-, aircraft-, and satellite-based sensors. A network of in situ observations, including reports from volunteers, citizen scientists and ships of opportunity, will be developed to provide data for calibration/validation of remote sensors and to monitor the spread of plastic pollution and other marine debris. IMDOS will interact with other observing systems monitoring physical, chemical, and biological processes in the ocean and on shorelines as well as state of the ecosystem, maritime activities and safety, drift of sea ice, etc. The synthesized data will support innovative multi-disciplinary research and serve diverse community of users.

Increasing anthropogenic pressure on marine ecosystems from fishing, pollution, climate change, and other sources is a big concern in marine conservation. Scientists have thus developed spatial models to map cumulative human impacts on marine ecosystems. However, these models are based on many assumptions and incorporate data that suffer from substantial incompleteness and inaccuracies. Rather than using a single model, we used Monte Carlo simulations to identify which parts of the oceans are subject to the most and least impact from anthropogenic Stressors under 7 simulated sources of uncertainty (factors: e.g., missing Stressor data and assuming linear ecosystem responses to stress). Most maps agreed that high-impact areas were located in the Northeast Atlantic, the eastern Mediterranean, the Caribbean, the continental shelf off northern West Africa, offshore parts of the tropical Atlantic, the Indian Ocean east of Madagascar, parts of East and Southeast Asia, parts of the northwestern Pacific, and many coastal waters. Large low-impact areas were located off Antarctica, in the central Pacific, and in the southern Atlantic. Uncertainty in the broad-scale spatial distribution of modeled human impact was caused by the aggregate effects of several factors, rather than being attributable to a single dominant source. In spite of the identified uncertainty in human-impact maps, they can—at broad spatial scales and in combination with other environmental and socioeconomic information—point to priority areas for research and management. El incremento de la presión antropogénica sobre los ecosistemas marinos a partir de la pesca, la contaminación, el cambio climático, y otras fuentes es causa de una gran preocupación dentro de la conservación marina. Por esto, los científicos han desarrollado modelos espaciales para mapear los impactos humanos acumulativos sobre los ecosistemas marinos. Sin embargo, estos modelos están basados en muchas suposiciones e incorporan datos que sufren de errores y falta de información sustanciales. En lugar de utilizar solamente un modelo, usamos simulaciones Monte Cario para identificar las regiones de los océanos que están sujetas al mayor y al menor impacto por estresantes antropogénicos bajo siete fuentes simuladas de incertidumbre (factores: p. ej., falta de datos sobre el estresante y la suposición de respuestas ambientales lineales ante el estrés). La mayoría de los mapas concordaron en que las áreas de alto impacto estaban localizadas en el noreste del Atlántico, el este del Mediterráneo, el Caribe, la plataforma continental del oeste de África, algunas regiones del litoral del Atlántico tropical, el océano índico al este de Madagascar, algunas partes del este y sureste de Asia, algunas partes del noroeste del Pacífico, y muchas aguas costeras. Las grandes áreas de bajo impacto se ubicaron en las costas de la Antártida, en el centro del Pacífico, y en el sur del Atlántico. La incertidumbre en la distribución espacial a escala general de los impactos humanos fue causada por los efectos agregados de varios factores, en lugar de ser atribuible a un solo origen dominante. A pesar de la incertidumbre identificada en los mapas de impacto humano, estos pueden - a escalas espaciales generalizadas y en combinación con otra información ambiental y socioeconómica - señalar hacia áreas prioritarias para la investigación y el manejo. 越来越多渔业、污染、气候变化和其它来源的人类活动压カ正在成为海洋生态系统保护的一大问题。科 学家为此开发了空间模型来模拟人类对海洋生态系统的累计影响。然而，这些模型建立在许多假说上，还整合了 大量不完整和不准确的数据。相比于单ー模型，我们则使用了蒙特卡罗模拟来确定在七个模拟的不确定性因素 (如缺失压力因素的数据、假设生态系统对压カ的响应是线性的) 下，海洋受到人类活动压カ影响最大和最小的 地区。大多数模拟结果都显示，受到影响较大的是大西洋东北部、地中海东部、加勒比海、西非北部大陆架、 热带大西洋近海地区、马达加斯加以东的印度洋、东亚和东南亚部分地区、太平洋西北部的部分地区，以及许 多沿海水域。而受到影响较小的大片区域则位于南极洲外、太平洋中部和大西洋南部。模拟人类影响的大尺 度空间分布分析中的不确定性来自多个因素的综合效应，而不能归因于某个单ー的主要因素。虽然人类影响效 应确实存在不确定性，但它们可以在较大空间尺度上, 結合其它环境和社会经济学信息，指出研究和管理的优先 区域。

Ocean acidification and warming are considered two of the greatest threats to marine biodiversity, yet the combined effect of these stressors on marine organisms remains largely unclear. Using a meta‐analytical approach, we assessed the biological responses of marine organisms to the effects of ocean acidification and warming in isolation and combination. As expected biological responses varied across taxonomic groups, life‐history stages, and trophic levels, but importantly, combining stressors generally exhibited a stronger biological (either positive or negative) effect. Using a subset of orthogonal studies, we show that four of five of the biological responses measured (calcification, photosynthesis, reproduction, and survival, but not growth) interacted synergistically when warming and acidification were combined. The observed synergisms between interacting stressors suggest that care must be made in making inferences from single‐stressor studies. Our findings clearly have implications for the development of adaptive management strategies particularly given that the frequency of stressors interacting in marine systems will be likely to intensify in the future. There is now an urgent need to move toward more robust, holistic, and ecologically realistic climate change experiments that incorporate interactions. Without them accurate predictions about the likely deleterious impacts to marine biodiversity and ecosystem functioning over the next century will not be possible. Meta‐analysis of the impacts of ocean acidification and warming for marine organisms demonstrates that these combined stressors generally led to stronger effects than when experienced in isolation. Moreover, the interaction of ocean warming and acidification led to synergistic effects for the majority of biological responses investigated. Such outcomes highlight the need to include multiple stressors in the development of effective adaptive management strategies, at the same time as highlighting some of the difficulties that need to be overcome to achieve this.

Over the past decades, Atlantic salmon (Salmo salar, Salmonidae) has emerged as a model system for sexual maturation research, owing to the high diversity of life history strategies, knowledge of trait genetic architecture, and their high economic value. The aim of this synthesis is to summarize the current state of knowledge concerning maturation in Atlantic salmon, outline knowledge gaps, and provide a roadmap for future work. We summarize the current state of knowledge: 1) maturation in Atlantic salmon takes place over the entire life cycle, starting as early as embryo development, 2) variation in the timing of maturation promotes diversity in life history strategies, 3) ecological and genetic factors influence maturation, 4) maturation processes are sex-specific and may have fitness consequences for each sex, 5) genomic studies have identified large-effect loci that influence maturation, 6) the brain-pituitary–gonadal axis regulates molecular and physiological processes of maturation, 7) maturation is a key component of fisheries, aquaculture, conservation, and management, and 8) climate change, fishing pressure, and other anthropogenic stressors likely have major effects on salmon maturation. In the future, maturation research should focus on a broader diversity of life history stages, including early embryonic development, the marine phase and return migration. We recommend studies combining ecological and genetic approaches will help disentangle the relative contributions of effects in different life history stages to maturation. Functional validation of large-effect loci should reveal how these genes influence maturation. Finally, continued research in maturation will improve our predictions concerning how salmon may adapt to fisheries, climate change, and other future challenges.

Jellyfish (Cnidaria, Scyphozoa) blooms appear to be increasing in both intensity and frequency in many coastal areas worldwide, due to multiple hypothesized anthropogenic stressors. Here, we propose that the proliferation of artificial structures - associated with (1) the exponential growth in shipping, aquaculture, and other coastal industries, and (2) coastal protection (collectively, \"ocean sprawl\") - provides habitat for jellyfish polyps and may be an important driver of the global increase in jellyfish blooms. However, the habitat of the benthic polyps that commonly result in coastal jellyfish blooms has remained elusive, limiting our understanding of the drivers of these blooms. Support for the hypothesized role of ocean sprawl in promoting jellyfish blooms is provided by observations and experimental evidence demonstrating that jellyfish larvae settle in large numbers on artificial structures in coastal waters and develop into dense concentrations of jellyfish-producing polyps.