Assessing the status of ocean acidification across ocean and coastal waters requires standardized procedures at all levels of data collection, dissemination, and analysis. Standardized procedures for assuring quality and accessibility of ocean carbonate chemistry data are largely established, but a common set of best practices for ocean acidification trend analysis is needed to enable global time series comparisons, establish accurate records of change, and communicate the current status of ocean acidification within and outside the scientific community. Here we expand upon several published trend analysis techniques and package them into a set of best practices for assessing trends of ocean acidification time series. These best practices are best suited for time series capable of characterizing seasonal variability, typically those with sub-seasonal (ideally monthly or more frequent) data collection. Given ocean carbonate chemistry time series tend to be sparse and discontinuous, additional research is necessary to further advance these best practices to better address uncharacterized variability that can result from data discontinuities. This package of best practices and the associated open-source software for computing and reporting trends is aimed at helping expand the community of practice in ocean acidification trend analysis. A broad community of practice testing these and new techniques across different data sets will result in improvements and expansion of these best practices in the future.

The California Current Marine Ecosystem is a highly productive system that exhibits strong natural variability and vulnerability to anthropogenic climate trends. Relating projections of ocean change to biological sensitivities requires detailed synthesis of experimental results. Here, we combine measured biological sensitivities with high-resolution climate projections of key variables (temperature, oxygen, and pCO₂) to identify the direction, magnitude, and spatial distribution of organism-scale vulnerabilities to multiple axes of projected ocean change. Among 12 selected species of cultural and economic importance, we find that all are sensitive to projected changes in ocean conditions through responses that affect individual performance or population processes. Response indices were largest in the northern region and inner shelf. While performance traits generally increased with projected changes, fitness traits generally decreased, indicating that concurrent stresses can lead to fitness loss. For two species, combining sensitivities to temperature and oxygen changes through the Metabolic Index shows how aerobic habitat availability could be compressed under future conditions. Our results suggest substantial and specific ecological susceptibility in the next 80 years, including potential regional loss of canopy-forming kelp, changes in nearshore food webs caused by declining rates of survival among red urchins, Dungeness crab, and razor clams, and loss of aerobic habitat for anchovy and pink shrimp. We also highlight fillable gaps in knowledge, including specific physiological responses to stressors, variation in responses across life stages, and responses to multistressor combinations. These findings strengthen the case for filling information gaps with experiments focused on fitness-related responses and those that can be used to parameterize integrative physiological models, and suggest that the CCME is susceptible to substantial changes to ecosystem structure and function within this century.

The global threat that ocean acidification poses to marine ecosystems has been recognized by the UN 2030 Agenda under Sustainable Development Goal, Target 14.3: to reduce ocean acidification. The Global Ocean Acidification Observing Network (GOA-ON) is a collaborative international network to detect and understand the drivers of ocean acidification in estuarine-coastal-open ocean environments, the resulting impacts on marine ecosystems, and to make the information available to optimize modelling studies. The Ocean Acidification Research for Sustainability (OARS) programme, endorsed by the 2021–2030 UN Decade of Ocean Science for Sustainable Development, will build on the work of GOA-ON through its seven Decade Action Outcomes. By employing a Theory of Change framework, and with the co-design of science in mind, OARS will develop an implementation plan for each Decade Action Outcome, which will identify the stakeholders and rights-holders, as well as the tools, means, and positive consequences required for their successful delivery. The organizational structure of GOA-ON, with nine regional hubs, will benefit OARS by providing a vital connection between local and global scales. GOA-ON regional hub case-studies illustrate how activities in the past and future, informed by global and regional priorities, support capacity building and the co-design of ocean acidification science.

Scaling climate change impacts from individual responses to population-level vulnerability is a pressing challenge for scientists and society. We assessed vulnerability of the most valuable fished species in the Northwest U.S. — Dungeness crab — to climate stressors using a novel combination of ocean, population, and larval transport models with stage-specific consequences of ocean acidification, hypoxia, and warming. Integration across pelagic and benthic life stages revealed increased population-level vulnerability to each stressor by 2100 under RCP 8.5. Under future conditions, chronic vulnerability to low pH emerged year-round for all life stages, whereas vulnerability to low oxygen continued to be acute, developing seasonally and impacting adults, which are critical to population growth. Our results demonstrate how ontogenetic habitat shifts and seasonal ocean conditions interactively impact population-level vulnerability. Because most valuable U.S. fisheries rely on species with complex life cycles in seasonal seas, chronic and acute perspectives are necessary to assess population-level vulnerability to climate change.

Global projections for ocean conditions in 2100 predict that the North Pacific will experience some of the largest changes. Coastal processes that drive variability in the region can alter these projected changes but are poorly resolved by global coarse-resolution models. We quantify the degree to which local processes modify biogeochemical changes in the eastern boundary California Current System (CCS) using multi-model regionally downscaled climate projections of multiple climate-associated stressors (temperature, O₂, pH, saturation state (Ω), and CO₂). The downscaled projections predict changes consistent with the directional change from the global projections for the same emissions scenario. However, the magnitude and spatial variability of projected changes are modified in the downscaled projections for carbon variables. Future changes in pCO₂ and surface Ω are amplified, while changes in pH and upper 200 m Ω are dampened relative to the projected change in global models. Surface carbon variable changes are highly correlated to changes in dissolved inorganic carbon (DIC), pCO₂ changes over the upper 200 m are correlated to total alkalinity (TA), and changes at the bottom are correlated to DIC and nutrient changes. The correlations in these latter two regions suggest that future changes in carbon variables are influenced by nutrient cycling, changes in benthic––pelagic coupling, and TA resolved by the downscaled projections. Within the CCS, differences in global and downscaled climate stressors are spatially variable, and the northern CCS experiences the most intense modification. These projected changes are consistent with the continued reduction in source water oxygen; increase in source water nutrients; and, combined with solubility-driven changes, altered future upwelled source waters in the CCS. The results presented here suggest that projections that resolve coastal processes are necessary for adequate representation of the magnitude of projected change in carbon stressors in the CCS.

Estuaries are recognized as one of the habitats most vulnerable to coastal ocean acidification due to seasonal extremes and prolonged duration of acidified conditions. This is combined with co-occurring environmental stressors such as increased temperature and low dissolved oxygen. Despite this, evidence of biological impacts of ocean acidification in estuarine habitats is largely lacking. By combining physical, biogeochemical, and biological time-series observations over relevant seasonal-to-interannual time scales, this study is the first to describe both the spatial and temporal variation of biological response in the pteropod Limacina helicina to estuarine acidification in association with other stressors. Using clustering and principal component analyses, sampling sites were grouped according to their distribution of physical and biogeochemical variables over space and time. This identified the most exposed habitats and time intervals corresponding to the most severe negative biological impacts across three seasons and three years. We developed a cumulative stress index as a means of integrating spatial-temporal OA variation over the organismal life history. Our findings show that over the 2014–2016 study period, the severity of low aragonite saturation state combined with the duration of exposure contributed to overall cumulative stress and resulted in severe shell dissolution. Seasonally-variable estuaries such as the Salish Sea (Washington, U.S.A.) predispose sensitive organisms to more severe acidified conditions than those of coastal and open-ocean habitats, yet the sensitive organisms persist. We suggest potential environmental factors and compensatory mechanisms that allow pelagic calcifiers to inhabit less favorable habitats and partially offset associated stressors, for instance through food supply, increased temperature, and adaptation of their life history. The novel metric of cumulative stress developed here can be applied to other estuarine environments with similar physical and chemical dynamics, providing a new tool for monitoring biological response in estuaries under pressure from accelerating global change.

Efforts to identify in situ the mechanisms underpinning the response of harmful algae to climate change demand frequent observations in dynamic and often difficult to access marine and freshwater environments. Increasingly, resource managers and researchers are looking to fill this data gap using unmanned systems. In this study we integrated the Environmental Sample Processor (ESP) into an autonomous platform to provide near real-time surveillance of harmful algae and the toxin domoic acid on the Washington State continental shelf over a three-year period (2016–2018). The ESP mooring design accommodated the necessary subsystems to sustain ESP operations, supporting deployment durations of up to 7.5 weeks. The combination of ESP observations and a suite of contextual measurements from the ESP mooring and a nearby surface buoy permitted an investigation into toxic Pseudo-nitzschia spp. bloom dynamics. Preliminary findings suggest a connection between bloom formation and nutrient availability that is modulated by wind-forced coastal-trapped waves. In addition, high concentrations of Pseudo-nitzschia spp. and elevated levels of domoic acid observed at the ESP mooring location were not necessarily associated with the advection of water from known bloom initiation sites. Such insights, made possible by this autonomous technology, enable the formulation of testable hypotheses on climate-driven changes in HAB dynamics that can be investigated during future deployments.

Oceanic uptake of anthropogenic carbon dioxide (CO₂) from the atmosphere has changed ocean biogeochemistry and threatened the health of organisms through a process known as ocean acidification (OA). Such large-scale changes affect ecosystem functions and can have impacts on societal uses, fisheries resources, and economies. In many large estuaries, anthropogenic CO₂-induced acidification is enhanced by strong stratification, long water residence times, eutrophication, and a weak acid–base buffer capacity. In this article, we review how a variety of processes influence aquatic acid–base properties in estuarine waters, including coastal upwelling, river–ocean mixing, air–water gas exchange, biological production and subsequent aerobic and anaerobic respiration, calcium carbonate (CaCO₃) dissolution, and benthic inputs. We emphasize the spatial and temporal dynamics of partial pressure of CO₂ (pCO₂), pH, and calcium carbonate mineral saturation states. Examples from three large estuaries — Chesapeake Bay, the Salish Sea, and Prince William Sound — are used to illustrate how natural and anthropogenic processes and climate change may manifest differently across estuaries, as well as the biological implications of OA on coastal calcifiers.

Summertime upwelling of deep, corrosive waters on the continental shelf of the northern California Current System can exacerbate ocean acidification conditions, providing unsuitable environments for development of calcifying organisms and finfish that are important to the local economy. To better understand the carbonate system in this dynamic region, two recently developed technologies were combined with other sensors to obtain high‐frequency carbon profile data from July 2017 to September 2017. The compact, low‐power sensor package was composed of an optical sensor for partial pressure of carbon dioxide (pCO₂ optode, Aanderaa model #4797) integrated onto a wave‐powered PRofiling crAWLER (PRAWLER). The PRAWLER profiled from 3 to 80 m, stopping at fixed depths for varying lengths of time to allow for pCO₂ equilibration. pCO₂ derived from a regional empirical algorithm was used to correct optode drift using data at 80 m. Near‐surface adjusted optode pCO₂ agreed within 6 ± 42 µ atm to surface pCO₂ from a nearby Moored Autonomous pCO₂ instrument. Throughout the water column, optode pCO₂ compared to algorithm pCO₂ within -28 ± 66 µ atm. Overall, optode uncertainty was 35–72 µ atm based on root‐mean‐square errors from all comparison data sets. Errors are attributed to optode calibration, adjustment, algorithm uncertainty, and environmental variability between optode and reference data. Improvements for optode performance within this profiling application include using more stable sensing foils, in situ calibration, and pumped flow over the sensing foil. Additionally, the study revealed undersaturated (corrosive) waters with respect to aragonite below 60 m throughout the deployment that reached up to 40 m by mid‐September.

The Dungeness crab (Metacarcinus magister) fishery is one of the highest value fisheries in the US Pacific Northwest, but its catch size fluctuates widely across years. Although the underlying causes of this wide variability are not well understood, the abundance of M. magister megalopae has been linked to recruitment into the adult fishery 4 years later. These pelagic megalopae are exposed to a range of ocean conditions during their dispersal period, which may drive their occurrence patterns. Environmental exposure history has been found to be important for some pelagic organisms, so we hypothesized that inclusion of recent environmental exposure history would improve our ability to predict inter-annual variability in M. magister megalopae occurrence patterns compared to using "in situ" conditions alone. We combined 8 years of local observations of M. magister megalopae and regional simulations of ocean conditions to model megalopae occurrence using a generalized linear model (GLM) framework. The modeled ocean conditions were extracted from JISAO's Seasonal Coastal Ocean Prediction of the Ecosystem (J-SCOPE), a high-resolution coupled physical-biogeochemical model. The analysis included variables from J-SCOPE identified in the literature as important for larval crab occurrence: temperature, salinity, dissolved oxygen concentration, nitrate concentration, phytoplankton concentration, pH, aragonite, and calcite saturation state. GLMs were developed with either in situ ocean conditions or environmental exposure histories generated using particle tracking experiments. We found that inclusion of exposure history improved the ability of the GLMs to predict megalopae occurrence 98% of the time. Of the six swimming behaviors used to simulate megalopae dispersal, five behaviors generated GLMs with superior fits to the observations, so a biological ensemble of these models was constructed. When the biological ensemble was used for forecasting, the model showed skill in predicting megalopae occurrence (AUC = 0.94). Our results highlight the importance of including exposure history in larval occurrence modeling and help provide a method for predicting pelagic megalopae occurrence. This work is a step toward developing a forecast product to support management of the fishery.

Instrumented moorings (hereafter referred to as moorings), which are anchored buoys or an anchored configuration of instruments suspended in the water column, are highly valued for their ability to host a variety of interchangeable oceanographic and meteorological sensors. This flexibility makes them a useful technology for meeting end user and science-driven requirements. Overall, societal needs related to human health, safety, national security, and economic prosperity in coastal areas are met through the availability of continuous data from coastal moorings and other complementary observing platforms within the Earth-observing system. These data streams strengthen the quality and accuracy of data products that inform the marine transportation industry, the tourism industry, fisheries, the military, public health officials, coastal and emergency managers, educators, and research scientists, among many others. Therefore, it is critical to sustain existing observing system networks, especially during this time of extreme environmental variability and change. Existing fiscal and operational challenges affecting the sustainability of observing networks will likely continue into the next decade, threatening the quality of downstream data and information products – especially those used for long-term monitoring, planning, and decision-making. This paper describes the utility of coastal moorings as part of an integrated coastal observing system, with an emphasis on stakeholder engagement to inform observing requirements and to ensure data products are tailored to user needs. We provide 10 recommendations for optimizing moorings networks, and thus downstream data products, to guide regional planners, and network operators:

1. Develop strategies to increase investment in coastal mooring networks
2. Collect stakeholder priorities through targeted and continuous stakeholder engagements
3. Include complementary systems and emerging technologies in implementation planning activities
4. Expand and sustain water column ecosystem moorings in coastal locations
5. Coordinate with operators and data managers across geographic scales
6. Standardize and integrate data management best practices
7. Provide open access to data
8. Promote environmental health and operational safety stewardship and regulatory compliance
9. Develop coastal mooring observing network performance metrics
10. Routinely monitor and assess the design of coastal mooring networks

The ocean knows no political borders. Ocean processes like summertime, wind-driven upwelling stretch thousands of kilometers along the Northeast Pacific (NEP) coast. This upwelling drives marine ecosystem productivity and is modulated by weather systems and seasonal to interdecadal ocean-atmosphere variability. Major ocean currents in the NEP transport water properties like heat, fresh water, nutrients, dissolved oxygen, pCO₂ and pH close to shore. The eastward North Pacific Current bifurcates offshore in the NEP, delivering open-ocean signals south into the California Current and north into the Gulf of Alaska. There are a large and growing number of NEP ocean observing elements operated by government agencies, Native American Tribes, First Nations groups, not-for-profit organizations, and private entities. Observing elements include moored and mobile platforms, shipboard repeat cruises, and land-based and estuarine stations. A wide range of multidisciplinary ocean sensors are deployed to track, for example, upwelling, downwelling, ocean productivity, harmful algal blooms, ocean acidification and hypoxia, seismic activity and tsunami wave propagation. Data delivery to shore and observatory control are done through satellite and cell phone communication, and via seafloor cables. Remote sensing from satellites and land-based coastal radar provide broader spatial coverage. Numerical circulation and biogeochemical modeling complement ocean observing efforts. Models span from the deep ocean into the inland Salish Sea and estuaries. NEP ocean observing systems are used to understand regional processes and, together with numerical models, to provide ocean forecasts. By sharing data, experiences and lessons learned, the regional ocean observatory is better than the sum of its parts.

Ship-based time series, some now approaching over 3 decades long, are critical climate records that have dramatically improved our ability to characterize natural and anthropogenic drivers of ocean carbon dioxide (CO₂) uptake and biogeochemical processes. Advancements in autonomous marine carbon sensors and technologies over the last 2 decades have led to the expansion of observations at fixed time series sites, thereby improving the capability of characterizing sub-seasonal variability in the ocean. Here, we present a data product of 40 individual autonomous moored surface ocean pCO₂ (partial pressure of CO₂) time series established between 2004 and 2013, 17 also include autonomous pH measurements. These time series characterize a wide range of surface ocean carbonate conditions in different oceanic (17 sites), coastal (13 sites), and coral reef (10 sites) regimes. A time of trend emergence (ToE) methodology applied to the time series that exhibit well-constrained daily to interannual variability and an estimate of decadal variability indicates that the length of sustained observations necessary to detect statistically significant anthropogenic trends varies by marine environment. The ToE estimates for seawater pCO₂ and pH range from 8 to 15 years at the open ocean sites, 16 to 41 years at the coastal sites, and 9 to 22 years at the coral reef sites. Only two open ocean pCO₂ time series, Woods Hole Oceanographic Institution Hawaii Ocean Time-series Station (WHOTS) in the subtropical North Pacific and Stratus in the South Pacific gyre, have been deployed longer than the estimated trend detection time and, for these, deseasoned monthly means show estimated anthropogenic trends of 1.9±0.3 and 1.6±0.3 µatm yr^-1, respectively. In the future, it is possible that updates to this product will allow for the estimation of anthropogenic trends at more sites; however, the product currently provides a valuable tool in an accessible format for evaluating climatology and natural variability of surface ocean carbonate chemistry in a variety of regions.

It is broadly assumed that organisms inhabiting seasonally hypoxic estuaries and fjords are stressed by low dissolved oxygen (DO) conditions. However, relatively few zooplankton have shown clear avoidance of hypoxic water except when oxygen was extremely low. We investigated vertical distributions and abundance of the euphausiid Euphausia pacifica in the seasonally hypoxic Hood Canal, Washington using depth-stratified zooplankton net tows and CTD casts, monthly from June to October in 2012 and 2013 at two sites that contrasted in oxygen conditions. We separated E. pacifica into five life stages based on their ontogenetic development and swimming ability and related their density (#/m³) within each depth layer to the corresponding environmental variables using delta Generalized Linear Mixed Models (GLMMs). The models detected strong seasonal and spatial differences with no additional significant effects of DO or temperature. GLMMs showed that whole water-column abundances of calyptopes and furcilia I–III stages were more strongly related to DO and temperature than other stages. Overall, only modest effects of DO were observed, possibly because of the low temperatures and moderate DO levels compared to recent years. Combined laboratory experiments and multi-year mooring data show that conditions in other years could have resulted in direct mortality.

Fingerprinting ocean acidification (OA) in US West Coast waters is extremely challenging due to the large magnitude of natural carbonate chemistry variations common to these regions. Additionally, quantifying a change requires information about the initial conditions, which is not readily available in most coastal systems. In an effort to address this issue, we have collated high-quality publicly available data to characterize the modern seasonal carbonate chemistry variability in marine surface waters of the US Pacific Northwest. Underway ship data from version 4 of the Surface Ocean CO₂ Atlas, discrete observations from various sampling platforms, and sustained measurements from regional moorings were incorporated to provide  ~100 000 inorganic carbon observations from which modern seasonal cycles were estimated. Underway ship and discrete observations were merged and gridded to a 0.1° x  0.1° scale. Eight unique regions were identified and seasonal cycles from grid cells within each region were averaged. Data from nine surface moorings were also compiled and used to develop robust estimates of mean seasonal cycles for comparison with the eight regions. This manuscript describes our methodology and the resulting mean seasonal cycles for multiple OA metrics in an effort to provide a large-scale environmental context for ongoing research, adaptation, and management efforts throughout the US Pacific Northwest. Major findings include the identification of unique chemical characteristics across the study domain. There is a clear increase in the ratio of dissolved inorganic carbon (DIC) to total alkalinity (TA) and in the seasonal cycle amplitude of carbonate system parameters when moving from the open ocean North Pacific into the Salish Sea. Due to the logarithmic nature of the pH scale (pH = –log₁₀[H⁺], where [H⁺] is the hydrogen ion concentration), lower annual mean pH values (associated with elevated DIC : TA ratios) coupled with larger magnitude seasonal pH cycles results in seasonal [H⁺] ranges that are  ~27 times larger in Hood Canal than in the neighboring North Pacific open ocean. Organisms living in the Salish Sea are thus exposed to much larger seasonal acidity changes than those living in nearby open ocean waters. Additionally, our findings suggest that lower buffering capacities in the Salish Sea make these waters less efficient at absorbing anthropogenic carbon than open ocean waters at the same latitude.

Pteropods, planktonic marine snails with a cosmopolitan distribution, are highly sensitive to changing ocean chemistry. Graphical abstract shows pteropod responses to be related to aragonite saturation state, with progressing decrease in Ω_ar causing deteriorating biological conditions. Under high saturation state (Ω_ar > 1.1; zone 0), pteropods are healthy with no presence of stress or shell dissolution. With decreasing Ω_ar (zone 1), pteropod stress is demonstrated through increased dissolution and reduced calcification. At Ω_ar < 0.8 (zones 2 and 3), severe dissolution and absence of calcification prevail; the impairment is followed by significant damages. Pteropods responses to OA are closely correlated to shell dissolution that is characterized by clearly delineated thresholds. Yet the practical utility of these species as indicators of the status of marine ecosystem integrity has been overlooked. Here, we set out the scientific and policy rationales for the use of pteropods as a biological indicator appropriate for low-cost assessment of the effect of anthropogenic ocean acidification (OA) on marine ecosystems. While no single species or group of species can adequately capture all aspects of ecosystem change, pteropods are sensitive, specific, quantifiable indicators of OA’s effects on marine biota. In an indicator screening methodology, shell dissolution scored highly compared to other indicators of marine ecological integrity. As the socio-economic challenges of changing ocean chemistry continue to grow in coming decades, the availability of such straightforward and sensitive metrics of impact will become indispensable. Pteropods can be a valuable addition to suites of indicators intended to support OA water quality assessment, ecosystem-based management, policy development, and regulatory applications.

Evidence of ocean acidification (OA) throughout the global ocean has galvanized some coastal communities to evaluate carbonate chemistry variations closer to home. An impediment to doing this effectively is that, often, only one carbonate system parameter is measured at a time, while two are required to fully constrain the inorganic carbon chemistry of seawater. In order to leverage the abundant single-carbonate-parameter datasets in Washington State for more rigorous OA research, we have characterized an empirical relationship between total alkalinity (TA) and salinity for regional surface waters that is robust in the salinity range from 20 to 35 for all seasons. The relationship was evaluated using 5 years of 3-h contemporaneous observations of salinity, carbon dioxide partial pressure (pCO2), and pH from a surface mooring on the outer coast of Washington. In situ pCO2 observations and salinity-based estimates of TA were used to calculate pH for comparison with in situ pH measurements. On average, the calculated pH values were 0.02 units lower than the measured pH values across multiple pH sensor deployments and showed extremely high fidelity in tracking the measured high-frequency pH variations. Our results indicate that the TA-salinity relationship will be a useful tool for expanding single-carbonate-parameter datasets in Washington State and quality controlling dual pCO2-pH time series.

Willapa Bay has received a great deal of attention in the context of rising atmospheric CO₂ and the concomitant effects of changes in bay carbonate chemistry, referred to as ocean acidification, and the potential effects on the bay’s naturalized Pacific oyster (Crassostrea gigas) population and iconic oyster farming industry. Competing environmental stressors, historical variability in the oyster settlement record, and the absence of adequate historical observations of bay-water carbonate chemistry all conspire to cast confusion regarding ocean acidification as the culprit for recent failures in oyster larval settlement. We present the first measurements of the aqueous CO₂ partial pressure (PCO₂) and the total dissolved carbonic acid (TCO₂) at the "fattening line," a location in the bay that has been previously identified as optimal for both larval oyster retention and growth, and collocated with a long historical time series of larval settlement. Samples were collected from early 2011 through late 2014. These measurements allow the first rigorous characterization of Willapa Bay aragonite mineral saturation state (Ω_ar), which has been shown to be of leading importance in determining the initial shell formation and growth of larval Crassostrea gigas. Observations show that the bay is usually below Ω_ar levels that have been associated with poor oyster hatchery production and with chronic effects noted in experimental work. Bay water only briefly rises to favorable Ω_ar levels and does so out of phase with optimal thermal conditions for spawning. Thermal and carbonate conditions are thus coincidentally favorable for early larval development for only a few weeks at a time each year. The limited concurrent exceedance of thermal and Ω_ar thresholds suggests the likelihood of high variability in settlement success, as seen in the historical record; however, estimates of the impact of elevated atmospheric CO₂ suggest that pre-industrial Ω_ar conditions were more persistently favorable for larval development and more broadly coincident with thermal optima.

Hypoxia can cause significant disturbances in aquatic ecosystems, but the impacts of moderately low dissolved oxygen (DO) where physiological tolerance levels vary among organisms and likely have the consequences for key food web linkages are not well understood. We hypothesized that the greater sensitivity of fish to DO, as compared to their zooplankton prey, would reduce spatial overlap between fish and zooplankton at moderately low DO (2 – 4 mg l^-1). We used a combination of multifrequency acoustics and net samples to characterize distributions and abundances of zooplankton and pelagic fish in Hood Canal, WA, a seasonally hypoxic fjord. We employed a sampling design that included both high and moderately low DO sites sampled prior to, during, and after the onset of seasonally low DO over two years. Contrary to our hypothesis, we found that fish and their zooplankton prey did not change horizontal or vertical distributions during periods and in locations with moderately low DO levels. Consequently, the vertical overlap between fish and zooplankton did not change with DO concentration. The apparent lack of response of fish to moderately low DO in our system may result from decreased metabolic oxygen demand due to cool temperatures, availability of prey in moderately low DO waters, increased predation risk at shallower depths, and/or phenotypic adaptations to chronic exposure. Stability in distributions of pelagic communities suggests resilience of trophic coupling to moderately low DO in Hood Canal.

Resource managers at the state, federal, and tribal levels make decisions on a weekly to quarterly basis, and fishers operate on a similar timeframe. To determine the potential of a support tool for these efforts, a seasonal forecast system is experimented with here. JISAO’s Seasonal Coastal Ocean Prediction of the Ecosystem (J-SCOPE) features dynamical downscaling of regional ocean conditions in Washington and Oregon waters using a combination of a high-resolution regional model with biogeochemistry and forecasts from NOAA's Climate Forecast System (CFS). Model performance and predictability were examined for sea surface temperature (SST), bottom temperature, bottom oxygen, pH, and aragonite saturation state through model hindcasts, reforecast, and forecast comparisons with observations. Results indicate J-SCOPE forecasts have measurable skill on seasonal timescales. Experiments suggest that seasonal forecasting of ocean conditions important for fisheries is possible with the right combination of components. Those components include regional predictability on seasonal timescales of the physical environment from a large-scale model, a high-resolution regional model with biogeochemistry that simulates seasonal conditions in hindcasts, a relationship with local stakeholders, and a real-time observational network. Multiple efforts and approaches in different regions would advance knowledge to provide additional tools to fishers and other stakeholders.

Highlights

303(d) assessments for ocean acidification are challenging.

Chemical assessment is limited by pH criteria at levels below that known to cause biological damage.

Biological assessments are limited by lack of co-location between biological and chemical monitoring.

Changes to existing criteria are needed to protect aquatic life and support acidification management.

Ocean acidification (OA) refers to the general decrease in pH of the global ocean as a result of absorbing anthropogenic CO₂ emitted in the atmosphere since preindustrial times (Sabine et al., 2004). There is, however, considerable variability in ocean acidification, and many careful measurements need to be made and compared in order to obtain scientifically valid information for the assessment of patterns, trends, and impacts over a range of spatial and temporal scales, and to understand the processes involved. A single country or institution cannot undertake measurements of worldwide coastal and open ocean OA changes; therefore, international cooperation is needed to achieve that goal. The OA data that have been, and are being, collected represent a significant public investment. To this end, it is critically important that researchers (and others) around the world are easily able to find and use reliable OA information that range from observing data (from time-series moorings, process studies, and research cruises), to biological response experiments (e.g., mesocosm), data products, and model output.

Carbonate chemistry variability is often poorly characterized in coastal regions and patterns of covariation with other biologically important variables such as temperature, oxygen concentration, and salinity are rarely evaluated. This absence of information hampers the design and interpretation of ocean acidification experiments that aim to characterize biological responses to future pCO₂ levels relative to contemporary conditions. Here, we analyzed a large carbonate chemistry data set from Puget Sound, a fjord estuary on the U.S. west coast, and included measurements from three seasons (winter, summer, and fall).

pCO2 exceeded the 2008–2011 mean atmospheric level (392 μatm) at all depths and seasons sampled except for the near-surface waters (< 10 m) in the summer. Further, undersaturated conditions with respect to the biogenic carbonate mineral aragonite were widespread (Ω_ar<1). We show that pCO₂ values were relatively uniform throughout the water column and across regions in winter, enriched in subsurface waters in summer, and in the fall some values exceeded 2500 μatm in near-surface waters. Carbonate chemistry covaried to differing levels with temperature and oxygen depending primarily on season and secondarily on region. Salinity, which varied little (27 to 31), was weakly correlated with carbonate chemistry.

We illustrate potential high-frequency changes in carbonate chemistry, temperature, and oxygen conditions experienced simultaneously by organisms in Puget Sound that undergo diel vertical migrations under present-day conditions. We used simple calculations to estimate future pCO₂ and Ω_ar values experienced by diel vertical migrators based on an increase in atmospheric CO₂. Given the potential for non-linear interactions between pCO₂ and other abiotic variables on physiological and ecological processes, our results provide a basis for identifying control conditions in ocean acidification experiments for this region, but also highlight the wide range of carbonate chemistry conditions organisms may currently experience in this and similar coastal ecosystems.

Ocean acidification has serious implications for the economy and ecology of the Pacific Northwest United States. A combination of factors renders the Pacific coast and coastal estuaries particularly vulnerable to acidified water. The Northwest Association of Networked Ocean Observing Systems, NANOOS, the Regional Association of the United States Integrated Ocean Observing System, IOOS, is set up to deliver coastal data to serve the needs and decisions of its region. NANOOS has worked through IOOS with the NOAA Ocean Acidification Program, NOAA PMEL, academic, local, and commercial and tribal shellfish growing partners to provide existing observing assets to accommodate pCO2 and pH sensors, to deliver data streams from these and other providers, including that from sensors in shellfish hatcheries, and to network this capacity regionally and nationally. This increase in data access regarding OA is of value to scientists, managers, educators, and shellfish growers who are especially appreciative of the near real-time readouts of the data, upon which to make hatchery and remote setting decisions. This is a regional example of NANOOS and IOOS contributions to societal impacts from ocean acidification.

The low-frequency oceanography of the Washington continental shelf has been studied in great detail over the last several decades owing in part to its high productivity but relatively weak upwelling winds compared to other systems. Interestingly, though many internal wave-resolving measurements have been made, there have been no reports on the region's internal wave climate and the possible feedbacks between internal waves and lower-frequency processes. This paper reports observations over two summers obtained from a new observing system of two moorings and a glider on the Washington continental shelf, with a focus on internal waves and their relationships to lower-frequency currents, stratification, dissolved oxygen, and nutrient distributions. We observe a rich, variable internal wave field that appears to be modulated in part by a coastal jet and its response to the region's frequent wind reversals. The internal wave spectral level at intermediate frequencies is consistent with the model spectrum of Levine (2002) developed for continental shelves. Superimposed on this continuum are (1) a strong but highly temporally variable semidiurnal internal tide field and (2) an energetic field of high-frequency nonlinear internal waves (NLIWs). Mean semidiurnal energy flux is about 80 W m^-1 to the north-northeast. The onshore direction of the flux and its lack of a strong spring/neap cycle suggest it is at least partly generated remotely. Nonlinear wave amplitudes reach 38 m in 100 m of water, making them among the strongest observed on continental shelves of similar depth. They often occur each 12.4 hours, clearly linking them to the tide. Like the internal tide energy flux, the NLIWs are also directed toward the north-northeast. However, their phasing is not constant with respect to either the baroclinic or barotropic currents, and their amplitude is uncorrelated with either internal-tide energy flux or barotropic tidal forcing, suggesting substantial modulation by the low-frequency currents and stratification.

The successful use of SOSUS to track broad-scale occurrence patterns in whale calls during the second half of the 20th century fostered the development of autonomous recorders that can be deployed virtually anywhere in the world ocean. Over the past decade, data from these recorders have provided dramatic insights to marine mammal ecology. Patterns of call reception have demonstrated the near year-round occurrence of some baleen whale species in Arctic and Antarctic waters, a discovery that challenges long-held assumptions about the phenology of seasonal migrations. Integration of year-long calling records with physical oceanographic measures at mooring-based ocean observatories provides a means to include large whales in ecosystem-based models. The reception of anthropogenic sounds on nearly all recorders, whether deployed in coastal or remote areas, emphasizes the need to develop regional "soundscapes" based upon integrative sampling and analytical protocols. Examples from several long-term research programs will be provided as the basis for the strong assertion that passive acoustic observation of marine mammals is a vital component of any ocean observing system. Opportunities for future collaborations and the challenges of data management and access will be discussed.

NANOOS is coordinating a regional effort to observe the status of ocean acidification in the coastal waters and estuaries of Washington and Oregon. There is strong partnership in this effort between federal and university scientists, as well as strong interest from shellfish growers, tribes, and other stakeholders in the region. NANOOS, as a regional association of US IOOS, can fill a key role in providing regional coordination for observing assets, access to data, and education and outreach regarding this important issue.

Puget Sound is a large estuary complex in the U.S. Pacific Northwest that is home to a diverse and economically important ecosystem threatened by anthropogenic impacts associated with climate change, urbanization, and ocean acidification. While ocean acidification has been studied in oceanic waters, little is known regarding its status in estuaries. Anthropogenically acidified coastal waters upwelling along the western North American continental margin can enter Puget Sound through the Strait of Juan de Fuca. In order to study the combined effects of ocean acidification and other natural and anthropogenic processes on Puget Sound waters, we made the first inorganic carbon measurements in this estuary on two survey cruises in February and August of 2008. Observed pH and aragonite saturation state values in surface and subsurface waters were substantially lower in parts of Puget Sound than would be expected from anthropogenic carbon dioxide (CO₂) uptake alone. We estimate that ocean acidification can account for 24–49% of the pH decrease in the deep waters of the Hood Canal sub-basin of Puget Sound relative to estimated pre-industrial values. The remaining change in pH between when seawater enters the sound and when it reaches this deep basin results from remineralization of organic matter due to natural or anthropogenically stimulated respiration processes within Puget Sound. Over time, however, the relative impact of ocean acidification could increase significantly, accounting for 49–82% of the pH decrease in subsurface waters for a doubling of atmospheric CO₂. These changes may have profound impacts on the Puget Sound ecosystem over the next several decades. These estimates suggest that the role ocean acidification will play in estuaries may be different from the open ocean.

The Northwest Association of Networked Ocean Observing Systems (NANOOS) is one of eleven Regional Associations of the US Integrated Ocean Observing System (IOOS). NANOOS serves the Pacific Northwest from the US/Canada border to Cape Mendocino on the northern California coast. Its mission is to coordinate and support the development, implementation, and operations of a regional coastal ocean observing system (RCOOS) for the Pacific Northwest region, as part of IOOS. A key objective for NANOOS is to provide data and user-defined products regarding the coast, estuaries and ocean to a diverse group of end users in a timely fashion, and at spatial and temporal scales appropriate for their needs.

To this end, NANOOS is developing a web mapping portal, the NANOOS Visualization System (NVS), that aggregates, displays and serves near real-time coastal, estuarine, oceanographic and meteorological data, derived from buoys, gliders, tide gauges, HF Radar, meteorological stations, satellites and shore based coastal stations, as well as model forecast information in such a way that it presents end users with a rich, informative and meaningful experience. NVS makes use of a variety of services, including the Google Maps service and a data translation and visualization service known as ERDDAP (Environmental Research Division's Data Access Program), compliant Open Geospatial Consortium (OGC) web standards such as the Sensor Observation Service (SOS), Web Map Service (WMS), and Keyhole Markup Language (KML), as well as the Open-source Project for a Network Data Access Protocol (OPeNDAP) as served and cataloged by the NANOOS THREDDS (Thematic Realtime Environmental Distributed Data Services) Data Server (TDS). These heterogeneous data streams are transformed on-the-fly to other formats or representations, which NVS makes available to the end user via a Google Maps interface.

We will describe in detail the NVS development process and will demonstrate the ability of NVS to serve as a portal for one-stop access to near real-time regional data and forecast products, including NOAA's first seven core variables (ocean currents, temperature, salinity, water level, waves, chlorophyll and surface winds), by describing the data flows from NANOOS funded coastal and ocean observing and forecasting assets as well as Federal assets. In addition, we will describe future development plans that include greater functionality, iteratively improving NVS based on feedback received at planned training workshops and from identified stakeholders, and updating NVS to be compliant with future IOOS and OGC standards.