Characterizing the Natural System : Toward Sustained , Integrated Coastal Ocean Acidification Observing Networks to Facilitate Resource Management and Decision Support

Author Posting. © The Oceanography Society, 2015. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 28, no. 2 (2015): 92-107, doi:10.5670/oceanog.2015.34.

responses to ocean acidification, as outlined in the vision statement of the Global Ocean Acidification Observing Network (GOA-ON; Newton et al., 2014).
As part of GOA-ON, scientists, stakeholders, and resource managers at international, national, regional, and local levels are jointly planning ocean acidification observing networks that will leverage existing programs and assets to: (1) provide a suite of consistent observations across scales, from open ocean to coastal and estuarine ecosystems, for detection of trends and associated ecological responses to ocean acidification (Figure 1, Level 1 of Goals 1 and 2); (2) provide a framework for process and attribution studies relevant to individual regions (Figure 1, Level 2 of Goals 1 and 2); (3) improve predictive models for ocean biogeochemistry and ecosystem responses (Figure 1, Goal 3); and (4) share data with indicators of the level of quality among all stakeholders at useful temporal and spatial scales (Figure 1, outer circles; Newton et al., 2014).Here, we discuss how the conceptual consensus recommendations for the coastal components of GOA-ON (Table 1, Figure 1) might be implemented in regional coastal areas where they will directly support effective decision making to address the most pressing societal challenges, such as fisheries for food security and liveli hoods, community resilience, and coastal protection.We use examples from a few types of continental and island coastal ecosystems.
Coastal oceans are biogeochemically and physically dynamic environments characterized by strong spatial and temporal variability; consequently, coastal zone habitats are exceptionally diverse.Coastal ecosystems are also among the most productive in the world, hosting 15-30% of oceanic primary production (Gattuso et al., 1998), producing 87% of the world's fish catch (FAO, 2014), and providing essential habitats for much of the diversity of marine life.For example, while coral reef ecosystems comprise less than 0.25% of seafloor area, they are home to over 25% of marine species (Knowlton et al., 2010), with a recent estimate of 550,000-1,330,000 species on coral reefs worldwide (Fisher et al., 2015).With greater than 50% of the world's human population living within 50 km of a coastline, coastal ecosystems are particularly

INTRODUCTION
Ocean acidification is expected to progressively impact marine ecosystems, biodiversity, fisheries, and societies at scales ranging from local to regional to global through the twenty-first century and beyond.In order to best inform and prepare coastal stakeholders and decision makers across these scales, it is critical to develop an integrated, interdisciplinary biogeochemical and ecological observing network capable of robustly detecting and attributing changes in ocean chemistry to changes in indicators of ecosystem condition (i.e., structure and function) and human well-being.Timeseries observations are needed to concurrently characterize variability in time and space of both biogeochemical conditions and ecological processes to better understand biological tolerances and societal ABSTRACT.Coastal ocean ecosystems have always served human populations-they provide food security, livelihoods, coastal protection, and defense.Ocean acidification is a global threat to these ecosystem services, particularly when other local and regional stressors combine with it to jeopardize coastal health.Monitoring efforts call for a coordinated global approach toward sustained, integrated coastal ocean health observing networks to address the region-specific mix of factors while also adhering to global ocean acidification observing network principles to facilitate comparison among regions for increased utility and understanding.Here, we generalize guidelines for scoping and designing regional coastal ocean acidification observing networks and provide examples of existing efforts.While challenging in the early stages of coordinating the design and prioritizing the implementation of these observing networks, it is essential to actively engage all of the relevant stakeholder groups from the outset, including private industries, public agencies, regulatory bodies, decision makers, and the general public.The long-term sustainability of these critical observing networks will rely on leveraging of resources and the strength of partnerships across the consortium of stakeholders and those implementing coastal ocean health observing networks.
" The long-term sustainability of these critical observing networks will rely on leveraging of resources and the strength of partnerships across the consortium of stakeholders and those implementing coastal ocean health observing networks.
vulnerable to impacts from human activities that result in habitat degradation and losses of biodiversity.In addition to local anthropogenic stressors such as coastal development and fishing, climate change and ocean acidification are affecting coastal ecosystems.Sustainable ecosystem-based management of human interactions with coastal ecosystems and the ability to develop effective mitigation and adaptation strategies depends on reliable and timely observations for decision support.Among many needs, coastal observations must detect ecological responses as well as facilitate attribution of observed shifts to climate variability or trends, ocean acidification, other human activities, or natural processes.Biogeochemical and ecological dyna-mics across various coastal ecosystems may be dominated by a range of influences, such as seasonal changes in winds, light, or temperature; inputs of freshwater, nutrients, or organic matter from land; and geomorphic factors (e.g., shelf width, bathymetric or coastline features).Thus, to be effective, a regional, integrated coastal ocean acidification observing network should be sufficiently consistent to facilitate comparison and improved understanding of biogeochemical processes and ecological responses across ecosystem types, as outlined by GOA-ON, yet must be sufficiently tailored to the dominant processes within each ecosystem type to allow for attribution of local observations to the underlying processes in that region (Figure 2).Overall, regional observing networks should be capable of making environmental and ecological measurements at temporal and spatial scales sufficient to: (1) establish spatial patterns and magnitudes of variability, (2) detect long-term changes from these envelopes of variability, (3) attribute ecological responses to environmental changes, (4) facilitate projections of future conditions, and ( 5) evaluate validity of models and hindcasts.In addition, observing assets within a regional network should be configured to address short-term regional stakeholder priorities.
Cognizant of diverse local to regional stressors for each ecosystem (see Breitburg et al., 2015, in this issue), as well as multiple compelling needs for longterm observations, regional observing networks are best framed when addressing coastal ocean health in an integrated, interdisciplinary manner, rather than solely based on carbonate chemistry and its impacts.Here, we delineate general guidelines for designing and implementing regional coastal ocean acidification observing networks that: (1) conform to GOA-ON principles for comparability, (2) are responsive to regional and local stakeholder needs, and (3) characterize critical attributes on local to regional scales.We offer examples highlighting key characteristics and needs for a few ecosystem types, stressing important scoping considerations (Table 2).These general guidelines and considerations apply, with some modifications, to other ecosystem types and locations.

GOA-ON AND REGIONAL COASTAL OBSERVING EFFORTS
In any nation, region, or area, a diversity of organizations and institutions may contribute to observations, longterm monitoring, and research on ocean acidification under various legal authorities or management mandates.The core goals of GOA-ON outlined above facilitate diagnosis of spatial patterns and temporal trends in ocean acidification across regions, attribution of processes and drivers behind these patterns and trends,

GOAL 1
Observe ocean conditions

Regional coastal ocean health observing network with integrated environmental and ecological observations LEVEL 2
Observations for enhanced interpretation and targeted complementary process and lab studies LEVEL 1 Critical minimum long-term observations LEVEL 3 Developing technologies FIGURE 1. Schematic diagram of the parts of the Global Ocean Acidification Observing Network (GOA-ON), showing the core goals of GOA-ON, the levels at which various activities address the core goals in the pyramid above, and in the outer rings, the ultimate societal needs that the activities fulfilling the coastal observing network goals are designed to address.Connections between the societal drivers and coastal GOA-ON activities are particularly strong in coastal systems due to the reliance of human populations on coastal resources worldwide.Courtesy of Amanda Dillon Parameters: Photosynthetically active radiation, turbidity/total suspended solids (tropical, nearshore), particulate inorganic carbon (polar, temperate), colored dissolved organic matter (tropical, nearshore), nutrients (nearshore).For warm-and cold-water coral habitats, further characterization of chemical environment, including sediment mineralogy/composition, organism mineral content, alkalinity anomalies, and vertical profiles of saturation state over time (cold-water corals).
Patterns: Biomass/abundance of phytoplankton, zooplankton (micro-and meso-), and benthic producers and consumers; biomass of calcified vs. non-calcified species; timing of changes in abundance (e.g., blooms, community shifts, pigment changes); phytoplankton functional types (polar, temperate); calcified to non-calcified plankton abundance (temperate, nearshore); and calcified to non-calcified benthos abundance (nearshore).For warm-and cold-water coral habitats, population structure of corals and macroalgae; biomass, population, and trophic structure of cryptobiota; population structure of urchins; and architectural complexity.
Processes: Ratio of net ecosystem production to net ecosystem calcification, food supply rate and quality, bioerosion rates at specific sites.

Level 2:
Where not already included above.

GOAL 3: ACQUIRE AND EXCHANGE DATA AND KNOWLEDGE NECESSARY TO OPTIMIZE MODELING OF OCEAN ACIDIFICATION AND ITS IMPACTS.
Parameters: Bio-optical and chemical sensors (e.g., nitrate, oxygen, pH) on Argo floats, develop ocean acidification indicators for key locations, models for key benthic and pelagic organisms to link habitat and ocean acidification conditions and connect to integrated ecosystem assessments.
Patterns: Large-scale surveys to constrain models, better spatial coverage of moorings linked to targeted process studies, extended spatial coverage of gliders, evaluate ocean acidification monitoring networks using observing system simulation experiments (OSSEs), integrate water quality and plankton community information into physical-biogeochemical models for three-dimensional distributions on dominant temporal scales.
Processes: Model-data comparison to determine coastal impacts on open ocean biogeochemistry/ecology, short-term forecasts to evaluate model performance at ocean acidification network locations, improve linkages with physical modeling capabilities within regions, highresolution circulation and wave models for coral reefs and extreme weather events.
prediction of future patterns and impacts, and support for informed and timely policy and management decisions (Table 1).
The US National Oceanic and Atmospheric Administration (NOAA) Ocean Acidification Observing Network (NOA-ON), with many partners, is consistent with GOA-ON design principles (NOAA Ocean Acidification Steering Committee, 2010; Interagency Working Group on Ocean Acidification, 2014).It provides an initial framework to guide the regional ocean acidification observing networks that have started to materialize through US Integrated Ocean Observing System (IOOS) regional associations.These regional observing networks provide data on regional trends and drivers related to ocean acidification and the associated ecosystem responses, thereby providing a foundation into which more detailed mechanistic process studies or ecosystem-specific observations of impacts can be integrated (e.g., Pfister et al., 2014).
The GOA-ON plan is a key aide for designing regional observing systems that are responsive to both longterm scientific and short-term stakeholder needs.GOA-ON delineates two respective levels of observational quality (1) "climate"-quality observations, which require the lowest uncertainty and highest confidence levels to detect long-term anthropogenic trends in carbon chemistry and related physical and chemical parameters, such as temperature, salinity, and nutrients, and (2) "weather"-quality observations to identify "relative spatial patterns and short-term variability" (Newton et al., 2014).In dynamic coastal ecosystems, a mechanistic interpretation of ecosystem changes attributable to ocean acidification and other interacting drivers requires climate-quality observations as well as high-resolution models to resolve signals with acceptable uncertainty.For many stakeholder and management needs, weather-quality measurements may suffice for correlation of environmental observations with ecosystem response data.
While detecting long-term global trends in ocean biogeochemistry is important, ecological responses tend to manifest primarily at local to regional scales due to the complexities of interactions across taxa "from the genes within species to biologically created habitats within ecosystems" (Duffy et al., 2013) and varying ecological community structure.Biogeochemical processes often vary over specific narrow frequencies (e.g., tidal, diel, seasonal), whereas organisms and communities within ecosystems reflect an integrated response to environmental variation over an even broader range of time scales due to varying life histories of each species.These considerations make broad partnerships and integration across complementary efforts (e.g., Duffy et al., 2013) important.
FIGURE 2. The nested scales of ocean acidification observing.Globally (top left), GOA-ON encompasses observing assets that meet consensus requirements.Map courtesy of Cathy Cosca A regional network (top right) encompasses assets designed and implemented by a consortium of stakeholders to address regional societal needs (e.g., the Northwest Association of Networked Ocean Observing Systems [NANOOS] for Washington State; http://nvs.nanoos.org).On the local scale (bottom), assets are targeted at understanding specific physical and biogeochemical processes within that particular ecosystem (e.g., moored and mobile assets off La Push, WA).Modified from Alford et al. (2012), courtesy of John Mickett GLOBAL REGIONAL

REGIONAL RECOMMENDATIONS FOR ESTABLISHING LONG-TERM, INTEGRATED COASTAL OCEAN HEALTH OBSERVATIONS
We make the following recommendations to facilitate more efficient planning and implementation for integrated coastal ocean acidification observing networks to maximize leveraging of existing institutional capabilities, resources, and other assets.

Recommendation 1
Identify and engage regional stakeholders with diverse interests in coastal resources, economic drivers, or uses that might be impacted by ocean acidification at the outset of the regional network design process.Stakeholders include researchers (observations, experiments, models, social science), resource managers, water and air quality monitoring agencies, tribal nations, industries relying on the marine environment or resources (capture fisheries, aquaculture, tourism), policy makers, organizations with outreach and education missions (schools, aquariums, zoos, visitors centers, media), and others.We provide a set of questions that can be applied across ecosystem types and that may help identify and engage stakeholders who may ultimately become strong partners in designing, planning, implementing, and sustaining regional interdisciplinary coastal ocean acidification observing networks (Table 2).

Recommendation 2
Identify existing observing or monitoring activities, assets, and programs, particularly those with ongoing time-series measurements.A detailed gap analysis may be beyond the feasible or desired level of effort for this, but identifying relevant efforts that can be integrated to form a more comprehensive coastal ocean health observing network that includes partners who monitor ecological impacts attributable to ocean acidification should be identified across the region.
For the key species and ecosystems identified through the stakeholder engagement process, it is helpful to identify key environmental drivers, which may vary by ecosystem type within the region and may represent either natural processes or additional human pressures on these coastal ecosystems (see Breitburg et al., 2015, in this issue).Leveraging existing activities to the extent appropriate will enhance regional observing networks and assist in efforts to attribute patterns across multiple drivers.IOOS regional associations are examples of organizing bodies that cut across and unite diverse sectors such as academia, government, and industry.Leveraging may provide opportunities to develop insights into the historical progression of ocean acidification and related patterns or trends in ecological communities.Through judicious application of historical and proxy data sets (Juranek et al., 2009;Alin et al., 2012), estimates of historical ocean acidification trajectories might be reconstructed for comparison with biological and ecological time series, paleoenvironmental records, or hindcast models.As an example of leveraging opportunities, it would be beneficial to couple ocean acidification observing efforts to the nascent marine Biodiversity Observation Network (Duffy et al., 2013).

Recommendation 3
Design, prioritize, and implement elements of regional observing networks to fill key gaps in understanding that will best enable the region to mitigate and/ or adapt to impacts of ocean acidification and interacting environmental stressors.Integrate new observations into existing programs wherever reasonable in order to maximize leveraging and engagement of all relevant stakeholders.Stakeholders should play a key role in prioritizing components of the regional network.
To contribute to global understanding of relative rates of change and the roles of interacting drivers across regions, the regional observing network should be capable of discerning long-term trends, dominant frequencies and spatial scales of variability, and ecosystem responses to changing environmental conditions.Other assets within a region should be targeted at shorter-term management applications or acquiring processlevel understanding.
TABLE 2. Scoping questions to help identify key stakeholders and important knowledge gaps within an ecosystem for coastal ocean acidification observing network.
1. Are there any species or groups of species that play a dominant role in structuring ecological or biogeochemical processes within this ecosystem, including keystone species?
2. What are the most ecologically and economically important marine species, communities, or ecosystem functions in the region?
3. What is their regional societal and economic relevance (ecosystem goods and services)?
4. What are the ecological or trophic linkages among species in the ecosystem?
5. What vulnerability do these species and ecosystems have to ocean acidification?
6. What are the dominant temporal and spatial scales of variability that affect this ecosystem?
7. What are the necessary and appropriate levels of sampling resolution for tracking changes in ecological composition and abundance through time and across the ecosystem (e.g., species vs. functional taxonomic groups, numerical abundance vs. biomass vs. percent cover)?
8. What are the dominant processes influencing variation in biogeochemistry and ecology?11.What are the information needs and applications of key stakeholders?
12. What are the gaps in understanding within the region or ecosystem type that need to be surmounted to provide the needed information to benefit society?
Recommendation 4 Develop and disseminate key data and information products needed by stakeholders.For some stakeholders, such as shellfish aquaculture managers, the needed data product is real-time or nearreal-time data about ocean conditions; leveraging existing resources, such as data portals provided by regional associations of IOOS, is a cost-effective and timely means of disseminating this information.Fisheries and coastal resource managers often need information about recent changes in and future predictions for the ecosystem that require different data products.Support is needed to develop and sustain key data products and appropriate information delivery conduits to ensure timely availability to decision makers.

Recommendation 5
Regularly re-engage stakeholders to assess the utility of observations and information products, and employ adaptive strategies to better support changing societal requirements.As new impacts become known and technologies to facilitate more efficient monitoring become available, the network will benefit from periodic, systematic evaluation and identification of remaining (or new) knowledge gaps.New sensors and methods for making environmental and ecological observations may provide opportunities to improve quality and cost effectiveness (Figure 1, Level 3 of Goals 1 and 2; e.g., Byrne, 2014;Pfister et al., 2014).
Stakeholder groups should carefully consider the critical importance of sustained, consistent, long-term time-series observations of both environmental and ecological conditions when deliberating whether to continue or alter the methods or locations of observations.Longterm climate monitoring principles provide a useful framework for evaluating such decisions (Karl et al., 1995;Trenberth et al., 2002).

KEY CONSIDERATIONS FOR REGIONAL OBSERVING NETWORKS IN A RANGE OF ECOSYSTEM TYPES
While GOA-ON guidance helps set first-order requirements, and our recommendations above and questions in Table 2 can refine them for specific regions, deciding on the key metrics of ecological variability within a given ecosystem is a very complex task, given the infinite range of possibilities for combinations of species (and higher taxonomic levels), genotypes, and functional groups within communities.Through the use of a few examples from ecosystem types with existing regional coastal ocean acidification observing networks (Figure 3), we demonstrate how an observing network can be designed to be responsive to regional stakeholder needs.These summaries focus on key characteristics of the ecosystems that did or should guide the design and implementation of regional coastal ocean health observing networks, highlighting some of the distinct challenges, stakeholder groups, and leveraging opportunities (Table 3).The myriad additional stressors affecting the four focal ecosystems are highlighted elsewhere in this issue (Breitburg et al., 2015).For other regions and ecosystem types, we highlight key attributes in Table 3, acknowledging the distinct management purviews and practices associated with each.

Coral Reefs (Pacific Islands)
Healthy coral reefs are among the most economically valuable ecosystems on Earth, providing vital ecosystem goods and services estimated to total between $29.8 billion and >$1 trillion annually, depending on the study methods (e.g.

2014
). Warm-water coral reef ecosystems are structurally defined by their reef-building corals and crustose coralline algae whose three-dimensional habitats support the highest levels of biodiversity of any marine ecosystem (Knowlton et al., 2010).From a human well-being perspective, coral reef ecosystems provide fisheries-related food security and livelihoods to hundreds of millions of people worldwide, with an estimated economic value of $5.7 billion; tourism-related livelihoods and revenue estimated at $9.6 billion; and protection to coastal communities from storm-induced waves, storm surges, tsunamis, and, when reef accretion rates suffice, some of the impacts of sea level rise.In addition, long-standing cultural practices and the livelihoods of indigenous populations around the world have evolved around these reefs over millennia (Bunce et al., 2000).
Major stakeholders include people living in "small island developing states" whose existence and subsistence depend on healthy coral reef resources; natural resource managers at various community, state, and federal levels; ecotourism and tourism industries; pearl oyster and aquarium trade industries; and nonprofit organizations with reef conservation missions.Stakeholder and decision-maker information needs vary widely from longterm (decadal and longer) projections of reef health and stability to immediate concerns about selecting sites for sustainable economic (e.g., fisheries and tourism) and cultural uses.
According to a broad range of species response experiments under different CO 2 emissions scenarios, coral reef communities will likely undergo significant ecological phase shifts this century as calcification of reef-building corals and crustose coralline algae is unable to keep pace with bioerosion and, potentially, dissolution processes (reviewed in Brainard et al., 2012).As this occurs, many of Krill: not commercially important in the U.S., but supports higher trophic levels of international conservation concern (penguins, seals, whales).
Seasonality, interannual variability, winter dynamics, under-ice dynamics.and balancing and compromising around logistical and operational constraints.In this case, the ocean acidification observations were primarily developed to align with and complement ongoing status and trends monitoring of Pacific RAMP/ NCRMP, which in turn was designed to monitor all of the coral reef ecosystems of the US Pacific Islands to meet requirements of the Coral Reef Conservation Act of 2000.The vastness and remoteness of the US Pacific Islands and budget realities constrain accessibility via relatively large ocean-going research vessels and limit surveys to a repeated three-year cycle of surveying the coral reefs of the main and Northwestern Hawaiian Islands in the first year; Commonwealth of Northern Mariana Islands, Guam, and Wake Atoll in year two; and American Samoa and Pacific Remote Islands Marine National Monument in year three.

Upwelling Systems
Along the US West Coast, shellfish and finfish industries supported by the region's high ecosystem productivity are economically important, with $32.7 billion in sales impacts and roughly 220,000 jobs supported by the commercial seafood industry in 2012 (NMFS, 2014).Calcifying invertebrates with benthic life stages and limited mobility represent four of the 10 most valuable commercial fisheries on the West Coast (Table 5).Recreational fishing accounted for 7.4 million fishing trips in 2012, supporting 18,800 jobs and yielding another $2.5 billion in sales (NMFS, 2014).Shellfish and finfish represent highly valued tribal nation resources for both subsistence and ceremonial uses (i.e., non-commercial harvests; Radtke, 2011).Healthy marine ecosystems represent high aesthetic and economic value for tourism and non-extractive recreation (e.g., whale watching, tidepooling).
Stakeholders are diverse.The economic importance of shellfish and finfish to West Coast state economies make these fisheries (both wild and hatcheryspawned), as well as those tasked with observing, forecasting, and managing them, important stakeholders.Larval mortality events at Pacific Northwest shellfish hatcheries associated with corrosive water events galvanized regional shellfish and finfish industries in support of ocean acidification monitoring, research, and mitigation efforts (Barton et al., 2015, in this issue).Fisheries managers require reliable forecasts of fisheries production and stock that rely on understanding prey availability and the factors that influence it.Coastal and estuarine water quality managers are responsible for declaring water bodies impaired with respect to pH if values stray outside specified limits under the Clean Water Act.Organizations with marine conservation missions, such as West Coast aquariums, are also critical stakeholders for building an ocean acidification observing network and can help both generate new results and communicate their importance to public and policy audiences.
Eastern boundary current upwelling systems like the California Current Large Marine Ecosystem (CCLME) constitute natural laboratories for studying ocean acidification in the context of multiple stressors (see Breitburg et al., 2015, in this issue).In addition to ocean acidification, wind-driven upwelling, intense production and in situ respiration on the shelf, and river inputs of waters high in CO 2 and low in calcium result in a wide dynamic range of values for carbonate chemistry, oxygen, and nutrients, with strong spatial and temporal variability.Summertime conditions are frequently corrosive to calcium carbonate and become hypoxic (e.g., Grantham et al., 2004;Feely et al., 2008).A growing number of marine species exhibit reduced growth and survival when exposed to corrosive conditions, particularly when they are compounded by hypoxia.Observed sensitivity in economically or ecologically important species include early life stages of some oyster, mussel, scallop, and clam species under experimental conditions (Gobler et al., 2014;Waldbusser et al., 2014), as well as calcifying pelagic snails under in situ conditions (pteropods; Bednaršek et al., 2014).Mortality of Dungeness crabs and other benthic organisms has been observed due to hypoxia events (e.g., Grantham et al., 2004), broadening the stakeholder base and policy relevance.Forecasts of increasing intensity, extent, and duration of undersaturated conditions along the West Coast are concerning for the CCLME (Gruber et al., 2012;Hauri et al., 2013).
Efforts to monitor ocean acidification and hypoxic conditions and ecosystem impacts in the CCLME have taken advantage of several complementary platforms and programs, some new since 2005, others pre-existing.NOAA and many partners support a network of moored time-series stations along the West Coast that provide highfrequency ocean acidification-relevant measurements (Figure 5).Since 2009, efforts to integrate biogeochemical measurements into biological and fisheries survey cruises and vice versa have been initiated.Autonomous shipboard analytical systems on NOAA Fisheries and other research vessels map relevant parameters at the surface.Water-column profiling surveys document subsurface conditions down to the depths of important demersal fisheries.Fisheries observations focused on quantifying phytoplankton and zooplankton, including ichthyoplankton, date back as far as the 1940s on the West Coast, but due to funding limitations, most only measure a subset of the chemical parameters needed to constrain ocean acidification and hypoxia conditions or only cover carbon measurements at a subset of stations.Although monitoring gaps abound, indicator species may provide insight into the timeintegrated stresses on organisms that form the energetic basis of marine ecosystems and fisheries.Pteropods, which are sensitive to subtle changes in saturation state (Bednaršek et al., 2014), have been suggested as useful indicator taxa for monitoring ecological impacts of ocean acidification.
The first West Coast carbon cruise in 2007 and the contemporaneous shellfish hatchery seed crisis resulted in a very effective research partnership in the Pacific Northwest and boosted efforts to create an integrated ocean acidification observing network on the West Coast (Feely et al., 2008;Barton et al., 2015, in this issue).The California Current Acidification Network (C-CAN) emerged from this partnership among West Coast ocean acidification stakeholders in 2010, as did real-time monitoring of seawater in hatcheries supported by state and federal funds (Barton et al., 2015, in this issue).C-CAN facilitates communication on monitoring priorities and best practices, management needs, and mitigation and adaptation strategies to diverse partners.Regional IOOS associations have also played a key role in coordination and communication among ocean acidification stakeholders, are partners in the West Coast ocean acidification observing network, and provide invaluable access to real-time data through Web-based portals.Finally, the Washington State Blue Ribbon Panel on Ocean Acidification and the West Coast Ocean Acidification and Hypoxia Science Panel have provided venues for communicating cutting-edge understanding of West Coast ocean acidification conditions and ecological vulnerability across a diverse network of stakeholders, and in so doing, have mobilized funding and political progress on ocean acidification mitigation and adaptation in West Coast states.

Estuaries
Estuaries teem with life as a result of intense primary production at the landocean boundary.Here, organisms occupy a variety of muddy, sandy, or rocky substrates.Seagrass meadows, tidal wetlands, or mangrove forests provide habitat and food while sequestering CO 2 from the atmosphere or surface seawater.Estuaries act as nurseries for many species of fish and birds.Historically, estuaries and freshwater-influenced bays have been important sites for abundant oyster growth in the United States, with many East Coast estuaries having formerly extensive oyster shell reefs.Oysters and other shellfish provide a number of valued ecosystem services, including water column filtration and shoreline protection.
Historically, humans have settled around estuaries, and their exploitation of resources has resulted in overfishing, seafloor dredging, and eutrophication and pollution of the waters.Yet, myriad stakeholders still depend on estuarine services and products.Those involved with monitoring and managing estuaries-including marine labs and aquariums, shellfish growers, and tribal, state, and local governments-should be encouraged to monitor for ocean acidification along with their other mandates.Such partners present important leveraging opportunities for installing carbon sensors and collecting carbonate system water samples.Nationally, NOAA's National Estuarine Research Reserve System is a network of 28 estuaries The current status of ocean acidification observing in estuaries varies greatly, but in general is underdeveloped.Estuarine ecosystems pose unique challenges for developing regional coastal ocean health observing networks to address stressors such as ocean acidification, eutrophication, and hypoxia.The high degree of spatial heteorogeneity and temporal variability of biogeochemical processes makes it difficult to adequately characterize the natural environment (e.g., Feely et al., 2010;Wallace et al., 2014).Freshwater runoff from land into estuaries is typically enriched in inorganic and organic carbon and nutrients relative to coastal waters, and this can fuel intense estuarine outgassing and in situ metabolism, driving CO 2 , O 2 , and nutrient content toward strong enrichment in some areas and depletion in other areas.

High-Latitude Systems
Together, climate change, ocean acidification, and potential species invasions pose grave threats to productive highlatitude ecosystems that support some of the world's most economically valuable fisheries (Table 6), as well as some of the world's most charismatic coastal fauna (e.g., polar bears and penguins).The polar oceans are essentially inverses of each other: the Arctic Ocean is surrounded by continents and receives abundant freshwater input to its shallow shelf ecosystems; in contrast, the deep Antarctic shelves surround a polar continent with little freshwater runoff (Aronson et al., 2011).Because of its oceanographic isolation, connection to the deep sea, and extreme cold, Antarctica's deep shelf ecosystems have 50−60% species-level endemism and lack the fast-moving, shell-crushing predators that dominate Arctic to sub-Antarctic benthic coastal food webs (Aronson et al., 2011).In contrast, seabirds, seals, whales, and walruses rely heavily on benthic invertebrates from shallow Arctic shelf ecosystems (Grebmeier, 2012).
The numerous stakeholders for polar ocean acidification include international science and policy communities, commercial fisheries, and indigenous populations (Arctic only).We include both Arctic and Antarctic marine ecosystems here because the United States plays a role in international monitoring of Antarctic coastal oceans.
The world's high-latitude oceans are productive marine ecosystems that harbor numerous endemic marine species and provide globally significant oceanic storage for anthropogenic CO 2 (Khatiwala et al., 2009).Calcium carbonate saturation states are expected to decline rapidly in high-latitude oceans as increased temperatures result in loss of sea ice that will affect net CO 2 uptake.Thus, the highlatitude oceans are projected to manifest some of the earliest and most persistent aragonite undersaturation in the world ocean (Steinacher et al., 2008;Feely et al., 2009).Because of short food chains and strong coupling between benthic and pelagic ecosystems, Arctic marine ecosystems are particularly prone to reorganization (Grebmeier, 2012).Some authors conjecture that ocean acidification will be the most significant habitat impact for Antarctic krill-which support penguins, whales, and other species of international conservation concern-and the deep-sea benthos (e.g., Constable et al., 2014).
Many profound knowledge gaps remain for both ecosystems, including the tolerances for changing temperature and ocean chemistry of many important prey species and the resilience of predator species to changing abundance and distribution of prey species (e.g., Fabry et al., 2009;Aronson et al., 2011;Constable et al., 2014).The impacts of multiple, simultaneous, and rapidly changing stressors on all trophic levels, many of which represent economically or ecologically important species, has only begun to be investigated (Breitburg et al., 2015, in this issue).Thus, high-latitude observing networks need to be well integrated to understand how physical changes in temperature, salinity, and ice dynamics due to warming, freshwater input, and ice melt, as well as biogeochemical changes due to ocean acidification and feedbacks from changing productivity, will affect high-latitude marine ecosystems.
There is a deficit in long-term observing resources in both polar oceans due in large part to the challenges of making observations under ice through the polar winters.Although a few exist in

OBSERVING IN SUPPORT OF FORECASTING
As noted from goal 3 of GOA-ON, observations to support forecasts are a critical need for coastal stakeholders.Developing models, scaled by and tested with observational data, is an important scientific direction; synergies with observing network development should be pursued.
Observations improve oceanographic and ecosystem models through model validation; in turn, model results inform the observing community about where additional observing assets or detailed process studies may be needed to further illuminate aspects of ocean acidification (e.g., Curchitser and Batchelder, 2013).Model development is needed on several scales: to project future conditions years out so coastal resource managers and decision makers can respond and to forecast conditions days out so that aquaculture and other fisheries can adapt their immediate practices.

CONCLUSIONS
Developing and sustaining a linked global network of integrated coastal ocean acidification observing networks is an overwhelming but critically important task in this era of rapid environmental change and decreasing funding for scientific research and long-term monitoring.Partnerships, stakeholder engagement, and institutional investment are imperative for the long-term sustainability of coastal ocean observing networks, but much of the needed growth in monitoring scope can be folded into existing water quality and natural resource monitoring efforts, requiring lower levels of funding than would be needed to implement completely new observing efforts.
In addition to validation of predictive models, coastal ocean health observing networks will provide a long-term context for process studies (Pfister et al., 2014), will be a framework for assessing potential adaptation and mitigation strategies, and will keep society, stakeholders, and decision makers abreast of evolving conditions of our coastal oceans, the rich living resources they host, and the essential ecosystem goods and services they provide to coastal communities.Beyond simply gaining scientific understanding of these important and complex ecosystems, a sustained, long-term observing network that will allow regular assessment of coastal ecosystem ocean health and the efficacy of adaptation and mitigation efforts is needed (see Schindler and Hilborn, 2015).
9. What additional stressors are important in the region or ecosystem, and are there existing monitoring efforts relevant to these? 10.What are the key indicators of ecosystem or organismal health, disease, or toxicity risks within the ecosystem or region, and what metrics, surveys, or assays can be used to track them?

TABLE 4 .
Photo quadrat or photomosaic surveys" " " To assess benthic taxonomic composition Initiated in 2013

FIGURE 4 .
FIGURE 4. Schematic diagram of the hierarchical coral reef sampling scheme occupied on a triennial basis by the Pacific Reef Assessment and Monitoring Program (Pacific RAMP) and NOAA's National Coral Reef Monitoring Program.Courtesy of Amanda Dillon

FIGURE 5 .
FIGURE 5. Ocean acidification observing assets in the California Current Large Marine Ecosystem and Puget Sound (inset), a large urbanized fjord estuary.Symbols represent sampling stations: moored time-series stations (yellow/orange stars on coast and blue circles in Puget Sound); time-series stations sampled by ship-or land-based researchers on a recurring basis (all other symbols).Courtesy of Dana Greeley

TABLE 6 .
(DeBroyer et al., 2014)or most economically valuable fisheries in Alaskan waters from 2003 to 2012. 2 Gray shaded entries represent invertebrates with some calcium carbonate hard parts.-latitudelocations,mooredtimeseriesstations equipped with carbon sensors are generally lacking in Arctic and Antarctic waters.International GO-SHIP/ Repeat Hydrography cruises have made decadal surveys of physical and biogeochemical parameters in Southern Ocean waters since the 1980s, but 2015 will bring the first Arctic decadal cruises.In Pacific Arctic waters (Bering and Chukchi Seas), a large number of biophysical moorings have been deployed for various periods, starting in 1990, and carbon sensors (pCO 2 and pH) were added to the longest deployed of them, M2 in the southern Bering Sea.In Arctic waters of the North Atlantic, the Iceland Sea time-series station established in 1983 has included carbon sensors since 2013.Recurring biological surveys to detect changes in productivity and biodiversity commenced in Arctic waters of the North Pacific in 2010, and the partners involved have facilitated international data sharing by providing online data portals.Similarly, because of the unique biodiversity in Antarctic waters, special attention was focused on analyzing biodiversity in the Southern Ocean as part of the International Polar Year (2007−2009) and the Census of Marine Life (2000−2010)(DeBroyer et al., 2014).Early efforts to develop coastal ocean acidification observing networks in Arctic and Antarctic shelf waters have recognized the dearth of observing resources in high-latitude oceans, the importance of considering multiple stressors, and the need for integrating physical, chemical, and biological observations within existing monitoring frameworks to the extent possible in order to best address impacts of the many rapid changes occurring in polar marine ecosystems(NOAA  Ocean Acidification Steering Committee,  2010; AMAP, 2013). high