This paper summarizes recent efforts on Observing System Evaluation (OS-Eval) by the Ocean Data Assimilation and Prediction (ODAP) communities such as GODAE OceanView and CLIVAR-GSOP. It provides some examples of existing OS-Eval methodologies, and attempts to discuss the potential and limitation of the existing approaches. Observing System Experiment (OSE) studies illustrate the impacts of the severe decrease in the number of TAO buoys during 2012–2014 and TRITON buoys since 2013 on ODAP system performance. Multi-system evaluation of the impacts of assimilating satellite sea surface salinity data based on OSEs has been performed to demonstrate the need to continue and enhance satellite salinity missions. Impacts of underwater gliders have been assessed using Observing System Simulation Experiments (OSSEs) to provide guidance on the effective coordination of the western North Atlantic observing system elements. OSSEs are also being performed under H2020 AtlantOS project with the goal to enhance and optimize the Atlantic in-situ networks. Potential of future satellite missions of wide-swath altimetry and surface ocean currents monitoring is explored through OSSEs and evaluation of Degrees of Freedom for Signal (DFS). Forecast Sensitivity Observation Impacts (FSOI) are routinely evaluated for monitoring the ocean observation impacts in the US Navy's ODAP system. Perspectives on the extension of OS-Eval to coastal regions, the deep ocean, polar regions, coupled data assimilation, and biogeochemical applications are also presented. Based on the examples above, we identify the limitations of OS-Eval, indicating that the most significant limitation is reduction of robustness and reliability of the results due to their system-dependency. The difficulty of performing evaluation in near real time is also critical. A strategy to mitigate the limitation and to strengthen the impact of evaluations is discussed. In particular, we emphasize the importance of collaboration within the ODAP community for multi-system evaluation and of communication with ocean observational communities on the design of OS-Eval, required resources, and effective distribution of the results. Finally, we recommend further developing OS-Eval activities at international level with the support of the international ODAP (e.g., OceanPredict and CLIVAR-GSOP) and observational communities.
Food for Thought
The Southern Ocean is disproportionately important in its effect on the Earth system, impacting climatic, biogeochemical, and ecological systems, which makes recent observed changes to this system cause for global concern. The enhanced understanding and improvements in predictive skill needed for understanding and projecting future states of the Southern Ocean require sustained observations. Over the last decade, the Southern Ocean Observing System (SOOS) has established networks for enhancing regional coordination and research community groups to advance development of observing system capabilities. These networks support delivery of the SOOS 20-year vision, which is to develop a circumpolar system that ensures time series of key variables, and delivers the greatest impact from data to all key end-users. Although the Southern Ocean remains one of the least-observed ocean regions, enhanced international coordination and advances in autonomous platforms have resulted in progress toward sustained observations of this region. Since 2009, the Southern Ocean community has deployed over 5700 observational platforms south of 40°S. Large-scale, multi-year or sustained, multidisciplinary efforts have been supported and are now delivering observations of essential variables at space and time scales that enable assessment of changes being observed in Southern Ocean systems. The improved observational coverage, however, is predominantly for the open ocean, encompasses the summer, consists of primarily physical oceanographic variables, and covers surface to 2000 m. Significant gaps remain in observations of the ice-impacted ocean, the sea ice, depths >2000 m, the air-ocean-ice interface, biogeochemical and biological variables, and for seasons other than summer. Addressing these data gaps in a sustained way requires parallel advances in coordination networks, cyberinfrastructure and data management tools, observational platform and sensor technology, two-way platform interrogation and data-transmission technologies, modeling frameworks, intercalibration experiments, and development of internationally agreed sampling standards and requirements of key variables. This paper presents a community statement on the major scientific and observational progress of the last decade, and importantly, an assessment of key priorities for the coming decade, toward achieving the SOOS vision and delivering essential data to all end-users.
Ocean boundary current systems are key components of the climate system, are home to highly productive ecosystems, and have numerous societal impacts. Establishment of a global network of boundary current observing systems is a critical part of ongoing development of the Global Ocean Observing System. The characteristics of boundary current systems are reviewed, focusing on scientific and societal motivations for sustained observing. Techniques currently used to observe boundary current systems are reviewed, followed by a census of the current state of boundary current observing systems globally. The next steps in the development of boundary current observing systems are considered, leading to several specific recommendations.
Humans interact with the oceans in diverse and profound ways. The scope, magnitude, footprint and ultimate cumulative impacts of human activities can threaten ocean ecosystems and have changed over time, resulting in new challenges and threats to marine ecosystems. A fundamental gap in understanding how humanity is affecting the oceans is our limited knowledge about the pace of change in cumulative impact on ocean ecosystems from expanding human activities – and the patterns, locations and drivers of most significant change. To help address this, we combined high resolution, annual data on the intensity of 14 human stressors and their impact on 21 marine ecosystems over 11 years (2003–2013) to assess pace of change in cumulative impacts on global oceans, where and how much that pace differs across the ocean, and which stressors and their impacts contribute most to those changes. We found that most of the ocean (59%) is experiencing significantly increasing cumulative impact, in particular due to climate change but also from fishing, land-based pollution and shipping. Nearly all countries saw increases in cumulative impacts in their coastal waters, as did all ecosystems, with coral reefs, seagrasses and mangroves at most risk. Mitigation of stressors most contributing to increases in overall cumulative impacts is urgently needed to sustain healthy oceans.
We present the first objective quantitative assessment of the threats to all 359 species of seabirds, identify the main challenges facing them, and outline priority actions for their conservation. We applied the standardised Threats Classification Scheme developed for the IUCN Red List to objectively assess threats to each species and analysed the data according to global IUCN threat status, taxonomic group, and primary foraging habitat (coastal or pelagic). The top three threats to seabirds in terms of number of species affected and average impact are: invasive alien species, affecting 165 species across all the most threatened groups; bycatch in fisheries, affecting fewer species (100) but with the greatest average impact; and climate change/severe weather, affecting 96 species. Overfishing, hunting/trapping and disturbance were also identified as major threats to seabirds. Reversing the top three threats alone would benefit two-thirds of all species and c. 380 million individual seabirds (c. 45% of the total global seabird population). Most seabirds (c. 70%), especially globally threatened species, face multiple threats. For albatrosses, petrels and penguins in particular (the three most threatened groups of seabirds), it is essential to tackle both terrestrial and marine threats to reverse declines. As the negative effects of climate change are harder to mitigate, it is vital to compensate by addressing other major threats that often affect the same species, such as invasive alien species, bycatch and overfishing, for which proven solutions exist.
Migration is a widespread but highly diverse component of many animal life histories. Fish migrate throughout the world's oceans, within lakes and rivers, and between the two realms, transporting matter, energy, and other species (e.g., microbes) across boundaries. Migration is therefore a process responsible for myriad ecosystem services. Many human populations depend on the presence of predictable migrations of fish for their subsistence and livelihoods. Although much research has focused on fish migration, many questions remain in our rapidly changing world. We assembled a diverse team of fundamental and applied scientists who study fish migrations in marine and freshwater environments to identify pressing unanswered questions. Our exercise revealed questions within themes related to understanding the migrating individual's internal state, navigational mechanisms, locomotor capabilities, external drivers of migration, the threats confronting migratory fish including climate change, and the role of migration. In addition, we identified key requirements for aquatic animal management, restoration, policy, and governance. Lessons revealed included the difficulties in generalizing among species and populations, and in understanding the levels of connectivity facilitated by migrating fishes. We conclude by identifying priority research needed for assuring a sustainable future for migratory fishes.
Sociality—collective living—confers multiple advantages to oceanic dolphins, including enhanced foraging, predator avoidance, and alloparental care and may be particularly important in oceanic environments where prey is patchy and refuge nonexistent. This chapter covers broad aspects of the social lives of the delphinid community that inhabits the vast eastern tropical Pacific Ocean (ETP). Our approach is socio-ecological: the chapter ties dolphin social structure and mating systems to environmental factors, including oceanographic patterns, distribution of prey, and risk of predation that shape behavior. By merging a top-down look at schools distributed over a variable environment, with a bottom-up look from the perspective of subgroups that comprise schools, a picture of fission–fusion societies emerges. We also consider impacts of the tuna purse seine fishery on the socio-ecology of affected dolphins and discuss likely effects on behavior, learning, social bonds, and population dynamics.
ETP dolphin societies are diverse, spatially and compositionally fluid (pure or mixed species), yet socially complex and structured. They have distinct schooling, reproductive, and sexual characteristics, different patterns of association with other species, and differing degrees of interaction with the tuna purse seine fishery. Individuals may have distinct roles (older, experienced, and post-reproductive females), form stable or at least semi-stable subgroups (female/young, adult male, juvenile), and leave or join the company of others in response to a variety of social and ecological factors, including distribution of prey and risk of predation. In some taxa, individuals school with a small number of companions who may be related and recognize one another (common bottlenose, Tursiops truncatus; Risso’s, Grampus griseus; rough-toothed, Steno bredanensis; and striped dolphins, Stenella coeruleoalba), while in other species school size is larger, membership is fluid, and unrelated individuals abound (pantropical spotted, Stenella attenuata; spinner, Stenella longirostris; and common dolphins,Delphinus delphis). Mating systems are variable among species and sometimes within species, likely reflecting differences in habitat productivity. In some taxa, e.g., eastern spinners (S. l. orientalis), a few sexually mature males may be responsible for most mating, while in other taxa, e.g., “whitebelly” spinners, large relative testes suggest a more “open” mating system where many males in the school engage in copulation.
For pantropical spotted and spinner dolphins in the ETP, the behavior of schooling with large tuna that has led to their ecological success and abundance has also led to their depletion by making them a target of purse seiners. Schooling and sociality, normally adaptive traits, have caused ETP dolphins to become collateral damage in the tuna fishery. Yet dolphins have learned some things from their experiences with purse seiners. Some individuals know how to evade capture or, alternatively, how to await a lowering of the net (“backdown”) to escape. But, behavior that helps to avoid capture can cause high stress, exertion, or social separation and disruption, and these could be factors slowing or inhibiting population recovery. Survival and reproductive success of oceanic dolphins likely depends largely on social and behavioral factors that may also help determine their ability to recover from severe depletion caused by human activities.
Primarily applied to land-based resources, academics have utilised the concept of commodity frontiers to understand the expansionary nature of capitalism, and the ways that existing hegemonies and systems of control and access of resources are challenged and altered. Following recent calls to expand this concept to marine spaces, this paper has used political ecology and in particular its focus on power and access to explore how capitalist expansion has impacted the means and methods of access to key resources in a small-scale marine fishing community in Ghana. The findings of the paper are based upon an eight-month field visit to Aboadze in the Western Region of Ghana, a traditional fishing community that is considered a ‘closing’ frontier, on account of recent research that suggests the small-pelagic fish stocks will collapse within a decade. The findings of the paper show that accessing fish and other necessary resources such as gear and capital has become increasingly difficult as stocks continue to dwindle, and those living in the case study community have to resort to unsustainable fishing methods in order to survive. The paper also finds that the vulnerability caused by decades of overfishing by foreign trawlers is felt disproportionately by certain members of the community, compounding existing vulnerabilities that arise through gender and class.
Species extinctions are occurring at an unprecedented rate and there is a global need to understand whether conservation effort is appropriately allocated to protect those species at risk. In this study three major measures of global conservation effort across IUCN Red List Threats and Habitats were assessed; staff time spent by the largest cluster of conservation organizations in the world—Cambridge Conservation Initiative, efforts by international NGOs through social media, and global conservation research publications since the year 2000. We find global conservation effort is generally aligned with global conservation priorities, but there are important outliers. Shrublands and rocky areas receive disproportionately little investment across all effort measures relative to the number of high extinction risk species, threats from residential and commercial development receive relatively low research and time investment despite social media attention, while marine areas and climate change receive more attention than expected. Governments and society must make critical conservation decisions in the context of rapid global change, and there is potential for key Threats or Habitats to receive less attention than required. The global conservation community would be wise to carefully consider and improve its understanding of effort-priority mismatches if the greatest number of high extinction risk species are to be protected.
By definition, the mesopelagic twilight zone extends from 200 to 1000 m depth. Rather than confining the twilight zone to a certain depth interval, we here propose a definition that covers absolute light intensities ranging from 10−9 to 10−1 μmol quanta m−2 s−1. The lowest intensity of this twilight habitat corresponds to the visual threshold of lanternfishes (Myctophidae). The highest intensity corresponds to the upper light exposure of pearlsides (Maurolicusspp.), which have a unique eye adapted to higher light intensities than the lanternfishes. By this definition, the daytime twilight habitat extends deeper than 1000 m in very clear oceanic water, while may even be largely located above 200 m in very murky coastal waters. During moonlit nights in clear water, the twilight habitat would still extend deep into the mesopelagic depth zone, while becoming compressed toward the surface in dark nights. Large variation in night light, from 10−3 μmol quanta m−2 s−1 during moonlit nights to 10−8 μmol quanta m−2 s−1 in dark overcast nights, implies that division of light into night- and daylight is insufficient to characterize the habitats and distributional patterns of twilight organisms. Future research will benefit from in situ light measurements, during night- as well as daytime, and habitat classification based on optical properties in addition to depth. We suggest some pertinent research questions for future exploration of the twilight zone.