Farming of marine organisms (mariculture) represented 36% of global aquaculture, with mollusks representing 58.8% in live weight. Mollusk populations in some locations are, however, threatened by degradation of the ecosystems and/or over-fishing. This threat is increasingly being addressed through Restorative Shellfish Mariculture (RSM), as opposed to mariculture alone. There is no general consensus in the literature on what can and cannot be considered RSM. While maximization of benefits other than provisioning services is often considered a prerequisite, in other cases the maximization of fisheries yields is prioritized. Here we define RSM as the farming of marine shellfish, implying some form of intervention during the species life cycle, in order to address negative socio-ecological issues arising from the unsustainable use of marine ecosystems, independent of the final ownership regime of the resource. Strategies for developing RSM were reviewed and classified along a gradient from the most conservation-oriented (e.g., habitat restoration, reintroduction of locally extinct endangered species), to the most fisheries-oriented (including some forms of fisheries enhancement), and classified as Non-hatchery Dependent or Hatchery Dependent strategies. We reviewed the targeted species and strategies implemented across 584 individual projects developed in the last decades in North America, Europe, Asia, Oceania and South America. We found that some 48 species, including 34 bivalves and 15 gastropods were targets of RSM in 34 countries. US projects accounted for ca. three quarters of the total (N = 438), with Philippines, Japan and Australia also being home to a large number. More than 90% of the projects involved five species, namely the eastern oyster (Crassostrea virginica, N = 379), the giant clam (Tridacna gigas, N = 65), the Olympia oyster (Ostrea lurida, N = 25), the bay scallop (Argopecten irradians, N = 25) and the hard clam (Mercenaria mercenaria, N = 15). Of the RSM projects, 51% used Non-hatchery dependent methods, mostly habitat restoration providing substrata for settlement, whereas some 49% involved hatcheries. 3% of the projects combined both methods. This review provides an overview of the breadth, depth and aims of RSM globally, develops a broad definition of the activity, and proposes a structure for classifying RSM.
New Zealand has a large exclusive economic zone (EEZ) of which the area between the 30 and 50 m bathymetric zone offers the most prospects for shellfish production. Only 0.3% of this zone would be required to increase New Zealand’s shellfish production by 150,000 t. The Enabling Open Ocean Aquaculture Program, funded by the New Zealand Ministry of Business, Innovation and Employment, is a collaboration aiming to develop technologies that will enable the extension of aquaculture into New Zealand’s harsh and challenging open ocean conditions, and facilitate adaptation to the escalating effects of climate change in inner shore environments. New Zealand has started expanding aquaculture into exposed environments, allowing farm expansion to meet increasing demand for aquaculture products but also enabling ventures into new aquatic products. Expansion into offshore developments is in direct response to mounting stakeholder interaction in inshore coastal areas. This document presents a brief overview of the potential zones for open ocean aquaculture, the influence of climate change, and two potential shellfish operational systems that may facilitate the expansion of shellfish aquaculture onto New Zealand’s exposed ocean sites.
Harp seals are the most abundant marine mammal in the north Atlantic. As an ice obligatory predator, they reflect changes in their environment, particularly during a period of climatic change. As the focus of a commercial hunt, a large historic data set exists that can be used to quantify changes. There are three populations of harp seals: White Sea/Barents Sea, Greenland Sea and Northwest Atlantic. The objective of this paper is to review their current status and to identify the factors that are influencing population dynamics in different areas. Although important historically, recent catches have been low and do not appear to be influencing trends in either of the two northeast Atlantic populations. Massive mortalities of White Sea/Barents Sea seals occurred during the mid 1980s due to collapses in their main prey species. Between 2004 and 2006, pup production in this population declined by 2/3 and has remained low. Body condition declined during the same period, suggesting that ecosystem changes may have resulted in reduced reproductive rates, possibly due to reduced prey availability and/or competition with Atlantic cod. The most recent estimate of pup production in the Greenland Sea also suggests a possible decline during a period of reduced hunting although the trend in this population is unclear. Pupping concentrations are closer to the Greenland coast due to the reduction in ice in the traditional area and increased drift may result in young being displaced from their traditional feeding grounds leading to increased mortality. Reduced ice extent and thickness has resulted in major mortality of young in the Northwest Atlantic population in some years. After a period of increase, the population remained relatively stable between 1996 and 2013 due to increased hunting, multiple years with increased ice-related mortality of young seals, and lower reproductive rates. With a reduction in harvest and improved survival of young, the population appears to be increasing although extremely large interannual variations in body condition and fecundity have been observed which were found to be influenced by variations in capelin biomass and ice conditions. Each of these populations has been impacted differently by changes in their ecosystems and hunting practices. By identifying the factors influencing these three populations, we can gain a better understanding of how species may respond to changes that are occurring in their ecosystems.
Autonomous platforms already make observations over a wide range of temporal and spatial scales, measuring salinity, temperature, nitrate, pressure, oxygen, biomass, and many other parameters. However, the observations are not comprehensive. Future autonomous systems need to be more affordable, more modular, more capable and easier to operate. Creative new types of platforms and new compact, low power, calibrated and stable sensors are under development to expand autonomous observations. Communications and recharging need bandwidth and power which can be supplied by standardized docking stations. In situ power generation will also extend endurance for many types of autonomous platforms, particularly autonomous surface vehicles. Standardized communications will improve ease of use, interoperability, and enable coordinated behaviors. Improved autonomy and communications will enable adaptive networks of autonomous platforms. Improvements in autonomy will have three aspects: hardware, control, and operations. As sensors and platforms have more onboard processing capability and energy capacity, more measurements become possible. Control systems and software will have the capability to address more complex states and sophisticated reactions to sensor inputs, which allows the platform to handle a wider variety of circumstances without direct operator control. Operational autonomy is increased by reducing operating costs. To maximize the potential of autonomous observations, new standards and best practices are needed. In some applications, focus on common platforms and volume purchases could lead to significant cost reductions. Cost reductions could enable order-of-magnitude increases in platform operations and increase sampling resolution for a given level of investment. Energy harvesting technologies should be integral to the system design, for sensors, platforms, vehicles, and docking stations. Connections are needed between the marine energy and ocean observing communities to coordinate among funding sources, researchers, and end users. Regional teams should work with global organizations such as IOC/GOOS in governance development. International networks such as emerging glider operations (EGO) should also provide a forum for addressing governance. Networks of multiple vehicles can improve operational efficiencies and transform operational patterns. There is a need to develop operational architectures at regional and global scales to provide a backbone for active networking of autonomous platforms.
Marine coastal (or “blue”) ecosystems provide valuable services to humanity and the environment, but global loss and degradation of blue ecosystems necessitates ecological restoration. However, blue restoration is an emerging field and is still relatively experimental and small-scale. Identification of the key barriers to scaling-up blue restoration will enable targeted problem solving and increase the likelihood of success. Here we describe the environmental, technical, social, economic, and political barriers to restoration of blue ecosystems, including saltmarsh, mangroves, seagrass, shellfish reefs, coral reefs, and kelp forests. We provide managers, practitioners, and decision-makers with solutions to construct barrier-informed blue restoration plans and illustrate these solutions through the use of case studies where barriers were overcome. We offer a way forward to build confidence in blue restoration for society, government, and restoration practitioners at larger and more ambitious scales.
Marine and coastal activities are closely interrelated, and conflicts among different sectors can undermine management and conservation objectives. Governance systems for fisheries, power generation, irrigation, aquaculture, marine biodiversity conservation, and other coastal and maritime activities are typically organized to manage conflicts within sectors, rather than across them. Based on the discussions around eight case studies presented at a workshop held in Brest in June 2019, this paper explores institutional approaches to move beyond managing conflicts within a sector. We primarily focus on cases where the groups and sectors involved are heterogeneous in terms of: the jurisdiction they fall under; their objectives; and the way they value ecosystem services. The paper first presents a synthesis of frameworks for understanding and managing cross-sectoral governance conflicts, drawing from social and natural sciences. We highlight commonalities but also conceptual differences across disciplines to address these issues. We then propose a novel analytical framework which we used to evaluate the eight case studies. Based on the main lessons learned from case studies, we then discuss the feasibility and key determinants of stakeholder collaboration as well as compensation and incentive schemes. The discussion concludes with future research needs to support policy development and inform integrated institutional regimes that consider the diversity of stakeholder interests and the potential benefits of cross-sectoral coordination.
Over 85% of the world's oyster reefs have been lost in the past two centuries, triggering a global effort to restore shellfish reef ecosystems and the ecosystem services they provide. While there has been considerable success in re-establishing oyster reefs, many challenges remain. These include: high incidence of failed restoration, high cost of restoration per unit area, and increasing stress from climate change. In order to leverage our past successes and progress the field, we must increase restoration efficiencies that not only reduce cost per unit area, but also increase the resilience of restored ecosystems. To help address this need, we qualitatively review the literature associated with the structure and function of oyster reef ecosystems to identify key positive species interactions (i.e., those species interactions where at least one partner benefits and no partners are harmed). We classified positive inter- and intraspecific interactions between oysters and organisms associated with oyster ecosystems into the following seven functional categories: (1) physical reef creation, (2) positive density dependence, (3) refugia from physical stress, (4) refugia from biological stress, (5) biodiversity enhancement, (6) settlement improvement, and (7) long-distance facilitation. We discuss each category of positive interaction and how restoration practitioners can use knowledge of such processes to enhance restoration success. We propose that systematic incorporation of positive species interactions into restoration practice will both enhance ecological services provided by restored reefs and increase restoration success.
Bycatch in fisheries is one of the greatest threats to marine megafauna such as sea turtles, and the Biodiversity Impact Mitigation Hierarchy (BIMH) has been proposed as an improved and holistic approach for integrating fisheries management with sea turtle conservation. The first three BIMH steps – avoid, minimize, and remediate – take place at sea where fishing activity is taking place. However, these at-sea measures are costly and difficult to effectively implement across the vast range of a highly migratory species. As such, some level of mortality continues, even when the first three steps of the BIMH are implemented as extensively as possible. These remaining negative impacts need to be addressed by compensatory conservation actions elsewhere, e.g., at sea turtle nesting beaches. As a case study, we use the critically endangered leatherback sea turtle nesting population in Papua Barat, Indonesia, to illustrate the opportunity for conservatory offsets to fisheries bycatch across the Pacific. We describe the community empowerment and nest protection programs that have been enhanced by the voluntary offsets from the tuna industry. While improved nest protection measures have helped optimize hatchling production, the engagement of the local communities, through activities that empower and enhance quality of life, has been a critical component to the successful increase in hatchlings. This momentum needs to be sustained and scaled-up to protect the majority of threatened nests over a consistent number of years to successfully provide the recruitment boost needed at the population level. These compensatory off-site conservation measures are also the most cost-effective means of achieving increases in leatherback populations, and perhaps one of the most critical components of the recovery strategy for Pacific leatherbacks.
Marine protected areas (MPAs) are essential to human well-being and usually part of spatial planning processes for managing coastal and marine areas. In Brazil, national-level spatial planning processes are still incipient. This article offers a systematic review through a comparative meta-analysis of the literature on MPAs and spatial planning based on the following questions: (I) What topics are investigated in spatial planning in MPAs worldwide? and (II) What are the advances and trends of these topics in Brazilian MPAs? Specific goals of this study are (I) to identify studies on Brazil; and (II) to compare and contrast these with studies performed elsewhere. The PRISMA report was used to select literature, with a focus on three spatial contexts (I) outside Brazil, analyzing studies from other countries; (II) in Brazil; and (III) a case study in Brazil that focuses on a sustainable-use area in northeastern Pará. Studies outside Brazil showed three major groups of themes: (I) planning and tools; (II) stakeholders; and (III) the ecology of non-human species. For the Brazilian context, studies were grouped into five major themes: (I) small-scale fishing practices and conflicts; (II) participation in protected areas; (III) technical aspects of the planning process, (IV) zoning; and (V) mapping. The local case study investigates socio-cultural sustainability and tourism. All identified studies relate to use, but have a greater focus on conservation and, especially abroad, on species and ecosystems. There are few reviews or comparative studies that could help to draw parallels between the different spatial planning settings. We conclude that synthesis work on spatial management strategies worldwide is needed, including the elaboration of frameworks to develop measures to address the widespread lack of data and spatial planning expertise. Collaborative networks of researchers and practitioners are needed for this. The novelty in our study is that it examines MPAs and spatial planning research at three spatial contexts with innovative methodologies to represent the current state of the spatial planning discourse in coastal and marine conservation.
An important technique used by climate modelers to isolate the impacts of increasing greenhouse gasses on Earth System processes is to simulate the impact of an abrupt increase in carbon dioxide. The spatial pattern of change provides a “fingerprint” that is generally much larger than natural variability. Insofar as the response to radiative forcing is linear (the impact of quadrupling CO2 is twice the impact of doubling CO2) this fingerprint can then be used to estimate the impact of historical greenhouse gas forcing. However, the degree to which biogeochemical cycles respond linearly to radiative forcing has rarely been tested. In this paper, we evaluate which ocean biogeochemical fields are likely to respond linearly to changing radiative forcing, which ones do not, and where linearity breaks down. We also demonstrate that the representation of lateral mixing by mesoscale eddies, which varies significantly across climate models, plays an important role in modulating the breakdown of linearity. Globally integrated surface rates of biogeochemical cycling (primary productivity, particulate export) respond in a relatively linear fashion and are only moderately sensitive to mixing. By contrast, the habitability of the interior ocean (as determined by hypoxia and calcite supersaturation) behaves non-linearly and is very sensitive to mixing. This is because the deep ocean, as well as certain regions in the surface ocean, are very sensitive to the magnitude of deep wintertime convection. The cessation of convection under global warming is strongly modulated by the representation of eddy mixing.
Coral reefs are widely regarded as one of the top science and conservation priorities globally, as previous research has demonstrated that these ecosystems harbor an extraordinary biodiversity, myriad ecosystem services, and are highly vulnerable to human stressors. However, most of this knowledge is derived from studies on nearshore and shallow-water reefs, with coral reef ecosystems remaining virtually unstudied in marine areas beyond national jurisdiction (ABNJ), commonly known as the high seas. We reviewed information on the spatial distribution of reef-building corals throughout their depth range, and compiled a total of 537,782 records, including 116 unique records from ABNJ at depths between 218–5,647 m. The majority of reef-building coral records in ABNJ were in association with geomorphological features that have steep topographies. These habitats, which include escarpments, seamounts, and submarine ridges accounted for >74% of the records in international waters. Such geomorphological features, particularly those that occur within close proximity to the sea surface, should be prioritized for future scientific exploration. The majority of the reef-building coral records in ABNJ (>77%) were recorded in unprotected waters, and this study discusses the challenges and opportunities for protecting marine biodiversity in ABNJ. Finally, this study offers a definition of high seas coral reefs, and provides a framework to better understand and conserve these fragile ecosystems.
Ocean acidification is a threat to the net growth of tropical and deep-sea coral reefs, due to gradual changes in the balance between reef growth and loss processes. Here we go beyond identification of coral dissolution induced by ocean acidification and identify a mechanism that will lead to a loss of habitat in cold-water coral reef habitats on an ecosystem-scale. To quantify this, we present in situ and year-long laboratory evidence detailing the type of habitat shift that can be expected (in situ evidence), the mechanisms underlying this (in situ and laboratory evidence), and the timescale within which the process begins (laboratory evidence). Through application of engineering principals, we detail how increased porosity in structurally critical sections of coral framework will lead to crumbling of load-bearing material, and a potential collapse and loss of complexity of the larger habitat. Importantly, in situ evidence highlights that cold-water corals can survive beneath the aragonite saturation horizon, but in a fundamentally different way to what is currently considered a biogenic cold-water coral reef, with a loss of the majority of reef habitat. The shift from a habitat with high 3-dimensional complexity provided by both live and dead coral framework, to a habitat restricted primarily to live coral colonies with lower 3-dimensional complexity represents the main threat to cold-water coral reefs of the future and the biodiversity they support. Ocean acidification can cause ecosystem-scale habitat loss for the majority of cold-water coral reefs.
Reversing the decline of coastal marine ecosystems will rely extensively on ecological restoration. This will in turn rely on ensuring adequate supply and survival of propagules — for the main habitat-forming taxa of coastal marine ecosystems these are mainly fruits, seeds, viviparous seedlings, zoospores or larvae. The likelihood of propagule survival — and so restoration success — depends on species- and context-specific knowledge to guide choices about appropriate methods to use. Here, we briefly review life-histories of the main habitat-forming taxa of six coastal marine ecosystems: mangrove forests, tidal marshes, seagrass meadows, kelp forests, coral reefs and bivalve reefs. Restoration of several of these ecosystems has long harnessed the unique properties of propagules, sometimes because they are simple to use (for example, planting propagules of some mangroves), and sometimes because we can draw on knowledge gained from other applications (for example using knowledge of oyster culture to restore bivalve reefs). For other ecosystems, like seagrass meadows, kelp forests and coral reefs, propagules have not yet been widely used, but there is compelling evidence that they can be. Most restoration efforts have used relatively simple techniques, such as manual collection and direct planting or seeding. Some approaches use more complex techniques which include a stage in which propagules are reared in nurseries or aquaria to a size or age at which they are viable, when they are then planted or released at the site to be restored. Other approaches use minimal intervention, and focus instead on providing the conditions that will promote growth from naturally dispersed propagules (such as restoring hydrological conditions to facilitate mangrove recruitment). Future approaches could incorporate knowledge applied from other fields, such as genetics and agriculture, and harness the possibilities provided by technology. Understanding the importance of propagule quality will likely also yield insights, as will effective use of models to help refine restoration methods for testing. Deeper partnerships between practitioners and researchers will help test and develop better methods so that we can learn from each other and strive to improve. Propagules offer multiple promising avenues to expand coastal marine restoration efforts and help achieve global ambitions.
The deep sea is the largest biome on Earth but the least explored. Our knowledge of it comes from scattered sources spanning different spatial and temporal scales. Implementation of marine policies like the European Union’s Marine Strategy Framework Directive (MSFD) and support for Blue Growth in the deep sea are therefore hindered by lack of data. Integrated assessments of environmental status require tools to work with different and disaggregated datasets (e.g. density of deep-sea habitat-forming species, body-size distribution of commercial fishes, intensity of bottom trawling) across spatial and temporal scales. A feasibility study was conducted as part of the four-year ATLAS project to assess the effectiveness of the open-access Nested Environmental status Assessment Tool (NEAT) to assess deep-sea environmental status. We worked at nine selected study areas in the North Atlantic focusing on five MSFD descriptors (D1-Biodiversity, D3-Commercial fish and shellfish, D4-Food webs, D6-Seafloor integrity, D10-Marine litter). The objectives of the present study were to i) explore and propose indicators that could be used in the assessment of deep-sea environmental status, ii) evaluate the performance of NEAT in the deep sea, and iii) identify challenges and opportunities for the assessment of deep-sea status. Based on data availability, data quality and expert judgement, in total 24 indicators (one for D1, one for D3, seven for D4, 13 for D6, two for D10) were used in the assessment of the nine study areas, their habitats and ecosystem components. NEAT analyses revealed differences among the study areas for their environmental status ranging from “poor” to “high”. Overall, the NEAT results were in moderate to complete agreement with expert judgement, previous assessments, scientific literature on human-pressure gradients and expected management outcomes. We suggest that the assessment of deep-sea environmental status should take place at habitat and ecosystem level (rather than at species level) and at relatively large spatial scales, in comparison to shallow-water areas. Limited knowledge across space (e.g. distribution of habitat-forming species) and the scarcity of long-term data sets limit our knowledge about natural variability and human impacts in the deep sea preventing a more systematic assessment of habitat and ecosystem components in the deep sea. However, stronger cross-sectoral collaborations, the use of novel technologies and open data-sharing platforms will be critical for establishing environmental baseline indicator values in the deep sea that will contribute to the science base supporting the implementation of marine policies and stimulating Blue Growth.
This work aimed to study the effects of recreational diving and snorkeling on the distribution, diversity, and abundance of surgeonfishes in six northern islands, different in their diving and snorkeling load, at the Hurghada area in the Egyptian Red Sea waters. SCUBA diving survey was conducted in summer 2019 using transect technique in the reef flat and reef slope in the study sites to compare total and single surgeonfish species census among sites and microhabitats. A total of six species of surgeonfish belonging to three genera were recorded during the current survey, including Zebrasoma xanthurum, Zebrasoma desjardinii, Acanthurus gahhm, Acanthurus sohal, Naso lituratus, and Naso unicornis. Z. desjardinii was the most abundant species, recording 41.2% relative abundance, followed by Acanthurus sohal (19%). In all sites, surgeonfish species diversity and average/total abundance in reef flat was always higher than that recorded in the reef slope. Meanwhile, the recreational effect results showed that, in reef flat habitats, surgeonfishes total/average abundance was inversely related to the numbers of divers and snorkelers across survey sites. In contrast, deeper habitat at the opened reef edge exhibited inverse distribution pattern, whereas, the obtained results showed that surgeonfish preferred the reef edge when the diving activities load increased.
Microplastics (MPs) can be ingested by marine organisms directly or indirectly through trophic transfer from contaminated prey. In the marine ecosystem, zooplankton are an important link between phytoplankton and higher trophic levels in the marine food web. Among them, copepods and gelatinous species have been recently reported to ingest MPs, but no potential MP transfer has been verified yet. In this study, a simplified two-level trophic chain – formed by nauplii of the Tigriopus fulvus copepod as prey, and the ephyrae stage of Aurelia sp. as predator – was selected to investigate MP trophic transfer. The experimental setup consisted in feeding ephyrae with nauplii previously exposed to fluorescent 1–5 μm polyethylene MPs and evaluating two ecotoxicological end-points: jellyfish immobility and pulsation frequency. After 24 h, the jellyfish ingested nauplii contaminated with MPs; however, neither immobility nor behavior was affected by MP transfer. These findings show that MPs can be transported at different trophic levels, but more research is needed to identify their potential effects on the marine food web.
Marine turtles are of conservation concern throughout their range, with past population declines largely due to exploitation through both legal and illegal take, and incidental capture in fisheries. Whilst much research effort has been focused on nesting beaches and elaborating migratory corridors, these species spend the vast majority of their life-cycle in foraging grounds, which are, in some species, quite discrete. To understand and manage these populations, empirical data are needed on distribution, space-use, and habitats to best inform design of protective measures. Here we describe space-use, occupancy, and wide-ranging movements derived from conventional flipper tagging and satellite tracking of sub-adult green turtles (Chelonia mydas) within the coastal waters of the Turks and Caicos Islands (TCI; 2011–2017). 623 turtles were fitted with flipper tags, with 69 subsequently recaptured, five of which in international waters. Sixteen individual turtles of between 63 and 81 cm curved carapace length were satellite tracked for a mean 226 days (range: 38–496). Data revealed extended periods of occupancy in the shallow coastal waters within a RAMSAR protected area. Satellite tracking and flipper tagging showed wide-ranging movements, with flipper tag recaptures occurring in waters off Nicaragua (n = 4), and Venezuela (n = 1). Also, four of 16 satellite tracked turtles exhibiting directed movements away (displaced >450 km) from TCI waters traveling through nine geo-political zones within the Caribbean-Atlantic basin, as well as on the High Seas. One turtle traveled to the Central American coast before settling on inshore habitat in Colombia’s waters for 162 days before transmission ceased, indicating ontogenetic dispersal to a distant foraging habitat. These data highlight connectivity throughout the region, displaying key linkages between countries that have previously only been linked by genetic evidence. This study also provides evidence of the importance of the Turks and Caicos Islands marine protected area network and importance of effective management of the sea turtle fishery for regional green turtle populations.
While the ubiquity and rising abundance of microplastic contamination is becoming increasingly well-known, there is very little empirical data for the scale of their historical inputs to the environment. For many pollutants, where long-term monitoring is absent, paleoecological approaches (the use of naturally-accumulating archives to assess temporal trends) have been widely applied to determine such historical patterns, but to date this has been undertaken only very rarely for microplastics, despite the enormous potential to identify the scale and extent of inputs as well as rates of change. In this paper, we briefly assess the long-term monitoring and paleoecological microplastic literature before considering the advantages and disadvantages of various natural archives (including lake and marine sediments, ice cores and peat archives) as a means to determine historical microplastic records, as well as the range of challenges facing those attempting to extract microplastics from them. We also outline some of the major considerations in chemical, physical and biological taphonomic processes for microplastics as these are critical to the correct interpretation of microplastic paleoecological records but are currently rarely considered. Finally, we assess the usefulness of microplastic paleoecological records as a stratigraphic tool, both as a means to provide potential chronological information, as well as a possible marker for the proposed Anthropocene Epoch.
In 2015, the Pacific marine heat wave, low river flows, and record high water temperatures in the Columbia River Basin contributed to a near-complete failure of the adult migration of endangered Snake River sockeye salmon (Oncorhynchus nerka, NOAA Fisheries 2016). These extreme weather events may become the new normal due to anthropogenic climate change, with catastrophic consequences for endangered species. Existing anthropogenic pressures may amplify vulnerability to climate change, but these potential synergies have rarely been quantified. We examined factors affecting survival of endangered sockeye (Oncorhynchus nerka) and threatened Chinook salmon (O. tshawytscha) as they migrated upstream through eight dams and reservoirs to spawning areas in the Snake River Basin. Our extensive database included histories of 17,279 individual fish that migrated since 2004. A comparison between conditions in 2015 and daily temperatures and flows in a regulated basin forced by output from global climate models showed that 2015 did have many characteristics of projected future mean conditions. To evaluate potential salmon responses, we modeled migration timing and apparent survival under historical and future climate scenarios (2040s). For Chinook salmon, adult survival from the first dam encountered to spawning grounds dropped by 4-15%, depending on the climate scenario. For sockeye, survival dropped by ~80% from their already low levels. Through sensitivity analyses, we observed that the adult sockeye migration would need to shift more than 2 weeks earlier than predicted to maintain survival rates typical of those seen during 2008-2017. Overall, the greater impacts of climate change on adult sockeye compared with adult Chinook salmon reflected differences in life history and environmental sensitivities, which were compounded for sockeye by larger effect sizes from other anthropogenic factors. Compared with Chinook, sockeye was more negatively affected by a history of juvenile transportation and by similar temperatures and flows. The largest changes in temperature and flow were projected to be upstream from the hydrosystem, where direct mitigation through hydrosystem management is not an option. Unfortunately, Snake River sockeye have likely lost much of their adaptive capacity with the loss of the wild population. Further work exploring habitat restoration or additional mitigation actions is urgently needed.
In the Baltic Sea, water is stratified due to differences in density and salinity. The stratification prevents water from mixing, which could affect sinking rates of microplastics in the sea. We studied the accumulation of microplastics to halocline and thermocline. We sampled water with a 100 μm plankton net from vertical transects between halo- and thermocline, and a 30 L water sampler from the end of halocline and the beginning of thermocline. Thereafter, microplastics in the whole sample volumes were analyzed with imaging Fourier transform infrared spectroscopy (FTIR). The plankton net results showed that water column between halo- and thermoclines contained on average 0.92 ± 0.61 MP m−3 (237 ± 277 ng/m−3; mean ± SD), whereas the 30 L samples from the end of halocline and the beginning of thermocline contained 0.44 ± 0.52 MP L−1 (106 ± 209 ng L−1). Hence, microplastics are likely to accumulate to thin layers in the halocline and thermocline. The vast majority of the found microplastics were polyethylene, polypropylene and polyethylene terephthalate, which are common plastic types. We did not observe any trend between the density of microplastics and the sampling depth, probably because biofilm formation affected the sinking rates of the particles. Our results indicate the need to sample deeper water layers in addition to surface waters at least in the stratified water bodies to obtain a comprehensive overview of the abundance of microplastics in the aquatic environment.