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Plankton community structure changes seasonally in response to the annual cycles of stratification, temperature, and primary productivity. These communities also change from year-to-year, in some cases exhibiting persistent regime shifts. How changes in physical conditions structure the plankton community and why conditions persist is a fundamental question in oceanography. Continuous plankton recorders have been used to sample the plankton community across the Gulf of Maine since 1961. Historically, this community has had a classic subarctic structure dominated by Calanus finmarchicus. However, during the 1990s, C. finmarchicus became less prominent, and a more diverse community of smaller copepods emerged. This shift was related to an influx of cold, low-salinity water. We show that a similar community shift occurred around 2012. We use high-resolution hydrographic data to link the shift to an influx of saltier water and warmer conditions. By comparing the 1990s with the recent decade, we develop a synthesis for how physical changes lead to community shifts. Our synthesis suggests that the link between the 1990s and 2010s is enhanced water column stratification. We further propose that ecological interactions link declines in C. finmarchicus with the emergence of the more diverse community, drawing parallels with classic food web ecology. [ABSTRACT FROM AUTHOR]

Anthropogenic warming is altering species abundance, distribution, physiology, and more. How changes observed at the species level alter emergent community properties is an active and urgent area of research. Trait‐based ecology and regime shift theory provide complementary ways to understand climate change impacts on communities, but these two bodies of work are only rarely integrated. Lack of integration handicaps our ability to understand community responses to warming, at a time when such understanding is critical. Therefore, we advocate for merging trait‐based ecology with regime shift theory. We propose a general set of principles to guide this merger and apply these principles to research on marine communities in the rapidly warming North Atlantic. In our example, combining trait distribution and regime shift analyses at the community level yields greater insight than either alone. Looking forward, we identify a clear need for expanding quantitative approaches to collecting and merging trait‐based and resilience metrics in order to advance our understanding of climate‐driven community change. [ABSTRACT FROM AUTHOR]

Greenhouse gas emissions are warming the ocean with profound consequences at all levels of organization, from organismal rates to ecosystem processes. The proximate driver is an interplay between anthropogenic warming (the trend) and natural fluctuations in local temperature. These two properties cause anomalously warm events such as marine heatwaves to occur with increasing frequency and magnitude. Because warming and variance are not uniform, there is a large degree of geographic variation in temporal temperature variability. We review the underappreciated interaction between trend and variance in the ocean and how it modulates ecological responses to ocean warming. For example, organisms in more thermally variable environments are often more acclimatized and/or adapted to temperature extremes and are thus less sensitive to anthropogenic heatwaves. Considering both trend and variability highlights the importance of processes like legacy effects and extinction debt that influence the rate of community transformation. [ABSTRACT FROM AUTHOR]

Unlike atmospheric weather forecasting, ocean forecasting is often reflexive; for many applications, the forecast and its dissemination can change the outcome, and is in this way, a part of the system. Reflexivity has implications for several ocean forecasting applications, such as fisheries management, endangered species management, toxic and invasive species management, and community science. The field of ocean system forecasting is experiencing rapid growth, and there is an opportunity to add the reflexivity dynamic to the conventional approach taken from weather forecasting. Social science has grappled with reflexivity for decades and can offer a valuable perspective. Ocean forecasting is often iterative, thus it can also offer opportunities to advance the general understanding of reflexive prediction. In this paper, we present a basic theoretical skeleton for considering iterative reflexivity in an ocean forecasting context. It is possible to explore the reflexive dynamics because the prediction is iterative. The central problem amounts to a tension between providing a reliably accurate forecast and affecting a desired outcome via the forecast. These two objectives are not always compatible. We map a review of the literature onto relevant ecological scales that contextualize the role of reflexivity across a range of applications, from biogeochemical (e.g., hypoxia and harmful algal blooms) to endangered species management. Formulating reflexivity mathematically provides one explicit mechanism for integrating natural and social sciences. In the context of the Anthropocene ocean, reflexivity helps us understand whether forecasts are meant to mitigate and control environmental changes, or to adapt and respond within a changing system. By thinking about reflexivity as part of the foundation of ocean system forecasting, we hope to avoid some of the unintended consequences that can derail forecasting programs. [ABSTRACT FROM AUTHOR]

The article by Meyer-Gutbrod and colleagues in this issue demonstrates that the endangered North Atlantic right whale's preferred prey has declined as the Northwest Atlantic has warmed. Right whales are now spending more time foraging in historically colder habitats, but they are producing fewer calves. The low calf production could reflect a delay between the decline in the potential productivity of their traditional habitats and its increase in their new habitats. This delay would result in a "climate deficit" in their fitness. Right whales must also learn to forage successfully in their new habitats, creating an additional loss of fitness termed an "adaptation deficit." Humans will also face unavoidable climate deficits, but we have more options for minimizing adaptation deficits. [ABSTRACT FROM AUTHOR]

The community of species, human institutions, and human activities at a given location have been shaped by historical conditions (both mean and variability) at that location. Anthropogenic climate change is now adding strong trends on top of existing natural variability. These trends elevate the frequency of "surprises"-conditions that are unexpected based on recent history. Here, we show that the frequency of surprising ocean temperatures has increased even faster than expected based on recent temperature trends. Using a simple model of human adaptation, we show that these surprises will increasingly challenge natural modes of adaptation that rely on historical experience. We also show that warming rates are likely to shift natural communities toward generalist species, reducing their productivity and diversity. Our work demonstrates increasing benefits for individuals and institutions from betting that trends will continue, but this strategy represents a radical shift that will be difficult for many to make. [ABSTRACT FROM AUTHOR]

Extreme environmental events are often catalysts for adaptive changes. Like many such events, the 2012 marine heatwave in the Gulf of Maine revealed unexpected connections within the ecosystem and between the natural and human components of the system. The strongest economic impacts were to Maine's valuable lobster fishery. In 2012, early and intense landings led to a backlog in the supply chain and a drop in price. This experience prompted the lobster industry to implement changes throughout the supply chain to avoid the severe drop in price should another warm year with early landings occur. Here we describe a second heatwave in the Gulf of Maine that occurred in 2016. Despite a similar pattern in monthly landings, dockside prices for lobster were higher than expected. The contrast with 2012 suggests that the adaptations in the supply chain were successful. The 2012 and 2016 heatwaves are part of a broader pattern of temperature changes in this region. Warmer autumns allow sea turtles to remain in the Gulf of Maine longer, increasing their risk of being stunned or killed by cold water, and warm years followed by cold years typically lead to a decline in lobster landings. While there is evidence for adaptation to rising temperatures in the Gulf of Maine, the adaptation brought a significant shock to the system. Forecasts may help foster adaptation while avoiding shocks, but this will require a substantial shift in the mindsets of both forecast producers and consumers. [ABSTRACT FROM AUTHOR]

Like most ectothermic species, American lobster growing in warmer environments mature at smaller sizes. A formal quantification of this pattern at multiple spatiotemporal scales has not been developed, impeding the development of tools to predict the impacts of climate change on American lobster life-history and fishery. In this study, data from sea sampling programs from southern New England to the Bay of Fundy are used to estimate female lobster size at maturity, and to quantify the effects of water temperature on maturity at three spatial scales: i) regional (∼1000 km), ii) stock (100 s km), and iii) Statistical Area (10 s km). Results show that female lobsters living in warmer waters mature at smaller sizes and that other factors, likely fishing, also contributed to the observed decrease in length at 50% maturity. This study suggests that adaptive management plans need to consider temperature-induced trends in size at maturity to ensure sustainability of the valuable American lobster fisheries. Additionally, this study provides a maturity function for use in models that aim to project effects of climate change on American lobster populations and fisheries dynamics. [ABSTRACT FROM AUTHOR]

Several studies have documented fish populations changing in response to long-term warming. Over the past decade, sea surface temperatures in the Gulf of Maine increased faster than 99% of the global ocean. The warming, which was related to a northward shift in the Gulf Stream and to changes in the Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation, led to reduced recruitment and increased mortality in the region's Atlantic cod (Gadus morhua) stock. Failure to recognize the impact of warming on cod contributed to overfishing. Recovery of this fishery depends on sound management, but the size of the stock depends on future temperature conditions. The experience in the Gulf of Maine highlights the need to incorporate environmental factors into resource management. [ABSTRACT FROM AUTHOR]

Zooplankton fecal pellet flux is a highly variable component of the biological carbon pump. While fecal pellets can comprise 0 to nearly 100% of particulate organic carbon collected in sediment traps, mechanisms for this variability remain poorly understood. Fecal pellet carbon flux is a complex function of several variables. We present a model that incorporates individual-scale metabolic processes to determine fecal pellet production rate, the relationship between body size and fecal pellet size, the relationship between fecal pellet size and sinking rate, and a function representing the breakdown of particles in the water column. When applied to copepod communities sampled by the continuous plankton recorder in the Gulf of Maine over 25 years, a seasonal pattern of fecal pellet carbon flux emerges. The interannual flux time series produced by the model reflects known oceanographic perturbations and shows how organism-scale processes can be scaled up to explain ecosystem level variability. We conclude that fecal pellet carbon flux in the Gulf of Maine is driven by copepod community size structure and copepod abundance, and that the fraction of fecal pellet carbon that reaches depth is a function of copepod size, rather than abundance. Changes in the physical environment which alter the size composition of the copepod community lead to variability in fecal pellet carbon flux. Our results indicate that incorporating size composition into biogeochemical models can more accurately constrain zooplankton-mediated carbon flux. [ABSTRACT FROM AUTHOR]

Preserving larger fish is often advocated as a conservation measure to help fish populations buffer environmental variation and fishing pressure. The rationale is that several size- and age-dependent reproductive traits confer a higher reproductive value to larger fish. The effects of variation in these reproductive traits on the dynamics of populations under various fishing patterns are however seldom evaluated. In this study, we develop a simulation model to evaluate how variation in three reproductive traits (fecundity-mass, hatching probability, and batch spawning) impacts the capacity of a fish population to withstand and recover from high fishing pressure. Biological functions of the model were calibrated based on the Gulf of Maine Atlantic cod stock, which is currently experiencing its lowest biomass level ever estimated. Results showed that variation in the shape of the fecundity-mass relationship had the most substantial impact on population resistance and recovery. Batch spawning and variation in hatching probability had limited impacts. Furthermore, results showed that preserving larger fish by imposing a slot fishery increased the resistance of the population to high fishing pressure, because it helped preserve the population reproductive potential determined by the high fecundity of large fish. The slot fishery, however, impeded population recovery, because it distributed the fishing pressure on intermediate-size classes which potential for biomass growth is maximal. This study underlines the importance of using precise size-dependent fecundity estimates when evaluating the productivity and sustainability of fisheries, as well as the importance of identifying priority among the components of population resilience (e.g. resistance or recovery) before implementing size-selective harvest strategies. [ABSTRACT FROM AUTHOR]

In ecosystems that are strongly structured by predation, reducing top predator abundance can alter several lower trophic levels--a process known as a trophic cascade. A persistent trophic cascade also fits the definition of a regime shift. Such 'trophic cascade regime shifts' have been reported in a few pelagic marine systems--notably the Black Sea, Baltic Sea and eastern Scotian Shelf--raising the question of how common this phenomenon is in the marine environment. We provide a general methodology for distinguishing top-down and bottom-up effects and apply this methodology to time series from these three ecosystems. We found evidence for top-down forcing in the Black Sea due primarily to gelatinous zooplankton. Changes in the Baltic Sea are primarily bottom-up, strongly structured by salinity, but topdown forcing related to changes in cod abundance also shapes the ecosystem. Changes in the eastern Scotian Shelf that were originally attributed to declines in groundfish are better explained by changes in stratification. Our review suggests that trophic cascade regime shifts are rare in open ocean ecosystems and that their likelihood increases as the residence time of water in the system increases. Our work challenges the assumption that negative correlation between consecutive trophic levels implies top-down forcing. [ABSTRACT FROM AUTHOR]

Understanding how oceanographic factors independently and interactively influence fish behavior, physiology, and survival is essential for predicting the impact of climate change on fish. Such predictions are especially challenging for highly migratory species such as salmon that experience a broad range of conditions. We applied a novel modeling approach that combines an individual-based particle model with a bioenergetics model to evaluate the effects of oceanographic variability on migration of post-smolt Atlantic salmon ( Salmo salar). Interannual variability in the surface current velocity and sea surface temperature differentially influenced post-smolt salmon migration. The magnitude, duration, and direction of the currents relative to a fish's intended swimming direction had the strongest influence on migration. Changes in ocean circulation led to changes in currents at a regional scale that have a similar, relative effect across multiple populations during out-migration. Results of this study suggest that the Nova Scotia Coastal Current has a strong influence on the migration pathways of migrating salmon through the Gulf of Maine. The influx of cool fresh water from the Arctic, observed in the early 1990s, changed the Nova Scotia Coastal Current and, as suggested by model results, could have dramatically influenced post-smolt salmon migration success. There was a trade-off between arriving at the destination quickly but at a small size and not arriving at the destination at all. Fish that took a long time to migrate had more opportunities to feed and encountered warmer summer waters, increasing their overall growth. [ABSTRACT FROM AUTHOR]

Record, N. R., Pershing, A. J., and Maps, F. 2014. The paradox of the “paradox of the plankton”. – ICES Journal of Marine Science, 71: 236–240.One of the central orienting questions in biodiversity theory and ecology is the “paradox of the plankton”, which asks how it is possible for many species to coexist on limited resources given the tendency for competition to exclude species. Over the past five decades, ecologists have offered dozens of solutions to the paradox, invoking game theory, chaos, stochastics, and many other concepts. Despite the plentitude of solutions to the paradox, ecologists continue to offer up novel solutions. Ocean modellers are now faced with the opposite paradox: given the overabundance and the diversity of solutions to the paradox, what is the appropriate way to build coexistence into ecosystem models? Ocean ecosystem models have a very standardized form—nutrient–phytoplankton–zooplankton (NPZ)-type systems of differential equations—where competitive exclusion is a common model behaviour. We suggest approaching the problem from the perspective of community-level patterns. We offer a prototype for building coexistence into NPZ models. The model allows for diverse assemblages of phytoplankton or zooplankton groups to persist and produces accurate community-level patterns. The approach is simple, adding only one additional parameter, and allows us to test the effects of trait distributions and environmental variables on diversity. [ABSTRACT FROM PUBLISHER]

North American Atlantic salmon ( Salmo salar) populations experienced substantial declines in the early 1990s, and many populations have persisted at low abundances in recent years. Abundance and productivity declined in a coherent manner across major regions of North America, and this coherence points toward a potential shift in marine survivorship, rather than local, river-specific factors. The major declines in Atlantic salmon populations occurred against a backdrop of physical and biological shifts in Northwest Atlantic ecosystems. Analyses of changes in climate, physical, and lower trophic level biological factors provide substantial evidence that climate conditions directly and indirectly influence the abundance and productivity of North American Atlantic salmon populations. A major decline in salmon abundance after 1990 was preceded by a series of changes across multiple levels of the ecosystem, and a subsequent population change in 1997, primarily related to salmon productivity, followed an unusually low NAO event. Pairwise correlations further demonstrate that climate and physical conditions are associated with changes in plankton communities and prey availability, which are ultimately linked to Atlantic salmon populations. Results suggest that poor trophic conditions, likely due to climate-driven environmental factors, and warmer ocean temperatures throughout their marine habitat area are constraining the productivity and recovery of North American Atlantic salmon populations. [ABSTRACT FROM AUTHOR]

The article discusses issues related to fisheries management in relation to the problem of climatic change. It describes the temperature in the Northwest Atlantic. It examines the ecological and economic impacts of the gradual warming of the ocean. It also mentions the need for climate adaptation planning within fisheries management as revealed by the impacts of the 2012 ocean heat wave.

Changes in marine plankton communities driven by environmental variability impact the marine food web and global biogeochemical cycles of carbon and other elements. To predict and assess these community shifts and their consequences, ecologists are increasingly investigating how the functional traits of plankton determine their relative fitness along environmental and biological gradients. Laboratory, field and modelling studies are adopting this trait-based approach to map the biogeography of plankton traits that underlies variations in plankton communities. Here, we review progress towards understanding the regulatory roles of several key plankton functional traits, including cell size, N2-fixation and mixotrophy among phytoplankton, and body size, ontogeny and feeding behaviour for zooplankton. The trait biogeographical approach sheds light on what structures plankton communities in the current ocean, as well as under climate change scenarios, and also allows for finer resolution of community function because community trait composition determines the rates of significant processes, including carbon export. Although understanding of trait biogeography is growing, uncertainties remain that stem, in part, from the paucity of observations describing plankton functional traits. Thus, in addition to recommending widespread adoption of the trait-based approach, we advocate for enhanced collection, standardisation and dissemination of plankton functional trait data. [ABSTRACT FROM AUTHOR]

Time series of American lobster ( Homarus americanus) postlarval settlement from southern New England to Atlantic Canada exhibit many common features, and a cluster analysis indicates a block of regions extending from Massachusetts to Maine that have coherent interannual variations. The spatial scale of this block suggests that variability in settlement is related to large-scale, rather than local, processes. We examined the association between settlement at six reference regions and monthly mean atmospheric conditions (temperature, geopotential height, westerly and southerly wind components, and wind curl) from the North American Regional Reanalysis. We first extracted the dominant modes of variability in monthly averaged geopotential height, temperature, and wind curl. The leading mode from September, which represents high geopotential height, warm temperatures, and negative wind curl throughout the study area, was strongly correlated with settlement at most of the regions. The third mode from August, which represents enhanced southwesterly winds, was correlated with settlement in Rhode Island. Correlations between local atmospheric conditions and lobster settlement confirm the principal component results. Settlement was correlated to varying degrees with geopotential height (positive), temperature (positive) and wind curl (negative) with lobster settlement at the northern sites, with temperature being a stronger indicator in the north and curl a stronger indicator in the south. Rhode Island settlement was strongly correlated with August westerly winds. The correlation between settlement and atmospheric conditions could improve our understanding of stock-recruit relationships for lobster populations and provides one mechanism for how climate change could impact lobsters. [ABSTRACT FROM AUTHOR]

Fish contribute to the export of carbon out of the euphotic zone. They ingest organic carbon fixed by phytoplankton, store it in their tissues for their lifetime, and contribute to long‐term sequestration by producing sinking fecal pellets, respiring at depth, or via their own sinking carcasses. While the flux of carbon through fish is small relative to the export flux by plankton, humans have a direct influence on fish communities and thus on the magnitude of carbon storage and flux. We use a size spectrum model to examine the combined effect of fishing and trophic dynamics on the total carbon stored as biomass of a simulated community of fish. By sampling 10,500 possible fishing strategies that randomize fishing mortality and size‐selectivity, we consider optimal strategies that balance several UN Sustainable Development Goals addressing (1) food security, (2) climate action, and (3) marine conservation. The model shows that fishery management strategies that preferentially conserve large species increase overall carbon stored in the fish community. This study presents a perspective for considering carbon storage and sequestration in fisheries management alongside alternative objectives such as food production and biodiversity conservation. Our study focused on the state (total carbon in the living community). Incorporating rate processes like fecal pellet flux, vertical migration, and natural mortality would build toward a more holistic carbon approach to fisheries management. [ABSTRACT FROM AUTHOR]

Maps, F., Pershing, A. J., and Record, N. R. 2012. A generalized approach for simulating growth and development in diverse marine copepod species. – ICES Journal of Marine Science, 69: 370–379.Predicting ecological changes under climate change requires mechanistic descriptions of the impact of environmental conditions on the physiology, life history, and population dynamics of target species. A generic framework has been developed to simulate the growth and development of copepods, a critical link in pelagic ecosystems that connects environmental variability and changes in primary production with higher trophic levels. The modelled copepods, referred to as “compupods”, are described by their body mass and developmental stage. The dynamics of the compupods are determined by three core equations: universal temperature-dependence, Holling's type II ingestion, and allometric scaling. This general framework was applied to four copepod taxa: Pseudocalanus newmani, Calanus finmarchicus, C. glacialis, and C. hyperboreus, spanning a wide range of body sizes. A genetic algorithm procedure was used to estimate the unknown parameters required to produce a good fit to observed species-specific growth and development data. The performance of the model was evaluated by comparing the influence of food and temperature on ingestion, gut clearance, and egg production rates with published relationships. Simulations of the four species suggest that small changes in the trade-off between growth and development are responsible for the interspecific diversity observed. [ABSTRACT FROM PUBLISHER]

Continuous plankton recorders (CPRs) have been used in the Northwest Atlantic for almost 50 years. While data collected by these surveys have provided valuable information on long-term variability in plankton populations, all previous analyses have been limited to only a portion of the geographic range of the available data. Here we present an analysis of the CPR data from the Mid Atlantic Bight to the Labrador Sea. Across this wide geographic range, we found many common associations among the taxa. In particular, the changes in most regions were strongly size structured, with small and medium copepods varying together and often positively related to indicators of phytoplankton abundance. The time series from nearby regions were strongly correlated; however, after 1990, the spatial pattern became more complex. During this period, several of the copepod taxa, noticeably Calanus finmarchicus and Centropages typicus, experienced a series of anomalies that appeared to propagate from northeast to southwest. Although the direction of propagation was consistent with the shelf circulation, the anomalies propagated at a rate much slower than typical current speeds. The timing of the copepod anomalies and their phase speed were similar in character to observed changes in salinity and the position of the Shelf Slope Front. The correspondence between the changes in the plankton community and changes in the physical environmental suggests that physical conditions are a strong driver of interannual variability in Northwest Atlantic Shelf ecosystems. [ABSTRACT FROM PUBLISHER]

Studies relating biodiversity to ecosystem processes typically do not take into account changes in biodiversity through time. Marine systems are highly dynamic, with biodiversity changing at diel, seasonal and inter-decadal timescales. We examined the dynamics of biodiversity in the Gulf of Maine pelagic zooplankton community. Taxonomic data came from the Gulf of Maine continuous plankton recorder (CPR) transect, spanning the years 1961–2006. The CPR transect also contains coincident information on temperature and phytoplankton biomass (measured by the phytoplankton color index). Taxonomic richness varied at all timescales considered. The relationships between temperature and richness, and between phytoplankton and richness, also depended on temporal scale. The temperature–richness relationship was monotonic at the multi-decadal scale, and tended to be hump-shaped at finer scales; the productivity–richness relationship was hump-shaped at the multi-decadal scale, and tended to be monotonic at finer scales. Seasonal biodiversity dynamics were linked to temperature; inter-decadal biodiversity dynamics were linked to phytoplankton. [ABSTRACT FROM PUBLISHER]

Background: Humans have reduced the abundance of many large marine vertebrates, including whales, large fish, and sharks, to only a small percentage of their pre-exploitation levels. Industrial fishing and whaling also tended to preferentially harvest the largest species and largest individuals within a population. We consider the consequences of removing these animals on the ocean's ability to store carbon. Methodology/Principal Findings: Because body size is critical to our arguments, our analysis focuses on populations of baleen whales. Using reconstructions of pre-whaling and modern abundances, we consider the impact of whaling on the amount of carbon stored in living whales and on the amount of carbon exported to the deep sea by sinking whale carcasses. Populations of large baleen whales now store 9.1×106 tons less carbon than before whaling. Some of the lost storage has been offset by increases in smaller competitors; however, due to the relative metabolic efficiency of larger organisms, a shift toward smaller animals could decrease the total community biomass by 30% or more. Because of their large size and few predators, whales and other large marine vertebrates can efficiently export carbon from the surface waters to the deep sea.We estimate that rebuilding whale populations would remove 1.6×105 tons of carbon each year through sinking whale carcasses. Conclusions/Significance: Even though fish and whales are only a small portion of the ocean's overall biomass, fishing and whaling have altered the ocean's ability to store and sequester carbon. Although these changes are small relative to the total ocean carbon sink, rebuilding populations of fish and whales would be comparable to other carbon management schemes, including ocean iron fertilization. [ABSTRACT FROM AUTHOR]

Arctic climate change from the Paleocene epoch to the present is reconstructed with the objective of assessing its recent and future impacts on the ecology of the North Atlantic. A recurring theme in Earth's paleoclimate record is the importance of the Arctic atmosphere, ocean, and cryosphere in regulating global climate on a variety of spatial and temporal scales. A second recurring theme in this record is the importance of freshwater export from the Arctic in regulating global- to basin-scale ocean circulation patterns and climate. Since the 1970s, historically unprecedented changes have been observed in the Arctic as climate warming has increased precipitation, river discharge, and glacial as well as sea-ice melting. In addition, modal shifts in the atmosphere have altered Arctic Ocean circulation patterns and the export of freshwater into the North Atlantic. The combination of these processes has resulted in variable patterns of freshwater export from the Arctic Ocean and the emergence of salinity anomalies that have periodically freshened waters in the North Atlantic. Since the early l990s, changes in Arctic Ocean circulation patterns and freshwater export have been associated with two types of ecological responses in the North Atlantic. The first of these responses has been an ongoing series of biogeographic range expansions by boreal plankton, including renewal of the trans-Arctic exchanges of Pacific species with the Atlantic. The second response was a dramatic regime shift in the shelf ecosystems of the Northwest Atlantic that occurred during the early 1990s. This regime shift resulted from freshening and stratification of the shelf waters, which in turn could be linked to changes in the abundances and seasonal cycles of phytoplankton, zooplankton, and higher trophic-level consumer populations. It is predicted that the recently observed ecological responses to Arctic climate change in the North Atlantic will continue into the near future if current trends in sea ice, freshwater export, and surface ocean salinity continue. It is more difficult to predict ecological responses to abrupt climate change in the more distant future as tipping points in the Earth's climate system are exceeded. [ABSTRACT FROM AUTHOR]

We used principal component analysis (PCA) to explore interannual changes in a time-series lasting more than 40 years of zooplankton abundance from NOAA''s Continuous Plankton Recorder (CPR) survey. This analysis identified a complex of taxa, including Centropages typicus, Oithona spp., Pseudocalanus spp., and Metridia lucens that followed a common pattern of interdecadal variability characterized by a dramatic increase in these taxa around 1990, followed by a rapid decline in 2002. All of these taxa showed a large proportional increase in winter abundance between the 1980s and 1990s. These changes could be driven by increased primary productivity during winter, caused by a large-scale freshening of the Northwest Atlantic Shelf. In addition to the “community shift” mode, the analysis found a strong mode of interannual variability attributed to previously described changes in the abundance of late-stage Calanus finmarchicus. To explore the impact of these modes on higher trophic levels, we correlated the zooplankton modes with recruitment time-series from 12 fish stocks from the Gulf of Maine region. Several significant correlations were found, suggesting that the changes in the zooplankton modes may reflect broad changes in the Gulf of Maine ecosystem. [Copyright &y& Elsevier]

Predicts the flip-side of the North Atlantic Oscillation (NAO) and modal shifts in slope-water circulation patterns. Maximum and minimum modal states of the coupled slope water system; Analysis of the NAO index; Observed and predicted time series of the regional slope water temperature index.

Presents a study which described a physical process that occurs in the Georges Bank region. Simulations of particle distributions within idealized circulation cells; Effect of the circulation cells on the ecology of the Georges Bank region; Conclusion.

Record, N. R., Pershing, A. J. and Maps, F. 2014. Plankton post-paradox. – ICES Journal of Marine Science, 71: 296–298.Classical theoretical ecology has largely focused on the coexistence of populations at the species level, particularly since the coining of the “paradox of the plankton”. The known mechanisms for coexistence, both mathematically and in nature, are myriad and diverse. Building on a dialogue in this journal (Cropp, R., and Norbury, J. 2014. Comment on “The paradox of the ‘paradox of the plankton’” by Record et al. ICES Journal of Marine Science; Record, N. R., Pershing, A. J., and Maps, F. 2014. The paradox of ‘the paradox of the plankton’. ICES Journal of Marine Science, 71: 235–239.), we outline a perspective whereby approaching the problem from a different organizational level—namely the community level—can offer valuable simplifications and insights. We expand on a prototype model that demonstrates the potential of this approach. [ABSTRACT FROM PUBLISHER]

Ocean waters of the Northeast US continental shelf have warmed rapidly in recent years, with sea surface temperatures rising 2.5 times faster than those of the global oceans. With this strong warming trend, the frequency and duration of marine heatwaves have increased. These temperature changes stood out as a distinct warm temperature regime during the 2010s. During this decade, fish population characteristics also differed from the past. Species distribution shifts were detected for many species, demonstrating one way species could adapt to warming conditions. However, for most species, distribution shifts were insufficient to avoid warmer surface or bottom temperatures. As species occupied warmer habitats, growth patterns aligned with expectations for warming temperatures. Consistent with the temperature-size rule, some species exhibited faster growth at early life stages but plateaued at smaller body sizes; other species, however, experienced reduced growth across all ages, indicating thermal stress. Finally, population productivity indexed by the recruit-to-spawner ratio declined significantly during the 2010s for some populations. Changes in these three processes—distribution, growth, and productivity—indicate the emergence of climate change signals across multiple Northeast US fish populations. These effects create new challenges for fishery managers and industry participants operating in the context of non-stationarity and uncertainty. [ABSTRACT FROM AUTHOR]

Palmer et al. and Swain et al. suggest that our "extra mortality" time series is spurious. In response, we show that including temperature-dependent mortality improves abundance estimates and that warming waters reduce growth rates in Gulf of Maine cod. Far from being spurious, temperature effects on this stock are clear, and continuing to ignore them puts the stock in jeopardy. [ABSTRACT FROM AUTHOR]

The article explains the reason of the sudden changes of the climate in the year 1990 in the northwest Atlantic. It states that these changes resulted from the outflow of low-salinity waters from the Arctic and freshening of shelf water from the Labrador Sea to the Mid-Atlantic Bight. This freshening altered circulation and stratification on the shelf and tremendous changes in the abundances and seasonal cycles of phytoplankton, zooplankton, and fish populations. Thus, two years after, atmospheric pressure at the sea surface began to decline.

The great whales (baleen and sperm whales), through their massive size and wide distribution, influence ecosystem and carbon dynamics. Whales directly store carbon in their biomass and contribute to carbon export through sinking carcasses. Whale excreta may stimulate phytoplankton growth and capture atmospheric CO 2 ; such indirect pathways represent the greatest potential for whale-carbon sequestration but are poorly understood. We quantify the carbon values of whales while recognizing the numerous ecosystem, cultural, and moral motivations to protect them. We also propose a framework to quantify the economic value of whale carbon as populations change over time. Finally, we suggest research to address key unknowns (e.g., bioavailability of whale-derived nutrients to phytoplankton, species- and region-specific variability in whale carbon contributions). As climate change accelerates, there is increasing interest in the ability of whales to trap carbon (i.e., whale carbon), yet it is currently undetermined if and how whale carbon should be used in climate-change mitigation strategies. Restoring whale populations will enhance carbon storage in whale biomass and sequestration in the deep sea via whale falls, though the global impact will be relatively small. Whale-stimulated primary productivity via nutrient provisioning may sequester substantially more carbon, though there is uncertainty regarding the carbon fate in these food webs. Recovery of whale populations via reduction of anthropogenic impacts can aid in carbon dioxide removal but its inclusion in climate policy needs to be grounded in the best available science and considered in tandem with other strategies known to directly reduce greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

Ostensibly separate fisheries are often linked through ecological, environmental, and human mediated processes that can impact their productivity, profitability, and resilience; however, managers rarely explicitly account for these linkages. We present a coupled bioeconomic model of the American lobster ( Homarus americanus) and Atlantic herring ( Clupea harengus) fisheries in the northeast United States. The model builds upon existing stock assessment models and includes key characteristics of both fisheries including size- or age-structured populations, seasonal patterns of lobster exploitation, and seasonal-spatial patterns of herring exploitation. The lobster and herring models are linked through a bait market module that drives behavior of the herring fleet and affects catches, costs, and revenues in both fisheries. The model illustrates how changes in management or ecosystem conditions in one fishery can propagate to another. The model suggests that the lobster fishery is robust to declines in herring recruitment and limited changes in the spatial allocation of the herring total allowable catch. However, herring catches and stocks are affected by changes in lobster management that impact effort levels. [ABSTRACT FROM AUTHOR]

Dormancy (diapause) is a key life-history strategy of pelagic copepods that allows them to thrive in highly seasonal environments. Successful dormancy of copepodid stages requires the ability to store energy efficiently (for example as lipids) and to slow down the rate of mobilization of this capital during the dormant period. The physiology of lipids in copepods has been extensively reviewed; however, data about the energetics of dormancy are currently scattered throughout the literature. Thus, we conducted a meta-analysis comparing the metabolism of active and dormant copepods in 15 species that undergo dormancy as copepodids. Linear mixed-effects models showed that the metabolic rate of dormant copepods is about one-fourth of the values for actively growing copepods, a level that remains consistent across a large range of body size or environmental conditions. Based on these metabolic rates, we used a numerical modelling approach to predict dormancy duration as a function of body mass and ambient temperature, and to explain the observed range of body masses at the initiation of dormancy. Our numerical approach also provides explanations for inter- and intra-specific variability in life-history strategies, such as which stages undergo dormancy and the prevalence of lipid-based reproduction in some copepod species. [ABSTRACT FROM PUBLISHER]

Species distribution shifts are a widely reported biological consequence of climate-driven warming across marine ecosystems, creating ecological and social challenges. To meet these challenges and inform management decisions, we need accurate projections of species distributions. Quantitative species distribution models (SDMs) are routinely used to make these projections, while qualitative climate change vulnerability assessments are becoming more common. We constructed SDMs, compared SDM projections to expectations from a qualitative expert climate change vulnerability assessment, and developed a novel approach for combining the two methods to project the distribution and relative biomass of 49 marine species in the Northeast Shelf Large Marine Ecosystem under a "business as usual" climate change scenario. A forecasting experiment using SDMs highlighted their ability to capture relative biomass patterns fairly well (mean Pearson's correlation coefficient between predicted and observed biomass = 0.24, range = 0–0.6) and pointed to areas needing improvement, including reducing prediction error and better capturing fine-scale spatial variability. SDM projections suggest the region will undergo considerable biological changes, especially in the Gulf of Maine, where commercially-important groundfish and traditional forage species are expected to decline as coastal fish species and warmer-water forage species historically found in the southern New England/Mid-Atlantic Bight area increase. The SDM projections only occasionally aligned with vulnerability assessment expectations, with agreement more common for species with adult mobility and population growth rates that showed low sensitivity to climate change. Although our blended approach tried to build from the strengths of each method, it had no noticeable improvement in predictive ability over SDMs. This work rigorously evaluates the predictive ability of SDMs, quantifies expected species distribution shifts under future climate conditions, and tests a new approach for integrating SDMs and vulnerability assessments to help address the complex challenges arising from climate-driven species distribution shifts. [ABSTRACT FROM AUTHOR]

Forecasts of marine environmental and ecosystem conditions are now possible at a range of time scales, from nowcasts to forecasts over seasonal and longer time frames. Delivery of these products offers resource managers and users relevant insight into ecosystem patterns and future conditions to support decisions these stakeholders face associated with a range of objectives. The pace of progress in forecast development is so rapid that the scientific community may not be considering fully the impacts on stakeholders and their incentives. Delivery of information, particularly about future conditions and the uncertainties associated with it, involves a range of judgements, or "ethical" considerations, including treatment of forecast failure, inequity in stakeholder response options, and winners and losers in commercial markets. Here, we explore these often unanticipated considerations via a set of case studies spanning commercial fishing, recreational fishing, aquaculture, and conservation applications. We suggest that consideration of ethical issues by scientists and their research partners is needed to maintain scientific integrity and fairness to end users. Based on these case studies and our experience, we suggest a set of ten principles that might be considered by developers and users of ecological forecasts to avoid these ethical pitfalls. Overall, an interdisciplinary approach, and co-production with end users will provide insurance against many unanticipated consequences. [ABSTRACT FROM AUTHOR]

As climate trends accelerate, ecosystems will be pushed rapidly into new states, reducing the potential efficacy of conservation strategies based on historical patterns. In the Gulf of Maine, climate-driven changes have restructured the ecosystem rapidly over the past decade. Changes in the Atlantic meridional overturning circulation have altered deepwater dynamics, driving warming rates twice as high as the fastest surface rates. This has had implications for the copepod Calanus finmarchicus, a critical food supply for the endangered North Atlantic right whale (Eubalaena glacialis). The oceanographic changes have driven a deviation in the seasonal foraging patterns of E. glacialis upon which conservation strategies depend, making the whales more vulnerable to ship strikes and gear entanglements. The effects of rapid climate-driven changes on a species at risk undermine current management approaches. [ABSTRACT FROM AUTHOR]

Despite widespread interest in describing and forecasting the impacts of climate change on species distributions, poor understanding of the climate variables that shape distributions and conflicting perspectives on the role that species traits play in mediating shifts have limited our ability to interpret and project changes in species distributions. Using standardized survey data along the northeast US continental shelf, we assessed the historical exposure and sensitivity of 81 species of marine chordates, arthropods, and molluscs to 24 sea surface temperature (SST) variables in two seasons. By comparing temperature trends in geographies available to species against temperature trends in geographies used by them we were able to identify which variables species track consistently through space and time. Logistic regression analyses were then used to assess whether species traits affected the likelihood of niche tracking while accounting for the season and temporal window in which temperatures were summarized and methodological constraints that might have limited our ability to detect tracking responses. A slight majority of species (52%) clearly shifted their distributions to track at least one temperature variable through space and time. Tracking rates were much lower on a per variable basis (5.1% of 3432 variables), despite widespread exposure to changing temperatures (89.2% of 3432 variables). None of the twelve ecological traits we investigated – including traits related to dispersal ability, ecological specialization, reproductive capacity, and commercial harvest – accounted for differences in tracking responses across species even after accounting for differences in climate exposure. Our results suggest widespread behavioral or physiological flexibility among our study species, or ongoing genetic adaptation to changing temperatures. They also suggest that divergent selection on climate sensitivities of close relatives may limit the utility of ecological traits for predicting distributional responses to future climate change. [ABSTRACT FROM AUTHOR]

Understanding how ocean conditions influence fish distributions is critical for elucidating the role of climate in ecosystem change and forecasting how fish may be distributed in the future. Traditional species distribution models are often applied to scientific‐survey data, which include species presence‐absence information, to predict distributions. Maximum entropy (MaxEnt) models are promising tools as they can be applied to presence‐only data (e.g., data collected from fishermen targeting a specific species or from observers in citizen‐science programs). We used MaxEnt models to relate occurrence records of three marine pelagic fish (Atlantic herring, Atlantic mackerel, and butterfish) in fishery‐dependent data to environmental conditions (sea surface temperature (SST) and chlorophyll‐a concentration from satellite remote sensing, bathymetry, and climate indices), and evaluated model performance by both cross‐validation and validation using fishery‐independent data. We developed monthly habitat suitability maps for these fish in the Northwest Atlantic Shelf area, and assessed the relative influence of environmental factors on their distributions. Across months, their suitable habitat areas varied with each species exhibiting inshore‐offshore and north‐south movements in response to changing environmental conditions. Overall, SST and chlorophyll‐a concentration had the greatest influence on the distributions of these fish, with bathymetry having moderate influence and climate indices having little influence. Our application of MaxEnt models enabled us to integrate presence‐only data and high resolution environmental data from satellite remote sensing to describe spatiotemporal distributions of marine pelagic fish. These models were used to hindcast species occurrence in relation to historical environmental conditions to evaluate their predictive performance, and have the potential to provide nowcasts in relation to current conditions or forecasts of species future distributions. [ABSTRACT FROM AUTHOR]

Managing natural resources in an era of increasing climate impacts requires accounting for the synergistic effects of climate, ecosystem changes, and harvesting on resource productivity. Coincident with recent exceptional warming of the northwest Atlantic Ocean and removal of large predatory fish, the American lobster has become the most valuable fishery resource in North America. Using a model that links ocean temperature, predator density, and fishing to population productivity, we show that harvester-driven conservation efforts to protect large lobsters prepared the Gulf of Maine lobster fishery to capitalize on favorable ecosystem conditions, resulting in the record-breaking landings recently observed in the region. In contrast, in the warmer southern New England region, the absence of similar conservation efforts precipitated warming-induced recruitment failure that led to the collapse of the fishery. Population projections under expected warming suggest that the American lobster fishery is vulnerable to future temperature increases, but continued efforts to preserve the stock's reproductive potential can dampen the negative impacts of warming. This study demonstrates that, even though global climate change is severely impacting marine ecosystems, widely adopted, proactive conservation measures can increase the resilience of commercial fisheries to climate change. [ABSTRACT FROM AUTHOR]

We describe a unique survey method that is able to cover a wide spatial and temporal range at a low cost. We utilised 10 individual small fishing vessels (lobster vessels) as acoustic research platforms to systematically survey a coastal population of Atlantic herring ( Clupea harengus) in the Gulf of Maine. We examined 38 transects spanning more than 200 miles of coastline. Due to the low cost of chartering the vessels, the survey was repeated weekly for nine weeks, resulting in over 2300 nautical miles of on-transect data. We calibrated single beam systems using a split beam guiding transducer to increase our confidence in the accuracy of the data and allow inter-ship comparisons. Although only one year of data has been analysed, the large spatial and temporal coverage of this survey provides preliminary information on herring population dynamics including spatial distribution throughout the survey area, timing of spawning and habitat associations of spawning aggregations. This survey will provide the template for longer term monitoring of herring spawning dynamics in Coastal Maine and how this may respond to climate and ocean variability. [ABSTRACT FROM AUTHOR]

Decadal-scale regime shifts in Northwest Atlantic shelf ecosystems can be remotely forced by climate-associated atmosphere--ocean interactions in the North Atlantic and Arctic Ocean Basins. This remote climate forcing is mediated primarily by basin- and hemispheric-scale changes in ocean circulation. We review and synthesize results from process-oriented field studies and retrospective analyses of time-series data to document the linkages between climate, ocean circulation, and ecosystem dynamics. Bottom-up forcing associated with climate plays a prominent role in the dynamics of these ecosystems, comparable in importance to that of top-down forcing associated with commercial fishing. A broad perspective, one encompassing the effects of basin- and hemispheric-scale climate processes on marine ecosystems, will be critical to the sustainable management of marine living resources in the Northwest Atlantic. [ABSTRACT FROM AUTHOR]

During recent decades, historically unprecedented changes have been observed in the Arctic as climate warming has increased precipitation, river discharge, and glacial as well as sea ice melting. Additionally, shifts in the Arctic's atmospheric pressure field have altered surface winds, ocean circulation, and freshwater storage in the Beaufort Gyre. These processes have resulted in variable patterns of freshwater export from the Arctic Ocean, including the emergence of great salinity anomalies propagating throughout the North Atlantic. Here, we link these variable patterns of freshwater export from the Arctic Ocean to the regime shifts observed in Northwest Atlantic shelf ecosystems. Specifically, we hypothesize that the corresponding salinity anomalies, both negative and positive, alter the timing and extent of water-column stratification, thereby impacting the production and seasonal cycles of phytoplankton, zooplankton, and higher-trophic-level consumers. Should this hypothesis hold up to critical evaluation, it has the potential to fundamentally alter our current understanding of the processes forcing the dynamics of Northwest Atlantic shelf ecosystems. [ABSTRACT FROM AUTHOR]

Calanus finmarchicus relies on dormancy to thrive in the seasonal environment of the boreal Atlantic. The lipid accumulation window (LAW) hypothesis proposes that a seasonal window of environmental conditions allows developing individuals to store enough lipids for dormancy to be safely initiated. Successful dormancy requires a sufficient amount of lipids to fulfil the reduced metabolic demand of the dormant individual and to sustain the final maturation process. We used a pattern-oriented modelling approach that implements the LAW hypothesis and employs a genetic algorithm for parameter estimation, in order to reproduce the observed phenology and demography of C. finmarchicus populations from the two contrasting regions, the Gulf of St. Lawrence (GSL) and the Gulf of Maine (GoM) in the northwest Atlantic shelf. In the GSL, the model reproduced the timing of dormancy, the abundance and individual condition of late copepodid stages. In the GoM, the model produced a semi-annual dormancy pattern, as no locally produced individual could last the 6–8 months of dormancy inferred from the available observations. Further testing requires extending demographic time series, including lipid condition of late copepodid stages in the GoM, and the implementation of a 3-D modelling framework that would explicitly address the complex interactions between circulation and population dynamics of C. finmarchicus over the entire northwest Atlantic shelf. [ABSTRACT FROM PUBLISHER]

Abstract: We put forward a combined observing and modeling strategy for evaluating effects of environmental forcing on the dynamics of spatially structured cod populations spawning in the western Gulf of Maine. Recent work indicates at least two genetically differentiated complexes in this region: a late spring spawning, coastal population centered in Ipswich Bay, and a population that spawns in winter inshore and on nearshore banks in the Gulf of Maine and off southern New England. The two populations likely differ in trophic interactions and in physiological and behavioral responses to different winter and spring environments. Coupled physical–biological modeling has advanced to the point where within-decade forecasting of environmental conditions for recruitment to each of the two populations is feasible. However, the modeling needs to be supported by hydrographic, primary production and zooplankton data collected by buoys, and by data from remote sensing and fixed station sampling. Forecasts of environmentally driven dispersal and growth of planktonic early life stages, combined with an understanding of possible population-specific predator fields, usage of coastal habitat by juveniles and adult resident and migratory patterns, can be used to develop scenarios for spatially explicit population responses to multiple forcings, including climate change, anthropogenic impacts on nearshore juvenile habitat, connectivity among populations and management interventions such as regional fisheries closures. [ABSTRACT FROM AUTHOR]

Energy variables, such as evapotranspiration, temperature, and productivity explain significant variation in the diversity of many groups of terrestrial plants and animals at local to global scales. Although the ocean represents the largest continuous habitat on earth with a vast spectrum of primary productivity and species richness, little is known about how productivity influences species diversity in marine systems. To search for general relationships between productivity and species richness in the ocean, we analyzed data from three different benthic marine ecosystems (epifaunal communities on subtidal rock walls, on navigation buoys in the Gulf of St. Lawrence, and Canadian Arctic macrobenthos) across local to continental spatial scales (<20 to >1000 km) using a standardized proxy for productivity, satellite-derived chlorophyll a. Theoretically, the form of the function between productivity and species richness is either monotonically increasing or decreasing, or curvilinear (hump- or U-shaped). We found three negative linear and three hump-shaped relationships between chlorophyll a and species richness out of 10 independent comparisons. Scale dependence was suggested by more prevalent diversity-productivity relationships at smaller (local, landscape) than larger (regional, continental) spatial scales. Differences in the form of the functions were more closely allied with community type than with scale, as negative linear functions were restricted to sessile epifauna while hump-shaped functions occurred in Arctic macrobenthos (mixed epifauna, infauna). In two of the data sets, (St. Lawrence epifauna and Arctic macrobenthos) significant effects of chlorophyll a co-varied with the effects of salinity, suggesting that environmental stress as well as productivity influences diversity in these marine systems. The co-varying effect of salinity may commonly arise in broad-scale studies of productivity and diversity in marine ecosystems when attempting to sample the largest range of productivity, often encompassing a coastal-oceanic gradient. [ABSTRACT FROM AUTHOR]

Climate change is a pervasive and growing global threat to biodiversity and ecosystems. Here, we present the most up-to-date assessment of climate change impacts on biodiversity, ecosystems, and ecosystem services in the U.S. and implications for natural resource management. We draw from the 4th National Climate Assessment to summarize observed and projected changes to ecosystems and biodiversity, explore linkages to important ecosystem services, and discuss associated challenges and opportunities for natural resource management. We find that species are responding to climate change through changes in morphology and behavior, phenology, and geographic range shifts, and these changes are mediated by plastic and evolutionary responses. Responses by species and populations, combined with direct effects of climate change on ecosystems (including more extreme events), are resulting in widespread changes in productivity, species interactions, vulnerability to biological invasions, and other emergent properties. Collectively, these impacts alter the benefits and services that natural ecosystems can provide to society. Although not all impacts are negative, even positive changes can require costly societal adjustments. Natural resource managers need proactive, flexible adaptation strategies that consider historical and future outlooks to minimize costs over the long term. Many organizations are beginning to explore these approaches, but implementation is not yet prevalent or systematic across the nation. • Climate change is affecting ecosystems at multiple scales. • Individual/species: changes in morphology and behavior, phenology, and range shifts observed • Ecosystems: shifts in productivity, species interactions, and emergent properties observed • Together, these changes are impacting ecosystem services and human well-being. • Natural resource managers need proactive, flexible approaches to deal with changes. [ABSTRACT FROM AUTHOR]