Climate-Ocean Variability and Ecosystem Response in the Northeast Pacific

Multiscale oscillations of the annual course of temperature affect the spawning events of rudd (Scardinus erythrophthalmus)

Identifying climate impacts on ecosystems and their components requires observing time series of sufficient length to ensure adequate statistical power and reasonable coverage of the historical range of variability inherent in the system. The complexity of the hierarchy of climate effects reflected in temporal patterns in time series creates a need to be accurately modeled. The life cycle phenomena of living organisms, including fish spawning, have the character of one-time or time-limited events in time. An approach to finding the relationship between continuous components of time dynamics of environment properties and life cycle events of living organisms was proposed. This approach allowed us to evaluate the role of temperature patterns in the phenology of spawning rudd (Scardinus erythrophthalmus Linnaeus, 1758) in the Dnipro River basin water bodies. The atmospheric temperature time series may be decomposed into the following components: trend, annual cycle, episodic component, harmonic component, extreme events, and noise. Systematically low water temperatures at the beginning of the spawning period were observed in the Protoka River system and the Obukhov floodplain, and systematically elevated temperatures were recorded in the Dnipro River. The annual temperature dynamics was shown to be presented as a composition of oscillatory processes of different scale levels. The sinusoidal trend was previously extracted from the temperature series data. The average annual temperature, amplitude, and phase shift were calculated on the basis of the sinusoidal regression model. The residuals of the sinusoidal trend were processed by means of redundancy analysis with variables derived from symmetric distance-based Moran’s eigenvector maps as explanatory predictors. A set of 104 orthogonal dbMEM variables was extracted from the annual time series. These temporal variables were divided into the broad-, medium-, and fine-scale components. The parameters of temperature dynamics and biotope type are able to explain 51–72% of variability of spawning event. The time of spawning in water bodies corresponds to the time of spawning start: the earlier spawning starts, the earlier it ends. The duration of the spawning season is influenced by the patterns of different scale levels, as well as the amplitude and shift of phases. In this case, the duration of spawning in all water bodies does not differ. Spawning temperature depends on medium- and fine-scale temperature patterns, but does not depend on the characteristics of the sinusoidal annual trend. The annual temperature variation has been shown to be such that it can be decomposed into a sinusoidal trend, patterns of a multiscale nature, and a random fraction. Over the time range studied, the trend of increasing mean annual temperature was not statistically significant for spawning events. The sinusoidal trend explains 78.3–87.6% of the temperature variations and depends on the mean annual temperature, the amplitude of temperature variations during the year, and the earlier or later seasons of the year. Amplitude and phase shift play a role in describing spawning phenology. The residuals of the sinusoidal trend have been explained using dbMEM variables. This variation was decomposed into large-scale, medium-scale, and small-scale components. Winter and spring temperature fluctuations prior to spawning initiation had the greatest effect on spawning. Water temperature determines the lower possible limit for the start of spawning, but the actual start of spawning is determined by the preceding temperature dynamics. The results of the study have implications for understanding the dynamics of fish populations and assessing the influence of environmental conditions on the harmonization of the various components of ecosystems.

Successful Long-Distance Breeding Range Expansion of a Top Marine Predator

Little is known about the effects of large-scale breeding range expansions on the ecology of top marine predators. We examined the effects of a recent range expansion on the breeding and foraging ecology of Laysan albatrosses (Phoebastria immutabilis). Laysan albatrosses expanded from historical breeding colonies in the Central Pacific Ocean to the Eastern Pacific Ocean around central Baja California, Mexico, leading to a 4,000-km shift from colonies located adjacent to the productive transition zone in the Central Pacific to colonies embedded within the eastern boundary current upwelling system of the Eastern Pacific California Current. We use electronic tagging and remote sensing data to examine the consequences of this range expansion on at-sea distribution, habitat use, foraging habitat characteristics, and foraging behavior at sea by comparing birds from historic and nascent colonies. We found the expansion resulted in distinct at-sea segregation and differential access to novel oceanographic habitats. Birds from the new Eastern Pacific colony on Guadalupe Island, Mexico have reduced ranges, foraging trip lengths and durations, and spend more time on the water compared to birds breeding in the Central Pacific on Tern Island, United States. Impacts of the range expansion to the post-breeding season were less pronounced where birds maintained some at-sea segregation but utilized similar habitat and environmental variables. These differences have likely benefited the Eastern Pacific colony which has significantly greater reproductive output and population growth rates. Laysan albatrosses have the plasticity to adapt to distinctly different oceanographic habitats and also provide insight on the potential consequences of range shifts to marine organisms.

Trophic ecology of yellowtail rockfish (Sebastes flavidus) during a marine heat wave off central California, USA

The yellowtail rockfish, Sebastes flavidus, is a widespread and abundant mesopredator in the California Current Large Marine Ecosystem. We utilized stomach content and stable isotope analyses to investigate the trophic ecology of this species at three sites off central California just before (August–October 2013) and during (August and October 2014) a marine heat wave. Sebastes flavidus largely consumed pelagic prey (zooplankton and micronekton). Diets were dominated by tunicates (salps and pyrosomes), pelagic crustaceans (euphausiids, hyperid amphipods, larval decapods), and fishes, with the relative contribution of these prey taxa varying spatially (sample location, longitude, depth) and temporally (year, month), based on complementary multivariate analyses. Prey-specific indices demonstrated that individual S. flavidus diet composition typically was dominated by one of these prey groups, and that prey switching occurred based on the relative availability of prey and their energetic importance. Stable isotope analysis of δ¹⁵N indicated that the S. flavidus populations sampled in 2014 had been feeding at an elevated trophic position and more variable prey spectrum relative to 2013, probably as a consequence of greater piscivory and the incorporation of temporal changes in diet composition. Because its opportunistic feeding behavior reflects the dynamism and heterogeneity of the pelagic forage preyscape, S. flavidus may be an important ecosystem indicator species. For example, the novel incorporation of pyrosomes as a large portion of the diet of S. flavidus during 2013–2014 directly related to the massive increase in pyrosome abundance in the California Current during the 2014 marine heat wave.

Oceanographic drivers of winter habitat use in Cassin's Auklets

Reduced prey abundance and severe weather can lead to a greater risk of mortality for seabirds during the non-breeding winter months. Resource patterns in some regions are shifting and becoming more variable in relation to past conditions, potentially further impacting survival and carryover to the breeding season. As animal tracking technologies and methods to analyze movement data have advanced, it has become increasingly feasible to draw fine-scale inference about how environmental variation affects foraging behavior and habitat use of seabirds during this critical period. Here, we used archival light-sensing tags to evaluate how interannual variation in oceanography affected the winter distribution of Cassin's Auklets from Southeast Farallon Island, California. Thirty-five out of 93 geolocators deployed from 2015 to 2017 were recovered and successfully recorded light-level data, from which geographic positions were estimated. Step-selection functions were applied to identify environmental covariates that best explained winter movement decisions and habitat use, revealing Cassin's Auklets dispersed farther from the colony during a winter with warm SST anomalies, but remained more centralized near the breeding colony during two average winters. Movement patterns were driven by avoidance of areas with higher sea surface temperatures and possible limits of dispersal from the breeding colony, and selection for areas with well-defined mesoscale fronts and cooler surface waters. Through multiple years of tagging and the application of step-selection functions, a robust and widely applied approach for analyzing animal movement in terrestrial species, we show how interannual differences in the movement patterns of a small seabird are driven by oceanographic variability across years. Understanding the winter habitat use of seabirds can help inform changes in population structure and measures of reproductive success, aiding managers in determining potential causes of breeding failures.

Regional processes are stronger determinants of rocky intertidal community dynamics than local biotic interactions

Understanding the relative roles of species interactions and environmental factors in structuring communities has historically focused on local scales where manipulative experiments are possible. However, recent interest in predicting the effects of climate change and species invasions has spurred increasing attention to processes occurring at larger spatial and temporal scales. The "meta-ecosystem" approach is an ideal framework for integrating processes operating at multiple scales as it explicitly considers the influence of local biotic interactions and regional flows of energy, materials, and organisms on community structure. Using a comparative-experimental design, we asked (1) what is the relative importance of local biotic interactions and oceanic processes in determining rocky intertidal community structure in the low zone within the Northern California Current System, and (2) what factors are most important in regulating this structure and why? We focused on functional group interactions between macrophytes and sessile invertebrates and their consumers (grazers, predators), how these varied across spatial scales, and with ocean-driven conditions (upwelling, temperature) and ecological subsidies (nutrients, phytoplankton, sessile invertebrate recruits). Experiments were conducted at 13 sites divided across four capes in Oregon and northern California. Results showed that biotic interactions were variable in space and time but overall, sessile invertebrates had no effect on macrophytes while macrophytes had weakly negative effects on sessile invertebrates. Consumers, particularly predators, also had weakly negative effects on both functional groups. Overall, we found that 40-49% of the variance in community structure at the local scale was explained by external factors (e.g., spatial scale, time, upwelling, temperature, ecological subsidies) vs. 19-39% explained by functional group interactions. When individual functional group interaction strengths were used, only 2-3% of the variation was explained by any one functional group while 28-54% of the variation was explained by external factors. We conclude that community structure in the low intertidal zone is driven primarily by external factors at the regional scale with local biotic interactions playing a secondary role.

Widespread shifts in the coastal biota of northern California during the 2014-2016 marine heatwaves

During 2014-2016, severe marine heatwaves in the northeast Pacific triggered well-documented disturbances including mass mortalities, harmful algal blooms, and declines in subtidal kelp beds. However, less attention has been directed towards understanding how changes in sea surface temperature (SST) and alongshore currents during this period influenced the geographic distribution of coastal taxa. Here, we examine these effects in northern California, USA, with a focus on the region between Point Reyes and Point Arena. This region represents an important biogeographic transition zone that lies <150 km north of Monterey Bay, California, where numerous southern species have historically reached their northern (poleward) range limits. We report substantial changes in geographic distributions and/or abundances across a diverse suite of 67 southern species, including an unprecedented number of poleward range extensions (37) and striking increases in the recruitment of owl limpets (Lottia gigantea) and volcano barnacles (Tetraclita rubescens). These ecological responses likely arose through the combined effects of extreme SST, periods of anomalous poleward flow, and the unusually long duration of heatwave events. Prolonged marine heatwaves and enhanced poleward dispersal may play an important role in longer-term shifts in the composition of coastal communities in northern California and other biogeographic transition zones.

Spatiotemporally explicit model averaging for forecasting of Alaskan groundfish catch

Fisheries management is dominated by the need to forecast catch and abundance of commercially and ecologically important species. The influence of spatial information and environmental factors on forecasting error is not often considered. I propose a forecasting method called spatiotemporally explicit model averaging (STEMA) to combine spatial and temporal information through model averaging. I examine the performance of STEMA against two popular forecasting models and a modern spatial prediction model: the autoregressive integrated moving averages with explanatory variables (ARIMAX) model, the Bayesian hierarchical model, and the varying coefficient model. I focus on applying the methods to four species of Alaskan groundfish for which catch data are available. My method reduces forecasting errors significantly for most of the tested models when compared to ARIMAX, Bayesian, and varying coefficient methods. I also consider the effect of sea surface temperature (SST) on the forecasting of catch, as multiple studies reveal a potential influence of water temperature on the survival and growth of juvenile groundfish. For most of the preferred models, inclusion of SST in the model improved forecasting of catch. It is advisable to consider both spatial information and relevant environmental factors in forecasting models to obtain more accurate projections of population abundance. The STEMA method is capable of accounting for spatial information in forecasting and can be applied to various types of data because of its flexible varying coefficient model structure. It is therefore a suitable forecasting method for application to many fields including ecology, epidemiology, and climatology.

A decade and a half of Pseudo-nitzschia spp. and domoic acid along the coast of southern California

Blooms of the marine diatom genus Pseudo-nitzschia that produce the neurotoxin domoic acid have been documented with regularity along the coast of southern California since 2003, with the occurrence of the toxin in shellfish tissue predating information on domoic acid in the particulate fraction in this region. Domoic acid concentrations in the phytoplankton inhabiting waters off southern California during 2003, 2006, 2007, 2011 and 2017 were comparable to some of the highest values that have been recorded in the literature. Blooms of Pseudo-nitzschia have exhibited strong seasonality, with toxin appearing predominantly in the spring. Year-to-year variability of particulate toxin has been considerable, and observations during 2003, 2006, 2007, 2011 and again in 2017 linked domoic acid in the diets of marine mammals and seabirds to mass mortality events among these animals. This work reviews information collected during the past 15 years documenting the phenology and magnitude of Pseudo-nitzschia abundances and domoic acid within the Southern California Bight. The general oceanographic factors leading to blooms of Pseudo-nitzschia and outbreaks of domoic acid in this region are clear, but subtle factors controlling spatial and interannual variability in bloom magnitude and toxin production remain elusive.

Hypoxia weakens mussel attachment by interrupting DOPA cross-linking during adhesive plaque curing

Marine mussels (Mytilus spp.) attach to a wide variety of surfaces underwater using a network of byssal threads, each tipped with a protein-based adhesive plaque that uses the surrounding seawater environment as a curing agent. Plaques undergo environmental post-processing, requiring a basic seawater pH be maintained for up to 8 days for the adhesive to strengthen completely. Given the sensitivity of plaques to local pH conditions long after deposition, we investigated the effect of other aspects of the seawater environment that are known to vary in nearshore habitats on plaque curing. The effect of seawater temperature, salinity and dissolved oxygen concentration were investigated using tensile testing, atomic force microscopy and amino acid compositional analysis. High temperature (30°C) and hyposalinity (1 PSU) had no effect on adhesion strength, while incubation in hypoxia (0.9 mg l-1) caused plaques to have a mottled coloration and prematurely peel from substrates, leading to a 51% decrease in adhesion strength. AFM imaging of the plaque cuticle found that plaques cured in hypoxia had regions of lower stiffness throughout, indicative of reductions in DOPA cross-linking between adhesive proteins. A better understanding of the dynamics of plaque curing could aid in the design of better synthetic adhesives, particularly in medicine where adhesion must take place within wet body cavities.

Periodic matrix models for seasonal dynamics of structured populations with application to a seabird population

For structured populations with an annual breeding season, life-stage interactions and behavioral tactics may occur on a faster time scale than that of population dynamics. Motivated by recent field studies of the effect of rising sea surface temperature (SST) on within-breeding-season behaviors in colonial seabirds, we formulate and analyze a general class of discrete-time matrix models designed to account for changes in behavioral tactics within the breeding season and their dynamic consequences at the population level across breeding seasons. As a specific example, we focus on egg cannibalism and the daily reproductive synchrony observed in seabirds. Using the model, we investigate circumstances under which these life history tactics can be beneficial or non-beneficial at the population level in light of the expected continued rise in SST. Using bifurcation theoretic techniques, we study the nature of non-extinction, seasonal cycles as a function of environmental resource availability as they are created upon destabilization of the extinction state. Of particular interest are backward bifurcations in that they typically create strong Allee effects in population models which, in turn, lead to the benefit of possible (initial condition dependent) survival in adverse environments. We find that positive density effects (component Allee effects) due to increased adult survival from cannibalism and the propensity of females to synchronize daily egg laying can produce a strong Allee effect due to a backward bifurcation.

Climate drivers and animal host use determine kelp performance over decadal scales in the kelp Pleurophycus gardneri (Laminariales, Phaeophyceae)

Primary producers respond to climate directly and indirectly due to effects on their consumers. In the temperate coastal ocean, the highly productive brown algae known as kelp have both strong climate and grazer linkages. We analyzed the demographic response of the kelp Pleurophycus gardneri over a 25-year span to determine the interaction between ocean climate indicators and invertebrate infestation rates. Pleurophycus hosts amphipod species that burrow in the stipe, increasing mortality. Although kelp performance is generally greater with more negative values of the Pacific Decadal Oscillation (PDO) and colder seawater temperatures, Pleurophycus showed the opposite pattern. When we compared the 1990s, a period of positive values for the PDO and warmer sea surface temperatures, with the following decade, a period characterized by negative PDO values, we documented a contradictory outcome for proxies of kelp fitness. In the 1990s, Pleurophycus unexpectedly showed greater longevity, faster growth, greater reproductive effort, and a trend toward decreased amphipod infestation compared with the 2006-2012 period. In contrast, the period from 2006 to 2012 showed opposite kelp performance patterns and with a trend toward greater amphipod infestation. Pleurophycus performance metrics suggest that some coastal primary producers will respond differently to climate drivers, particularly if they interact strongly with grazers.

"Canary Islands (NE Atlantic) as a biodiversity 'hotspot' of Gambierdiscus: Implications for future trends of ciguatera in the area"

In the present study the geographical distribution, abundance and composition of Gambierdiscus was described over a 600km longitudinal scale in the Canary Islands. Samples for cell counts, isolation and identification of Gambierdiscus were obtained from five islands (El Hierro, Tenerife, Gran Canaria, Fuerteventura and Lanzarote). Average densities of Gambierdiscus spp. between 0 and 2200cellsg^-1 blot dry weight of macrophyte were recorded. Morphological (light microscopy and SEM techniques) and molecular analyses (LSU and SSU rDNA sequencing of cultures and single cells from the field) of Gambierdiscus was performed. Five Gambierdiscus species (G. australes, G. caribaeus, G. carolinianus, G. excentricus and G. silvae), together with a new putative species (Gambierdiscus ribotype 3) were identified. These results suggest that some cases of CFP in the region could be associated with the accumulation of ciguatoxins in the marine food web acquired from local populations of Gambierdiscus. This unexpected high diversity of Gambierdiscus species in an area which a priori is not under risk of ciguatera, hints at an ancient settlement of Gambierdiscus populations, likely favored by warmer climate conditions in the Miocene Epoch (when oldest current Canary Islands were created), in contrast with cooler present ones. Currently, warming trends associated with climate change could contribute to extend favorable environmental conditions in the area for Gambierdiscus growth especially during winter months.

Interactive effects of temperature, food and skeletal mineralogy mediate biological responses to ocean acidification in a widely distributed bryozoan

Marine invertebrates with skeletons made of high-magnesium calcite may be especially susceptible to ocean acidification (OA) due to the elevated solubility of this form of calcium carbonate. However, skeletal composition can vary plastically within some species, and it is largely unknown how concurrent changes in multiple oceanographic parameters will interact to affect skeletal mineralogy, growth and vulnerability to future OA. We explored these interactive effects by culturing genetic clones of the bryozoan Jellyella tuberculata (formerly Membranipora tuberculata) under factorial combinations of dissolved carbon dioxide (CO₂), temperature and food concentrations. High CO₂ and cold temperature induced degeneration of zooids in colonies. However, colonies still maintained high growth efficiencies under these adverse conditions, indicating a compensatory trade-off whereby colonies degenerate more zooids under stress, redirecting energy to the growth and maintenance of new zooids. Low-food concentration and elevated temperatures also had interactive effects on skeletal mineralogy, resulting in skeletal calcite with higher concentrations of magnesium, which readily dissolved under high CO₂ For taxa that weakly regulate skeletal magnesium concentration, skeletal dissolution may be a more widespread phenomenon than is currently documented and is a growing concern as oceans continue to warm and acidify.

Persistence of trophic hotspots and relation to human impacts within an upwelling marine ecosystem

Human impacts (e.g., fishing, pollution, and shipping) on pelagic ecosystems are increasing, causing concerns about stresses on marine food webs. Maintaining predator-prey relationships through protection of pelagic hotspots is crucial for conservation and management of living marine resources. Biotic components of pelagic, plankton-based, ecosystems exhibit high variability in abundance in time and space (i.e., extreme patchiness), requiring investigation of persistence of abundance across trophic levels to resolve trophic hotspots. Using a 26-yr record of indicators for primary production, secondary (zooplankton and larval fish), and tertiary (seabirds) consumers, we show distributions of trophic hotspots in the southern California Current Ecosystem result from interactions between a strong upwelling center and a productive retention zone with enhanced nutrients, which concentrate prey and predators across multiple trophic levels. Trophic hotspots also overlap with human impacts, including fisheries extraction of coastal pelagic and groundfish species, as well as intense commercial shipping traffic. Spatial overlap of trophic hotspots with fisheries and shipping increases vulnerability of the ecosystem to localized depletion of forage fish, ship strikes on marine mammals, and pollution. This study represents a critical step toward resolving pelagic areas of high conservation interest for planktonic ecosystems and may serve as a model for other ocean regions where ecosystem-based management and marine spatial planning of pelagic ecosystems is warranted.

Contrasting Responses to Harvesting and Environmental Drivers of Fast and Slow Life History Species

According to their main life history traits, organisms can be arranged in a continuum from fast (species with small body size, short lifespan and high fecundity) to slow (species with opposite characteristics). Life history determines the responses of organisms to natural and anthropogenic factors, as slow species are expected to be more sensitive than fast species to perturbations. Owing to their contrasting traits, cephalopods and elasmobranchs are typical examples of fast and slow strategies, respectively. We investigated the responses of these two contrasting strategies to fishing exploitation and environmental conditions (temperature, productivity and depth) using generalized additive models. Our results confirmed the foreseen contrasting responses of cephalopods and elasmobranchs to natural (environment) and anthropogenic (harvesting) influences. Even though a priori foreseen, we did expect neither the clear-cut differential responses between groups nor the homogeneous sensitivity to the same factors within the two taxonomic groups. Apart from depth, which affected both groups equally, cephalopods and elasmobranchs were exclusively affected by environmental conditions and fishing exploitation, respectively. Owing to its short, annual cycle, cephalopods do not have overlapping generations and consequently lack the buffering effects conferred by different age classes observed in multi-aged species such as elasmobranchs. We suggest that cephalopods are sensitive to short-term perturbations, such as seasonal environmental changes, because they lack this buffering effect but they are in turn not influenced by continuous, long-term moderate disturbances such as fishing because of its high population growth and turnover. The contrary would apply to elasmobranchs, whose multi-aged population structure would buffer the seasonal environmental effects, but they would display strong responses to uninterrupted harvesting due to its low population resilience. Besides providing empirical evidence to the theoretically predicted contrasting responses of cephalopods and elasmobranchs to disturbances, our results are useful for the sustainable exploitation of these resources.

Spatial Distribution and Temporal Patterns of Cassin's Auklet Foraging and Their Euphausiid Prey in a Variable Ocean Environment

Krill (Euphausiids) play a vital ecosystem role in many of the world’s most productive marine regions, providing an important trophic linkage. We introduce a robust modeling approach to link Cassin’s auklet (Ptychoramphus aleuticus) abundance and distribution to large-scale and local oceanic and atmospheric conditions and relate these patterns to similarly modeled distributions of an important prey resource, krill. We carried out at-sea strip transect bird surveys and hydroacoustic assessments of euphausiids (2004–2013). Data informed separate, spatially-explicit predictive models of Cassin’s auklet abundance (zero-inflated negative binomial regression) and krill biomass (two-part model) based on these surveys. We established the type of prey responsible for acoustic backscatter by conducting net tows of the upper 50 m during surveys. We determined the types of prey fed to Cassin’s auklet chicks by collecting diet samples from provisioning adults. Using time-depth-recorders, we found Cassin’s auklets utilized consistent areas in the upper water column, less than 30 m, where krill could be found (99.5% of dives were less than 30 m). Birds primarily preyed upon two species of euphausiids, Euphausia pacifica and Thysanoessa spinifera, which were available in the upper water column. Cassin’s auklet abundance was best predicted by both large scale and localized oceanic processes (upwelling) while krill biomass was best predicted by local factors (temperature, salinity, and fluorescence) and both large scale and localized oceanic processes (upwelling). Models predicted varying krill and bird distribution by month and year. Our work informs the use of Cassin’s auklet as a valuable indicator or krill abundance and distribution and strengthens our understanding of the link between Cassin’s auklet and its primary prey. We expect future increases in frequency and magnitude of anomalous ocean conditions will result in decreased availability of krill leading to declines in the Farallon Islands population of Cassin’s auklets.

Evidence of climate-driven ecosystem reorganization in the Gulf of Mexico

The Gulf of Mexico is one of the most ecologically and economically valuable marine ecosystems in the world and is affected by a variety of natural and anthropogenic phenomena including climate, hurricanes, coastal development, agricultural runoff, oil spills, and fishing. These complex and interacting stressors, together with the highly dynamic nature of this ecosystem, present challenges for the effective management of its resources. We analyze a compilation of over 100 indicators representing physical, biological, and economic aspects of the Gulf of Mexico and find that an ecosystem-wide reorganization occurred in the mid-1990s. Further analysis of fishery landings composition data indicates a major shift in the late 1970s coincident with the advent of US national fisheries management policy, as well as significant shifts in the mid-1960s and the mid-1990s. These latter shifts are aligned temporally with changes in a major climate mode in the Atlantic Ocean: the Atlantic Multidecadal Oscillation (AMO). We provide an explanation for how the AMO may drive physical changes in the Gulf of Mexico, thus altering higher-level ecosystem dynamics. The hypotheses presented here should provide focus for further targeted studies, particularly in regard to whether and how management should adjust to different climate regimes or states of nature. Our study highlights the challenges in understanding the effects of climatic drivers against a background of multiple anthropogenic pressures, particularly in a system where these forces interact in complex and nonlinear ways.

Slow science: the value of long ocean biogeochemistry records

Sustained observations (SOs) have provided invaluable information on the ocean's biology and biogeochemistry for over 50 years. They continue to play a vital role in elucidating the functioning of the marine ecosystem, particularly in the light of ongoing climate change. Repeated, consistent observations have provided the opportunity to resolve temporal and/or spatial variability in ocean biogeochemistry, which has driven exploration of the factors controlling biological parameters and processes. Here, I highlight some of the key breakthroughs in biological oceanography that have been enabled by SOs, which include areas such as trophic dynamics, understanding variability, improved biogeochemical models and the role of ocean biology in the global carbon cycle. In the near future, SOs are poised to make progress on several fronts, including detecting climate change effects on ocean biogeochemistry, high-resolution observations of physical-biological interactions and greater observational capability in both the mesopelagic zone and harsh environments, such as the Arctic. We are now entering a new era for biological SOs, one in which our motivations have evolved from the need to acquire basic understanding of the ocean's state and variability, to a need to understand ocean biogeochemistry in the context of increasing pressure in the form of climate change, overfishing and eutrophication.

Climate change. Climate change and wind intensification in coastal upwelling ecosystems

In 1990, Andrew Bakun proposed that increasing greenhouse gas concentrations would force intensification of upwelling-favorable winds in eastern boundary current systems that contribute substantial services to society. Because there is considerable disagreement about whether contemporary wind trends support Bakun's hypothesis, we performed a meta-analysis of the literature on upwelling-favorable wind intensification. The preponderance of published analyses suggests that winds have intensified in the California, Benguela, and Humboldt upwelling systems and weakened in the Iberian system over time scales ranging up to 60 years; wind change is equivocal in the Canary system. Stronger intensification signals are observed at higher latitudes, consistent with the warming pattern associated with climate change. Overall, reported changes in coastal winds, although subtle and spatially variable, support Bakun's hypothesis of upwelling intensification in eastern boundary current systems.

Coral luminescence identifies the Pacific Decadal Oscillation as a primary driver of river runoff variability impacting the southern Great Barrier Reef

The Pacific Decadal Oscillation (PDO) is a large-scale climatic phenomenon modulating ocean-atmosphere variability on decadal time scales. While precipitation and river flow variability in the Great Barrier Reef (GBR) catchments are sensitive to PDO phases, the extent to which the PDO influences coral reefs is poorly understood. Here, six Porites coral cores were used to produce a composite record of coral luminescence variability (runoff proxy) and identify drivers of terrestrial influence on the Keppel reefs, southern GBR. We found that coral skeletal luminescence effectively captured seasonal, inter-annual and decadal variability of river discharge and rainfall from the Fitzroy River catchment. Most importantly, although the influence of El Niño-Southern Oscillation (ENSO) events was evident in the luminescence records, the variability in the coral luminescence composite record was significantly explained by the PDO. Negative luminescence anomalies (reduced runoff) were associated with El Niño years during positive PDO phases while positive luminescence anomalies (increased runoff) coincided with strong/moderate La Niña years during negative PDO phases. This study provides clear evidence that not only ENSO but also the PDO have significantly affected runoff regimes at the Keppel reefs for at least a century, and suggests that upcoming hydrological disturbances and ecological responses in the southern GBR region will be mediated by the future evolution of these sources of climate variability.

Temporal variation in population size of European bird species: effects of latitude and marginality of distribution

In the Northern Hemisphere, global warming has been shown to affect animal populations in different ways, with southern populations in general suffering more from increased temperatures than northern populations of the same species. However, southern populations are also often marginal populations relative to the entire breeding range, and marginality may also have negative effects on populations. To disentangle the effects of latitude (possibly due to global warming) and marginality on temporal variation in population size, we investigated European breeding bird species across a latitudinal gradient. Population size estimates were regressed on years, and from these regressions we obtained the slope (a proxy for population trend) and the standard error of the estimate (SEE) (a proxy for population fluctuations). The possible relationships between marginality or latitude on one hand and slopes or SEE on the other were tested among populations within species. Potentially confounding factors such as census method, sampling effort, density-dependence, habitat fragmentation and number of sampling years were controlled statistically. Population latitude was positively related to regression slopes independent of marginality, with more positive slopes (i.e., trends) in northern than in southern populations. The degree of marginality was positively related to SEE independent of latitude, with marginal populations showing larger SEE (i.e., fluctuations) than central ones. Regression slopes were also significantly related to our estimate of density-dependence and SEE was significantly affected by the census method. These results are consistent with a scenario in which southern and northern populations of European bird species are negatively affected by marginality, with southern populations benefitting less from global warming than northern populations, thus potentially making southern populations more vulnerable to extinction.

Multi-scale sampling to evaluate assemblage dynamics in an oceanic marine reserve

To resolve the capacity of Marine Protected Areas (MPA) to enhance fish productivity it is first necessary to understand how environmental conditions affect the distribution and abundance of fishes independent of potential reserve effects. Baseline fish production was examined from 2002–2004 through ichthyoplankton sampling in a large (10,878 km²) Southern Californian oceanic marine reserve, the Cowcod Conservation Area (CCA) that was established in 2001, and the Southern California Bight as a whole (238,000 km² CalCOFI sampling domain). The CCA assemblage changed through time as the importance of oceanic-pelagic species decreased between 2002 (La Niña) and 2003 (El Niño) and then increased in 2004 (El Niño), while oceanic species and rockfishes displayed the opposite pattern. By contrast, the CalCOFI assemblage was relatively stable through time. Depth, temperature, and zooplankton explained more of the variability in assemblage structure at the CalCOFI scale than they did at the CCA scale. CalCOFI sampling revealed that oceanic species impinged upon the CCA between 2002 and 2003 in association with warmer offshore waters, thus explaining the increased influence of these species in the CCA during the El Nino years. Multi-scale, spatially explicit sampling and analysis was necessary to interpret assemblage dynamics in the CCA and likely will be needed to evaluate other focal oceanic marine reserves throughout the world.

Theoretical predictions for how temperature affects the dynamics of interacting herbivores and plants

Concern about climate change has spurred experimental tests of how warming affects species' abundance and performance. As this body of research grows, interpretation and extrapolation to other species and systems have been limited by a lack of theory. To address the need for theory for how warming affects species interactions, we used consumer-prey models and the metabolic theory of ecology to develop quantitative predictions for how systematic differences between the temperature dependence of heterotrophic and autotrophic population growth lead to temperature-dependent herbivory. We found that herbivore and plant abundances change with temperature in proportion to the ratio of autotrophic to heterotrophic metabolic temperature dependences. This result is consistent across five different formulations of consumer-prey models and over varying resource supply rates. Two models predict that temperature-dependent herbivory causes primary producer abundance to be independent of temperature. This finding contradicts simpler extensions of metabolic theory to abundance that ignore trophic interactions, and is consistent with patterns in terrestrial ecosystems. When applied to experimental data, the model explained 77% and 66% of the variation in phytoplankton and zooplankton abundances, respectively. We suggest that metabolic theory provides a foundation for understanding the effects of temperature change on multitrophic ecological communities.

Seasonal Synechococcus and Thaumarchaeal population dynamics examined with high resolution with remote in situ instrumentation

Monterey Bay, CA is an Eastern boundary upwelling system that is nitrogen limited much of the year. In order to resolve population dynamics of microorganisms important for nutrient cycling in this region, we deployed the Environmental Sample Processor with quantitative PCR assays targeting both ribosomal RNA genes and functional genes for subclades of cyanobacteria (Synechococcus) and ammonia-oxidizing Archaea (Thaumarchaeota) populations. Results showed a strong correlation between Thaumarchaea abundances and nitrate during the spring upwelling but not the fall sampling period. In relatively stratified fall waters, the Thaumarchaeota community reached higher numbers than in the spring, and an unexpected positive correlation with chlorophyll concentration was observed. Further, we detected drops in Synechococcus abundance that occurred on short (that is, daily) time scales. Upwelling intensity and blooms of eukaryotic phytoplankton strongly influenced Synechococcus distributions in the spring and fall, revealing what appear to be the environmental limitations of Synechococcus populations in this region. Each of these findings has implications for Monterey Bay biogeochemistry. High-resolution sampling provides a better-resolved framework within which to observe changes in the plankton community. We conclude that controls on these ecosystems change on smaller scales than are routinely assessed, and that more predictable trends will be uncovered if they are evaluated within seasonal (monthly), rather than on annual or interannual scales.

Long-term population trends of Sooty Shearwater (Puffinus griseus) revealed by hunt success

The annual hunt of Muttonbirds (chicks of the Sooty Shearwater, Puffinus griseus), undertaken by the Rakiura Māori people of southern New Zealand, is economically and socially integral to their cultural identity. Muttonbirders concerned at ensuring that the hunt remains viable for coming generations have provided catch records to help ascertain historic trends in hunt success. Analysis of eight catch diaries for a 67-year period demonstrates considerable consistency across diaries in the variability of hunt success, as measured by annualized mean daily hunt tallies. A conservative estimate of the overall annual decline in hunt success is -1.89% (95% CI: -1.14% to -2.65%). Birders' observations of a changing relationship between chick quality and hunt success was evidenced across diaries. Reduced hunt success from the 1990s indicates that possible adult "knockdowns" and/or sustained substantial reductions in breeding proportions have occurred. Chick size has remained constant, suggesting little change in the provisioning environment. Catch per unit effort data, provided by a single diary, confirms a link between variability in annual hunt success and chick abundance. The Pacific Decadal Oscillation (PDO) and the Southern Annular Mode (SAM) are correlated with hunt success and chick size, respectively. Interannual PDO+ (or PDO-) values are correlated with higher (or lower) tallies, whereas SAM+ (or SAM) values are associated with larger (or smaller) chick size. Uncertainty in the relationship between the breeding Sooty Shearwater population, chick catch, and environmental perturbation in their feeding grounds could be reduced with the inclusion of hunt time in all diary records. Ongoing prolonged decline in a top-trophic-level predator such as the Sooty Shearwater raises serious concern that long-term oceanic changes have been occurring and that long-term sustainability of muttonbirding is in doubt.

Recent salmon declines: a result of lost feeding opportunities due to bad timing?

As the timing of spring productivity blooms in near-shore areas advances due to warming trends in global climate, the selection pressures on out-migrating salmon smolts are shifting. Species and stocks that leave natal streams earlier may be favoured over later-migrating fish. The low post-release survival of hatchery fish during recent years may be in part due to static release times that do not take the timing of plankton blooms into account. This study examined the effects of release time on the migratory behaviour and survival of wild and hatchery-reared coho salmon (Oncorhynchus kisutch) using acoustic and coded-wire telemetry. Plankton monitoring and near-shore seining were also conducted to determine which habitat and food sources were favoured. Acoustic tags (n = 140) and coded-wire tags (n = 266,692) were implanted into coho salmon smolts at the Seymour and Quinsam Rivers, in British Columbia, Canada. Differences between wild and hatchery fish, and early and late releases were examined during the entire lifecycle. Physiological sampling was also carried out on 30 fish from each release group. The smolt-to-adult survival of coho salmon released during periods of high marine productivity was 1.5- to 3-fold greater than those released both before and after, and the fish's degree of smoltification affected their downstream migration time and duration of stay in the estuary. Therefore, hatchery managers should consider having smolts fully developed and ready for release during the peak of the near-shore plankton blooms. Monitoring chlorophyll a levels and water temperature early in the spring could provide a forecast of the timing of these blooms, giving hatcheries time to adjust their release schedule.

A Conceptual Model of Natural and Anthropogenic Drivers and Their Influence on the Prince William Sound, Alaska, Ecosystem

Prince William Sound (PWS) is a semi-enclosed fjord estuary on the coast of Alaska adjoining the northern Gulf of Alaska (GOA). PWS is highly productive and diverse, with primary productivity strongly coupled to nutrient dynamics driven by variability in the climate and oceanography of the GOA and North Pacific Ocean. The pelagic and nearshore primary productivity supports a complex and diverse trophic structure, including large populations of forage and large fish that support many species of marine birds and mammals. High intra-annual, inter-annual, and interdecadal variability in climatic and oceanographic processes as drives high variability in the biological populations. A risk-based conceptual ecosystem model (CEM) is presented describing the natural processes, anthropogenic drivers, and resultant stressors that affect PWS, including stressors caused by the Great Alaska Earthquake of 1964 and the Exxon Valdez oil spill of 1989. A trophodynamic model incorporating PWS valued ecosystem components is integrated into the CEM. By representing the relative strengths of driver/stressors/effects, the CEM graphically demonstrates the fundamental dynamics of the PWS ecosystem, the natural forces that control the ecological condition of the Sound, and the relative contribution of natural processes and human activities to the health of the ecosystem. The CEM illustrates the dominance of natural processes in shaping the structure and functioning of the GOA and PWS ecosystems.

Climate change, coral reef ecosystems, and management options for marine protected areas

Marine protected areas (MPAs) provide place-based management of marine ecosystems through various degrees and types of protective actions. Habitats such as coral reefs are especially susceptible to degradation resulting from climate change, as evidenced by mass bleaching events over the past two decades. Marine ecosystems are being altered by direct effects of climate change including ocean warming, ocean acidification, rising sea level, changing circulation patterns, increasing severity of storms, and changing freshwater influxes. As impacts of climate change strengthen they may exacerbate effects of existing stressors and require new or modified management approaches; MPA networks are generally accepted as an improvement over individual MPAs to address multiple threats to the marine environment. While MPA networks are considered a potentially effective management approach for conserving marine biodiversity, they should be established in conjunction with other management strategies, such as fisheries regulations and reductions of nutrients and other forms of land-based pollution. Information about interactions between climate change and more "traditional" stressors is limited. MPA managers are faced with high levels of uncertainty about likely outcomes of management actions because climate change impacts have strong interactions with existing stressors, such as land-based sources of pollution, overfishing and destructive fishing practices, invasive species, and diseases. Management options include ameliorating existing stressors, protecting potentially resilient areas, developing networks of MPAs, and integrating climate change into MPA planning, management, and evaluation.

Warming and resource availability shift food web structure and metabolism

Experimental warming of a marine food web suggests that ocean warming can lead to greater consumer abundance but reduced overall biomass, providing a potentially species-independent response to environmental warming.

Climate change disrupts ecological systems in many ways. Many documented responses depend on species' life histories, contributing to the view that climate change effects are important but difficult to characterize generally. However, systematic variation in metabolic effects of temperature across trophic levels suggests that warming may lead to predictable shifts in food web structure and productivity. We experimentally tested the effects of warming on food web structure and productivity under two resource supply scenarios. Consistent with predictions based on universal metabolic responses to temperature, we found that warming strengthened consumer control of primary production when resources were augmented. Warming shifted food web structure and reduced total biomass despite increases in primary productivity in a marine food web. In contrast, at lower resource levels, food web production was constrained at all temperatures. These results demonstrate that small temperature changes could dramatically shift food web dynamics and provide a general, species-independent mechanism for ecological response to environmental temperature change.

Humans rely on marine ecosystems for economic and nutritional sustenance—including about 16% of animal protein consumed by humans—making it especially important for natural scientists, economists, conservationists and long-term policy planners to understand how climate change is likely to affect oceanic food webs. Yet the general effects of warming on food web productivity are completely unknown. The productivity of consumers (such as zooplankton), in food webs is determined in large part by their metabolic rates and the availability and productivity of their limiting metabolic resources. A general theory relating food web dynamics to temperature suggests that fundamental differences between consumers and primary producers (such as phytoplankton) may lead to predictable shifts in their relative abundance and productivity with warming. We experimentally tested the effects of warming on food web structure and productivity under two resource supply scenarios. Our results show that warming alone can strengthen the role of consumers in the food web, increasing consumer biomass relative to producer biomass, and reducing the total biomass of the food web despite increases in primary productivity. In contrast, when resources were less available, food web production was constrained at all temperatures. These results demonstrate that small changes in water temperature could drive dramatic shifts in marine food web structure and productivity, and potentially provide a general, species-independent mechanism of ecological response to climate change.

Contributions of long-term research and time-series observations to marine ecology and biogeochemistry

Time-series observations form a critical element of oceanography. New interdisciplinary efforts launched in the past two decades complement the few earlier, longer-running time series to build a better, though still poorly resolved, picture of lower-frequency ocean variability, the climate processes that drive variability, and the implications for food web dynamics, carbon storage, and climate feedbacks. Time series also enlarge our understanding of ecological processes and are integral for improving models of physical-biogeochemical-ecological ocean dynamics. The major time-series observatories go well beyond simple monitoring of core ocean properties, although that important activity forms the critical center of all time-series efforts. Modern ocean time series have major process and experimental components, entrain ancillary programs, and have integrated modeling programs for deriving a better understanding of the observations and the changing, three-dimensional ocean in which the observatories are embedded.