Climate change and marine life

Reorganization of seagrass communities in a changing climate

Although climate change projections indicate significant threats to terrestrial biodiversity, the effects are much more profound and striking in the marine environment. Here we explore how different facets of locally distinctive α- and β-diversity (changes in spatial composition) of seagrasses will respond to future climate change scenarios across the globe and compare their coverage with the existing network of marine protected areas. By using species distribution modelling and a dated phylogeny, we predict widespread reductions in species' range sizes that will result in increases in seagrass weighted and phylogenetic endemism. These projected increases of endemism will result in divergent shifts in the spatial composition of β-diversity leading to differentiation in some areas and the homogenization of seagrass communities in other regions. Regardless of the climate scenario, the potential hotspots of these projected shifts in seagrass α- and β-diversity are predicted to occur outside the current network of marine protected areas, providing new priority areas for future conservation planning that incorporate seagrasses. Our findings report responses of species to future climate for a group that is currently under represented in climate change assessments yet crucial in maintaining marine food chains and providing habitat for a wide range of marine biodiversity.

Environmental Stress Selects for Innovations That Drive Vibrio Symbiont Diversity

Symbiotic bacteria in the Vibrionaceae are a dynamic group of γ-Proteobacteria that are commonly found throughout the world. Although they primarily are free-living in the environment, they can be commonly found associated with various Eukarya, either as beneficial or pathogenic symbionts. Interestingly, this dual lifestyle (free-living or in symbiosis) enables the bacteria to have enormous ecological breadth, where they can accommodate a variety of stresses in both stages. Here, we discuss some of the most common stressors that Vibrio bacteria encounter when in their free-living state or associated with an animal host, and how some of the mechanisms that are used to cope with these stressors can be used as an evolutionary advantage that increases their diversity both in the environment and within their specific hosts.

Thorson J. Are we ready to track climate-driven shifts in marine species across international boundaries? - A global survey of scientific bottom trawl data

Marine biota are redistributing at a rapid pace in response to climate change and shifting seascapes. While changes in fish populations and community structure threaten the sustainability of fisheries, our capacity to adapt by tracking and projecting marine species remains a challenge due to data discontinuities in biological observations, lack of data availability, and mismatch between data and real species distributions. To assess the extent of this challenge, we review the global status and accessibility of ongoing scientific bottom trawl surveys. In total, we gathered metadata for 283,925 samples from 95 surveys conducted regularly from 2001 to 2019. We identified that 59% of the metadata collected are not publicly available, highlighting that the availability of data is the most important challenge to assess species redistributions under global climate change. Given that the primary purpose of surveys is to provide independent data to inform stock assessment of commercially important populations, we further highlight that single surveys do not cover the full range of the main commercial demersal fish species. An average of 18 surveys is needed to cover at least 50% of species ranges, demonstrating the importance of combining multiple surveys to evaluate species range shifts. We assess the potential for combining surveys to track transboundary species redistributions and show that differences in sampling schemes and inconsistency in sampling can be overcome with spatio-temporal modeling to follow species density redistributions. In light of our global assessment, we establish a framework for improving the management and conservation of transboundary and migrating marine demersal species. We provide directions to improve data availability and encourage countries to share survey data, to assess species vulnerabilities, and to support management adaptation in a time of climate-driven ocean changes.

Century-long cod otolith biochronology reveals individual growth plasticity in response to temperature

Otolith biochronologies combine growth records from individual fish to produce long-term growth sequences, which can help to disentangle individual from population-level responses to environmental variability. This study assessed individual thermal plasticity of Atlantic cod (Gadus morhua) growth in Icelandic waters based on measurements of otolith increments. We applied linear mixed-effects models and developed a century-long growth biochronology (1908-2014). We demonstrated interannual and cohort-specific changes in the growth of Icelandic cod over the last century which were mainly driven by temperature variation. Temperature had contrasting relationships with growth-positive for the fish during the youngest ages and negative during the oldest ages. We decomposed the effects of temperature on growth observed at the population level into within-individual effects and among-individual effects and detected significant individual variation in the thermal plasticity of growth. Variance in the individual plasticity differed across cohorts and may be related to the mean environmental conditions experienced by the group. Our results underscore the complexity of the relationships between climatic conditions and the growth of fish at both the population and individual level, and highlight the need to distinguish between average population responses and growth plasticity of the individuals for accurate growth predictions.

Large-scale distribution of tuna species in a warming ocean

Tuna are globally distributed species of major commercial importance and some tuna species are a major source of protein in many countries. Tuna are characterized by dynamic distribution patterns that respond to climate variability and long-term change. Here, we investigated the effect of environmental conditions on the worldwide distribution and relative abundance of six tuna species between 1958 and 2004 and estimated the expected end-of-the-century changes based on a high-greenhouse gas concentration scenario (RCP8.5). We created species distribution models using a long-term Japanese longline fishery dataset and two-step generalized additive models. Over the historical period, suitable habitats shifted poleward for 20 out of 22 tuna stocks, based on their gravity centre (GC) and/or one of their distribution limits. On average, tuna habitat distribution limits have shifted poleward 6.5 km per decade in the northern hemisphere and 5.5 km per decade in the southern hemisphere. Larger tuna distribution shifts and changes in abundance are expected in the future, especially by the end-of-the-century (2080-2099). Temperate tunas (albacore, Atlantic bluefin, and southern bluefin) and the tropical bigeye tuna are expected to decline in the tropics and shift poleward. In contrast, skipjack and yellowfin tunas are projected to become more abundant in tropical areas as well as in most coastal countries' exclusive economic zones (EEZ). These results provide global information on the potential effects of climate change in tuna populations and can assist countries seeking to minimize these effects via adaptive management.

The revolution of crossdating in marine palaeoecology and palaeoclimatology

Over the past century, the dendrochronology technique of crossdating has been widely used to generate a global network of tree-ring chronologies that serves as a leading indicator of environmental variability and change. Only recently, however, has this same approach been applied to growth increments in calcified structures of bivalves, fish and corals in the world's oceans. As in trees, these crossdated marine chronologies are well replicated, annually resolved and absolutely dated, providing uninterrupted multi-decadal to millennial histories of ocean palaeoclimatic and palaeoecological processes. Moreover, they span an extensive geographical range, multiple trophic levels, habitats and functional types, and can be readily integrated with observational physical or biological records. Increment width is the most commonly measured parameter and reflects growth or productivity, though isotopic and elemental composition capture complementary aspects of environmental variability. As such, crossdated marine chronologies constitute powerful observational templates to establish climate-biology relationships, test hypotheses of ecosystem functioning, conduct multi-proxy reconstructions, provide constraints for numerical climate models, and evaluate the precise timing and nature of ocean-atmosphere interactions. These 'present-past-future' perspectives provide new insights into the mechanisms and feedbacks between the atmosphere and marine systems while providing indicators relevant to ecosystem-based approaches of fisheries management.

Using bivalve chronologies for quantifying environmental drivers in a semi-enclosed temperate sea

Annual growth increments formed in bivalve shells are increasingly used as proxies of environmental variability and change in marine ecosystems, especially at higher latitudes. Here, we document that well-replicated and exactly dated chronologies can also be developed to capture oceanographic processes in temperate and semi-enclosed seas, such as the Mediterranean. A chronology is constructed for Glycymeris pilosa from a shallow embayment of the northern Adriatic and extends from 1979 to 2016. The chronology significantly (p < 0.05) and positively correlates to winter sea surface temperatures, but negatively correlates to summer temperatures, which suggests that extreme winter lows and extreme summer highs may be limiting to growth. However, the strongest and most consistent relationships are negative correlations with an index of the Adriatic-Ionian Bimodal Oscillating System (BiOS) for which positive values indicate the inflow of the ultraoligotrophic Eastern Mediterranean waters to the Adriatic. In contrast, the substantial freshwater flows that discharge into the Adriatic do not correlate to the bivalve chronology, emphasizing the importance of remote oceanographic processes to growth at this highly coastal site. Overall, this study underscores the potential of bivalve chronologies to capture biologically relevant, local- to regional-scale patterns of ocean circulation in mid-latitude, temperate systems.

Climate-driven changes in functional biogeography of Arctic marine fish communities

Climate change triggers poleward shifts in species distribution leading to changes in biogeography. In the marine environment, fish respond quickly to warming, causing community-wide reorganizations, which result in profound changes in ecosystem functioning. Functional biogeography provides a framework to address how ecosystem functioning may be affected by climate change over large spatial scales. However, there are few studies on functional biogeography in the marine environment, and none in the Arctic, where climate-driven changes are most rapid and extensive. We investigated the impact of climate warming on the functional biogeography of the Barents Sea, which is characterized by a sharp zoogeographic divide separating boreal from Arctic species. Our unique dataset covered 52 fish species, 15 functional traits, and 3,660 stations sampled during the recent warming period. We found that the functional traits characterizing Arctic fish communities, mainly composed of small-sized bottom-dwelling benthivores, are being rapidly replaced by traits of incoming boreal species, particularly the larger, longer lived, and more piscivorous species. The changes in functional traits detected in the Arctic can be predicted based on the characteristics of species expected to undergo quick poleward shifts in response to warming. These are the large, generalist, motile species, such as cod and haddock. We show how functional biogeography can provide important insights into the relationship between species composition, diversity, ecosystem functioning, and environmental drivers. This represents invaluable knowledge in a period when communities and ecosystems experience rapid climate-driven changes across biogeographical regions.

Decadal-scale variation in diet forecasts persistently poor breeding under ocean warming in a tropical seabird

Climate change effects on population dynamics of natural populations are well documented at higher latitudes, where relatively rapid warming illuminates cause-effect relationships, but not in the tropics and especially the marine tropics, where warming has been slow. Here we forecast the indirect effect of ocean warming on a top predator, Nazca boobies in the equatorial Galápagos Islands, where rising water temperature is expected to exceed the upper thermal tolerance of a key prey item in the future, severely reducing its availability within the boobies' foraging envelope. From 1983 to 1997 boobies ate mostly sardines, a densely aggregated, highly nutritious food. From 1997 until the present, flying fish, a lower quality food, replaced sardines. Breeding success under the poor diet fell dramatically, causing the population growth rate to fall below 1, indicating a shrinking population. Population growth may not recover: rapid future warming is predicted around Galápagos, usually exceeding the upper lethal temperature and maximum spawning temperature of sardines within 100 years, displacing them permanently from the boobies' island-constrained foraging range. This provides rare evidence of the effect of ocean warming on a tropical marine vertebrate.

Fisheries regulatory regimes and resilience to climate change

Climate change is already producing ecological, social, and economic impacts on fisheries, and these effects are expected to increase in frequency and magnitude in the future. Fisheries governance and regulations can alter socio-ecological resilience to climate change impacts via harvest control rules and incentives driving fisher behavior, yet there are no syntheses or conceptual frameworks for examining how institutions and their regulatory approaches can alter fisheries resilience to climate change. We identify nine key climate resilience criteria for fisheries socio-ecological systems (SES), defining resilience as the ability of the coupled system of interacting social and ecological components (i.e., the SES) to absorb change while avoiding transformation into a different undesirable state. We then evaluate the capacity of four fisheries regulatory systems that vary in their degree of property rights, including open access, limited entry, and two types of rights-based management, to increase or inhibit resilience. Our exploratory assessment of evidence in the literature suggests that these regulatory regimes vary widely in their ability to promote resilient fisheries, with rights-based approaches appearing to offer more resilience benefits in many cases, but detailed characteristics of the regulatory instruments are fundamental.

Evidence for climate-driven synchrony of marine and terrestrial ecosystems in northwest Australia

The effects of climate change are difficult to predict for many marine species because little is known of their response to climate variations in the past. However, long-term chronologies of growth, a variable that integrates multiple physical and biological factors, are now available for several marine taxa. These allow us to search for climate-driven synchrony in growth across multiple taxa and ecosystems, identifying the key processes driving biological responses at very large spatial scales. We hypothesized that in northwest (NW) Australia, a region that is predicted to be strongly influenced by climate change, the El Niño Southern Oscillation (ENSO) phenomenon would be an important factor influencing the growth patterns of organisms in both marine and terrestrial environments. To test this idea, we analyzed existing growth chronologies of the marine fish Lutjanus argentimaculatus, the coral Porites spp. and the tree Callitris columellaris and developed a new chronology for another marine fish, Lethrinus nebulosus. Principal components analysis and linear model selection showed evidence of ENSO-driven synchrony in growth among all four taxa at interannual time scales, the first such result for the Southern Hemisphere. Rainfall, sea surface temperatures, and sea surface salinities, which are linked to the ENSO system, influenced the annual growth of fishes, trees, and corals. All four taxa had negative relationships with the Niño-4 index (a measure of ENSO status), with positive growth patterns occurring during strong La Niña years. This finding implies that future changes in the strength and frequency of ENSO events are likely to have major consequences for both marine and terrestrial taxa. Strong similarities in the growth patterns of fish and trees offer the possibility of using tree-ring chronologies, which span longer time periods than those of fish, to aid understanding of both historical and future responses of fish populations to climate variation.

Ecological and methodological drivers of species' distribution and phenology responses to climate change

Climate change is shifting species' distribution and phenology. Ecological traits, such as mobility or reproductive mode, explain variation in observed rates of shift for some taxa. However, estimates of relationships between traits and climate responses could be influenced by how responses are measured. We compiled a global data set of 651 published marine species' responses to climate change, from 47 papers on distribution shifts and 32 papers on phenology change. We assessed the relative importance of two classes of predictors of the rate of change, ecological traits of the responding taxa and methodological approaches for quantifying biological responses. Methodological differences explained 22% of the variation in range shifts, more than the 7.8% of the variation explained by ecological traits. For phenology change, methodological approaches accounted for 4% of the variation in measurements, whereas 8% of the variation was explained by ecological traits. Our ability to predict responses from traits was hindered by poor representation of species from the tropics, where temperature isotherms are moving most rapidly. Thus, the mean rate of distribution change may be underestimated by this and other global syntheses. Our analyses indicate that methodological approaches should be explicitly considered when designing, analysing and comparing results among studies. To improve climate impact studies, we recommend that (1) reanalyses of existing time series state how the existing data sets may limit the inferences about possible climate responses; (2) qualitative comparisons of species' responses across different studies be limited to studies with similar methodological approaches; (3) meta-analyses of climate responses include methodological attributes as covariates; and (4) that new time series be designed to include the detection of early warnings of change or ecologically relevant change. Greater consideration of methodological attributes will improve the accuracy of analyses that seek to quantify the role of climate change in species' distribution and phenology changes.

Eight decades of sampling reveal a contemporary novel fish assemblage in coastal nursery habitats

In order to adequately monitor biodiversity trends through time and their responses to natural or anthropogenic impacts, researchers require long time series that are often unavailable. This general lack of datasets that are several decades or longer makes establishing a background or baseline of diversity metrics difficult - especially when attempting to understand species composition changes against a backdrop of climate and ecological variability. Here, we present an analysis of a community of juvenile nearshore fishes based on nearly 8 decades of highly standardized Norwegian survey records. Using multivariate statistical techniques, we: (i) characterize the change in taxonomic community composition through time, (ii) determine whether there has been an increase in warm-water affinity species relative to their cold water affinity counterparts, and (iii) characterize the temporal change in the species' functional trait assemblage. Our results strongly indicate a shift toward a novel fish assemblage between the late 1990s and 2000s. The context of changes within the most recent two decades is in stark contrast to those during the 1960s and 1970s, but similar to those during the previous warm period during the 1930s and 1940s. This novel assemblage is tightly linked to the warming temperatures in the region portrayed by the increased presence of warm-water species and a higher incidence of pelagic, planktivorous species. The results indicate a clear influence of ocean temperature on the region's juvenile fish community that points to climate-mediated effects on the species assemblages of an important fish nursery area.

Edging along a Warming Coast: A Range Extension for a Common Sandy Beach Crab

Determining the position of range edges is the first step in developing an understanding of the ecological and evolutionary dynamics in play as species’ ranges shift in response to climate change. Here, we study the leading (poleward) range edge of Ocypode cordimanus, a ghost crab that is common along the central to northern east coast of Australia. Our study establishes the poleward range edge of adults of this species to be at Merimbula (36.90°S, 149.93°E), 270 km (along the coast) south of the previous southernmost museum record. We also establish that dispersal of pelagic larvae results in recruitment to beaches 248 km (along the coast; 0.9° of latitude) beyond the adult range edge we have documented here. Although we cannot conclusively demonstrate that the leading range edge for this species has moved polewards in response to climate change, this range edge does fall within a “hotspot” of ocean warming, where surface isotherms are moving southwards along the coast at 20–50 km.decade^-1; coastal air temperatures in the region are also warming. If these patterns persist, future range extensions could be anticipated. On the basis of their ecology, allied with their occupancy of ocean beaches, which are home to taxa that are particularly amenable to climate-change studies, we propose that ghost crabs like O. cordimanus represent ideal model organisms with which to study ecological and evolutionary processes associated with climate change. The fact that “hotspots” of ocean warming on four other continents correspond with poleward range edges of ghost crab species suggests that results of hypothesis tests could be generalized, yielding excellent opportunities to rapidly progress knowledge in this field.

Direct quantification of energy intake in an apex marine predator suggests physiology is a key driver of migrations

Pacific bluefin tuna (Thunnus orientalis) are highly migratory apex marine predators that inhabit a broad thermal niche. The energy needed for migration must be garnered by foraging, but measuring energy intake in the marine environment is challenging. We quantified the energy intake of Pacific bluefin tuna in the California Current using a laboratory-validated model, the first such measurement in a wild marine predator. Mean daily energy intake was highest off the coast of Baja California, Mexico in summer (mean ± SD, 1034 ± 669 kcal), followed by autumn when Pacific bluefin achieve their northernmost range in waters off northern California (944 ± 579 kcal). Movements were not always consistent with maximizing energy intake: the Pacific bluefin move out of energy rich waters both in late summer and winter, coincident with rising and falling water temperatures, respectively. We hypothesize that temperature-related physiological constraints drive migration and that Pacific bluefin tuna optimize energy intake within a range of optimal aerobic performance.

Force majeure: Will climate change affect our ability to attain Good Environmental Status for marine biodiversity?

The EU Marine Strategy Framework Directive (MSFD) requires that Good Environmental Status (GEnS), is achieved for European seas by 2020. These may deviate from GEnS, its 11 Descriptors, targets and baselines, due to endogenic managed pressures (from activities within an area) and externally due to exogenic unmanaged pressures (e.g. climate change). Conceptual models detail the likely or perceived changes expected on marine biodiversity and GEnS Descriptors in the light of climate change. We emphasise that marine management has to accommodate 'shifting baselines' caused by climate change particularly during GEnS monitoring, assessment and management and 'unbounded boundaries' given the migration and dispersal of highly-mobile species. We suggest climate change may prevent GEnS being met, but Member States may rebut legal challenges by claiming that this is outside its control, force majeure or due to 'natural causes' (Article 14 of the MSFD). The analysis is relevant to management of other global seas.

Impacts of multiple stressors during the establishment of fouling assemblages

Limited knowledge of the mechanisms through which multiple stressors affect communities and ecosystems limits capacity to predict their effects. Less clear is how stressors impact early colonization of newly available habitats due to scarcity of studies. The present study tested whether copper and freshwater input affect colonization of hard substrata independently or interactively and assessed differences in community respiration and total biomass among early stage assemblages which developed under different regimes of copper and freshwater input. While copper influenced effectively the colonization of individual species, freshwater effect was weak or null. Apart from a significant effect on total community composition, the interactive effect between stressors was weak and mainly driven by antagonistic interactions between copper and water flow. Total biomass and respiration of the community studied were not affected by stressors. These findings contradict the expectation that changes in community structure are likely to cause changes in functioning.

Climate-change impacts on sandy-beach biota: crossing a line in the sand

Sandy ocean beaches are iconic assets that provide irreplaceable ecosystem services to society. Despite their great socioeconomic importance, beaches as ecosystems are severely under-represented in the literature on climate-change ecology. Here, we redress this imbalance by examining whether beach biota have been observed to respond to recent climate change in ways that are consistent with expectations under climate change. We base our assessments on evidence coming from case studies on beach invertebrates in South America and on sea turtles globally. Surprisingly, we find that observational evidence for climate-change responses in beach biota is more convincing for invertebrates than for highly charismatic turtles. This asymmetry is paradoxical given the better theoretical understanding of the mechanisms by which turtles are likely to respond to changes in climate. Regardless of this disparity, knowledge of the unique attributes of beach systems can complement our detection of climate-change impacts on sandy-shore invertebrates to add rigor to studies of climate-change ecology for sandy beaches. To this end, we combine theory from beach ecology and climate-change ecology to put forward a suite of predictive hypotheses regarding climate impacts on beaches and to suggest ways that these can be tested. Addressing these hypotheses could significantly advance both beach and climate-change ecology, thereby progressing understanding of how future climate change will impact coastal ecosystems more generally.

Radiocarbon dating and wood density chronologies of mangrove trees in arid Western Australia

Mangrove trees tend to be larger and mangrove communities more diverse in tropical latitudes, particularly where there is high rainfall. Variation in the structure, growth and productivity of mangrove forests over climatic gradients suggests they are sensitive to variations in climate, but evidence of changes in the structure and growth of mangrove trees in response to climatic variation is scarce. Bomb-pulse radiocarbon dating provides accurate dates of recent wood formation and tree age of tropical and subtropical tree species. Here, we used radiocarbon techniques combined with X-ray densitometry to develop a wood density chronology for the mangrove Avicennia marina in the Exmouth Gulf, Western Australia (WA). We tested whether wood density chronologies of A. marina were sensitive to variation in the Pacific Decadal Oscillation Index, which reflects temperature fluctuations in the Pacific Ocean and is linked to the instrumental rainfall record in north WA. We also determined growth rates in mangrove trees from the Exmouth Gulf, WA. We found that seaward fringing A. marina trees (~10 cm diameter) were 48 ± 1 to 89 ± 23 years old (mean ± 1 σ) and that their growth rates ranged from 4.08 ± 2.36 to 5.30 ± 3.33 mm/yr (mean ± 1 σ). The wood density of our studied mangrove trees decreased with increases in the Pacific Decadal Oscillation Index. Future predicted drying of the region will likely lead to further reductions in wood density and their associated growth rates in mangrove forests in the region.

Climate-driven ichthyoplankton drift model predicts growth of top predator young

Climate variability influences seabird population dynamics in several ways including access to prey near colonies during the critical chick-rearing period. This study addresses breeding success in a Barents Sea colony of common guillemots Uria aalge where trophic conditions vary according to changes in the northward transport of warm Atlantic Water. A drift model was used to simulate interannual variations in transport of cod Gadus morhua larvae along the Norwegian coast towards their nursery grounds in the Barents Sea. The results showed that the arrival of cod larvae from southern spawning grounds had a major effect on the size of common guillemot chicks at fledging. Furthermore, the fraction of larvae from the south was positively correlated to the inflow of Atlantic Water into the Barents Sea thus clearly demonstrating the mechanisms by which climate-driven bottom-up processes influence interannual variations in reproductive success in a marine top predator.

Climate change and eutrophication induced shifts in northern summer plankton communities

Marine ecosystems are undergoing substantial changes due to human-induced pressures. Analysis of long-term data series is a valuable tool for understanding naturally and anthropogenically induced changes in plankton communities. In the present study, seasonal monitoring data were collected in three sub-basins of the northern Baltic Sea between 1979 and 2011 and statistically analysed for trends and interactions between surface water hydrography, inorganic nutrient concentrations and phyto- and zooplankton community composition. The most conspicuous hydrographic change was a significant increase in late summer surface water temperatures over the study period. In addition, salinity decreased and dissolved inorganic nutrient concentrations increased in some basins. Based on redundancy analysis (RDA), warming was the key environmental factor explaining the observed changes in plankton communities: the general increase in total phytoplankton biomass, Cyanophyceae, Prymnesiophyceae and Chrysophyceae, and decrease in Cryptophyceae throughout the study area, as well as increase in rotifers and decrease in total zooplankton, cladoceran and copepod abundances in some basins. We conclude that the plankton communities in the Baltic Sea have shifted towards a food web structure with smaller sized organisms, leading to decreased energy available for grazing zooplankton and planktivorous fish. The shift is most probably due to complex interactions between warming, eutrophication and increased top-down pressure due to overexploitation of resources, and the resulting trophic cascades.

Meta-analysis reveals complex marine biological responses to the interactive effects of ocean acidification and warming

Ocean acidification and warming are considered two of the greatest threats to marine biodiversity, yet the combined effect of these stressors on marine organisms remains largely unclear. Using a meta-analytical approach, we assessed the biological responses of marine organisms to the effects of ocean acidification and warming in isolation and combination. As expected biological responses varied across taxonomic groups, life-history stages, and trophic levels, but importantly, combining stressors generally exhibited a stronger biological (either positive or negative) effect. Using a subset of orthogonal studies, we show that four of five of the biological responses measured (calcification, photosynthesis, reproduction, and survival, but not growth) interacted synergistically when warming and acidification were combined. The observed synergisms between interacting stressors suggest that care must be made in making inferences from single-stressor studies. Our findings clearly have implications for the development of adaptive management strategies particularly given that the frequency of stressors interacting in marine systems will be likely to intensify in the future. There is now an urgent need to move toward more robust, holistic, and ecologically realistic climate change experiments that incorporate interactions. Without them accurate predictions about the likely deleterious impacts to marine biodiversity and ecosystem functioning over the next century will not be possible.