A Pleistocene legacy structures variation in modern seagrass ecosystems.

Distribution of Earth's biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate-trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth's environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass (Zostera marina), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more recent within-basin bottlenecks and genetic differentiation. This evolutionary legacy in turn influences the biomass of associated algae and invertebrates that fuel coastal food webs, with effects comparable to or stronger than effects of current environmental forcing. Such historical lags in phenotypic acclimatization may constrain ecosystem adjustments to rapid anthropogenic climate change, thus altering predictions about the future functioning of ecosystems.

Temperature dependence of competitive ability is cold-shifted compared to that of growth rate in marine phytoplankton.

The effect of climate warming on community composition is expected to be contingent on competitive outcomes, yet approaches to projecting ecological outcomes often rely on measures of density-independent performance across temperatures. Recent theory suggests that the temperature response of competitive ability differs in shape from that of population growth rate. Here, we test this hypothesis empirically and find thermal performance curves of competitive ability in aquatic microorganisms to be systematically left-shifted and flatter compared to those of exponential growth rate. The minimum resource requirement for growth, R*-an inverse indicator of competitive ability-changes with temperature following a U-shaped pattern in all four species tested, contrasting from their left-skewed density-independent growth rate thermal performance curves. Our results provide new evidence that exploitative competitive success is highest at temperatures that are sub-optimal for growth, suggesting performance estimates of density-independent variables might underpredict performance in cooler competitive environments.

Aquatic biodiversity enhances multiple nutritional benefits to humans.

Humanity depends on biodiversity for health, well-being, and a stable environment. As biodiversity change accelerates, we are still discovering the full range of consequences for human health and well-being. Here, we test the hypothesis-derived from biodiversity-ecosystem functioning theory-that species richness and ecological functional diversity allow seafood diets to fulfill multiple nutritional requirements, a condition necessary for human health. We analyzed a newly synthesized dataset of 7,245 observations of nutrient and contaminant concentrations in 801 aquatic animal taxa and found that species with different ecological traits have distinct and complementary micronutrient profiles but little difference in protein content. The same complementarity mechanisms that generate positive biodiversity effects on ecosystem functioning in terrestrial ecosystems also operate in seafood assemblages, allowing more diverse diets to yield increased nutritional benefits independent of total biomass consumed. Notably, nutritional metrics that capture multiple micronutrients and fatty acids essential for human well-being depend more strongly on biodiversity than common ecological measures of function such as productivity, typically reported for grasslands and forests. Furthermore, we found that increasing species richness did not increase the amount of protein in seafood diets and also increased concentrations of toxic metal contaminants in the diet. Seafood-derived micronutrients and fatty acids are important for human health and are a pillar of global food and nutrition security. By drawing upon biodiversity-ecosystem functioning theory, we demonstrate that ecological concepts of biodiversity can deepen our understanding of nature's benefits to people and unite sustainability goals for biodiversity and human well-being.

The fitness value of ecological information in a variable world.

Information processing is increasingly recognized as a fundamental component of life in variable environments, including the evolved use of environmental cues, biomolecular networks, and social learning. Despite this, ecology lacks a quantitative framework for understanding how population, community, and ecosystem dynamics depend on information processing. Here, we review the rationale and evidence for 'fitness value of information' (FVOI), and synthesize theoretical work in ecology, information theory, and probability behind this general mathematical framework. The FVOI quantifies how species' per capita population growth rates can depend on the use of information in their environment. FVOI is a breakthrough approach to linking information processing and ecological and evolutionary outcomes in a changing environment, addressing longstanding questions about how information mediates the effects of environmental change and species interactions.

Effects of thermal fluctuations on biological processes: a meta-analysis of experiments manipulating thermal variability.

Thermal variability is a key driver of ecological processes, affecting organisms and populations across multiple temporal scales. Despite the ubiquity of variation, biologists lack a quantitative synthesis of the observed ecological consequences of thermal variability across a wide range of taxa, phenotypic traits and experimental designs. Here, we conduct a meta-analysis to investigate how properties of organisms, their experienced thermal regime and whether thermal variability is experienced in either the past (prior to an assay) or present (during the assay) affect performance relative to the performance of organisms experiencing constant thermal environments. Our results-which draw upon 1712 effect sizes from 75 studies-indicate that the effects of thermal variability are not unidirectional and become more negative as mean temperature and fluctuation range increase. Exposure to variation in the past decreases performance to a greater extent than variation experienced in the present and increases the costs to performance more than diminishing benefits across a broad set of empirical studies. Further, we identify life-history attributes that predictably modify the ecological response to variation. Our findings demonstrate that effects of thermal variability on performance are context-dependent, yet negative outcomes may be heightened in warmer, more variable climates.

Limited recovery following a massive seagrass decline in subarctic eastern Canada.

Over the last few decades, there has been an increasing recognition for seagrasses' contribution to the functioning of nearshore ecosystems and climate change mitigation. Nevertheless, seagrass ecosystems have been deteriorating globally at an accelerating rate during recent decades. In 2017, research into the condition of eelgrass (Zostera marina) along the eastern coast of James Bay, Canada, was initiated in response to reports of eelgrass decline by the Cree First Nations of Eeyou Istchee. As part of this research, we compiled and analyzed two decades of eelgrass cover data and three decades of eelgrass monitoring data (biomass and density) to detect changes and assess possible environmental drivers. We detected a major decline in eelgrass condition between 1995 and 1999, which encompassed the entire east coast of James Bay. Surveys conducted in 2019 and 2020 indicated limited changes post-decline, for example, low eelgrass cover (<25%), low aboveground biomass, smaller shoots than before 1995, and marginally low densities persisted at most sites. Overall, the synthesized datasets show a 40% loss of eelgrass meadows with >50% cover in eastern James Bay since 1995, representing the largest scale eelgrass decline documented in eastern Canada since the massive die-off event that occurred in the 1930s along the North Atlantic coast. Using biomass data collected since 1982, but geographically limited to the sector of the coast near the regulated La Grande River, generalized additive modeling revealed eelgrass meadows are affected by local sea surface temperature, early ice breakup, and higher summer freshwater discharge. Our results caution against assuming subarctic seagrass ecosystems have avoided recent global declines or will benefit from ongoing climate warming.

Linking the influence and dependence of people on biodiversity across scales.

Biodiversity enhances many of nature's benefits to people, including the regulation of climate and the production of wood in forests, livestock forage in grasslands and fish in aquatic ecosystems. Yet people are now driving the sixth mass extinction event in Earth's history. Human dependence and influence on biodiversity have mainly been studied separately and at contrasting scales of space and time, but new multiscale knowledge is beginning to link these relationships. Biodiversity loss substantially diminishes several ecosystem services by altering ecosystem functioning and stability, especially at the large temporal and spatial scales that are most relevant for policy and conservation.

The International Initiative to Measure Perceived Risk in Arthroplasty: The Results From a Multinational Survey.

BACKGROUND: There is an inherent moral imperative to avoid complications from arthroplasty. Doing so at ideal cost is also associated with surgeon reputation, and, increasingly in health care delivery systems that measure and competitively score outcomes, reimbursement to the surgeons and their hospitals. As a result, patients who are perceived to be in higher risk comorbidity groups, such as the obese and diabetics, as well as those challenged by socioeconomic factors may face barriers to access elective arthroplasty. METHODS: In this initiative, surveys were sent to surgeons in 8 different countries, each adapted for their own unique payment, remuneration, and punitive models. The questions in the surveys pertained to surgeons' perception of risk regarding medical and socioeconomic factors in patients indicated for total hip or knee arthroplasty. This paper primarily reports on the results from Canada, Ireland, and the United Kingdom. RESULTS: The health care systems varied between a universal/state funded health care system (Canada) to those that were almost exclusively private (India). Some health care systems have "bundled" payment with retention of fees for postoperative complications requiring readmission/reoperation and including some with public publication of outcome data (United States and the United Kingdom), whereas others had none (Canada). There were some major discrepancies across different countries regarding the perceived risk of diabetic patients, who have variable Hemoglobin A1c cut-offs, if any used. However, overall the perception of risk for age, body mass index, age, sex, socioeconomic, and social situations remained surprisingly consistent throughout the health care systems. Any limitations set were primarily driven by surgeon decision making and not external demands. CONCLUSION: Surgeons will understandably try and optimize the health status of patients who have reversible risks as shown by best available evidence. The evidence is of variable quality, and, especially for irreversible social risk factors, limited due to concerns over cost and quality outcomes that can be influenced by experience-driven perceptions of risk. The results show that perceptions of risk do have such influence on access across many health care delivery environments. The authors recommend better risk-adjustment models for medical and socioeconomic risk factors with possible stratification/exclusions regarding reimbursement adjustments and reporting to help reverse disparities of access to arthroplasty.

An Empiricist's Guide to Using Ecological Theory.

AbstractA scientific understanding of the biological world arises when ideas about how nature works are formalized, tested, refined, and then tested again. Although the benefits of feedback between theoretical and empirical research are widely acknowledged by ecologists, this link is still not as strong as it could be in ecological research. This is in part because theory, particularly when expressed mathematically, can feel inaccessible to empiricists who may have little formal training in advanced math. To address this persistent barrier, we provide a general and accessible guide that covers the basic, step-by-step process of how to approach, understand, and use ecological theory in empirical work. We first give an overview of how and why mathematical theory is created, then outline four specific ways to use both mathematical and verbal theory to motivate empirical work, and finally present a practical tool kit for reading and understanding the mathematical aspects of ecological theory. We hope that empowering empiricists to embrace theory in their work will help move the field closer to a full integration of theoretical and empirical research.

The biogeography of community assembly: latitude and predation drive variation in community trait distribution in a guild of epifaunal crustaceans.

While considerable evidence exists of biogeographic patterns in the intensity of species interactions, the influence of these patterns on variation in community structure is less clear. Studying how the distributions of traits in communities vary along global gradients can inform how variation in interactions and other factors contribute to the process of community assembly. Using a model selection approach on measures of trait dispersion in crustaceans associated with eelgrass (Zostera marina) spanning 30° of latitude in two oceans, we found that dispersion strongly increased with increasing predation and decreasing latitude. Ocean and epiphyte load appeared as secondary predictors; Pacific communities were more overdispersed while Atlantic communities were more clustered, and increasing epiphytes were associated with increased clustering. By examining how species interactions and environmental filters influence community structure across biogeographic regions, we demonstrate how both latitudinal variation in species interactions and historical contingency shape these responses. Community trait distributions have implications for ecosystem stability and functioning, and integrating large-scale observations of environmental filters, species interactions and traits can help us predict how communities may respond to environmental change.

Seagrass (Zostera marina) transplant experiment reveals core microbiota and resistance to environmental change.

Zostera marina (seagrass) is a coastal marine angiosperm that sustains a diverse and productive ecosystem. Seagrass-associated microbiota support host health, yet the ecological processes that maintain biodiversity and stability of the seagrass leaf microbiota are poorly understood. We tested two hypotheses: (1) Microbes select seagrass leaves as habitat such that they consistently host distinct microbiota and/or core taxa in comparison to nearby substrates, and (2) seagrass leaf microbiota are stable once established and are resistant to change when transplanted to a novel environment. We reciprocally transplanted replicate seagrass shoots (natural and surface sterilized/dead tissue treatments) among four meadows with different environmental conditions and deployed artificial seagrass treatments in all four meadows. At the end of the 5-day experiment, the established microbiota on natural seagrass partially turned over to resemble microbial communities in the novel meadow, and all experimental treatments hosted distinct surface microbiota. We consistently found that natural and sterilized/dead seagrass hosted more methanol-utilizing bacteria compared to artificial seagrass and water, suggesting that seagrass core microbiota are shaped by taxa that metabolize seagrass exudates coupled with minor roles for host microbial defence and/or host-directed recruitment. We found evidence that the local environment strongly influenced the seagrass leaf microbiota in natural meadows and that transplant location explained more variation than experimental treatment. Transplanting resulted in high turnover and variability of the seagrass leaf microbiota, suggesting that it is flexibly assembled in a wide array of environmental conditions which may contribute to resilience of seagrass in future climate change scenarios.

Trophic interactions modify the temperature dependence of community biomass and ecosystem function.

Aquatic ecosystems worldwide continue to experience unprecedented warming and ecological change. Warming increases metabolic rates of animals, plants, and microbes, accelerating their use of energy and materials, their population growth, and interaction rates. At a much larger biological scale, warming accelerates ecosystem-level processes, elevating fluxes of carbon and oxygen between biota and the atmosphere. Although these general effects of temperature at finer and broader biological scales are widely observed, they can lead to contradictory predictions for how warming affects the structure and function of ecological communities at the intermediate scale of biological organization. We experimentally tested the hypothesis that the presence of predators and their associated species interactions modify the temperature dependence of net ecosystem oxygen production and respiration. We tracked a series of independent freshwater ecosystems (370 L) over 9 weeks, and we found that at higher temperatures, cascading effects of predators on zooplankton prey and algae were stronger than at lower temperatures. When grazing was weak or absent, standing phytoplankton biomass declined by 85%-95% (<1-fold) over the temperature gradient (19-30 °C), and by 3-fold when grazers were present and lacked predators. These temperature-dependent species interactions and consequent community biomass shifts occurred without signs of species loss or community collapse, and only modestly affected the temperature dependence of net ecosystem oxygen fluxes. The exponential increases in net ecosystem oxygen production and consumption were relatively insensitive to differences in trophic interactions among ecosystems. Furthermore, monotonic declines in phytoplankton standing stock suggested no threshold effects of warming across systems. We conclude that local changes in community structure, including temperature-dependent trophic cascades, may be compatible with prevailing and predictable effects of temperature on ecosystem functions related to fundamental effects of temperature on metabolism.

Scaling effects of temperature on parasitism from individuals to populations.

Parasitism is expected to change in a warmer future, but whether warming leads to substantial increases in parasitism remains unclear. Understanding how warming effects on parasitism in individual hosts (e.g. parasite load) translate to effects on population-level parasitism (e.g. prevalence, R0 ) remains a major knowledge gap. We conducted a literature review and identified 24 host-parasite systems that had information on the temperature dependence of parasitism at both individual host and host population levels: 13 vector-borne systems and 11 environmentally transmitted systems. We found a strong positive correlation between the thermal optima of individual- and population-level parasitism, although several of the environmentally transmitted systems exhibited thermal optima >5°C apart between individual and population levels. Parasitism thermal optima were close to vector performance thermal optima in vector-borne systems but not hosts in environmentally transmitted systems, suggesting these thermal mismatches may be more common in certain types of host-parasite systems. We also adapted and simulated simple models for both types of transmission modes and found the same pattern across the two modes: thermal optima were more strongly correlated across scales when there were more traits linking individual- to population-level processes. Generally, our results suggest that information on the temperature dependence, and specifically the thermal optimum, at either the individual or population level should provide a useful-although not quantitatively exact-baseline for predicting temperature dependence at the other level, especially in vector-borne parasite systems. Environmentally transmitted parasitism may operate by a different set of rules, in which temperature dependence is decoupled in some systems, requiring the need for trait-based studies of temperature dependence at individual and population levels.

Grand challenges in biodiversity-ecosystem functioning research in the era of science-policy platforms require explicit consideration of feedbacks.

Feedbacks are an essential feature of resilient socio-economic systems, yet the feedbacks between biodiversity, ecosystem services and human wellbeing are not fully accounted for in global policy efforts that consider future scenarios for human activities and their consequences for nature. Failure to integrate feedbacks in our knowledge frameworks exacerbates uncertainty in future projections and potentially prevents us from realizing the full benefits of actions we can take to enhance sustainability. We identify six scientific research challenges that, if addressed, could allow future policy, conservation and monitoring efforts to quantitatively account for ecosystem and societal consequences of biodiversity change. Placing feedbacks prominently in our frameworks would lead to (i) coordinated observation of biodiversity change, ecosystem functions and human actions, (ii) joint experiment and observation programmes, (iii) more effective use of emerging technologies in biodiversity science and policy, and (iv) a more inclusive and integrated global community of biodiversity observers. To meet these challenges, we outline a five-point action plan for collaboration and connection among scientists and policymakers that emphasizes diversity, inclusion and open access. Efforts to protect biodiversity require the best possible scientific understanding of human activities, biodiversity trends, ecosystem functions and-critically-the feedbacks among them.

The metabolic theory of ecology and the cost of parasitism.

With over 1 million species on earth, each biologically unique, do we have any hope of understanding whether species will persist in a warming world? We might, because it turns out that there is surprising regularity in how warming accelerates the major metabolic processes that power life. A persistent challenge has been to understand ecological effects of temperature in the context of species interactions, especially when individuals not only experience temperature but also mortality due to parasitism or predation. Kirk et al. have shown how the effects of parasites vary with warming in a manner entirely consistent with general temperature dependence of host and parasite metabolism.

Microeukaryotic Communities Associated With the Seagrass Zostera marina Are Spatially Structured.

Epibiotic microorganisms link seagrass productivity to higher trophic levels, but little is known about the processes structuring these communities, and which taxa consistently associate with seagrass. We investigated epibiotic microeukaryotes on seagrass (Zostera marina) leaves, substrates, and planktonic microeukaryotes in ten meadows in the Northeast Pacific. Seagrass epibiotic communities are distinct from planktonic and substrate communities. We found sixteen core microeukaryotes, including dinoflagellates, diatoms, and saprotrophic stramenopiles. Some likely use seagrass leaves as a substrate, others for grazing, or they may be saprotrophic organisms involved in seagrass decomposition or parasites; their relatives have been previously reported from marine sediments and in association with other hosts such as seaweeds. Core microeukaryotes were spatially structured, and none were ubiquitous across meadows. Seagrass epibiota were more spatially structured than planktonic communities, mostly due to spatial distance and changes in abiotic conditions across space. Seawater communities were relatively more similar in composition across sites and more influenced by the environmental component, but more variable over time. Core and transient taxa were both mostly structured by spatial distance and the abiotic environment, with little effect of host attributes, further indicating that those core taxa would not show a strong specific association with Z. marina.

Intersectionality of Net Worth and Race Relative to Utilization of Total Hip and Knee Arthroplasty.

BACKGROUND: Although the number of total hip arthroplasty and total knee arthroplasty (THA and TKA) increases, individuals of color continue to be less likely to undergo these procedures. Socioeconomic status may be a key influencer of THA and TKA utilization and outcomes. We explore the influence of net worth and race on THA and TKA utilization and outcomes of length of stay and readmissions using a large patient database. METHODS: The StrataSphere data set, an aggregation of 49 health systems representing 209 hospitals, was used for primary THA and TKA procedures performed in the calendar year 2019. Net worth was determined from Market Vue Partners' data sources. Statistical analyses were performed to investigate relationships between net worth and patients undergoing THA or TKA. RESULTS: When comparing our overall patient cohorts with the US population using Census data, we found differences in the utilization pattern indicated by index ratios most clearly in the lowest net worth categories. In the <$10K net worth category, THA and TKA index ratios were 0.51 and 0.54, respectively. In addition, we found that patients in the $100-250 and $250-500K net worth categories had increased utilization of both THA (index ratios of 1.39, 1.53) and TKA (index ratios of 1.45, 1.47) surgeries. CONCLUSION: Net worth is a strong driver of disparities in utilization of THA and TKA with lower utilization of these surgeries in patients with net worth <$10K and increased utilization in patients with net worth from $100-250 and $250-500K.

Perception of Risk: A Poll of American Association of Hip and Knee Surgeons Members.

BACKGROUND: Providers of total hip and knee replacements are being judged regarding quality/cost by payers using competition-based performance measures with poor medical and no socioeconomic risk adjustment. Providers might assume that other providers shed risk and the perception of added risk can influence practice. A poll was collected to examine such perceptions. METHODS: In 2019 a poll was sent to the 2800 surgeon members of the American Association of Hip and Knee Surgeons using Survey Monkey while protecting respondent anonymity/confidentiality. The questions asked whether the perception of poorly risk-adjusted medical comorbidities and socioeconomic risk factors influence surgeons to selectively offer surgery. RESULTS: There were 474 surgeon responses. Prior to elective total hip arthroplasty/total knee arthroplasty, 95% address modifiable risk factors; 52% require a body mass index <40, 64% smoking cessation, 96% an adequate hemoglobin A1C; 82% check nutrition; and 63% expect control of alcohol 2. Due to lack of socioeconomic risk adjustment, 83% reported feeling pressure to avoid/restrict access to patients with limited social support, specifically the following: Medicaid/underinsured, 81%; African Americans, 29%; Hispanics/ethnicities, 27%; and low socioeconomic status, 73%. Of the respondents, 93% predicted increased access to care with more appropriate risk adjustment. CONCLUSION: Competition-based quality/cost performance measures influence surgeons to focus on medical risk factors in offering lower extremity arthroplasty. The lack of socioeconomic risk adjustment leads to perceptions of added risk from such factors as well. This leads to marginal loss of access for patients within certain medical and socioeconomic classes, contributing to existing healthcare disparities. This represents an unintended consequence of competition-based performance measures.

Geographical limits to species-range shifts are suggested by climate velocity.

The reorganization of patterns of species diversity driven by anthropogenic climate change, and the consequences for humans, are not yet fully understood or appreciated. Nevertheless, changes in climate conditions are useful for predicting shifts in species distributions at global and local scales. Here we use the velocity of climate change to derive spatial trajectories for climatic niches from 1960 to 2009 (ref. 7) and from 2006 to 2100, and use the properties of these trajectories to infer changes in species distributions. Coastlines act as barriers and locally cooler areas act as attractors for trajectories, creating source and sink areas for local climatic conditions. Climate source areas indicate where locally novel conditions are not connected to areas where similar climates previously occurred, and are thereby inaccessible to climate migrants tracking isotherms: 16% of global surface area for 1960 to 2009, and 34% of ocean for the 'business as usual' climate scenario (representative concentration pathway (RCP) 8.5) representing continued use of fossil fuels without mitigation. Climate sink areas are where climate conditions locally disappear, potentially blocking the movement of climate migrants. Sink areas comprise 1.0% of ocean area and 3.6% of land and are prevalent on coasts and high ground. Using this approach to infer shifts in species distributions gives global and regional maps of the expected direction and rate of shifts of climate migrants, and suggests areas of potential loss of species richness.