Community-level Metrics Research Articles

Taxonomic and functional-trait metrics track recovery of demersal fish and shrimp communities following system collapse

Monitoring programs that integrate both structural and functional ecosystem components play integral roles in ecosystem management and conservation planning. In the early 1990’s, the marine ecosystem of the waters surrounding Newfoundland and Labrador (NL) underwent a regime shift. Several demersal and pelagic fish stocks collapsed simultaneously, and this had significant ecological and socioeconomic consequences. As this regime shift impacted numerous commercial and non-commercial species, assessments based on individual species would be insufficient. We explored a variety of metrics that capture different facets of diversity across multiple species to provide a more robust ecosystem assessment. These were species richness, evenness, community-weighted means of maximum body length and trophic level (i.e., the mean maximum body size or trophic level of the species present in a community), and functional dispersion (FDis). The objectives of this study were 1) to assess trends in community structure of the NL demersal community during the post-collapse period (1995-2018), 2) explore how the various community-level metrics differ or are redundant, and 3) investigate how these metrics are associated with important covariates. Several metrics were redundant and displayed strongly positive, temporal trends being consistent with expectations for a recovery encompassing the entire demersal community. In particular, unweighted community-weighted means of body length and trophic level displayed nearly equal temporal patterns, showing increasing trends throughout the study period which were most prominent in the northern study area and within a limited depth range at the upper shelf break. Corresponding biomass-weighted metrics were also correlated with each other but only showed similar increasing tendencies after the first decade. In contrast, species richness did not show any temporal increase. Evenness and biomass-weighted FDis showed similar temporal patterns, decreasing during the first decade followed by strong increases during subsequent years, patterns that were directly linked to variation in Northern shrimp and Atlantic cod biomass. This study demonstrates how a variety of community metrics can provide insight into different aspects of the post-collapse recovery of the demersal community and help us better understand the complexity of the changes the ecosystem is undergoing.

Trophic Structure and a Temporal Shift in Trophic Diversity of Mobile Consumers in a Subarctic Estuary

Quantifying trophic relationships within and between species in terms of trophic position, ontogeny and trophic diversity provides information on community-level structure and function. Little attention has been focused on examining the trophic structure and temporal changes of communities in freshwater-marine coupled systems in the subarctic and associated impacts of anthropogenic activity on trophic interactions. Therefore, the objective of this study was to quantify the trophic position of mobile consumers (15 species in total) within the lower Churchill River area (Churchill, Manitoba, Canada), examine trophic position variation in relation to ontogeny, and measure the trophic diversity of a fish assemblage before (1993–1995) and after (2019–2020) the installation of the Churchill River weir in the late 1990s. We used stable isotopes (δ13C and δ15N) to quantify individual and group-level variation in trophic position of thirteen fish species and two seal species and also assessed six community-level metrics of a three fish species assemblage between time periods. Overall, species that mainly foraged on freshwater resources occupied lower trophic positions than species that mainly consumed marine resources. Trophic position increased with fish age only in cisco, fourhorn sculpin, Greenland cod and northern pike. A temporal shift from a trophically diverse to a more trophically redundant fish assemblage occurred between 1993–1995 and 2019–2020. As a result, these predator species now play similar trophic roles. Information on the long-term change in trophic structure of this sub-Arctic estuarine system may help with understanding how anthropogenic activity and climate change have influenced the trophic diversity of a fish assemblage inhabiting this system.

Abstract 18709: Disparities in Socioeconomic Metrics Associated With Adverse Outcomes Among Medicare Beneficiaries Undergoing Peripheral Endovascular Intervention

Background Low socioeconomic status (SES) is associated with an increased incidence of peripheral artery disease, however there is a lack of granularity in the specific metrics that contribute to this discrepancy. We examine the association of community-level economic distress with adverse outcomes in patients undergoing peripheral endovascular intervention (PVI). Hypothesis: Socioeconomically distressed communities have non-healthcare-related, structural disparities that contribute to incident PVI and adverse outcomes. Methods: Medicare beneficiaries ≥66 years of age from 2016 to 2018 were evaluated to determine the incidence of femoropopliteal PVI. The Distressed Community Index (DCI) was used to categorize adults as distressed (DCI ≥80) or not distressed (DCI <80). Composite outcome of death and major amputation within 1 year of PVI were examined by level of distress using individual community-level metrics. Results: Socioeconomically distressed adults underwent 158 PVIs per 100000 distressed beneficiaries compared with 109 PVIs per 100000 non-distressed beneficiaries (risk ratio, 1.45 [95% CI, 1.42-1.48]; P<0.001). Distressed adults who underwent PVI were more likely to be female (45.5% versus 43.1%; P<0.001) and Black race (21.9% versus 10.1%; P<0.001) (Table I). There was a strong association between distress and the composite outcome at 1 year (incidence rate ratio, 1.11 [95% CI 1.07-1.16; P=0.0001]). Distressed adults lacked high school diplomas (11.88% versus 11.15%; P<0.001), had higher rates of unemployment (24.11% versus 22.76%; P<0.001), and greater housing vacancy rates (9.74% versus 9.31%; P<0.001). Conclusion: Socioeconomic distress is associated with higher rates of PVI-incidence and post-PVI adverse outcomes. This may be driven by structural inadequacies inherent to low SES communities that need to be addressed in order to narrow the gap in care among distressed adults undergoing PVI.

Moving upstream: healthcare partnerships addressing social determinants of health through community wealth building

BackgroundHealthcare-based interventions addressing social needs such as food and housing generally fail to impact the upstream wealth and power inequities underlying those needs. However, a small number of US healthcare organizations have begun addressing these upstream inequities by partnering with community wealth building initiatives. These initiatives include community land trusts, resident-owned communities, and worker cooperatives, which provide local residents ownership and control over their housing and workplaces. While these partnerships represent a novel, upstream approach to the social determinants of health, no research has yet evaluated them.MethodsTo assess the current state and key aspects of healthcare-community wealth building partnerships, we conducted a multiple case study analysis using semi-structured interviews with thirty-eight key informants across ten partnerships identified through the Healthcare Anchor Network. To analyze the interviews, we used a two-stage coding process. First, we coded responses based on the phase of the intervention to which they corresponded: motivation, initiation, implementation, or evaluation. Then we assessed responses within each aspect for common themes and variation on salient topics.ResultsPartnerships were generally motivated by a combination of community needs, such as affordable housing and living wage jobs, and health system interests, such as workforce housing and supply chain resilience. Initiating projects required identifying external partners, educating leadership, and utilizing risk mitigation strategies to obtain health system buy-in. Implementation took various forms, with healthcare organizations providing financial capital in the form of grants and loans, social capital in the form of convening funders and other stakeholders, and/or capacity building support in the form of strategic planning or technical assistance resources. To evaluate projects, healthcare organizations used more process and community-level metrics rather than metrics based on individual health outcomes or returns on investment. Based on best practices from each partnership phase, we provide a roadmap for healthcare organizations to develop effective community wealth building partnerships.ConclusionsAssessing healthcare partnerships with community wealth building organizations yields key strategies healthcare organizations can use to develop more effective partnerships to address the upstream causes of poor health.

Protocol of a prospective community-based study about the onset and course of depression in a nationally representative cohort of adults in China: the China Depression Cohort Study-I

BackgroundDepression is the second most important cause of disability worldwide. Reducing this major burden on global health requires a better understanding of the etiology, risk factors, and course of the disorder. With the goal of improving the prevention, recognition, and appropriate management of depressive disorders in China, the China Depression Cohort Study will establish a nationally representative sample of at least 85,000 adults (the China Depression Cohort Study-I) and 15,000 middle school students (the China Depression Cohort Study-II) and follow them over time to identify factors that influence the onset, characteristics, and course of depressive disorders. This protocol describes the China Depression Cohort Study-I.MethodsA multistage stratified random sampling method will be used to identify a nationally representative community-based cohort of at least 85,000 adults (i.e., ≥ 18 years of age) from 34 communities in 17 of mainland China’s 31 provincial-level administrative regions. Baseline data collection includes 1) demographic, social and clinical data, 2) diagnostic information, 3) biological samples (i.e., blood, urine, hair), 4) brain MRI scans, and 5) environmental data (e.g., community-level metrics of climate change, air pollution, and socio-economic characteristics). Baseline findings will identify participants with or without depressive disorders. Annual reassessments will monitor potential risk factors for depression and identify incident cases of depression. Cox Proportional-Hazards Regression, Network analysis, Disease trajectory modelling, and Machine learning prediction models will be used to analyze the collected data. The study’s main outcomes are the occurrence of depressive disorders; secondary outcomes include adverse behaviors (e.g., self-harm, suicide), the recurrence of depression and the incidence other mental disorders.DiscussionThe China Depression Cohort Study-I will collect a comprehensive, nationally representative set of individual-level and community-level variables over time. The findings will reframe the understanding of depression from a ‘biology-psychology-society’ perspective. This perspective will improve psychiatrists’ understanding of depression and, thus, promote the development of more effective subgroup-specific antidepressant drugs and other interventions based on the new biomarkers and relationships identified in the study.Trail registrationThe protocol has been registered on the Chinese Clinical Trial Registry (No. ChiCTR2200059016).

Evolutionary effects of nitrogen are not easily predicted from ecological responses.

Anthropogenic nitrogen (N) addition alters the abiotic and biotic environment, potentially leading to changes in patterns of natural selection (i.e., trait-fitness relationships) and the opportunity for selection (i.e., variance in relative fitness). Because N addition favors species with light acquisition strategies (e.g., tall species), we predicted that N would strengthen selection favoring those same traits. We also predicted that N could alter the opportunity for selection via its effects on mean fitness and/or competitive asymmetries. We quantified the strength of selection and the opportunity for selection in replicated populations of the annual grass Setaria faberi (giant foxtail) growing in a long-term N addition experiment. We also correlated these population-level parameters with community-level metrics to identify the proximate causes of N-mediated evolutionary effects. N addition increased aboveground productivity, light asymmetry, and reduced species diversity. Contrary to expectations, N addition did not strengthen selection for trait values associated with higher light acquisition such as greater height and specific leaf area (SLA); rather, it strengthened selection favoring lower SLA. Light asymmetry and species diversity were associated with selection for height and SLA, suggesting a role for these factors in driving N-mediated selection. The opportunity for selection was not influenced by N addition but was negatively associated with species diversity. Our results indicate that anthropogenic N enrichment can affect evolutionary processes, but that evolutionary changes in plant traits within populations are unlikely to parallel the shifts in plant traits observed at the community level.

The combined effects of land use and seasonal environmental factors on stream food web structure

Land use and seasonal changes in environmental conditions influence biological communities and their trophic interactions in riverine ecosystems. However, how land use and the seasonality of environmental conditions jointly influence the food web structure of riverine ecosystems remains unclear. Here, we conducted a comparative study on basal resources, macroinvertebrates, and fish at woodland and urban sites to explore the combined effects of land use and environmental conditions during spring, autumn, and winter on the food web structure of a subtropical river in China. We used δ13C and δ15N to trace consumers’ diets and calculate community-level metrics within food webs. At woodland sites, we found that allochthonous sources contributed significantly more to consumers’ diets in the high flow season (53%) than in the low flow season (around 30%), but allochthonous sources contributed less than 30% at urban sites. The seasonal flooding facilitated the acquisition of terrestrial sources at woodland sites, while the impervious surface cover at urban sites cut off the influx of terrestrial inputs. The isotopic niche space of basal resources at both woodland and urban sites was significantly higher in the high flow season. However, the isotopic niche space of consumers at urban sites was not significantly different between seasons. Trophic length, niche width, and trophic redundancy showed no seasonal differences at urban sites, but trophic length increased significantly during the high flow season at woodland sites. Our temporal food web study at urban and woodland rivers illustrated the combined effects of land use and seasonal environmental conditions on the food web structure, and highlighted the role of allochthonous carbon in supporting biological communities and the importance of lateral and longitudinal connectivity in river ecosystems.

Time-lagged effects of habitat fragmentation on terrestrial mammals in Madagascar.

Biodiversity is severely threatened by habitat destruction. As a consequence of habitat destruction, the remaining habitat becomes more fragmented. This results in time-lagged population extirpations in remaining fragments when these are too small to support populations in the long term. If these time-lagged effects are ignored, the long-term impacts of habitat loss and fragmentation will be underestimated. We quantified the magnitude of time-lagged effects of habitat fragmentation for 157 nonvolant terrestrial mammal species in Madagascar, one of the biodiversity hotspots with the highest rates of habitat loss and fragmentation. We refined species' geographic ranges based on habitat preferences and elevation limits and then estimated which habitat fragments were too small to support a population for at least 100 years given stochastic population fluctuations. We also evaluated whether time-lagged effects would change the threat status of species according to the International Union for the Conservation of Nature (IUCN) Red List assessment framework. We used allometric relationships to obtain the population parameters required to simulate the population dynamics of each species, and we quantified the consequences of uncertainty in these parameter estimates by repeating the analyses with a range of plausible parameter values. Based on the median outcomes, we found that for 34 species (22% of the 157 species) at least 10% of their current habitat contained unviable populations. Eight species (5%) had a higher threat status when accounting for time-lagged effects. Based on 0.95-quantile values, following a precautionary principle, for 108 species (69%) at least 10% of their habitat contained unviable populations, and 51 species (32%) had a higher threat status. Our results highlight the need to preserve continuous habitat and improve connectivity between habitat fragments. Moreover, our findings may help to identify species for which time-lagged effects are most severe and which may thus benefit the most from conservation actions.

Evaluating the Performance of Centers for Disease Control and Prevention COVID-19 Community Levels as Leading Indicators of COVID-19 Mortality.

Centers for Disease Control and Prevention (CDC) defines low, medium, and high "COVID-19 community levels" to guide interventions, but associated mortality rates have not been reported. To evaluate the diagnostic performance of CDC COVID-19 community level metrics as predictors of elevated community mortality risk. Time series analysis over the period of 30 May 2021 through 4 June 2022. U.S. states and counties. U.S. population. CDC "COVID-19 community level" metrics based on hospital admissions, bed occupancy, and reported cases; reported COVID-19 deaths; and sensitivity, specificity, and predictive values for CDC and alternative metrics. Mean and median weekly mortality rates per 100000 population after onset of high COVID-19 community level 3 weeks prior were, respectively, 2.6 and 2.4 (interquartile range [IQR], 1.7 to 3.1) across 90 high episodes in states and 4.3 and 2.1 (IQR, 0 to 5.4) across 7987 high episodes in counties. In 85 of 90 (94%) episodes in states and 4801 of 7987 (60%) episodes in counties, lagged weekly mortality after onset exceeded 0.9 per 100000 population, and in 57 of 90 (63%) episodes in states and 4018 of 7987 (50%) episodes in counties, lagged weekly mortality after onset exceeded 2.1 per 100000, which is equivalent to approximately 1000 daily deaths in the national population. Alternative metrics based on lower hospital admissions or case thresholds were associated with lower mortality and had higher sensitivity and negative predictive value for elevated mortality, but the CDC metrics had higher specificity and positive predictive value. Ratios between cases, hospitalizations, and deaths have varied substantially over time. Aggregate mortality does not account for nonfatal outcomes or disparities. Continuing evolution of viral variants, immunity, clinical interventions, and public health mitigation strategies complicate prediction for future waves. Designing metrics for public health decision making involves tradeoffs between identifying early signals for action and avoiding undue restrictions when risks are modest. Explicit frameworks for evaluating surveillance metrics can improve transparency and decision support. Council of State and Territorial Epidemiologists.

Assessing fish communities in a multiple-use marine protected area using an underwater drone (Aegean Sea, Greece)

AbstractMarine protected areas (MPAs) have been demonstrated to positively affect various aspects of their ecosystems and communities. In the present study, the effectiveness of varying protection levels on the coastal fish populations within a multiple-use marine park in Greece was assessed through community-level metrics using a non-destructive underwater recording method (underwater drone/mini remotely operated vehicle). Two factors were examined, i.e. protection level (fully, partially and least protected area) and time period (early and late summer: beginning and towards the end of the fishing and touristic season). Our study demonstrated some first results that protection benefited both the commercial species and the entire fish community as a whole, in terms of diversity, abundance and richness, while non-commercial species did not differ among the studied protection levels. This finding, along with the fact that the prevailing conditions (water temperature, depth, habitat type) were similar in all three studied areas, that corresponded to different protection levels, and in both sampling periods, indicated that the observed results may be attributed to the varying protection levels. The studied fish communities did not seem to be affected by the more intense fishing and touristic period over the summer. In conclusion, protection from fishing seems to positively affect the studied coastal fish community as a whole and particularly the commercially important species that find a refuge within core areas of the Alonissos marine park.

Trophic structure in response to land use in subtropical streams

Land use in the uplands can substantially impact the biological community in stream ecosystems, but how the trophic structure of aquatic communities within riverine food webs respond to catchment land use changes within their respective catchment remains unclear. Here, we investigated the impact of land use on aquatic communities in two streams in subtropical China. We measured isotopic compositions of basal resources, four macroinvertebrate functional feeding groups (scrapers, collectors, shredders, and predators with 132 taxa), and three fish functional feeding groups (herbivores, omnivores, and piscivores with 26 species) in three land uses (woodland, agricultural, and urban). Isotopic values of δ13C and δ15N were used to estimate the dietary proportions of consumers (macroinvertebrates and fish) and community-level metrics (niche width and trophic diversity). We found that isotopic values of basal resources, macroinvertebrates, and fish varied significantly among sampling sites adjacent to the three land uses. Dietary analysis showed that terrestrial resources contributed relatively less (~20%) than aquatic resources to consumers (macroinvertebrates and fish) in higher trophic levels, especially in the urban sites. Compared to woodland sites, food webs in the urban sites had lower niche width and higher trophic redundancy, and agricultural sites had higher trophic length and lower niche width. Trophic structure alterations in response to land use primarily resulted from availability and variability of basal resources in the upstream river channel and the riparian zone, and also the feeding plasticity of macroinvertebrates and/or fish. These empirical findings indicate the importance of diversity across all trophic levels in the management of stream ecosystems in urban and agricultural landscapes.

Short-term effects of instream habitat restoration on macroinvertebrates and a comparison of sampling approaches

Many streams and rivers worldwide are restored with the intention to mitigate degradation caused by human activities, but these rehabilitation projects often involve physical instream work with diggers or other heavy machinery. The short-term effects of such restoration works on stream ecosystems are rarely investigated. The primary aim of our study was to assess the short-term effects of physical instream restoration works (which likely increased instream fine sediment load temporarily) on the benthic macroinvertebrate community in a lowland soft-bottomed stream, and our second aim was to compare the results of semi-quantitative kick-net and quantitative Surber sampling in this assessment. Invertebrates were collected using these two methods from three Control and three Impact sites, before and two days after recontouring the stream banks and installing instream woody cover features. Three of seven macroinvertebrate community-level indexes suggested positive short-term effects of the restoration works, whereas none indicated negative effects. By contrast, seven of the 14 most common taxa were negatively affected by the restoration works, possibly due to increased fine sediment levels reducing habitat quality for these taxa. These differences imply that taxon-specific invertebrate responses may be more suitable for detecting short-term impacts of instream restoration works than community-level metrics. Community indexes and common taxa were also likely affected by a drought in the spring and summer before restoration, which may have obscured some effects of the restoration works. Finally, kick-net and Surber sampling methods yielded similar findings for the community-level metrics but differed more for the common taxa, probably because the two methods sampled different microhabitats within the stream. Consequently, we recommend that for routine monitoring of macroinvertebrate communities in lowland soft-bottomed streams, the semi-quantitative kick-net sampling method should be used.

Long-term effects of combined land-use and climate changes on local bird communities in mosaic agricultural landscapes

Rural landscapes of western Europe have considerably changed in the last decades under the combined pressure of climate and land use changes, leading to a dramatic decline of farmland biodiversity, including common farmland birds. The respective roles of climate and land use and cover changes in driving bird population trends are primarily assessed at national or continental levels. Yet, it is often challenging to integrate their intertwined effects at such large scales due to the lack of data on fine-scale land cover changes. Here, we used a long-term bird monitoring scheme, combined with a land cover survey, conducted during 30 years (1981–2011) across 780 sites in a 20,000 ha study area in south-western France, dominated by low-intensity farming systems. We tested the direct effect of temporal changes in climate and land use on the dynamics of two community-level metrics: the bird Community Thermal Index (CTI) and bird Community Generalization Index (CGI). We used a novel method to assess the contribution of species-specific dynamics to CTI and CGI trends. We observed a significant increase in CTI and a significant decrease in CGI between 1981 and 2011, i.e., bird communities now have higher thermal preferences and are more specialized than 30 years ago. Bird CTI and CGI changes were both related to local climate- and land use-related drivers, especially mean temperature increase and hedgerow loss. Trends in CTI and CGI were primarily driven by the loss of cold-dwelling and generalist species, and secondly by a gain in hot-dwelling specialists. Our long-term study brings new empirical evidence that the effects of climate and land cover changes on bird communities are intrinsically intertwined, and need to be considered together to monitor and predict the future of farmland biodiversity. It also suggests that low-input, diversified agriculture combined with the maintenance of semi-natural habitat cover can contribute to the conservation of both specialist and generalist bird communities in agricultural landscapes experiencing rapid climate change.

Detecting the Effects of Deep-Seabed Nodule Mining: Simulations Using Megafaunal Data From the Clarion-Clipperton Zone

The International Seabed Authority is in the process of preparing exploitation regulations for deep-seabed mining (DSM). DSM has the potential to disturb the seabed over wide areas, yet there is little information on the ecological consequences, both at the site of mining and surrounding areas where disturbance such as sediment smothering could occur. Of critical regulatory concern is whether the impacts cause “serious harm” to the environment. Using metazoan megafaunal data from the Clarion-Clipperton Zone (northern equatorial Pacific), we simulate a range of disturbances from very low to severe, to determine the effect on community-level metrics. Two kinds of stressors were simulated: one that impacts organisms based on their affinity to nodules, and another that applies spatially stochastic stress to all organisms. These simulations are then assessed using power analysis to determine the amount of sampling required to distinguish the disturbances. This analysis is limited to modelling lethal impacts on megafauna. It provides a first indication of the effect sizes and ecological nature of mining impacts that might be expected across a broader range of taxa. To detect our simulated ‘tipping point’, power analyses suggest impact monitoring samples should each have at least 500-750 individual megafauna; and, at least five such samples, as well as control samples should be assessed. In the region studied, this translates to approximately 1500 – 2300 m2 seabed per impact monitoring sample; i.e., 7500 - 11 500 m2 in total for a given location and/or habitat. Detecting less severe disturbances requires more sampling. The numerical density of individuals and Pielou’s evenness of communities appear most sensitive to simulated disturbances and may provide suitable ‘early warning’ metrics for monitoring. To determine the sampling details for detecting the desired threshold(s) for harm, statistical effect sizes will need to be determined and validated. The determination of what constitutes serious harm is a legal question that will need to consider socially acceptable levels of long-term harm to deep-sea life, and may change as new information becomes available. Monitoring details, data, and results including power analyses should be made fully available, to facilitate independent review and evidence-based policy decisions.

Restauración de interacciones ecológicas: medidas y consecuencias a escala de comunidad

Garcia-Callejas, D., Torres, A. 2019. Restoration of ecological interactions: metrics and outcomes at the community scale. Ecosistemas 28(2): 42-49. Doi.: 10.7818/ECOS.1748 The restoration of ecological interactions is key for recovering the biodiversity and other attributes of degraded ecosystems. In particular, each interaction has the potential to alter the structure of the resulting community through direct and indirect effects (e.g., predation), which may result in changes in community stability or resilience against perturbations.In this study, we analyze using theoretical models how the restoration of ecological interactions in a multitrophic community modifies 1) the feasibility domain of the community, 2) the average number of species that persist in it, and 3) the importance of indirect effects on species dynamics. We simulate the progressive establishment of floral, frugivore and predator visitants in a community and measure its impact on such metrics.Our results show the overall complex effect of restoring interactions at the top of the trophic chains. Communities with higher trophic structure are in average more persistent, whereas their feasibility domain is lower than in plant-only communities. This apparent dichotomy is explained by the dual role of the introduced interactions: an increase in the number of interactions is destabilizing, but it simultaneously mitigates destabilizing variations on demographic rates. Overall, our results emphasize the need to integrate community-level metrics, such as those proposed here, in studies aiming at improving our understanding of the restoration of ecological interactions and ecosystems trajectories.

Chronic nutrient inputs affect stream macroinvertebrate communities more than acute inputs: An experiment manipulating phosphorus, nitrogen and sediment

Freshwaters worldwide are affected by multiple stressors. Timing of inputs and pathways of delivery can influence the impact stressors have on freshwater communities. In particular, effects of point versus diffuse nutrient inputs on stream macroinvertebrates are poorly understood. Point-source inputs tend to pose a chronic problem, whereas diffuse inputs tend to be acute with short concentration spikes. We manipulated three key agricultural stressors, phosphorus (ambient, chronic, acute), nitrogen (ambient, chronic, acute) and fine sediment (ambient, high), in 112 stream mesocosms (26 days colonisation, 18 days of manipulations) and determined the individual and combined effects of these stressors on stream macroinvertebrate communities (benthos and drift). Chronic nutrient treatments continuously received high concentrations of P and/or N. Acute channels received the same continuous enrichment, but concentrations were doubled during two 3-hour periods (day 6, day 13) to simulate acute nutrient inputs during rainstorms. Sediment was the most pervasive stressor in the benthos, reducing total macroinvertebrate abundance and richness, EPT (mayflies, stoneflies, caddisflies) abundance and richness. By contrast, N or P enrichment did not affect any of the six studied community-level metrics. In the drift assemblage, enrichment effects became more prevalent the longer the experiment went on. Sediment was the dominant driver of drift responses at the beginning of the experiment. After the first acute nutrient pulse, sediment remained the most influential stressor but its effects started to fade. After the second pulse, N became the dominant stressor. In general, impacts of either N or P on the drift were due to chronic exposure, with acute nutrient pulses having no additional effects. Overall, our findings imply that cost-effective management should focus on mitigating sediment inputs first and tackle chronic nutrient inputs second. Freshwater managers should also take into account the length of exposure to high nutrient concentrations, rather than merely the concentrations themselves.

The Effect of Disturbance on Macroinvertebrate Community Structure in Northeastern Oregon

Biodiversity in aquatic ecosystems is generally viewed as a reliable indicator of ecosystem health. High biodiversity indicates a healthy ecosystem that functions properly because of the right combination of physical, chemical, and biological factors. Anthropogenic disturbance decreases biodiversity by modifying these factors. The Grande Ronde and Imnaha River basins in northeastern Oregon are occupied by land uses that could be disturbing aquatic ecosystems. Biological assessments (bioassessments) were used in this study to determine the effects of disturbance on macroinvertebrate community structure within the Grande Ronde, Wallowa, and Imnaha rivers. Macroinvertebrate distribution and abundance data collected from upstream and downstream sites on each river were used to calculate species- and community-level metrics (e.g., richness, abundance and the Family Biotic Index [FBI]) for each site. These metrics revealed differences between sites and between rivers, as well as a decrease in water quality and biodiversity for the Grande Ronde and Imnaha rivers. The Wallowa River did not conform to this trend, likely because the upstream site was directly below an oligotrophic lake. In general, metrics were not indicative of impaired macroinvertebrate communities, but management efforts should be taken to conserve biodiversity in lower reaches of rivers within the Grande Ronde and Imnaha river basins.

A century of climate and land-use change cause species turnover without loss of beta diversity in California's Central Valley.

Climate and land-use changes are thought to be the greatest threats to biodiversity, but few studies have directly measured their simultaneous impacts on species distributions. We used a unique historic resource-early 20th-century bird surveys conducted by Joseph Grinnell and colleagues-paired with contemporary resurveys a century later to examine changes in bird distributions in California's Central Valley, one of the most intensively modified agricultural zones in the world and a region of heterogeneous climate change. We analyzed species- and community-level occupancy using multispecies occupancy models that explicitly accounted for imperfect detection probability, and developed a novel, simulation-based method to compare the relative influences of climate and land-use covariates on site-level species richness and beta diversity (measured by Jaccard similarity). Surprisingly, we show that mean occupancy, species richness and between-site similarity have remained remarkably stable over the past century. Stability in community-level metrics masked substantial changes in species composition; occupancy declines of some species were equally matched by increases in others, predominantly species with generalist or human-associated habitat preferences. Bird occupancy, richness and diversity within each era were driven most strongly by water availability (precipitation and percent water cover), indicating that both climate and land-use are important drivers of species distributions. Water availability had much stronger effects than temperature, urbanization and agricultural cover, which are typically thought to drive biodiversity decline.

How different are species distribution model predictions?—Application of a new measure of dissimilarity and level of significance to giant panda Ailuropoda melanoleuca

Species distribution models (SDMs) are widely used for predicting species' spatial distributions. Different model setup and data input however can lead to variable model predictions. Existing studies on quantifying SDM dissimilarity primarily rely on partitioning the variability in SDM-produced community level metrics such as species richness and turnover rate which are threshold-dependent and are generated with binary range maps of multiple species. Most existing measurements of spatial dissimilarity constitute geometric comparisons, which is limited compared to a more information-theoretic application of statistical dissimilarity measures using SDM predictions as direct input without renormalization. We introduce a novel method to quantify the degree of dissimilarity and its level of significance between unscaled SDM predictions of a single species. We apply the method to giant panda Ailuropoda melanoleuca data as well as pairs of simulated species distributions. We utilize a pixel-based Bhattacharyya distance to quantify the degree of dissimilarity among predictions of giant panda habitat of different combinations of model types, Global Climate Models (GCMs) and Representative Concentration Pathways (RCPs). Comparisons are also made between pairs of simulated species with different degrees of dissimilarity in spatial distribution. To evaluate the level of significance, the observed dissimilarity measure is compared against a null distribution that captures the level of dissimilarity caused by small and random variations. Specific pairs of climate scenarios (HadGEM2-ES with HadGEM2-AO and HadGEM2-AO with MIROC5) consistently produce statistically similar predictions of giant panda habitat; the highest level of RCP tends to result in more similar predictions, suggesting a convergence of model predictions. The simulated scenarios also show that the proposed method is able to effectively differentiate a range of artificial species with varying degree of dissimilarity in their resource selection preference. Our method can also reflect the dissimilarity that cannot be quantified by traditional metrics that rely on geometric comparisons. The proposed method supplements existing studies by utilizing a novel application of statistical comparisons to measure dissimilarity between user-defined pairs of models. It provides a robust way to construct the null distribution of dissimilarity that contrasts the degree of the observed dissimilarity with the intrinsic model variability. Our study provides useful insight to facilitate building more computationally efficient and robust ensemble SDMs, and it lends a practical tool to help understand the processes that contribute to prediction variability among SDMs.

A macrophysiology approach to watershed science and management

Freshwaters are among the most imperiled ecosystems on the planet such that much effort is expended on environmental monitoring to support the management of these systems. Many traditional monitoring efforts focus on abiotic characterization of water quantity or quality and/or indices of biotic integrity that focus on higher scale population or community level metrics such as abundance or diversity. However, these indicators may take time to manifest in degraded systems and delay the identification and restoration of these systems. Physiological indicators manifest rapidly and portend oncoming changes in populations that can hasten restoration and facilitate preventative medicine for degraded habitats. Therefore, assessing freshwater ecosystem integrity using physiological indicators of health is a promising tool to improve freshwater monitoring and restoration. Here, we discuss the value of using comparative, longitudinal physiological data collected at a broad spatial (i.e. watershed) scale (i.e. macrophysiology) as a tool for monitoring aquatic ecosystem health within and among local watersheds to develop timely and effective management plans. There are emerging tools and techniques available for rapid, cost-effective, and non-lethal physiological sampling and we discuss how these can be integrated into management using fish as sentinel indicators in freshwater. Although many examples of this approach are relatively recent, we foresee increasing use of macrophysiology in monitoring, and advocate for the development of more standard tools for consistent and reliable assessment.