Anthropogenic Disturbance Research Articles

Assessing Residency and Site Fidelity in Bottlenose Dolphins: A Literature Review and Bibliometric Analysis

Residency and site fidelity are important parameters in population ecology for many species as they indicate the temporal and spatial use for individuals. Although both terms are clearly different, they are used interchangeably due to lack of clarity in their definitions and the ways to assess them, especially in bottlenose dolphins (Tursiops spp.). Individuals with well-defined patterns of residency and site fidelity may be more vulnerable to anthropogenic disturbances; thus, the study of these parameters may help to better assess such impacts. However, interspecific differences and logistical restrictions for the study of dolphins have prevented consensus. We set out to investigate the factors that have influenced measurements of residency and site fidelity in bottlenose and a set of other dolphin species through a retrospective (~30 y: 1990 to 2019) literature review. We found 117 scientific papers with a two-fold increasing trend approximately every 15 years, with 50% published in only four journals. Most of the studies were developed in the United States, followed by Australia and Europe, likely due to strict policies for marine mammal conservation. Author collaboration network analysis showed highly atomized national groups in which North American organizations formed the biggest cluster, followed by Australia, Africa, and Europe. However, large worldwide gaps still exist, possibly because of the heterogeneity in marine mammal sampling efforts and limited information availability in the North Pacific, Central and South America, Africa, Asia, and the Indian Ocean. We found 30 different classification methods in which 12 were based on defined categories. We provide conceptual aid to distinguish between the use of both terms, as well as guidance to tackle the challenge of defining patterns of temporal use due to the variability of thresholds for classifying individuals. A paradigm shift is needed to create comprehensive, standardized, and generalized assessments of residency and site fidelity, which can be compared based on their performance across different populations of bottlenose dolphins around the world.

Environmental conditions influencing the early colonization stage of Ludwigia hexapetala , an aquatic plant recently invasive in Italy

Freshwater ecosystems are among the most susceptible to biological invasions. The South American Ludwigia hexapetala is an aquatic plant that is becoming an increasing threat in many European waterbodies, recently including Italy. This study aimed to define the main parameters influencing the early colonization stage of L. hexapetala by overlapping the percentage cover of this species with environmental parameter data collected at 24 aquatic sites from six waterbodies in north-central Italy. At each site, chemical and physical characteristics of the water (temperature, pH, dissolved oxygen, conductivity, nitrates, phosphates, ammonia, depth, transparency), grain size of the substrate and level of anthropogenic disturbance were evaluated. The results showed that although L. hexapetala prefers shallow, warm, alkaline, moderately rich in ions and nutrients (especially phosphates) and oxygen-poor waters, it can grow in a wide range of environmental conditions. Moreover, as a typical invasive alien species, it spreads opportunistically in disturbed, unstable sites. Thus, L. hexapetala can invade freshwater habitats with different environmental conditions and subjected to anthropogenic disturbance. However, the results suggest that water depth may be a limiting factor in the early colonization stage of this species, which does not seem to be able to colonise waters deeper than 1 m in investigated sites, while it has been observed in significantly deeper waters in other European countries with a longer invasion history. Detecting the environmental parameters that most influence the growth of L. hexapetala becomes crucial both to identify the sites most at-risk of invasion in which to initiate timely monitoring actions for the species, and to be able to develop better management and control actions for this alien species in sites that have already been invaded.

Anthropogenic disturbance produces divergent effects in the community structure and composition of tropical semi-evergreen forests in the Eastern Himalaya

Studies documenting anthropogenic disturbance-driven changes in forest communities of the Eastern Himalaya, a global biodiversity hot spot, are largely lacking. We studied six forest sites of tropical semi-evergreen forests in Arunachal Pradesh in the Eastern Himalaya to understand the effects of varying disturbance intensities on the forest community structure and composition. Based on the magnitude of disturbance, forest sites were classified as experiencing low, moderate and high disturbance. Mean species richness (SR) of trees and shrubs decreased from low disturbance to high disturbance. Mean SR of herbs was maximum in moderately disturbed forest sites. Maximum values of the Shannon-Wiener Diversity Index (SD) were recorded for trees at sites with low disturbance, for shrubs at sites with high disturbance and for herbs in moderately disturbed forests. Pilelou Evenness Index (EI) values were maximum for trees at sites with high disturbance, while maximum EI values for shrubs and herbs were recorded in the forest sites with low disturbance. The number of tree families decreased from 18 to 13 in the forests with low and high disturbance, respectively. Moderate disturbance led to increased herb species richness and diversity, while increasing disturbance produced contrasting effects on trees. High anthropogenic disturbance led to low species richness, but high diversity amongst shrubs. Our investigations suggest that the magnitude of disturbance elicits differential responses in different physiognomic classes in the forest ecosystems and further our understanding of the effects of disturbance in tropical forest ecosystems of a global biodiversity hotspot.

Deep seafloor hydrothermal vent communities buried by volcanic ash from the 2022 Hunga eruption

Mass mortality of marine animals due to volcanic ash deposition is present in the fossil record but has rarely been documented in real time. Here, using remotely-operated vehicle video footage and analysis of ash collected at the seafloor, we describe the devastating effect of the record-breaking 2022 Hunga submarine volcanic eruption on endangered and vulnerable snail and mussel species that previously thrived at nearby deep-sea hydrothermal vents. In contrast to grazing, scavenging, filter-feeding, and predatory vent taxa, we observed mass mortality, likely due to smothering during burial by thick ash deposits, of the foundation species, which rely on symbiotic chemosynthetic bacteria for the bulk of their nutrition. This is important for our broad understanding of the natural disturbance of marine ecosystems by volcanic eruptions and for predicting the effects of anthropogenic disturbance, like deep-sea mining, on these unique seafloor habitats.

How to count bird calls? Vocal activity indices may provide different insights into bird abundance and behaviour depending on species traits

Abstract Passive acoustic monitoring (PAM) has become an important tool for surveying birds, and there is a growing demand for approaches to obtain abundance and behavioural information from PAM recordings. Changes in bird populations have been assessed by counting recorded calls and calculating the vocal activity rate (VAR, i.e. the number of calls per recording time). However, bird calls could be counted in various ways and depending on species traits, these call counts could give us different insights on bird abundance, vocal behaviour and/or habitat use. Our study had two goals: (1) to present and evaluate two new indices based on call counts, the detection rate (DR, i.e. the number of 1‐min recordings in which the presence of a target vocalization is detected) and the maximum count per minute (MAX, i.e. the maximum number of calls found in a 1‐min recording); and (2) to present a conceptual framework showing how the interpretations of VAR, DR and MAX could depend on the index and on species traits. For three Neotropical bird species with distinct traits, we calculated VAR, DR and MAX based on PAM data from 25 sites in the Yucatan Peninsula (Mexico) that varied in their degree of anthropogenic habitat disturbance. We found moderate to high correlations between the indices and higher temporal variability in VAR compared to DR and MAX. We also found different effect sizes of habitat disturbance on the three species and indices. We suggest that DR might be a more reliable index of relative abundance than VAR for species whose calling behaviour exhibits a high cue rate and that MAX may be suitable for estimating family or flock size in gregarious birds. Our findings show the potential usefulness of developing new indices based on call counts to generate ecological hypotheses and assess changes in bird abundance and behaviour.

Unmixing-based forest recovery indicators for predicting long-term recovery success

Recovery from forest disturbances is a pivotal metric of forest resilience. Forests globally are facing unprecedented levels of both natural and anthropogenic disturbances, yet our understanding of their recovery from these disturbances remains incomplete. Remote sensing is an effective tool for understanding post-disturbance recovery, but existing approaches largely rely on spectral recovery indicators that are difficult to interpret and require long time series after disturbance, which limits their applicability to recent disturbance pulses. We here introduce a novel, ecologically informed set of recovery indicators based on fractional cover maps derived from spectral unmixing analysis of Landsat and Sentinel-2 time series. We estimated annual pre- and post-disturbance tree cover and bare ground fractions over the eastern Alps (∼130,000 km2) for the period from 1990 to 2021. From these fraction time series, we derived recovery intervals defined as the time it takes to reach a pre-defined tree cover threshold after disturbance, referred to as canopy recovery. We found mean recovery intervals between 5.5 and 13.4 years, depending on recovery threshold and disturbance severity. Comparing our results to traditional remote sensing-based approaches of mapping forest recovery, we found that spectral unmixing-based recovery indicators give considerably more realistic recovery intervals than approaches based on spectral indices because they effectively distinguish tree regeneration from other post-disturbance vegetation (e.g., shrubs, grasses). Finally, we were able to accurately predict the long-term forest recovery success based on the information available only three years after disturbance, which underlines the high importance of a short window of reorganization post-disturbance, and highlights the utility of remote sensing to inform post-disturbance forest management (e.g., in identifying areas in need of tree planting). Our study thus provides an important step ahead in the remote sensing-based monitoring of forest recovery and resilience, which is urgently needed in a time of rapid forest change.

Saharo-Sindian endemic flora of Egypt: critical checklist, floristic analysis, habitats, and phytogeographic distribution

The Saharo-Sindian region is characterized by savannas, semi-deserts, and hot deserts. This floristic region includes Morocco, Mauretania, Algeria, Libya, Egypt, Palestine, Kuwait, Saudi Arabia, Qatar, Bahrain, United Arab Emirates, Oman, Yemen, South of Jordan, Syria, Iraq, Afghanistan, Pakistan, in addition to the Sind region. The Sudano-Zambezian region, part of the Paleotropical Kingdom, and the Mediterranean and Irano-Turanian regions, included in the Holarctic Kingdom, share a significant portion of their flora with the studied region. This study initiates the examination of the Saharo-Sindian endemic plants occurring in Egypt. Its objectives include assessing the list of endemic plants within this floristic region, and studying various aspects such as: life forms, habitats, rarity forms, flowering times, dispersal types, and phytogeographical distribution. Twenty field trips were conducted from spring 2020 to September 2023, investigating different regions in Egypt. In addition, all the previous studies performed in the investigated area, scientific literature, and specimens from the region housed in different herbaria have been taken into consideration. The inventory of plants that are endemic to the Saharo-Sindian floristic region in Egypt comprises 126 plant taxa (109 species, 17 subspecies) distributed across 87 genera and 37 families. These endemics are found in 11 habitat types, with the most abundant occurrences observed in inland rocky areas (82 taxa) and temperate shrublands (57 taxa). Moreover, South Sinai stands out as the richest region for Saharo-Sindian endemics, hosting a remarkable 83 taxa, which constitute 65.9% of the total endemics. Among these, the chamaephytes group leads with 56 taxa, followed by the therophytes with 32 taxa. Pogonochores (45 taxa) are the most represented dispersal type. This study holds significant importance in evaluating a critical checklist of plants endemic to the Saharo-Sindian region in Egypt, contributing to our understanding of species diversity in regions facing severe anthropogenic disturbance. This list provides a foundational reference for future monitoring programs.

Bryofloristic diversity and conservation value of a protected area in the Brazilian semi-arid region

We collected 137 samples (71—rainy season; 66—dry) for the Brazilian state of Paraíba. With a total of 23 species (one hornwort, 14 mosses and nine liverworts), we updated the bryoflora of Paraíba, a hotspot of bryophytes, by one rare species (Weissia controversa), increasing the total number of species to 188. The floristic composition in the Poeta e Repentista Juvenal de Oliveira State Park is affected by chronic anthropogenic disturbances, and is typical of arid environments, regardless of the season. This indicates homogenization of the habitat from the loss of ecological niche due to the disordered use of local natural resources. However, the record of Philonotis hastata, categorized as Near Threatened by the IUCN; the geographic expansion of a species; and the presence of rare species for Brazil reinforce the importance of the Conservation Unit for bryophyte biodiversity. Despite the floristic composition, we identified that interpretations about biology, environmental functionality and species distribution are more consistent for environmental assessment and decision-making on conservation actions.

Estimating beluga whale abundance from space: using drones to ground‐validate VHR satellite imagery

AbstractRoutine monitoring of cetaceans is imperative for understanding their population trends and making informed management decisions. However, the inherent nature of cetaceans and the marine ecosystems they inhabit make annual population surveys logistically and economically challenging with current survey methods. One emerging solution is utilizing very high‐resolution (VHR) satellite imagery, which is a logistically efficient method for providing an instantaneous view of areas spanning hundreds of square kilometers. The objective of this study was to determine two factors required to reliably conduct beluga whale population abundance estimates with VHR satellite imagery: (1) depths that beluga whales are visible in VHR satellite images, which are used to define availability bias correction factors, and (2) a comparison of abundance estimates in VHR satellite imagery to current aerial methods. We submerged beluga whale models to different depths in two different water clarities and determined that beluga whales are distinguished only at the surface in turbid water (Secchi depth: 2.56 m) and at depths of 0–2 m in clear water (Secchi depth: 4.04 m). Based on the proportion of time beluga whales spend at these depths, an availability bias correction factor for Western Hudson Bay beluga whales was defined as 2.40 ± 0.16 for turbid water and 1.89 ± 0.05 for clear water. Synchronous ground‐validation surveys determined availability corrected beluga whale abundance estimates in 0.31 m VHR satellite imagery (n = 173 beluga whales) and imagery that was HD sharpened using a proprietary algorithm to approximate 0.15 m resolution (n = 170) to be comparable to drone imagery (n = 164). VHR satellite imagery has the potential to increase the frequency of beluga whale population surveys, which has become increasingly important as beluga whales face rapid ecosystem changes and increased anthropogenic disturbances.

Electrosensory and metabolic responses of weakly electric fish to changing water conductivity.

Weakly electric Gymnotiform fishes use self-generated electric organ discharges (EODs) to navigate and communicate. The electrosensory range for these processes is a function of EOD amplitude, determined by the fish's electric organ (EO) output and the electrical conductivity of the surrounding water. Anthropogenic activity, such as deforestation, dams, and industrial/agricultural runoff, are known to increase water conductivity in neotropical habitats, likely reducing the electrosensory range of these fish. We investigated whether fish modulate EO output as means of re-expanding electrosensory range after a rapid increase in water conductivity in the pulse-type Brachyhypopomus gauderio and the wave-type Eigenmannia virescens. Furthermore, because EOD production incurs significant metabolic costs, we assessed whether such compensation is associated with an increase in metabolic rate. Following the conductivity increase B. gauderio increased EOD amplitude by 20.2±4.3% over six days but with no associated increase in metabolic rate, whereas the EOD amplitude of E. virescens remained constant, accompanied by an unexpected decrease in metabolic rate. Our results suggest that B. gauderio uses a compensation mechanism that requires no metabolic investment, such as impedance matching, or a physiological tradeoff wherein energy is diverted from other physiological processes to increase EO output. These divergent responses between species could be the result of differences in reproductive life history or evolutionary adaptations to different aquatic habitats. Continued investigation of electrosensory responses to changing water conditions will be essential for understanding the effects of anthropogenic disturbances on gymnotiforms, and potential physiological mechanisms for adapting to a rapidly changing aquatic environment.

Validating a Non-Invasive Method for Assessing Cortisol Concentrations in Scraped Epidermal Skin from Common Bottlenose Dolphins and Belugas.

Society is showing a growing concern about the welfare of cetaceans in captivity as well as cetaceans in the wild threatened by anthropogenic disturbances. The study of the physiological stress response is increasingly being used to address cetacean conservation and welfare issues. Within it, a newly described technique of extracting cortisol from epidermal desquamation may serve as a non-invasive, more integrated measure of a cetacean's stress response and welfare. However, confounding factors are common when measuring glucocorticoid hormones. In this study, we validated a steroid hormone extraction protocol and the use of a commercial enzyme immunoassay (EIA) test to measure cortisol concentrations in common bottlenose dolphin (Tursiops truncatus) and beluga (Delphinapterus leucas) epidermal samples. Moreover, we examined the effect of sample mass and body location on cortisol concentrations. Validation tests (i.e., assay specificity, accuracy, precision, and sensitivity) suggested that the method was suitable for the quantification of cortisol concentrations. Cortisol was extracted from small samples (0.01 g), but the amount of cortisol detected and the variability between duplicate extractions increased as the sample mass decreased. In common bottlenose dolphins, epidermal skin cortisol concentrations did not vary significantly across body locations while there was a significant effect of the individual. Overall, we present a contribution towards advancing and standardizing epidermis hormone assessments in cetaceans.

Long-term, medium-term and acute stress response of urban populations of Eurasian red squirrels affected by different levels of human disturbance.

Animals in urban areas often encounter novel and potentially stressful conditions. It is important to understand how wildlife cope with anthropogenic disturbance. To investigate this specific adaptation we live-trapped squirrels in two study sites in Warsaw: a forest reserve and an urban park and we estimated stress responses at three levels: long-term and medium-term stress (the level of stress hormones, i.e. cortisol and cortisone concentrations, in hair and feces) and acute reaction to human-induced stress (measured during handling with the aid of the three indices: breath rate, struggle rate, and vocalization). According to GLMM models no difference in the stress hormones level was found between the two populations. The only differences in cortisol concentrations clearly depended on the season, i.e. being higher in autumn and winter comparying to other seasons. There was no influence of sex, or reproductive status on stress hormones. Forest squirrels had significantly higher breath rates, suggesting they were more stressed by handling. There was no difference in the struggle rate between study areas, this index was mostly affected by season (i.e. being highest in winter). First-trapped squirrels vocalized less than during the subsequent trappings. Assumingly, during the first, and more stressful trapping, squirrels used 'freezing' and/or little vocalization, while during next captures they used alarm calls to warn conspecifics. Overall, we showed that the two squirrel populations differed only in terms of their breath rate. This suggests that they did not differ in medium-term and long-term stress in general, but they can differ in acute response to handling. This also suggests that both populations were similarly affected by environmental factors. The lack of clear effects may also be due to population heterogeneity. Thus, in order to assess the effects of anthropogenic stressors a broader range of indicators and diverse analytical methods, including behavioral analyses, should be employed.

Deer activity levels and patterns vary along gradients of food availability and anthropogenic development

Animal activity reflects behavioral decisions that depend upon environmental context. Prior studies typically estimated activity distributions within few areas, which has limited quantitative assessment of activity changes across environmental gradients. We examined relationships between two response variables, activity level (fraction of each day spent active) and pattern (distribution of activity across a diel cycle) of white-tailed deer (Odocoileus virginianus), with four predictors—deer density, anthropogenic development, and food availability from woody twigs and agriculture. We estimated activity levels and patterns with cameras in 48 different 10.36-km2 landscapes across three larger regions. Activity levels increased with greater building density, likely due to heightened anthropogenic disturbance, but did not vary with food availability. In contrast, activity patterns responded to an interaction between twigs and agriculture, consistent with a functional response in habitat use. When agricultural land was limited, greater woody twig density was associated with reduced activity during night and evening. When agricultural land was plentiful, greater woody twig density was associated with more pronounced activity during night and evening. The region with the highest activity level also experienced the most deer-vehicle collisions. We highlight how studies of spatial variation in activity expand ecological insights on context-dependent constraints that affect wildlife behavior.

A case study on the function of turf algae as suitable habitat for peracarid crustaceans in disturbed environments from SW Mediterranean Sea

ABSTRACT In the summer of 2014, a field study was carried out in four coastal rocky bottoms from the southeast coast of Spain. In this region, dense canopies of Ericaria mediterranea characterize the undisturbed areas and cover much of the infralittoral stage. Turfs composed of the coralline algae Ellisolandia elongata replace the canopy in places where any anthropogenic disturbance occurs. The main objective of this study was to compare the peracarid fauna inhabiting within the two types of phytal substrate, and to conduct several statistical analyses to detect significant differences between the two assemblages. Contrary to expected, the analyses showed that in E. elongata there was a higher population density of peracarids, as well as higher species richness and values for α-diversity indexes. However, none of these differences was statistically significant, although site-to-site comparison indicated greater differences between locations with the same physical cover. The data pointed out that the assemblage that inhabits the coralline turfs in the area was not an impoverished version of that found in pristine locations, so these algae can act as a suitable habitat for peracarids in case of mild human disturbance.

A meta‐analysis of the effects of anthropogenic disturbances on tropical mammal functional diversity

Abstract Understanding the processes that shape biological communities under a variety of perturbations is a central challenge in ecology and conservation. Mammals contribute to critical functional processes of an ecosystem, such as seed dispersal to maintain forest carbon stocks. The analysis of functional diversity, which measures the range and value of the ecological traits of organisms, provides critical information to understanding the link between biodiversity and ecosystem functioning. A growing number of studies have investigated the effects of anthropogenic disturbances on mammalian functional diversity; however, their results are very heterogeneous. Here, we conduct a comprehensive meta‐analysis of the effects of such anthropogenic disturbances on mammalian functional diversity in the tropics. We highlight major trends and analyse the influence of the type of anthropogenic disturbance, subgroups, and the functional diversity index used/applied. Our results indicate a negative effect of anthropogenic disturbances on mammalian functional diversity, particularly on functional richness (FRic) and functional dispersion (FDis). Habitat isolation was the stressor with the strongest effect, while agriculture and urbanisation showed a positive link with functional diversity. These results indicate that anthropogenic disturbances not only affect taxonomic diversity, but also reduce the functional diversity of mammals, which is likely to affect ecosystem functioning and possibly ecosystem service provision.

Seasonal dynamic of the benthic food web in subtidal sandbanks

Submarine sandbanks are prevalent worldwide but, paradoxically, these ecosystems and their dynamics remain largely unknown. As submarine sandbanks are targeted by a large variety of human activities, there is an urgent need for sound scientific knowledge for environmental impact assessments (EIAs) and the appropriate management of biodiversity in these areas. To our knowledge, the present study is the first to investigate the seasonal dynamics of the benthic food web in sandbank areas. We performed a stable isotope analysis in the French part of the southern North Sea. This area is typified by numerous sandbanks and by massive phytoplankton blooms in spring. We found a very simple food web structure that is heavily dependent on organic matter particles in seawater. Primary consumers, i.e. deposit feeders and, to a lesser extent, suspension feeders, dominate the benthic biomass. Small predator-scavengers such as annelids, shrimps and crabs prey upon them. Fish predators such as Echiichthys vipera represent a very restricted proportion of the biomass. We observed that the general structure of the food web is relatively well preserved over seasons. We thus propose that the functioning of the ecosystem is resilient to natural disruptions—such as dune migrations—and, probably, to anthropogenic disturbances.

Quantifying the relative importance of influencing factors on NPP in Hengduan Mountains of the Tibetan Plateau from 2002 to 2021: A Dominance Analysis

Net primary productivity (NPP) stands as a crucial indicator of ecosystem health and carbon cycling, shaped by a complex interplay of climate change and anthropogenic disturbances. Understanding the relative contributions of these factors is essential for informing strategies aimed at achieving carbon neutrality and peaking emissions. In this study, we used the Carnegie-Ames-Stanford-Approach (CASA) model to assess NPP dynamics in the ecologically fragile area of the middle Hengduan Mountains on the southeastern Tibetan Plateau (TPHM). Dominance Analysis (DA) was employed to quantify and visualize the relative importance of climate change and anthropogenic disturbances on NPP. Our findings revealed significant annual fluctuations in NPP, with 61.8% of the area experiencing improvement in NPP, although the overall trend was not statistically significant. Needleleaf forests and mixed forests below medium elevation (< 4000 m) suffered negative impacts from human activity intensity, while vegetation at medium-high elevation (4000–5000 m) showed positive effects. The area dominated by anthropogenic disturbances influencing NPP accounted for 49.16% of the study area, followed by combined effects (36.86%) and climatic factors (13.98%). Human activity intensity, particularly in nature reserves, emerged as the predominant driver of NPP in plateau regions, while climatic factors primarily drove NPP decline in river valleys and a few alpine mountains. Moreover, combined effects contributed to NPP enhancement in most regions. This study underscores the critical role of human activity intensity in shaping NPP dynamics in high-elevation regions of the Tibetan Plateau, providing valuable insights for ecological conservation and carbon stock enhancement efforts in ecologically fragile areas.

Integration of a battery of biomarkers to evaluate the health status of field-collected frogs of Leptodactylus luctator living in ecosystems with different anthropogenic disturbances

Amphibians are the most threatened group of vertebrates because they have certain biological and ecological characteristics that make them sensitive to environmental changes. The aim of this study was to evaluate the health status of field-collected adult frogs of Leptodactylus luctator (Amphibia, Anura) living in sites with different anthropogenic disturbances (florihorticulture, petrochemical industry and sewage discharges) and a reference site without any detectable influence of such activities. To this end, a battery of 21 biomarkers (hematological, biochemical and individual biomarkers) was studied using a multivariate approach that allows us to evaluate the relationship between them and provide information on their usefulness. The frogs at the florihorticulture, petrochemical and sewage discharges sites exhibited several biomarkers far from homeostasis. In addition, we identified 11 of 21 biomarkers that were useful indicators of the health status of the frogs and allowed discrimination between study sites in the following order: lymphocytes (98 %), neutrophils (45 %), hemoglobin (42 %), monocytes (41 %), fat body index (35 %), eosinophils (35 %), hepatosomatic index (33 %), mean corpuscular hemoglobin (32 %), thrombocytes (27 %), catalase in liver (26 %), and GST in liver (26 %). The results suggest that hematological biomarkers contribute the most to site separation, whereas biochemical biomarkers contribute the least. The integral interpretation of the results also allowed us to diagnose the different health status of L. luctator: The frogs from the petrochemical industry were the most negatively affected, followed by the frogs from the sewages discharges and finally the frogs from the florihorticulture and reference sites. This is the first field study with anurans in which so many biomarkers were examined.

Chronic anthropogenic disturbance mediates the bottom-up influence of plant diversity on arthropods in tropical forests.

Understanding how primary productivity and diversity affect secondary productivity is an important debate in ecology with implications for biodiversity conservation. Particularly, how plant diversity influences arthropod diversity contributes to our understanding of trophic cascades and species coexistence. Previous studies show a positive correlation between plant and arthropod diversity. The theory of associational resistance suggests that plant herbivory rate will decrease with increasing plant diversity indicating feedbacks between primary diversity, productivity, and secondary productivity rates. However, our understanding of how these relations are mediated by anthropogenic disturbance is still limited. We surveyed 10 forest sites, half of which are disturbed by fire, logging, and tree pruning, distributed in two climatic zones in Benin, West Africa. We established 100 transects to record plant species and sampled arthropods using pitfall traps, ceramic plates with bait, and sweeping nets. We developed a structural equation model to test the mediating effect of chronic anthropogenic disturbance on plant diversity and how it influences arthropod diversity and abundance. Arthropod diversity increased but arthropod abundance decreased with increasing intensity of disturbance. We found no significant bottom-up influence of the plant diversity on arthropod diversity but a significant plant diversity-arthropod abundance relationship. Some arthropod guilds were significantly affected by plant diversity. Finally, herbivory rates were positively associated with arthropod diversity. Synthesis. Our results highlight how chronic anthropogenic disturbance can mediate the functional links between trophic levels in terms of diversity and productivity. Our study demonstrated a decoupled response of arthropod diversity and abundance to disturbance. The direct positive influence of plant diversity on herbivory rates we found in our study provides counter-support for the theory of associational resistance.

Linking Dissolved Organic Matter Composition to Landscape Properties in Wetlands Across the United States of America

AbstractWetlands are integral to the global carbon cycle, serving as both a source and a sink for organic carbon. Their potential for carbon storage will likely change in the coming decades in response to higher temperatures and variable precipitation patterns. We characterized the dissolved organic carbon (DOC) and dissolved organic matter (DOM) composition from 12 different wetland sites across the USA spanning gradients in climate, landcover, sampling depth, and hydroperiod for comparison to DOM in other inland waters. Using absorption spectroscopy, parallel factor analysis modeling, and ultra‐high resolution mass spectroscopy, we identified differences in DOM sourcing and processing by geographic site. Wetland DOM composition was driven primarily by differences in landcover where forested sites contained greater aromatic and oxygenated DOM content compared to grassland/herbaceous sites which were more aliphatic and enriched in N and S molecular formulae. Furthermore, surface and porewater DOM was also influenced by properties such as soil type, organic matter content, and precipitation. Surface water DOM was relatively enriched in oxygenated higher molecular weight formulae representing HUPHigh O/C compounds than porewaters, whose DOM composition suggests abiotic sulfurization from dissolved inorganic sulfide. Finally, we identified a group of persistent molecular formulae (3,489) present across all sites and sampling depths (i.e., the signature of wetland DOM) that are likely important for riverine‐to‐coastal DOM transport. As anthropogenic disturbances continue to impact temperate wetlands, this study highlights drivers of DOM composition fundamental for understanding how wetland organic carbon will change, and thus its role in biogeochemical cycling.