Invertebrate Abundance Research Articles

Drought at a coastal wetland affects refuelling and migration strategies of shorebirds

Droughts can affect invertebrate communities in wetlands, which can have bottom-up effects on the condition and survival of top predators. Shorebirds, key predators at coastal wetlands, have experienced widespread population declines and could be negatively affected by droughts. We explored, in detail, the effects of drought on multiple aspects of shorebird stopover and migration ecology by contrasting a year with average wet/dry conditions (2016) with a year with moderate drought (2017) at a major subarctic stopover site on southbound migration. We also examined the effects of drought on shorebird body mass during stopover across 14 years (historical: 1974–1982 and present-day: 2014–2018). For the detailed comparison of two years, in the year with moderate drought we documented lower invertebrate abundance at some sites, higher prey family richness in shorebird faecal samples, lower shorebird refuelling rates, shorter stopover durations for juveniles, and, for most species, a higher probability of making a subsequent stopover in North America after departing the subarctic, compared to the year with average wet/dry conditions. In the 14-year dataset, shorebird body mass tended to be lower in drier years. We show that even short-term, moderate drought conditions can negatively affect shorebird refuelling performance at coastal wetlands, which may carry-over to affect subsequent stopover decisions. Given shorebird population declines and predicted changes in the severity and duration of droughts with climate change, researchers should prioritize a better understanding of how droughts affect shorebird refuelling performance and survival.

Annual changes in the Biodiversity Intactness Index in tropical and subtropical forest biomes, 2001–2012

Few biodiversity indicators are available that reflect the state of broad-sense biodiversity—rather than of particular taxa—at fine spatial and temporal resolution. One such indicator, the Biodiversity Intactness Index (BII), estimates how the average abundance of the native terrestrial species in a region compares with their abundances in the absence of pronounced human impacts. We produced annual maps of modelled BII at 30-arc-second resolution (roughly 1 km at the equator) across tropical and subtropical forested biomes, by combining annual data on land use, human population density and road networks, and statistical models of how these variables affect overall abundance and compositional similarity of plants, fungi, invertebrates and vertebrates. Across tropical and subtropical biomes, BII fell by an average of 1.9 percentage points between 2001 and 2012, with 81 countries seeing an average reduction and 43 an average increase; the extent of primary forest fell by 3.9% over the same period. We did not find strong relationships between changes in BII and countries’ rates of economic growth over the same period; however, limitations in mapping BII in plantation forests may hinder our ability to identify these relationships. This is the first time temporal change in BII has been estimated across such a large region.

Invasive Plants Differentially Impact Forest Invertebrates, Providing Taxon-Specific Benefits by Enhancing Structural Complexity

Exotic plant species often negatively affect native herbivores due to the lack of palatability of the invading plant. Although often unsuitable as food, certain invasive species may provide non-nutritional ecological benefits through increased habitat structural complexity. To understand the potential for common invasive forest plant species of the eastern United States to benefit invertebrate communities, we examined the functional and taxonomic community composition of forest insects and spiders in long-term monitoring plots that contained invasive plant species. The extent of invasive plant species ground cover significantly altered spider community composition as categorized by hunting guild. Areas with higher invasive herbaceous and grass cover contained a higher abundance of space web-weaving and hunting spiders, respectively. Spider species richness and total invertebrate abundance also increased with greater invasive grass cover. Still, these trends were driven by just two invasive plant species, garlic mustard and Japanese stiltgrass, both of which have previously been shown to provide structural benefits to native invertebrate taxa. While these two species may improve the structural component of understory forest habitat, many invertebrate groups were not significantly correlated with other prevalent invasive plants and one species, mock strawberry, negatively affected the abundance of certain insect taxa. Particularly in forests with reduced native plant structure, invasive plant management must be conducted with consideration for holistic habitat quality, including both plant palatability and structure.

RESEARCH OF KIROVSK RESERVOIR FOR DEVELOPING MOBILE ACTIVE HYDROACOUSTIC FISH PROTECTING DEVICE

The hydrological, hydrobiological and ichthyological parameters of the Kirovsk Reservoir in the West Kazakhstan region of the Republic of Kazakhstan are described. The reservoir was selected as a model for realization of the grant project No. AP09058066 “Developing mobile active hy-droacoustic fish protecting device to protect fish and juveniles from entering the dam spillways of large hydroelectric power plants and reservoirs” of the Ministry of Education and Science of the Republic of Kazakhstan. Hydrological, hydrobiological and ichthyological studies were aimed to obtain data for making optimal decisions on the design, equipment and working algorithm of the fish protection device. Hydrological studies include measuring depths and current speed in the water area of the reservoir and in front of the dam spillway. The species composition, abundance and biomass of forage invertebrates of zooplankton and zoobenthos were studied as hydrobiological indicators. The main biological indicators, fish abundance and biomass, species composition and concentration of juveniles were taken into account when studying ichthyological data. The obtained hydrological, hydrobiological and ichthyological parameters of the Kirov Reservoir served as the basis for developing the concept of a mobile active hydroacoustic fish protecting device to prevent fish and juveniles from entering the spillways of dams at the large hydroelectric power plants and reservoirs

Interactions between invertebrate and microbial communities in decomposing camphor and Masson pine litter varied with seasonal rainfall

To reveal the changes in the interactions between invertebrates and microbes in decomposing litter with seasonal rainfall, litterbags containing camphor (Cinnamomum longepaniculatum) and Masson pine (Pinus massoniana) litter were therefore in situ incubated on the floor of Masson pine-camphor mixed plantations in the subtropical region of China. Different mesh sizes of litterbags were used to control the access of the invertebrates. The invertebrates in litterbags were collected by funnel method, and microbial communities were detected by phospholipid fatty acid (PLFA) method in slightly rainy season (SRS; November 1–December 24), micro rainy season (MRS; December 25–March 7), early rainy season (ERS; March 8–June 15) and rainy season (RS; June 16–October 31) during two decomposition years. The abundance and composition of microbial and invertebrate communities varied significantly with seasonal rainfall and tree species. Invertebrate exclusion generally decreased the bacterial and fungal biomass, and the biomass of Gram-positive bacteria and Gram-negative bacteria in Masson pine needle litter, but generally increased these indices in camphor foliar litter. Invertebrate exclusion decreased the mass loss rate of Masson pine litter, but increased the mass loss rate of camphor litter. Total microbial biomass and bacterial biomass in both foliar litters were generally higher in SRS and MRS than these in ERS and RS during the first decomposition year, whereas the situation reversed during the second decomposition year. The abundance of invertebrates increased gradually from the first SRS to the second SRS and decreased gradually afterwards. Briefly, the interactions between invertebrate and microbial communities varied greatly with litter types and seasons. Positive and negative interactions between invertebrate and microbes were respectively observed in Masson pine and camphor litters, and differential responses of microbial biomass and mass loss rate to invertebrate exclusion were found in two litter types. In turn, the interactions between invertebrates and microbes run the litter decomposition.

Physical drivers of epi- and infauna communities related to dominating macrophytes in shallow bays in the Northern Baltic Sea

Shallow coastal bays with dense aquatic phytobenthic communities are important but vulnerable habitats and nursery areas for fish and invertebrates in the Baltic Sea. These habitats are under increasing anthropogenic stress, and understanding their dynamics is a prerequisite for management and conservation. In this study, we examined the effects of isolation of the bay from the sea, water and sediment characteristics, and macrophyte species on the invertebrate communities. In each bay, both epifauna and infauna were sampled in pairs of monospecific patches of dominating habitat-forming macrophytes (Stuckenia pectinata, Chara tomentosa and Ceratophyllum demersum). We found that the invertebrate community was mainly affected by bay isolation, which correlated with other environmental variables, and thus likely drives many processes in the bays. Further, the epifauna community responded to both the median grainsize and geometric standard deviation across both the isolation gradient (S. pectinata alone) and in the S. pectinata - C. demersum macrophyte pair, whereas the median grainsize affected the epifauna in the S. pectinata - C. tomentosa macrophyte pair. The infauna community responded to either the median grainsize or the geometric standard deviation across the isolation gradient and in both macrophyte pairs. Only minor differences between the dominating macrophyte species were seen regarding invertebrate abundance, taxon richness and diversity, although the more structurally complex C. demersum supported the highest epifauna diversity and lowest infauna abundance. However, at local, within bay scale, epifauna communities varied between most pairs of macrophyte species, suggesting that habitat-forming macrophytes have important roles in structuring local invertebrate community patterns. This study emphasizes the complexity of biotic and abiotic interactions within and among shallow coastal bays, and the challenges with studying and comparing processes in these unique ecosystems.

Robots Versus Humans: Automated Annotation Accurately Quantifies Essential Ocean Variables of Rocky Intertidal Functional Groups and Habitat State

Standardized methods for effectively and rapidly monitoring changes in the biodiversity of marine ecosystems are critical to assess status and trends in ways that are comparable between locations and over time. In intertidal and subtidal habitats, estimates of fractional cover and abundance of organisms are typically obtained with traditional quadrat-based methods, and collection of photoquadrat imagery is a standard practice. However, visual analysis of quadrats, either in the field or from photographs, can be very time-consuming. Cutting-edge machine learning tools are now being used to annotate species records from photoquadrat imagery automatically, significantly reducing processing time of image collections. However, it is not always clear whether information is lost, and if so to what degree, using automated approaches. In this study, we compared results from visual quadrats versus automated photoquadrat assessments of macroalgae and sessile organisms on rocky shores across the American continent, from Patagonia (Argentina), Galapagos Islands (Ecuador), Gorgona Island (Colombian Pacific), and the northeast coast of the United States (Gulf of Maine) using the automated software CoralNet. Photoquadrat imagery was collected at the same time as visual surveys following a protocol implemented across the Americas by the Marine Biodiversity Observation Network (MBON) Pole to Pole of the Americas program. Our results show that photoquadrat machine learning annotations can estimate percent cover levels of intertidal benthic cover categories and functional groups (algae, bare substrate, and invertebrate cover) nearly identical to those from visual quadrat analysis. We found no statistical differences of cover estimations of dominant groups in photoquadrat images annotated by humans and those processed in CoralNet (binomial generalized linear mixed model or GLMM). Differences between these analyses were not significant, resulting in a Bray-Curtis average distance of 0.13 (sd 0.11) for the full label set, and 0.12 (sd 0.14) for functional groups. This is the first time that CoralNet automated annotation software has been used to monitor “Invertebrate Abundance and Distribution” and “Macroalgal Canopy Cover and Composition” Essential Ocean Variables (EOVs) in intertidal habitats. We recommend its use for rapid, continuous surveys over expanded geographical scales and monitoring of intertidal areas globally.

Habitat restoration for brown trout (Salmo trutta) has limited effects on macroinvertebrate communities in a historically metal-contaminated stream.

Quantifying the success of stream remediation or restoration projects that are designed to improve water quality or habitat, respectively, is often challenging because of insufficient posttreatment monitoring, poorly defined restoration goals, and failure to consider fundamental aspects of ecological theory. We measured the effects of habitat restoration on aquatic and terrestrial prey resources in a system recovering from the long-term effects of mining pollution. The study was conducted in the Upper Arkansas River, a Rocky Mountain stream located in central Colorado, USA. Remediation of California Gulch, a United States Environmental Protection Agency (USEPA) Superfund Site that discharged metals from past mining operations into the stream, was completed in 2000, resulting in significant improvements in water quality, benthic macroinvertebrate communities, and brown trout (Salmo trutta) populations. A large-scale restoration project designed to improve habitat and increase the density and biomass of brown trout was completed in 2014. To assess the effectiveness of these habitat improvements on invertebrate communities in this system, we sampled sites for 9 years before (2010-2014) and after (2015-2018) restoration was completed. In contrast to our expectations, we observed few changes in the abundance of aquatic or terrestrial invertebrates after restoration. The most common response was an overall reduction in abundance resulting from significant instream disturbances during and immediately after restoration, followed by a gradual return to pretreatment conditions. Despite reductions in prey abundance, the number of prey items in the diet of brown trout increased significantly after restoration. We discuss several explanations for these responses, including the effects of residual metals, increased predation by brown trout, and the recalcitrance of novel communities dominated by metal-tolerant species. Our results suggest that the effectiveness of remediation and restoration differed between macroinvertebrates and fish. Benthic macroinvertebrates were more dependent on water quality improvements at the watershed scale, whereas brown trout populations responded to both improvements in water quality and reach-scale improvements in habitat.Integr Environ Assess Manag 2022;18:1047-1055. © 2021 SETAC.

Aerial invertebrate functional groups respond to landscape composition with only detritivores and predators responding to agri-environment scheme management

Landscape-scale agricultural intensification is a major driver of biodiversity loss. Highly mobile species, such as aerial invertebrates may be disproportionately affected by land cover at large spatial scales due to their ability to disperse. Assessing the efficacy of environmentally friendly farming, such as Agri-Environment Schemes (AES), therefore, requires establishing the influence of land cover beyond focal farms or fields, contextualising the impact of agricultural management. This study measured the response of aerial invertebrate functional groups to AES management in improved and semi-improved upland grasslands accounting for spatial autocorrelation and multi-scale effects of land cover within buffers varying from 100 m to 5 km at 88 paired fields. Total aerial invertebrate abundance and diversity, including detritivores, herbivores, nectivores, predators and parasitoids all responded to different land cover types at varying scales indicative of highly complex and idiosyncratic functional group responses to landscape.After accounting for spatial autocorrelation and multi-scale landscape composition, total aerial invertebrate abundance was unaffected by agricultural management but diversity was (5%) higher in AES than conventionally managed fields. Detritivore (mostly Mycetophilidae fungus gnat) diversity and abundance were higher in AES than conventional fields, but only on improved grasslands, while predator (adult Muscidae house fly, Scathophagidae dung fly and Dolichopodidae long-legged fly) diversity was lower but abundance higher in AES than conventional fields. Aerial invertebrate herbivores (Anthomyiidae root-maggot flies and Cecidomyiidae gall midges and gnats), nectivores (Syrphidae hoverflies and Apoidea bees) and parasitoids (Ichneumonidae wasps) responded to landscape composition, but not agricultural management. Synthesis and Applications: this study suggests that landscape composition drives aerial invertebrate functional group diversity and abundance at multiple spatial scales. Nevertheless, the responses of some functional groups (detritivores and predators) to local agricultural management suggest that AES management may contribute to the maintenance or enhancement of ecosystem service delivery (nutrient cycling and pest biocontrol). Explicitly accounting for multi-scale landscape effects is necessary when assessing the impact of agricultural management on highly mobile taxa.

Relating environmental pressures to littoral biological water quality indicators in Western Balkan lakes: Can we fill the largest gaps?

Along six transects in each of six lakes across the Western Balkans, we collected data for three groups of littoral biological water quality indicators: epilithic diatoms, macrophytes, and benthic invertebrates. We assessed the relationships between them and three environmental pressures: nutrient load (eutrophication), hydro-morphological alteration of the shoreline, and water level variation, separating the effect of individual lakes and continuous explanatory variables. Lake water total phosphorus concentration (TP) showed substantial variation but was not related to any of the tested biological indicators, nor to any of the tested pressures. We suggest that this may be due to feedback processes such as P removal in the lake littoral zone. Instead, we found that a gradient in surrounding land-use towards increasing urbanization, and a land-use-based estimate of P run-off, served as a better descriptor of eutrophication. Overall, eutrophication and water level fluctuation were most important for explaining variation in the assessed indicators, whereas shoreline hydro-morphological alteration was less important. Diatom indicators were most responsive to all three pressures, whereas macrophyte biomass and species number responded only to water level fluctuation. The Trophic Diatom Index for Lakes (TDIL) was negatively related to urbanization and wave exposure. This indicates that it is a suitable indicator for pressures related to urbanization, although a confounding effect of wave exposure is possible. Invertebrate abundance responded strongly to eutrophication, but the indicator based on taxonomic composition (Average Score Per Taxon) did not. Our results suggest that our metrics can be applied in Western Balkan lakes, despite the high number of endemic species present in some of these lakes. We argue that local water management should focus on abating the causes of eutrophication and water level fluctuation, whilst preserving sufficient lengths of undeveloped shoreline to ensure good water quality in the long run.

Artificial reefs in the North –East Atlantic area: Present situation, knowledge gaps and future perspectives

Artificial reefs have been deployed in multiple regions of the world for different purposes including habitat restoration and protection, biodiversity and fish stock enhancement, fisheries management and recreation. Artificial reefs can be a valuable tool for ecosystem protection and rehabilitation, helping mitigate the effects of anthropogenic impacts that we face today. However, knowledge on artificial reefs is unevenly distributed worldwide, with some regions having much more quality information available and published (e.g. European Mediterranean Sea area), while others, for instance the North-East Atlantic area, do not. Here, we provide a characterization of purposely built artificial reefs in North-East Atlantic area based on all available literature (i.e. research papers and reports), highlighting the needs and gaps that are vital for establishing future perspectives for artificial reef deployment and research. In the North-East Atlantic area, sixty-one purposely built artificial reefs have been deployed since 1970, mostly between the years 1990–2009, with Spain being the country with the highest number of artificial reefs. The most reported purpose for their deployment is fisheries productivity and habitat/species protection, although, most artificial reefs are multipurpose in order to maximise the benefits of a given financial investment. The majority of artificial reefs were submerged at < 50 m, mainly between 10 and 20 m of depth. The most used designs were cubic blocks and complex designs made by an array of combined shapes, which mostly consist of concrete (79%). From all the analysed data on artificial reefs, 67% of the cases reported surveys to assess biodiversity after the deployment. However, in 26% of those cases, data was not available. When data was available, only 31% of cases reported long-term biomonitoring surveys (3 years or more). Based upon these findings, we noticed a general lack of scientifically robust data, including records of species and abundance of both fish and invertebrates, as well as macroalgae, preventing an adequate determination of the best balance between shape, construction material and bio-colonization. Critiques and suggestions are discussed in the light of currently available data in order to perform more efficient research, evaluation and functioning of future artificial reefs.

Floating along marsh edges: The impact of invasive water hyacinth (Eichornia crassipes) on estuarine species assemblages and predation risk

Estuaries are dynamic environments where the safety of habitat refuges can be altered by a variety of natural and anthropogenic disturbances. After tropical storms or other high water run off events, water hyacinth (Eichhornia crassipes), an invasive floating freshwater plant, can enter estuarine habitats where it can colonize marsh edges and may impact the abundance and distribution of estuarine species. In freshwater environments, hyacinth reduces water quality, increases habitat complexity, and alters freshwater aquatic invertebrate abundance and diversity. Yet, little is known about how this plant impacts estuarine species as it floats from freshwater tributaries to oceanic environments. To examine how water hyacinth impacts estuarine marsh fauna, we examined the effects of water hyacinth on nekton communities and fish predation risk using trapping and tethering techniques along a marsh edge that had been recently colonized by water hyacinth. We placed funnel traps under water hyacinth and in open water habitats to examine how water hyacinth impacted macrofaunal abundance and diversity. We also examined how water hyacinth impacted predation risk by tethering killifish at increasing distances from the marsh edge in open water and water hyacinth habitats. We found that shrimp, blue crabs, and killifish were generally more abundant under water hyacinth, but there was no difference in species richness or diversity between the two habitats. In tethering studies, killifish survival was generally similar between water hyacinth and open water likely due to the increased abundance of blue crabs underneath water hyacinth. This result suggests water hyacinth does not alter predation risk overall, but may alter the distribution of blue crabs and piscivorous fish predators. We did observe short term increases in killifish survival underneath small migrating hyacinth patches indicating patch size may further affect blue crab colonization and predation. Our results indicate that water hyacinth alters the safety of marsh edge habitats by increasing blue crab abundance, ultimately increasing their encounter rates with fish prey. Climate driven increases in tropical storms and coastal restoration efforts that alter salinity gradients will likely increase the abundance of water hyacinth in estuarine marshes offering important post-disturbance habitat structure to fish and invertebrates and increasing predation rates of blue crabs along marsh edges.

Plastic responses to hot temperatures homogenize riparian leaf litter, speed decomposition, and reduce detritivores.

Efforts to maintain the function of critical ecosystems under climate change often begin with foundation species. In the southwestern United States, cottonwood trees support diverse communities in riparian ecosystems that are threatened by rising temperatures. Genetic variation within cottonwoods shapes communities and ecosystems, but these effects may be modified by phenotypic plasticity, where genotype traits change in response to environmental conditions. Here, we investigated plasticity in Fremont cottonwood (Populus fremontii) leaf litter traits as well as the consequences of plasticity for riparian ecosystems. We used three common gardens each planted with genotypes from six genetically divergent populations spanning a 12°C temperature gradient, and a decomposition experiment in a common stream environment. We found that leaf litter area, specific leaf area, and carbon to nitrogen ratio (C:N) were determined by interactions between genetics and growing environment, as was the subsequent rate of litter decomposition. Most of the genetic variation in leaf litter traits appeared among rather than within source populations with distinct climate histories. Source populations from hotter climates generally produced litter that decomposed more quickly, but plasticity varied the magnitude of this effect. We also found that hotter growing conditions reduced the variation in litter traits produced across genotypes, homogenizing the litter inputs to riparian ecosystems. All genotypes in the hottest garden produced comparatively small leaves that decomposed quickly and supported lower abundances of aquatic invertebrates, whereas the same genotypes in the coldest garden produced litter with distinct morphologies and decomposition rates. Our results suggest that plastic responses to climate stress may constrict the expression of genetic variation in predictable ways that impact communities and ecosystems. Understanding these interactions between genetic and environmental variation is critical to our ability to plan for the role of foundation species when managing and restoring riparian ecosystems in a warming world.

The stoichiometric signature of high‐frequency fire in forest floor food webs

AbstractFire regimes are shifting under climate change. Decadal‐scale shifts in fire regime can disrupt the biogeochemical cycling of carbon (C), nitrogen (N), and phosphorus (P) within forest ecosystems, but the full extent of these disruptions is unknown. It is also unclear whether these disruptions have consequences for the ecological characteristics (e.g., biomass, abundance, and composition) of microbial and invertebrate communities, which together comprise the majority of terrestrial biodiversity and underpin many ecosystem processes. The theoretical framework of ecological stoichiometry has great potential in this context, but it has rarely been used to develop an integrated understanding of the biogeochemical and ecological effects of altered fire regime across trophic levels. Using one of the world's longest‐running fire experiments, located in Queensland, Australia, we carried out a comprehensive investigation into the stoichiometric consequences of a decadal‐scale divergence in prescribed fire frequency and their links to coinciding changes in various ecological characteristics of forest floor microbial and invertebrate communities. Compared to long‐term fire exclusion, forty‐three years of biennial burning led to significantly N‐depleted and/or P‐enriched stoichiometry in soil, leaf litter, leaf litter–associated microbial biomass, and certain groups of invertebrates, although total invertebrate community stoichiometry was not affected. Microbial biomass was 42% lower in biennially burned soils. Invertebrate community composition differed between fire regime treatments on some sampling dates, but fire regime did not have consistent effects on invertebrate biomass or abundance. Microbial biomass and the abundances of some invertebrate taxa were depressed at particularly low and/or high resource N:P, consistent with a coupling of these variables to the stoichiometric effects of decadal‐scale fire regime. Litter transplants likewise indicated that some invertebrate abundances were sensitive to litter properties over 12 months. Together, our results indicate that long‐term changes in fire regime can decouple the within‐ecosystem cycling of N and P, with N and P cycling growing more and less conservative, respectively, under high‐frequency fire in a way that propagates throughout forest floor food webs. Our study provides new insights into the coupled biogeochemical and ecological responses of forest ecosystems to novel fire regimes and establishes a basis for a stoichiometric framework for fire ecology.

Food availability and temperature optima shaped functional composition of chironomid assemblages during the Late Glacial–Holocene transition in Northern Europe

Non-biting midges (Chironomidae) are the most diverse and abundant invertebrate group in boreal lakes and are strongly responsive to climate change, thus they are a valuable palaeoecological proxy for studying aquatic biodiversity response in the face of climate change. Here, we aim to decipher the influence of climate-induced changes on temporal patterns in chironomid assemblages. We apply a novel approach combining traditional taxon-based analysis and species-trait framework to subfossil chironomid assemblages in a sediment core covering the Late Glacial–Holocene transition in Northern Europe. We produce pollen-based July and January temperature reconstructions to characterize past climate fluctuations that show a distinct Early Holocene warming for continuous 1700 years with considerably greater warming in winter (ca. 10 °C) than summer (ca. 4 °C) temperature. Overall, chironomid taxonomic changes were mainly induced by the temperature tolerances and optima of species, as temporal dynamics showed agreement with temperature reconstructions. Our results suggest that vegetation dynamics could also play a role in structuring chironomid assemblages by selecting taxa with the highest ability to exploit available food resources, thus potentially confounding chironomid-based summer climate reconstructions. We demonstrate that the study of the hidden chironomid functional composition could help to identify secondary drivers and thus strengthen the reliability of climate reconstruction based on subfossil chironomids.

Impact of Nesting Socotra Cormorants on Terrestrial Invertebrate Communities

Simple SummarySeabirds that breed on remote islands often form dense nesting colonies. Nesting activities during the course of a breeding season could result in the deposition of large quantities of feces that could influence soil biodiversity. We determined the impact nesting activities of Socotra Cormorants on soil invertebrates using artificial substrate samplers. Nesting activities had variable effects on soil invertebrates. Isopods and spiders declined in due to nesting activities. Beetles and ants seemed to be unaffected by nesting activities. Ticks increased significantly but in non-nesting areas. Our study shows that seabird breeding activities determine long-term community structure of remote islands by affecting different invertebrate taxa in different ways.Seabirds and some inland waterbirds nest in densely aggregated colonies. Nesting activities for a duration of months could lead to large quantities of guano deposition that affects the soil chemistry, flora and fauna. We assessed the effects of nesting Socotra Cormorants on soil invertebrates on Siniya Island, United Arab Emirates. Artificial substrate traps were set in nesting and non-nesting areas to sample invertebrates both before and after nesting had occurred. Diversity of soil invertebrate taxa decreased significantly in nesting areas compared to non-nesting areas after the commencement of nesting. This indicated that nesting activities had a negative effect on diversity. Among selected taxa, isopods and spiders decreased significantly in response to nesting activities. In contrast, ants were likely affected by habitat while beetles did not change significantly in response to nesting activities, suggesting that their numbers probably fluctuated in relation to seasonality. Ticks increased significantly but only in non-nesting areas. Thus, the impact of nesting varied between taxa depending on life history and seasonality. Our observations reflect the dynamic nature of invertebrate abundance that is affected by seasonality and the hyper-abundance of nesting seabirds.

No evidence of top‐down effects by ants on litter decomposition in a temperate grassland

AbstractAnts play multiple roles in ecosystems, but their ability to affect decomposition processes in temperate grasslands is relatively unknown. We investigated whether the suppression of ant populations influenced litter decomposition in grasslands via predation of some decomposers (e.g., mites and springtails) and/or microbial activity and composition. We performed two successful ant suppression treatments (seven weeks, 37% suppression, year 1, 10 weeks, 70% suppression, year 2) over the course of a 59‐week experiment. We then assayed the effects of ant suppression using coarse‐ and fine‐mesh litterbags and evaluated litter chemistry, microbial and arthropod communities, and microbial enzyme activity. Ant suppression efforts reduced ant abundance and altered ant, arthropod decomposer, and non‐ant predator community composition. However, ant suppression did not affect decomposer arthropod abundance, litter mass loss, microbial composition, or enzyme activity in litterbags. Litterbag mesh size did not alter microbial composition, perhaps due to a failure to exclude decomposers, as mites and springtails were more or equally abundant in fine‐mesh bags. Nevertheless, mesh size did change litter chemistry, suggesting that mesh size‐mediated microenvironments affect decomposition environment regardless of invertebrate exclusion. Coarse‐mesh litterbags had higher concentrations of microbial sugars, lignin, and N and lower concentrations of litter C and crystalline cellulose than fine‐mesh litterbags. Litterbag mesh size may alter decomposition processes irrespective of invertebrate abundance. We found no evidence that ant predation was an important driver of decomposer populations or decomposition in these systems, and we suspect redundancy at the top of the detrital food web dilutes the role of ants.

Метод отлова малого канадского журавля Grus сanadensis canadensis в местах гнездования

Catching of Lesser Sandhill Cranes of the Eurasian population was carried out to study the features of their migration using GPS-GSM transmitters. During 2018-2019 we caught 11 adult flying cranes using self-tightening leg loops in the Chaun Lowland, Chukotka, Eastern Siberia. The method has been proven to be the most effective and non-traumatic for catching cranes during summer. Setting of loops along the edge of feeding habitat, the lake with abundant invertebrates primarily crustaceans Conchostraca, was found to be the most effective method of capturing. The construction is cheap and easy to use, install and transport.

Nitrogen and phosphorus enrichment cause declines in invertebrate populations: a global meta-analysis.

Human-driven changes in nitrogen (N) and phosphorus (P) inputs are modifying biogeochemical cycles and the trophic state of many habitats worldwide. These alterations are predicted to continue to increase, with the potential for a wide range of impacts on invertebrates, key players in ecosystem-level processes. Here, we present a meta-analysis of 1679 cases from 207 studies reporting the effects of N, P, and combined N+P enrichment on the abundance, biomass, and richness of aquatic and terrestrial invertebrates. Nitrogen and phosphorus additions decreased invertebrate abundance in terrestrial and aquatic ecosystems, with stronger impacts under combined N+P additions. Likewise, N and N+P additions had stronger negative impacts on the abundance of tropical than temperate invertebrates. Overall, the effects of nutrient enrichment did not differ significantly among major invertebrate taxonomic groups, suggesting that changes in biogeochemical cycles are a pervasive threat to invertebrate populations across ecosystems. The effects of N and P additions differed significantly among invertebrate trophic groups but N+P addition had a consistent negative effect on invertebrates. Nutrient additions had weaker or inconclusive impacts on invertebrate biomass and richness, possibly due to the low number of case studies for these community responses. Our findings suggest that N and P enrichment affect invertebrate community structure mainly by decreasing invertebrate abundance, and these effects are dependent on the habitat and trophic identity of the invertebrates. These results highlight the important effects of human-driven nutrient enrichment on ecological systems and suggest a potential driver for the global invertebrate decline documented in recent years.

Can soil invertebrates indicate soil biological quality on well pads reclaimed back to cultivated lands?

Integrating soil physico-chemical properties and soil invertebrate bioindicators could prove a practical and robust method for assessing reclamation and soil biological quality of cultivated lands disturbed by oil and natural gas activities. Until the current study, there have been no data or analyses showing these relationships in cultivated lands. We examined a fine line between two types of disturbance (i.e., cropland, oil & gas reclaimed cropland) and the invertebrates that could tolerate these disturbed conditions. We aimed to determine 1) if crop type, age class, reclamation criteria, soil type, disturbance history (reclaimed wellsite) or a combination of these factors, influenced invertebrate abundance; 2) if invertebrate community abundance correlated with soil physico-chemical properties or with the presence of major mesofauna taxa, and 3) if reclamation efforts, plus the additional yearly cultivation activities, ameliorate the biological effects of oil and gas disturbance. Although we identified a clear trend in the densities and abundances of major mesofauna taxa, they did not differ significantly between groups. Reclaimed sites appeared more susceptible to crop pests (Psocoptera and Hemiptera), especially on younger sites, which could have been driven by higher bulk density (low aeration). There were clear differences in soil physico-chemical properties bulk density, pH, and total organic carbon (TOC), which were not reflected in the Acari:Collembola (A:C) ratios, invertebrate density or community results. There were some correlations between physico-chemical properties and specific invertebrate groups. Oribatida were positively correlated with electrical conductivity; Astigmata, Oribatida, and Symphyla were negatively correlated with bulk density; Prostigmata, Collembola, and Mesostigmata were negatively correlated with pH, and Mesostigmata were positively correlated with TOC. The site age results indicate that cultivation activities may reset mesofauna community succession each year, creating densities and abundances similar to that of adjacent cultivated fields and masking long-term industrial effects. For these reasons, neither broad invertebrate taxa nor A:C ratios should be used as indicators of reclamation quality or biological recovery on industrially reclaimed, cultivated sites if the comparable references are also cultivated. We foresee expansions of this research with functional trait analysis, as well as exploring differences at a finer taxonomic level within invertebrates.