Invertebrate Feeding Research Articles

Feeding and growth are regulated by light and opsins-mediated phototransduction in sea cucumber Apostichopus japonicus

Light is a crucial environmental ecological factor that affects physiological processes including feeding and growth of marine invertebrates. Although nonvisual photosensitivity has long been known in echinoderms, the underlying molecular regulation mechanism remains unclear. Here, we firstly reported opsins-mediated phototransduction signaling and the cross-talk between light and feeding/growth in Apostichopus japonicus, an important economic species with high medicinal and nutritional values. Molecular characterization analysis of Ajopsins revealed that they were mainly distributed in the epidermis of potential photosensitive tissues (tentacles, papillae and tube feet). And all four Ajopsins including Rhodopsin 5-like (AjRH5), long-wavelength-sensitive opsin (AjLWS), peropsin (AjPOP), and peropsin-like (AjPOPL) exhibited different expression patterns in response to different light conditions. Moreover, four Ajopsins all conjugated with Gαi/o to reduce intracellular cAMP levels. Besides, three Ajopsins (AjRH5, AjPOP and AjPOPL) conjugated with Gαq to activate Gαq/Ca2+/PKC signaling. And all four opsins could activate downstream ERK1/2 phosphorylation. In addition, the photosensitivities of these four Ajopsins were different in response to different wavelength of light, AjPOP and AjPOPL were sensitive to short-medium-long wavelength light, AjRH5 and AjLWS were sensitive to medium-long wavelength light. Furthermore, indoor aquaculture experiment showed that 150 lx and 300 lx light intensity could significantly promote feeding and growth of A. japonicus, which might be mediated by AjOXP1 and AjMAP2K4. Under different light wavelength treatment, red light (655–665 nm) significantly promoted the feeding and growth of A. japonicus, which may be mediated by AjOXP1/2, AjMAP2K4 and AjMegf6. And siRNA experiment further confirmed the crosstalk between AjPOPL and AjOXP1, suggesting AjPOPL may regulate feeding by AjOXP1 in A. japonicus. Our findings showed a comprehensive description of Ajopsins signaling, providing new insights on the molecular mechanism of photoreception involved in regulating feeding and growth in A. japonicus and suggested the optimum light conditions for optimizing the lighting scheme of A. japonicus aquaculture.

Dual Effect of Microplastics and Cadmium on Stream Litter Decomposition and Invertebrate Feeding Behavior

This study investigates the combined effect of microplastics and cadmium on the decomposition of litter, the structure of fungal communities, and the feeding behavior of invertebrates in an aquatic ecosystem. Through a series of microcosm experiments, we demonstrate that exposure to MPs and Cd significantly reduced the decomposition of leaf litter. Notably, the cumulative impact of combined MP and Cd exposure was found to be greater than their individual effects. During this process, the carbon–nitrogen ratio of the litter increased, while dehydrogenase activity and fungal biomass were inhibited. Additionally, the relative abundance of Ascomycota and Basidiomycota fungi decreased, weakening their role in the decomposition of leaf litter. Conversely, MPs and Cd reduced the relative content of leaf litter lignin, improving its quality as food, thereby leading to an increase in the feeding rate of invertebrates. This dual effect indicates that micropollutants suppress the decomposition of litter by regulating microbial metabolic activity and fungal community structure but promote invertebrate feeding. Our findings provide crucial insights into the adverse effects of MPs and Cd on the structure and diversity of aquatic fungal communities, which could have long-term impacts on the food webs and nutrient cycling progress of aquatic ecosystems.

Fine sediment and the insecticide chlorantraniliprole inhibit organic‐matter decomposition in streams through different pathways

Abstract Intensive agriculture drives an ongoing deterioration of stream biodiversity and ecosystem functioning across the planet. Key agricultural stressors include increased deposited fine sediment and insecticides flushed from adjacent land into streams. The individual and combined effects on aquatic biota are increasingly studied, but the functional consequences of biodiversity loss associated with agricultural stressors remain poorly understood. We addressed this knowledge gap by examining the effects of fine sediment and different concentrations of the insecticide chlorantraniliprole on organic‐matter decomposition. We conducted an outdoor stream mesocosm experiment. Mesocosms contained a standardised organic‐matter assay (the cotton‐strip assay), which was used to assess organic‐matter decomposition rates (as tensile‐strength loss of the fabric) and microbial respiration of the cotton strips. The decomposition rate of strips buried under fine sediment was inhibited, a result we attribute to the limited accessibility for invertebrate feeding and microbial activities, as well as the limited nutrient and dissolved oxygen exchange. The insecticide also inhibited decay rates, a finding we relate to reduced invertebrate grazing and associated excessive algal growth. In contrast to decomposition rates, we did not observe stressor effects on microbial respiration. An interaction between fine sediment and chlorantraniliprole was not identified. Our results suggest that stressors induced by agriculture affect functions of stream ecosystems through a variety of pathways and operate by modifying habitats and biotic interactions. By examining a combination of stressors and responses that have not been addressed before, this study gives important insights into the effects of agricultural practices on streams. Understanding the effects of chlorantraniliprole is especially important since it is likely to become more widely used in future agricultural practice due to the increasing ban on neonicotinoid insecticides. Furthermore, most experimental studies address multiple stressor effects on biota. For a comprehensive understanding of complex stressor effects on ecosystems, ecosystem functions also need to be studied, such as the organic‐matter decomposition within streams.

Farmland practices are driving bird population decline across Europe

Declines in European bird populations are reported for decades but the direct effect of major anthropogenic pressures on such declines remains unquantified. Causal relationships between pressures and bird population responses are difficult to identify as pressures interact at different spatial scales and responses vary among species. Here, we uncover direct relationships between population time-series of 170 common bird species, monitored at more than 20,000 sites in 28 European countries, over 37 y, and four widespread anthropogenic pressures: agricultural intensification, change in forest cover, urbanisation and temperature change over the last decades. We quantify the influence of each pressure on population time-series and its importance relative to other pressures, and we identify traits of most affected species. We find that agricultural intensification, in particular pesticides and fertiliser use, is the main pressure for most bird population declines, especially for invertebrate feeders. Responses to changes in forest cover, urbanisation and temperature are more species-specific. Specifically, forest cover is associated with a positive effect and growing urbanisation with a negative effect on population dynamics, while temperature change has an effect on the dynamics of a large number of bird populations, the magnitude and direction of which depend on species' thermal preferences. Our results not only confirm the pervasive and strong effects of anthropogenic pressures on common breeding birds, but quantify the relative strength of these effects stressing the urgent need for transformative changes in the way of inhabiting the world in European countries, if bird populations shall have a chance of recovering.

Assessing the Influence of Anthropogenic Land-Use Changes on Bird Diversity and Feeding Guilds—A Case Study of Kalametiya Lagoon (Southern Sri Lanka)

Kalametiya Lagoon, a highly threatened Sri Lankan wetland, has undergone drastic hydrological changes in recent decades, due to an upstream irrigation project. These changes led to the invasion of the lagoon water by monospecific Sonneratia caseolaris mangrove stands and Typha angustifolia reedbeds. As Kalametiya has been a nationally recognized bird sanctuary since 1984, this invasion is expected to have brought significant changes upon local avifauna. Therefore, this study aimed at determining the lagoon’s current bird diversity and distribution in relation with habitat types and environmental variables. Thirty-seven point-count stations were studied, between January and April 2022. Seventy-nine bird species, including four endemic and ten nationally threatened species, were encountered during the study period. Invertebrate feeders and polyphages were the richest and most diverse guilds. Bird communities were also found richer and more diverse in T. angustifolia reedbeds than in S. caseolaris mangroves. As feeding guild composition was significantly influenced by several environmental variables (i.e., water nitrate content, water TDS, water pH, soil pH), guilds could have great potential as bioindicators of the ecosystem if further studies are done to explore these relationships. Considering the important bird diversity found in the new habitats, this research brings additional proof that a management aiming at restoring the lagoon to its past state would bring significant changes to its avifaunal community. These changes could, in the future, be more precisely defined by a thorough comparison with past inventories of the lagoon’s bird community.

Fish assemblage and guild structure in the Ashtamudi Estuary, a tropical Ramsar site in India

A first hand study on guild structure of fish species (n = 148) in Ashtamudi Estuary, a Ramsar Site of International importance, was carried out from May 2019 to April 2020 based on temporal (monsoon, pre-monsoon and post-monsoon seasons) and spatial (upper, middle and lower zones) data. Guild composition consisted of eight estuarine use guilds (marine estuarine opportunist, marine estuarine dependent, estuarine resident species, anadromous species, freshwater migrants, freshwater stragglers, catadromous and marine stragglers) and eight feeding guilds (zooplanktivore, zoobenthivore, carnivores, herbivores, invertebrate feeders, omnivores, detritus feeders and piscivores). The most dominant estuarine use guilds comprised of marine migrants (marine estuarine opportunist and marine estuarine dependent), whereas carnivore, omnivore and zooplanktivore formed the dominant feeding guilds in Ashtamudi Estuary. The species diversity decreased from upper to lower zone and was highest during the post-monsoon period. The present study has seen a decrease in estuarine resident and freshwater species due to reduced freshwater inflow, saltwater intrusion, unsustainable fishing and inadequate environmental management practices. Hence, we propose a management framework to improve the ecosystem of Ashtamudi Estuary with a special focus on its fish species and their estuarine use.

Mycorrhiza-feeding soil invertebrates in two coniferous forests traced with 13C labelling.

Mycorrhizal fungi represent a potentially abundant carbon resource for soil animals, but their role in soil food webs remains poorly understood. To detect taxa that are trophically linked to the extraradical mycelium of mycorrhizal fungi, we used stable isotope (13C) labelling of whole trees in combination with the in-growth mesh bag technique in two coniferous forests. This allowed us to detect the flux of carbon in the mycelium of mycorrhizal fungi, and consequently in the tissues of soil invertebrates. The mycorrhizal fungal genera constituted 93.5% of reads in mycelium samples from the in-growth mesh bags. All mycelium from in-growth mesh bags and about 32% of the invertebrates sampled (in total 11 taxa) received the 13C label after 45days of exposure. The extent of feeding of soil invertebrates on the mycelium of mycorrhizal fungi depended on the taxonomic affinity of the animals. The strongest trophic link to the mycorrhiza-derived carbon was detected in Isotomidae (Collembola) and Oppiidae (Oribatida). The label was also observed in the generalist predators, indicating the propagation of mycorrhiza-derived carbon into the higher trophic levels of the soil food web. Higher 13C labelling in the tissues of euedaphic Collembola and Oribatida compared to atmobiotic and hemiedaphic families indicates the importance of mycorrhizal fungi as a food resource for invertebrates in deeper soil horizons.

Identifying trade-offs and reference points in support of ecosystem approaches to managing Gulf of Mexico menhaden

Gulf menhaden (Brevoortia patronus) support the largest fishery by yield in the Gulf of Mexico (GoM) and are a key forage species for many marine predators. While menhaden stock assessments indicated that overfishing was not likely to have occurred in the past, concerns have been raised regarding the possible effects of menhaden fishing on their predators. In this study, we used a US Gulfwide Ecopath with Ecosim (EwE) model to explore the predicted effects of increased menhaden harvest on the GoM ecosystem and focused our analyses on Gulf menhaden predators. Key menhaden predators identified included king mackerel (Scomberomorus cavalla), Spanish mackerel (Scomberomorus maculatus), sea trout (Cynoscion spp.), red drum (Sciaenops ocellatus), and pelagic coastal piscivores [e.g., bluefish (Pomatomus saltatrix)]. As expected, these predators exhibited reduced biomass in response to increased Gulf menhaden harvest, with a predicted 11% decrease in predator biomass at simulated fishing levels near historical highs. Our results indicate strong relationships between the effects of menhaden fishing and the predator fishing mortality for king mackerel and intermediate relationships for Spanish mackerel, blacktip shark (Carcharhinus limbatus), red drum, large coastal sharks, and pelagic coastal piscivores. Biomass of predator groups such as demersal coastal invertebrate feeders [e.g., drums and croakers (Sciaenidae)] are more affected by menhaden harvest (through trophodynamics interactions and bycatch removal) compared to the isolated effect of their fishing mortality. For almost all the groups examined in the trade-off analysis, with the exception of sea trout, current biomass (2016) was higher than their target biomass representing 75% of their biomass at maximum sustainable yield. In comparison to the time series of fishing mortality rates estimated by the most recent Gulf menhaden stock assessment, the mean ecological reference point (ERP) of 0.862 was exceeded in all but 1 year from 1977 to 2007; however, neither the target nor threshold upper ERP value has been exceeded since 2008. The observed Gulf menhaden landings from 2003 to the present were generally within the range of the projected equilibrium landings (i.e., within confidence intervals) at both the ERP target and threshold values except for three recent years.

Macroalgal input into the coastal food web along a gradient of seasonal sea ice cover along the Western Antarctic Peninsula

Coastal food webs that are supported by multiple primary producer sources are considered to be more stable against perturbations. Here, we investigated how declining macroalgal abundance and diversity might influence coastal food web structure along an annual sea ice cover gradient along the Western Antarctic Peninsula (WAP). The most common benthic invertebrate consumers, macroalgae, and surface particulate organic matter were collected at 15 stations along the WAP. Stable carbon and nitrogen isotope values of primary producers changed negligibly in relation to the sea ice cover gradient, while isotope values of most invertebrate feeding groups increased with higher sea ice cover, although at low explanatory power. Food web length became shorter and consumer trophic niche width smaller in regions with higher sea ice cover. Changes in food web structure were mostly associated with shifts in trophic position of lower trophic levels. Food web structure in higher ice-covered regions resembled that of more generalist feeders with a loss of specialist species, concurrent with an increased reliance on a more reworked detrital food source. These results suggest that a number of benthic invertebrates are able to adjust to differences in basal energy sources. Conversely, these food webs dominated by generalist feeders are likely less efficient in energy transfer, which can create less-stable systems with lower adaptive capacity to disturbance. The predicted sea ice loss along the WAP may ultimately lead to a longer food web with higher macroalgal abundance, more specialist species, and wider consumer trophic niches in the currently more ice-covered regions.

Seasonal responses and host uniqueness of gut microbiome of Japanese macaques in lowland Yakushima.

BackgroundChanges in the gut microbial composition is an important response to cope with the seasonal fluctuations in the environment such as food availability. We examined the bacterial gut microbiome of the wild nonhuman primate, Japanese macaque (Macaca fuscata) in Yakushima over 13 months by noninvasive continuous sampling from three identified adult females.ResultsDietary composition varied considerably over the study period and displayed marked shifts with the seasons. Feeding of leaves, fruits, and invertebrates were their main foods for at least one month. Diet had a significant influence on the gut microbiome. We also confirmed significant effect of host uniqueness in the gut microbiome among the three macaques. Leaf-dominated diet shaped unique gut microbiome structures where the macaques had the highest alpha diversity and their gut microbiome was enriched with Spirochaetes and Tenericutes. Diet-related differences in the putative function were detected, such as a differentially abundant urea cycle during the leaf-feeding season.ConclusionBoth diet and host individuality exerted similar amounts of effect on gut microbe community composition. Major bacterial taxa showed a similar response to monthly fluctuations of fruit and invertebrate feeding, which was largely opposite to that of leaf feeding. The main constituents of fruits and invertebrates are both digestible with the enzyme of the host animals, but that of leaves is not available as an energy source without the aid of the fermentation of the gut microbiome.Supplementary InformationThe online version contains supplementary material available at 10.1186/s42523-022-00205-9.

Linking fish ecomorphotypes to food categories and local‐scale habitat uses along a Brazilian coastal stream

AbstractFish ecomorphological analyses often deal with several traits simultaneously, making it challenging to interpret general patterns, and have not addressed the longitudinal component of streams in morphology‐habitat relationships. We identified ecomorphotypes of fishes and correlated their morphological variation with food, structural/hydrological variables, and abundances to detect their links with diet and local‐scale habitat categories. Eighteen morphometric traits were obtained from specimens collected by electrofishing in a coastal Atlantic stream in Brazil. To test for morphology‐habitat associations, headwaters, middle, and mouth reaches were divided into shorter sampling sites, with the middle reach being classified into riffle, run, and pool mesohabitats. Multivariate analyses highlighted the morphological variations and associated the form categories of 18 fish species with food and habitat categories. It resulted in four combined trophic and habitat ecomorphotypes: (1) benthic AB/lithophilic, composed of smaller to longer loricariids, detritivores, of fast‐water, and pebbly habitats; (2) benthic C/lithophilic of very fast‐waters, algal and detritus scrapers, with longer intestines than the other benthic species, wider suctorial mouths, inhabitants of headwaters, and riffles habitats; (3) nektobenthic/lithophilic with streamlined bodies, invertebrate feeders, and dwellers of faster‐water, cobbly habitats; and (4) nektonic/limnophilic composed mainly by characins, which had strong correlations with terrestrial insect consumption, and lentic/pool, sandy habitats. The morphology–environment correlations linked these ecomorphotypes to the broad habitat gradient arrayed in longitudinal and local scales. These results permit inferring the larger form patterns expected for local fish assemblages and emphasise the fish trait categorisation as a possible surrogate to reveal broader ecomorphological associations.

Working with UK farmers to investigate anecic earthworm middens and soil biophysical properties

AbstractThe conversion from conventional tillage to no‐tillage soil management practices is generally associated with an improvement in aggregate stability and anecic earthworm populations. We worked with UK farmers who measured Lumbricus terrestris midden area (%) and earthworm numbers associated with middens compared to the general soil. They found that middens covered up to 42% of the soil surface. Middened soil (i.e., soil underlying the middens) was associated with significantly more earthworms than the general soil (i.e., non‐middened soil) in agreement with research from scientific field trials. We compared the biophysical properties of middened soil to general soil across an experimental field trial recently converted to no‐tillage soil management practices. We measured water‐stable aggregation, soil porosity at scales relevant to water storage and gas diffusion and invertebrate feeding activity. Middened areas covered up to 13% of the field trial and were associated with significantly improved aggregate stability and porosity compared to the general soil. Our findings highlight the importance of considering middens when surveying soil quality and health in arable systems.

Microplastics alter multiple biological processes of marine benthic fauna

Marine sediments are a sink for microplastics, making seabed organisms particularly exposed. We used meta-analysis to reveal general patterns in a surge in experimental studies and to test for microplastic impact on biological processes including invertebrate feeding, survival and energetics. Using Hedge's effect size (g), which assesses the mean response of organisms exposed to microplastics compared to control groups, we found negative impacts (significant negative g values) across all life stages (overall effect size (g) = −0.57 95 % CI [−0.76, −0.38]), with embryos most strongly affected (g = −1.47 [−2.21, −0.74]). Six of seven biological process rates were negatively impacted by microplastic exposure, including development, reproduction, growth and feeding. Survival strongly decreased (g = −0.69 [−1.21, −0.17]), likely due to cumulative effects on other processes such as feeding and growth. Among feeding habits, omnivores and deposit feeders were most negatively impacted (g = −0.93 [−1.69, −0.16] and −0.92 [−1.53, −0.31], respectively). The study incorporated the first meta-analysis to contrast the effects of leachates, virgin, aged and contaminated particles. Exposure to leachates had by far the strongest negative effects (g = −0.93 [−1.35, −0.51]), showing studies of contaminants and leachates are critical to future research. Overall, our meta-analysis reveals stronger and more consistent negative impacts of microplastics on seabed invertebrates than recorded for other marine biota. Seabed invertebrates are numerous and diverse, and crucial to bottom-up processes, including nutrient remineralisation, bentho-pelagic coupling and energy transfer through the ocean food web. Marine sediments will store microplastics over long timescales. The reveal that microplastics impinge on multiple fundamental biological processes of seabed fauna implies plastic pollution could have significant and enduring effects on the functioning of the ocean.

Reef fish assemblages associated to new mat-forming zoantharian communities in the Canary Islands

Proliferations of zoantharians along tropical and subtropical regions are increasingly common and usually associated with anthropogenic impacts and ecosystem degradation. In the Canary Islands, we studied how the dominance in the substrate of Palythoa caribaeorum and Zoanthus pulchellus affected fish communities. For that purpose, we recorded the composition and biodiversity of fish assemblages associated to both zoantharian and macroalgae dominated habitats. In general terms, we found significant reductions of total fish abundance and richness at P. caribaeorum dominated habitats compared with macroalgae stands. However, in terms of trophic structure, there were significant changes within both zoantharian habitats depending on their coverages of the substrate. Herbivores and small invertebrate feeders, which are more adapted to forage in the macroalgae canopy, were less abundant in zoantharian habitats. This study demonstrates that the increasing dominance of zoantharians throughout the archipelago restructure the ecosystems and impact the native fish communities, that may offer a positive feedback for invasive tropical species to thrive.

Known and Potential Invertebrate Vectors of Raspberry Viruses.

The estimated global production of raspberry from year 2016 to 2020 averaged 846,515 tons. The most common cultivated Rubus spp. is European red raspberry (Rubus idaeus L. subsp. idaeus). Often cultivated for its high nutritional value, the red raspberry (Rubus idaeus) is susceptible to multiple viruses that lead to yield loss. These viruses are transmitted through different mechanisms, of which one is invertebrate vectors. Aphids and nematodes are known to be vectors of specific raspberry viruses. However, there are still other potential raspberry virus vectors that are not well-studied. This review aimed to provide an overview of studies related to this topic. All the known invertebrates feeding on raspberry were summarized. Eight species of aphids and seven species of plant-parasitic nematodes were the only proven raspberry virus vectors. In addition, the eriophyid mite, Phyllocoptes gracilis, has been suggested as the natural vector of raspberry leaf blotch virus based on the current available evidence. Interactions between vector and non-vector herbivore may promote the spread of raspberry viruses. As a conclusion, there are still multiple aspects of this topic that require further studies to get a better understanding of the interactions among the viral pathogens, invertebrate vectors, and non-vectors in the raspberry agroecosystem. Eventually, this will assist in development of better pest management strategies.

Current ionising radiation doses in the Chernobyl Exclusion Zone do not directly impact on soil biological activity.

Although soil organisms are essential for ecosystem function, the impacts of radiation on soil biological activity at highly contaminated sites has been relatively poorly studied. In April-May 2016, we conducted the first largescale deployment of bait lamina to estimate soil organism (largely soil invertebrate) feeding activity in situ at study plots in the Chernobyl Exclusion Zone (CEZ). Across our 53 study plots, estimated weighted absorbed dose rates to soil organisms ranged from 0.7 μGy h-1 to 1753 μGy h-1. There was no significant relationship between soil organism feeding activity and estimated weighted absorbed dose rate. Soil biological activity did show significant relationships with soil moisture content, bulk density (used as a proxy for soil organic matter) and pH. At plots in the Red Forest (an area of coniferous plantation where trees died because of high radiation exposure in 1986) soil biological activity was low compared to plots elsewhere in the CEZ. It is possible that the lower biological activity observed in the Red Forest is a residual consequence of what was in effect an acute high exposure to radiation in 1986.

Impacts of low concentrations of nanoplastics on leaf litter decomposition and food quality for detritivores in streams

In forested streams, leaf litter decomposition is a vital ecosystem process, governed primarily by aquatic hyphomycetes. These fungi are crucial mediators of nutrients and energy to invertebrates and higher trophic levels. Very little information is available on the impact of low concentrations of different sizes of nanoplastic particles (NPPs) on leaf litter decomposition and aquatic hyphomycetes communities. Besides, NPPs impact on leaf litter nutritional quality and invertebrate feeding behaviour is unknown. We conducted a microcosm assay with varying concentrations (0–25 μg L-1) of small (100 nm; SNPPs) and large (1000 nm; LNPPs) plastic particles to assess their impact on leaf litter decomposition, sporulation rates and community structure of aquatic hyphomycetes. Furthermore, leaf litter was retrieved and fed to invertebrates to assess feeding rates. Our results indicated that leaf litter decomposition, fungal sporulation and abundance were significantly affected by NPPs concentrations and sizes. By contrast, leaf litter nutritional quality was impacted only by sizes. The NPPs, particularly SNPPs, augmented leaf litter polyunsaturated fatty acids (18–31%), consequently improving food quality; however, invertebrates' feeding rates were not impacted. Overall, our study provides novel insights on the risks posed by NPPs with pronounced impact at the basal trophic level.

Does restoring native forest restore ecosystem functioning? Evidence from a large‐scale reforestation project in the Scottish Highlands

Given the worldwide plans for extensive tree planting, we urgently need to understand how and where implementation will contribute to goals such as those for carbon sequestration. We used a long‐term, large‐scale native reforestation project in the Scottish Highlands to assess the response of carbon storage and other ecosystem functions to reforestation and grazing exclusion. We measured aboveground carbon, topsoil carbon, topsoil nitrogen, decomposition rates, soil invertebrate feeding activity, tree regeneration, and ground‐layer and moss height at 14 sites that are in the early stages of reforestation and fenced to exclude grazing. Reforestation areas were compared to unforested and mature forest areas that are both grazed and ungrazed, using 10 × 10 m plots. Aboveground carbon in the reforestation plots (1.4 kg/m2 [95% CI: 0.6, 2.6], average age 20 years since reforestation) was c. 8% of the mature forest plots (17.1 kg/m2 [13.1, 21.8]). Topsoil carbon was lower in the reforestation plots (18.78 kg/m2 [11.79, 25.78]) than in the unforested (29.82 kg/m2 [24.34, 35.29]) or mature forest (31.39 kg/m2 [22.91, 39.88]) plots. Responses of other functions to the reforestation and grazing interventions varied. Our results suggest that reforestation may trigger carbon loss from areas with high initial soil carbon even with low disturbance establishment, at least in the short term. Our work emphasizes where we lack knowledge: on the potential for long‐term re‐accumulation of soil carbon under semi‐natural native reforestation, soil carbon sequestration in the deeper soil layers, and the response of soil carbon to natural regeneration.

Does feeding type matter? Contribution of organic matter sources to benthic invertebrates on the Arctic Chukchi Sea shelf

Benthic communities play an important role in the nutrient cycling of settling organic matter and provide an energy link to higher trophic levels. These benthic communities are highly dependent on the food sources provided through sinking organic material, with pelagic-benthic coupling particularly strong on Arctic shelf systems. Arctic shelves, however, are experiencing shifts in the timing of sea ice breakup that can have severe implications on the amount and composition of organic matter from different primary production sources supplied to the benthos. The role of benthic invertebrates in processing organic matter is typically classified by feeding types. The goal of this study was to evaluate if benthic invertebrate feeding types are a useful concept for understanding how organic matter from various biosynthetic sources is used by benthic invertebrates across the Arctic Chukchi Sea. We employed essential amino acid (EAA) specific stable isotope fingerprinting to identify proportional contributions of three EAA sources (from bacterial, phytoplankton, and terrestrial production) as a proxy of carbon sources to the diets of benthic consumers. When grouped by feeding types, the proportional contributions of the three EAA sources were similar among suspension, deposit feeders and predators/scavengers. Different genera within the same feeding type, however, showed significant differences among the EAA sources, indicating that EAA use is genus-specific rather than feeding type-specific. We discuss characteristics other than feeding mode among genera that could account for different EAA use, including mobility, selectivity of available EAA in sediments, and other trophic aspects such as assimilation efficiency. These characteristics provide useful additional considerations when grouping organisms by feeding types. High proportions of terrestrial EAA were found in the majority of benthic genera across all feeding types and characteristics in this study, reflecting the high proportions of this organic matter source in sediments and confirming that this source is being used by benthic consumers in the Arctic. EAA contributions to various benthic genera across the Chukchi Sea shelf had only weak correlations with environmental variables. While the distinctly different uses of different EAA sources by benthic-feeding genera but not by feeding types may represent high trophic plasticity in Arctic benthic invertebrates, expected climate change-driven shifts in the supply of EAA sources to the Chukchi Sea shelf benthos may still have implications for the composition of benthic communities and energy flow through the benthic food web, including energy pathways that support current top predators.

Ungulate herbivory reduces abundance and fluctuations of herbivorous insects in a boreal old-growth forest

Ecological theory predicts the strongest ecosystem effects of herbivory when dominant and ecologically important species are consumed. Bilberry, Vaccinium myrtillus, is such a key plant species, attractive to many other species in the boreal forests, for example ungulate and invertebrate herbivores. Large herbivores may remove substantial biomass and alter plant quality and therefore affect abundance and populations of invertebrate animals sharing the same food plant. We combined experimental exclusion of ungulates with a browsing intensity gradient to investigate the 15-year effect of ungulate (Cervus elaphus and Ovis aries) browsing on bilberry plant size and on bilberry-feeding herbivorous larvae (Lepidoptera and Symphyta), in a Norwegian old growth boreal forest ecosystem. Bilberry ramets in exclosure plots had nearly nine times higher dry mass and three times higher abundance of invertebrates feeding on them than in ungulate-access plots. Sweep-netting data verified these findings as larval numbers were twice as high in exclosure plots. The pattern in the large herbivore effects on bilberry size and abundance of herbivorous larvae were identical along the browsing gradient. Differences in larval abundance between treatments, as indicated by leaf-chewing, increased during the 15-year study period, and the community fluctuations were larger when ungulate herbivores were excluded. The browsing effect was moderated by plant quality as larval densities were lowest on both heavily-browsed and non-browsed plants, and highest on ramets that had 50–74% of annual shoots browsed. Our study supports previous findings in that bilberry is relatively disturbance tolerant and may recover quickly, but that ungulates may compete with herbivorous larvae for food biomass. Additionally, our results strongly indicates that population insect community peaks and fluctuations are dampened by ungulate consumption. Our findings add to the understanding on how ungulates may structure forest ecosystems directly and indirectly.