Terrestrial Macroinvertebrates Research Articles

Assessment of heavy metals in soil, leaf litter, and their bioaccumulation in terrestrial macroinvertebrates in Sohag Governorate, Egypt.

The presence of elevated levels of heavy metals in soil poses a significant environmental concern with implications for human health and other organisms. The main objective of our study was to reduce the gap information of seasonal abundance, distribution of heavy metals in soil, leaf litter, and some macroinvertebrates in a citrus orchard (Citrus sinensis) in Sohag Governorate, Egypt. The heavy metals copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd) were determined by atomic absorption spectrometry. Degree of contamination (DC) was determined for both soil and leaf litter contamination. However, the bioaccumulation factor (BAF) was estimated to determine metal accumulation in the macroinvertebrates including earwigs Anisolabis maritima, chilopoda Scolopendra moristans, spider Dysdera crocata, and earthworm Aporrectodea caliginosa. The study area had clay-loam with varying organic matter, salinity, and pH levels. The degree of contamination varied among seasons, with the highest levels typically observed in autumn in both soil and leaf litter. The soil ranged from low contamination (1.82) to high contamination levels (4.4), while the leaf litter showed extremely high (30.03) to ultra-high (85.92) contamination levels. The mean ecological risk index results indicated that the sampling area had moderate ecological risk levels for Cd (44.3), Zn (42.17), and Pb (80.05), and extremely high levels for Cu (342.5). Heavy metal concentrations in the selected fauna were the highest in autumn, and the bioaccumulation factor varied among species and seasons with some species classified as e-concentrators, micro-concentrators, and macro-concentrators of certain heavy metals. Scolopendra moristans exhibited the highest mean metal concentrations (Cd, Pb, and Zn), while Aporrectodea caliginosa had the lowest. Thus, the differences in heavy metal concentrations found in different soil taxa highlight the significance of taxing a holistic understanding of feeding mechanisms into account when evaluating the potential risk for animals that consume invertebrates.

Infrequent Long-Range Dispersal and Evolution of a Top Terrestrial Arthropod Predator in the Sub-Antarctic.

AbstractThe sub-Antarctic terrestrial ecosystems survive on isolated oceanic islands in the path of circumpolar currents and winds that have raged for more than 30 million years and are shaped by climatic cycles that surpass the tolerance limits of many species. Surprisingly little is known about how these ecosystems assembled their native terrestrial fauna and how such processes have changed over time. Here, we demonstrate the patterns and timing of colonization and speciation in the largest and dominant arthropod predators in the eastern sub-Antarctic: spiders of the genus Myro. Our results indicate that this lineage originated from Australia before the Plio-Pleistocenic glacial cycles and underwent an adaptive radiation on the Crozet archipelago, from where one native species colonized multiple remote archipelagos via the Antarctic circumpolar current across thousands of kilometers. The results indicate limited natural connectivity between terrestrial macroinvertebrate faunas in the eastern sub-Antarctic and partial survival of repeated glaciations in the Plio-Pleistocene. Furthermore, our findings highlight that by integrating arthropod taxa from multiple continents, the climatically more stable volcanic Crozet archipelago played a critical role in the evolution and distribution of arthropod life in the sub-Antarctic.

Beach-cast and drifting seaweed wrack is an important resource for marine and terrestrial macroinvertebrates in high latitudes

Seaweeds are foundation species across near-subtidal and intertidal zones, including when detached and free-floating and then cast ashore as wrack. Wrack is sometimes removed by humans for aesthetics or to be used as fertilizer. The study of wrack as an important habitat and resource for macroinvertebrates in high latitudes has been limited. To determine which taxa might be impacted when wrack is removed, the composition and relative abundance of macroinvertebrates were quantified monthly and compared in areas with and without wrack in Kachemak Bay, Alaska. Relationships were assessed between macroinvertebrates and wrack line (tidal height, moisture content, seaweed biomass) and beach characteristics (wave exposure, beach slope, substrate types). Approximately 47,000 animals were counted and a total of 87 taxa were identified from beach-cast wrack, drifting wrack, and bare sediment habitats. Macroinvertebrate communities within beach-cast wrack and bare sediment habitats were significantly different. Beach-cast wrack generally had more terrestrially-derived animals, especially Coleoptera and Diptera. Bare beach sediment was predominantly occupied by Enchytraeida (annelids). Macroinvertebrate communities were most strongly influenced by seaweed biomass and tidal height of the wrack line. Beach-cast wrack and bare sediments were also compared to drifting wrack in shallow, nearshore waters. Drifting wrack was different and generally occupied by more marine-derived animals, especially Amphipoda, Gastropoda, Mytilida, and Polychaeta. Ecological succession in decaying beach-cast wrack was documented, with decomposers (e.g., Amphipoda and Diptera) being early colonizers, and predators (e.g., Coleoptera and Hymenoptera) arriving later. Understanding the importance of this unique and ecologically important habitat to macroinvertebrates is essential, as removals and reductions in wrack availability could influence macroinvertebrate community structure, higher trophic level consumers, and key ecological processes on beaches. This study is the first direct investigation into seaweed wrack-associated macroinvertebrate communities in a sub-Arctic system.

Collection of human and environmental data on pesticide use in Europe and Argentina: Field study protocol for the SPRINT project.

Current farm systems rely on the use of Plant Protection Products (PPP) to secure high productivity and control threats to the quality of the crops. However, PPP use may have considerable impacts on human health and the environment. A study protocol is presented aiming to determine the occurrence and levels of PPP residues in plants (crops), animals (livestock), humans and other non-target species (ecosystem representatives) for exposure modelling and impact assessment. To achieve this, we designed a cross-sectional study to compare conventional and organic farm systems across Europe. Environmental and biological samples were/are being/will be collected during the 2021 growing season, at 10 case study sites in Europe covering a range of climate zones and crops. An additional study site in Argentina will inform the impact of PPP use on growing soybean which is an important European protein-source in animal feed. We will study the impact of PPP mixtures using an integrated risk assessment methodology. The fate of PPP in environmental media (soil, water and air) and in the homes of farmers will be monitored. This will be complemented by biomonitoring to estimate PPP uptake by humans and farm animals (cow, goat, sheep and chicken), and by collection of samples from non-target species (earthworms, fish, aquatic and terrestrial macroinvertebrates, bats, and farm cats). We will use data on PPP residues in environmental and biological matrices to estimate exposures by modelling. These exposure estimates together with health and toxicity data will be used to predict the impact of PPP use on environment, plant, animal and human health. The outcome of this study will then be integrated with socio-economic information leading to an overall assessment used to identify transition pathways towards more sustainable plant protection and inform decision makers, practitioners and other stakeholders regarding farming practices and land use policy.

Control of invasive Phragmites australis (European common reed) alters macroinvertebrate communities

Wetland restoration often involves invasive‐plant suppression to encourage the recovery of native‐dominated vegetation communities. However, assessment of recovery is usually focused only on vegetation, and the response of other critical wetland biota, such as macroinvertebrates, is seldom assessed. We characterized the aquatic, semi‐aquatic, and terrestrial macroinvertebrate communities in remnant, uninvaded marsh to identify restoration targets and compared this to the communities in Phragmites australis‐invaded marsh and in the formerly invaded marsh that was treated with the herbicide glyphosate in 2016 to simultaneously evaluate the effects of invasion and invasive‐species suppression. We sampled invertebrates in 2017 and 2018 to track 2 years following herbicide treatment. The invertebrate community composition was similar between P. australis invaded and remnant marsh, suggesting invasion has little effect on macroinvertebrate community structure. There was also high concordance between the aquatic and emerging‐invertebrate communities in the invaded and uninvaded habitats. In contrast, herbicide‐treated sites had a unique community composition, characterized by very high densities of Chironomidae (Diptera) and low taxa richness and evenness. Herbicide‐treated sites also exhibited low concordance between the aquatic and emerging‐invertebrate communities, potentially attributable to the sparse, emergent‐vegetation cover providing limited substrates for emergence. Herbicide‐based, invasive‐species control resulted in considerable changes to the macroinvertebrate community in freshwater marshes for at least 2 years after treatment, which may have consequences for aquatic food webs and species that rely on macroinvertebrates as prey.

A preliminary survey of the abundance, diversity and distribution of terrestrial macroinvertebrates of Gcwihaba cave, northwest Botswana

Inventories of cave species and in-depth understanding of cave ecosystems are essential for informing conservation approaches for the unique and vulnerable cave fauna. Gcwihaba cave is the largest cave in Botswana but its ecology is poorly understood. This study set out to provide the first quantitative survey of the cave’s terrestrial macroinvertebrates. Macroinvertebrates were collected from sample sites at 10 m intervals into the cave from the cave entrance. At each site, macroinvertebrates on the cave floor were collected by quadrat sampling while macroinvertebrate from cave walls were collected by visual opportunistic searches. Moisture content, pH and electrical conductivity of the cave floor substrate were measured at each site to examine the influence of the floor properties on the distribution of macroinvertebrates on the cave floor. Twelve species in 10 families and 8 orders of terrestrial macroinvertebrates were collected. The occurrence of taxa varied across the sites, with most taxa occurring in the light and twilight sectors of the cave (within 30 m), whereas the dark sector (beyond 30 m) was dominated by cave cockroaches (Gyna sp.). The abundance of the cave cockroaches, darkling beetles (Tenebrionidae, Tenebrio sp.) and cave wasps (Sphecidae) positively correlated with floor substrate of high moisture content and high electrical conductivity, which became increasingly common with distance into the cave. The abundance of other taxa from the cave floor positively correlated with a floor substrate of high pH and low moisture, which was common near the cave entrance.

Does metal pollution affect the stoichiometry of soil-litter food webs?

To date, the field of ecological stoichiometry has focused mainly on macro-elements in aquatic systems. We investigated terrestrial systems and included micro-elements in the study to assess the elemental transfer in a detritivorous food web. We compared the food webs of six sites differing in the type and degree of metal pollution along two forest transects contaminated with copper or zinc. We measured 11 elements in the litter, herbivores, detritivores, predators and omnivores. Based on the concentrations of the elements, the differences between the trophic groups were visualized using PCA. At all the sites, the litter C:N, C:P, C:K and C:Na ratios were higher than those in the animals. The C:Cu, C:Zn and C:Ca ratios of the invertebrate trophic groups were significantly different from each other. The calculated resource:consumer N:P ratio suggests that invertebrates in the studied forests are N limited but not P limited. The presence of similar patterns at all the sites suggests that metal pollution at the studied intensity somewhat affects the transfer of elements in terrestrial macro-invertebrate food webs.

All change at the water\u2019s edge: invasion by non-native riparian plants negatively impacts terrestrial invertebrates

Riparian zones are complex, dynamic habitats that play a critical role in river ecosystem functioning. Terrestrial invertebrates comprise much of the diversity found in riparian habitats and facilitate the transfer of energy between aquatic and terrestrial systems. However, the consequences for terrestrial invertebrates of invasion of riparian zones by invasive non-native plants (INNP) remain poorly understood. Responses of terrestrial macroinvertebrate morphospecies to invasion by two common INNP, Fallopia japonica (Japanese knotweed) and Impatiens glandulifera (Himalayan balsam) were assessed, relative to local environmental factors. Terrestrial invertebrates were collected from 20 sites on low order streams in June and August alongside data on physical attributes and land use. Greater cover of F. japonica and I. glandulifera cover reduced total invertebrate abundance and morphospecies diversity at the individual sample scale, whilst increasing spatial heterogeneity of invertebrates at the site scale. Impatiens glandulifera reduced morphospecies diversity at the site scale with increasing cover, but this was not observed for F. japonica. INNP affected terrestrial invertebrate morphospecies abundance and diversity, to a greater extent than prevailing environmental conditions. Our findings therefore offer support for managing riparian plant invasions to improve habitat heterogeneity, restore terrestrial invertebrate diversity and repair aquatic-terrestrial linkages.

Divergent in shape and convergent in function: Adaptive evolution of the mandible in Sub-Antarctic mice.

Convergent evolution in similar environments constitutes strong evidence of adaptive evolution. Transported with people around the world, house mice colonized even remote areas, such as Sub-Antarctic islands. There, they returned to a feral way of life, shifting towards a diet enriched in terrestrial macroinvertebrates. Here, we test the hypothesis that this triggered convergent evolution of the mandible, a morphological character involved in food consumption. Mandible shape from four Sub-Antarctic islands was compared to phylogeny, tracing the history of colonization, and climatic conditions. Mandible shape was primarily influenced by phylogenetic history, thus discarding the hypothesis of convergent evolution. The biomechanical properties of the jaw were then investigated. Incisor in-lever and temporalis out-lever suggested an increase in the velocity of incisor biting, in agreement with observations on various carnivorous and insectivorous rodents. The mechanical advantage related to incisor biting also revealed an increased functional performance in Sub-Antarctic populations, and appears to be an adaptation to catch prey more efficiently. The amount of change involved was larger than expected for a plastic response, suggesting microevolutionary processes were evolved. This study thus denotes some degree of adaptive convergent evolution related to changes in habitat-related changes in dietary items in Sub-Antarctic mice, but only regarding simple, functionally relevant aspects of mandible morphology.

Food habits of imperiled Plains Topminnow and diet overlap with invasive Western Mosquitofish in the Central Great Plains

Plains Topminnow (Fundulus sciadicus) populations have experienced large declines throughout the Central Great Plains, with Western Mosquitofish (Gambusia affinis) introductions suggested as a contributing factor. There are limited studies identifying the food habits of Plains Topminnow and the trophic interactions with Western Mosquitofish. This study sought to determine if a diet overlap exists between the Plains Topminnow and the introduced Western Mosquitofish by identifying the feeding habits of both species. We analyzed diets from lentic and lotic populations of Plains Topminnow captured in August and found lentic topminnows employed a generalist diet while lotic topminnow selected for gastropods. Additionally, Western Mosquitofish diets from regionally proximate lotic and lentic populations also displayed a generalist diet consisting of benthic, littoral and terrestrial macroinvertebrates. The two species did not show overlapping diets based on Schoener’s Index. Therefore we suggest the introduced Western Mosquitofish do not likely impact Plains Topminnow populations through food resource competition.

The palatability of undyed carrot surface-coated with repellents, or dyed blue or green to a terrestrial macroinvertebrate

ABSTRACTBirds are at risk of being poisoned during pest control operations not only through eating toxic baits, but potentially by preying on invertebrates that have, themselves, consumed the toxic baits. Blue baits coated with anthraquinone and/or mint-scented repellents are avoided by some bird species compared with green baits coated with cinnamon oil; however, data on invertebrate avoidance patterns have not been explored. In our first experiment, we measured consumption rates in a large invertebrate, the Auckland tree wētā (Hemideina thoracica) for carrot that had been surface-coated with three repellent formulations: anthraquinone (0.8 g kg−1) (a secondary repellent); anthraquinone (0.8 g kg−1) and pennyroyal oil (a mint-scented product which acts as a primary repellent) (0.5 g kg−1); and cinnamon oil (0.15 g kg−1) (a primary repellent), over 4 days. In a second experiment, we tested whether tree wētā preferred carrot dyed either blue or green over 2 days. Tree wētā ate similar quantities of carrot from all three of the repellent formulations tested, but consumption of all three formulations was significantly lower than the control from the third day of the experiment. Tree wētā ate less blue-dyed carrot than green-dyed carrot on both days of the second experiment, but differences were not significant (day 1, P= 0.057; day 2, P = 0.145). Our findings complement the results of previous studies on some bird species. Together they show the potential of surface-coating baits with anthraquinone and/or mint oil and dyeing them blue in pest control operations to reduce non-target avian by-kill, while not increasing the risk of secondary poisoning of insectivorous species. Our results also indicate that cinnamon oil can be used not only as a toxin mask but also as a repellent to wētā.

Macro-invertebrate Biodiversity of a Coastal Prairie with Vernal Pool Habitat.

BackgroundThe California Coastal Prairie has the highest biodiversity of North America's grasslands, but also has the highest percentage of urbanization. The most urbanized part of the California Coastal Prairie is its southernmost area, in Los Angeles County. This southernmost region, known as the Los Angeles Coastal Prairie, was historically dotted with vernal pools, and has a unique biodiverse composition. More than 99.5% of its estimated original 95 km2 (23,475 acres), as well as almost all its vernal pool complexes, have been lost to urbanization.The Madrona Marsh Preserve, in Torrance, California, safeguards approximately 18 hectares (44 acres) of Los Angeles Coastal Prairie and includes a complex of vernal pools. Its aquatic biodiversity had been studied, predominantly to genus level, but its terrestrial macro-invertebrates were virtually unknown, aside from butterfly, dragonfly, and damselfly observations.New informationIn order to better understand the biodiversity at the Madrona Marsh Preserve, a minimally-invasive macro-invertebrate inventory was conducted. The results of this inventory, with 689 invertebrate organisms recorded, covering eight phyla, 13 classes, 39 orders, and 222 families, are presented in this document.

Can translocated native fishes retain their trophic niche when confronted with a resident invasive?

AbstractDiet interactions between native and non‐native fishes may influence the establishment of native species within their historical range (i.e., reintroduction). Therefore, we illustrated the food web structure of and followed the transition of the federally endangered humpback chub Gila cypha into a novel food web following translocation and determined the potential for a non‐native species, rainbow trout Oncorhynchus mykiss, to influence translocation success. Humpback chub and rainbow trout used resources high in the food web and assimilated similar proportions of native fishes, suggesting non‐native rainbow trout may occupy an ecological role similar to humpback chub. Subsequently, humpback chub may be well suited to colonise tributaries because of their ability to consume resources high in the food web. Additionally, diet partitioning may occur between all members of the fish community as indicated by separation in trophic niche space and little trophic overlap; although all species, particularly bluehead sucker Catostomus discobolus, used a broad range of food resources. Rainbow trout stomach content analysis corroborated stable isotope analysis and suggested rainbow trout diet consisted of aquatic and terrestrial macroinvertebrates, while larger rainbow trout (>120 mm total length) consumed a greater proportion of fish (incidence of piscivory = 5.3%). Trophic interactions may reveal an underutilized niche space or biotic resistance to the establishment of translocated native fishes. Continued translocation of humpback chub into tributaries appears to be one option for conservation. However, successful establishment of humpback chub may depend on continued removal of non‐native trout, increasing availability of diet sources at higher trophic levels.

Terrestrial Macroinvertebrates as Key Elements for Sustainable Beach Management

COLOMBINI, I., FALLACI, M and CHELAZZI, L., 2011. Terrestrial Macroinvertibrates as Key Elements for Sustainable Beach Management. In: Micallef, A. (ed.), MCRR3-2010 Conference Proceedings, Journal of Coastal Research, Special Issue, No. 61, pp. 24–35. Grosseto, Tuscany, Italy, ISSN 0749-0208.Recreational activities on sandy beaches are basically human centred and there is little concern of their biological components. Terrestrial sandy shore are often regarded as void boxes of sand to be reconstructed where missing, decorated with coastal vegetation and mechanically cleaned for aesthetic and sanitary reasons. But what costs, in terms of biodiversity loss, are we dealing with? Can beach management be sustainable without considering the fact that terrestrial beach macroinvertebrates are hardly taken into account in management practices? Do beach managers know the importance of terrestrial macroinvertebrates for ecosystem functioning? What measures are needed to avoid the massive loss of species? To address these questions a ten year period of study was conducted on the beach of the Maremma Regional Park (Grosseto, Italy). Here direct impacts due to human activities (beach recreation, trampling, etc) were relatively low, but indirect ones (a severe problem of beach erosion at the Ombrone river mouth) were taking place and large sections of the beach had already been destroyed. Since one of the main attractions of the Maremma Regional Park was the beauty of its beaches (used for summer bathing activities), concerns of the public opinion and of park managers were extremely high. A first approach of our study was to evaluated the health of the beach environment through a baseline ecological study and to pin pointed the main factors causing the erosion process. The study showed that the system was in a dynamic equilibrium with an erosion process going on one side and a accretion process on the other. Biodiversity levels followed linear gradients with increasing levels at increasing distance from the river mouth and were related to increases in habitat complexity. Changes rapidly occurring around the river mouth had produced a shift of the macroinvertebrate community in a buffer area at a higher distance from the river mouth where populations were still consistent in species number and abundance. Furthermore, studying beach populations at increasing distances from the river mouth on a monthly basis demonstrated that terrestrial beach invertebrates (amphipods, isopods, tenebrionids), strictly inhabiting the sand, tended to shift horizontally along the beach to avoid human disturbance according to the season. This finding not only has an ecological importance for the resilience of the ecosystem, showing the value of buffer areas as resources for biodiversity, but also it presents practical aspects as it can be used by beach managers to plan actions for sustainable management. In other beaches where impacts are high this tool could be employed to fine tune spatial and temporal beach cleaning events to avoid further losses of beach species and/or the recovery of others. The study, however, suggests the need of an active interaction between scientists, stakeholders and managers. Communication is also needed between beach ecologists and coastal recreational managers to whom this conference is addressed as more often it has occurred that defence measures have been taken without considering the impacts on the biotic components of the beach ecosystem.

Terrestrial macroinvertebrates captured with a baited ramp-pitfall trap from five limestone caves in North Alabama and Georgia (USA) and their association with soil organic matter

Abundance and species richness of terrestrial cave invertebrates are not well known but are thought to be constrained by nutrient (food) supplies. A standard sampling procedure for collecting cave invertebrates does not exist. The majority of cave systems in the southeastern USA (e.g. Alabama and Georgia) have not been extensively sampled for invertebrates. We tested a baited ramp-pitfall trap for collecting terrestrial invertebrates from caves and investigated whether macroinvertebrate abundance and species richness follow total organic matter (TOM) levels from cave soils. In 14-day sampling periods, we captured 21,204 invertebrates from 14 orders comprising at least 44 species from five caves in north Alabama and Georgia. Diptera was the most frequently captured order, comprising 18 species and over 91% of our captures. Overall, our traps were successful at sampling terrestrial invertebrates from caves; however, species richness and abundance did not always correlate with TOM concentration.

Food webs of a sandy beach macroinvertebrate community using stable isotopes analysis

The study examines the food webs of macroinvertebrates along a gradient from the sandy shore to a dune slack in the retrodune. The study was conducted at the Maremma Regional Park in an area subjected to beach progradation. Transects with pitfall traps were set perpendicular to the sea to capture macroinvertebrates, whereas vegetation biomass was evaluated using quadrats. Marine allochthonous material was also examined. Stable isotopes of δ 13C and δ 15N were analysed both in plants and macroinvertebrates of marine and terrestrial origins. Hierarchical cluster analysis was used to group species with similar values. Multi-source mixing models were used to analyse the contribution of carbon of marine origin to the diets, to calculate trophic levels and to estimate the diets of certain species. The results indicate a decrease in the contribution of marine carbon in the diets of terrestrial macroinvertebrates along the sea–land axis.

River channelization reduces nutrient flow and macroinvertebrate diversity at the aquatic terrestrial transition zone

Aquatic and terrestrial ecosystems are linked through lateral interactions that support and maintain biodiversity in both regions. However, in many places, river regulation and channelization have isolated rivers from surrounding riparian areas. We evaluated the effects of channelization on the linkages between aquatic and terrestrial invertebrate assemblages in the Rio Grande, New Mexico via comparison of quantitative macroinvertebrate survey data and analyses of carbon and nitrogen isotopes to test for changes in nutrient flow between channelized and non-channelized reaches of this highly regulated system. Aquatic and terrestrial macroinvertebrates were surveyed in summer 2008 at channelized and non-channelized reaches. Average densities of aquatic macroinvertebrates were 50% lower in the channelized reaches. Taxonomic richness and densities of macroinvertebrates in the transition zone between the river and forested floodplain were also lower in channelized reaches and this effect was especially pronoun...

Do bare-nosed wombat (Vombatus ursinus) mounds influence terrestrial macroinvertebrate assemblages in agricultural riparian zones?

Riparian ecosystems contain a complex mosaic of habitat structure types that can support distinct macroinvertebrate communities. Bare-nosed wombats (Vombatus ursinus) are often an integral component of agricultural riparian systems in south-eastern Australia. In these systems, wombats construct large burrow systems and mounds in the stream banks. Wombat mound structures vary markedly from the surrounding landscape and they may influence macroinvertebrate assemblages. We examined this ecosystem-engineering role of wombats as well as the ecological variability within our agricultural riparian study sites on the possible influence on macroinvertebrate assemblages. There were no detectable effects of wombat mounds on the richness or abundance of macroinvertebrates on the soil surface. At the site level, however, macroinvertebrate assemblages were most influenced by litter depth, upper canopy cover, cattle hoof prints and slope. The ecological variables within the study sites strongly affected macroinvertebrate assemblages. These findings reflect an influence of anthropogenic impact on communities of ground-dwelling invertebrates that have been found in other studies. It is possible that a finer resolution of taxa may highlight a unique pattern of macroinvertebrate use of wombat mounds.

Effects of stream restoration and wastewater treatment plant effluent on fish communities in urban streams

Summary1. Fish community characteristics, resource availability and resource use were assessed in three headwater urban streams in Piedmont North Carolina, U.S.A. Three site types were examined on each stream; two urban (restored and unrestored) and a forested site downstream of urbanisation, which was impacted by effluent from a wastewater treatment plant (WWTP). Stream basal resources, aquatic macroinvertebrates, terrestrial macroinvertebrates and fish were collected at each site.2. The WWTPs affected isotope signatures in the biota. Basal resource, aquatic macroinvertebrate and fish δ15N showed significant enrichments in the downstream sites, although δ13C signatures were not greatly influenced by the WWTP. Fish were clearly deriving a significant part of their nutrition from sewage effluent‐derived sources. There was a trend towards lower richness and abundance of fish at sewage‐influenced sites compared with urban restored sites, although the difference was not significant.3. Restored stream sites had significantly higher fish richness and a trend towards greater abundance compared with unrestored sites. Although significant differences did not exist between urban restored and unrestored areas for aquatic and terrestrial macroinvertebrate abundances and biotic indices of stream health, there appeared to be a trend towards improvements in restored sites for these parameters. Additional surveys of these sites on a regular basis, along with maintenance of restored features are vital to understanding and maximising restoration effectiveness.4. A pattern of enriched δ13C in fish in restored and unrestored streams in conjunction with enriched δ13C of terrestrial invertebrates at these sites suggests that these terrestrial subsidies are important to the fish, a conclusion also supported by isotope cross plots. Furthermore, enriched δ13C observed for terrestrial invertebrates is consistent with some utilisation of the invasive C4 plants that occur in the urban riparian areas.

The diet and impact of house mice on a sub-Antarctic island

An analysis of the stomach contents of house mice (Mus musculus L.) at three sites on Marion Island (47°S, 38°E) over a 1-year period showed that the mice feed mostly on terrestrial macroinvertebrates but that plants (mainly seed) are an important component of the diet in mid- to late summer. Larvae of a flightless moth, weevil larvae and adults and, at one of the sites, earthworms were the invertebrate items that showed the highest importance value over the year. Diet diversity was slightly lower in summer and autumn than in winter and spring. Diet variety was lowest in midsummer and highest in either autumn or winter, depending on the site. Mean stomach-content mass was significantly higher in midwinter than during the rest of the year. When offered prey of different types and sizes, mice selected moth larvae first in 92% of the trials; earthworms or weevil adults were most frequently selected second, and weevil larvae fourth. An introduced slug species was selected only once, as the last choice and only part of it was eaten. With both moth larvae and earthworms, the heaviest individual offered was almost always chosen first. Surprisingly, mice never consumed more than about half of the seed offered to them and their condition deteriorated severely during the trials with seed; in a third of the trials with two types of seed, the mice completely ignored the seed. The impact of mice predation on invertebrates was assessed at two of the sites – a dry mire and a coastal biotic herbfield that is influenced by seabird and seal manuring. Moth larvae and adults, weevil larvae and adults, earthworms, spiders and flies made up >90% of the animal remains in the stomach contents over the year and, on average, the mice daily consumed 45 g (dry mass) ha–1 of those invertebrates at the mire and 194 g ha–1 at the biotic site. Moth larvae made up a substantial proportion of these amounts; average daily consumption was 30 g ha–1 at the mire and 107 g ha–1 at the biotic site. In terms of the amount consumed in relation to biomass, the heaviest impact of mice at both sites was on weevil adults; at the biotic site mice daily consumed 13% of weevil adult biomass in autumn and nearly 6 times the annual average biomass over the year. At the mire, slightly more than the annual average weevil adult biomass was consumed over the year. The consumption of invertebrates by mice found in this study (1992/1993) was about 20% greater than in 1979/1980. The most striking changes in annual average consumption rate between 1979/1980 and 1992/1993 were for weevil larvae (increased nearly fourfold) and earthworms (increased sixfold at the biotic site and threefold at the mire). In contrast, the consumption of spiders at both sites decreased between 1979/1980 and 1992/1993.