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Ongoing inputs, in the form of sediment deposition along with associated dissolved contaminants, have challenged the assessment of cap performance at contaminated sediment sites. To address this issue, thin 2–3 cm layer sand caps amended with activated carbon (AC) were investigated for the remediation of polychlorinated biphenyl (PCB) contaminated marine sediments using 90-day mesocosms. All treatments were challenged with (1) ongoing clean or marker-PCB-spiked sediment inputs and (2) bioturbation. Bioaccumulation in hard clams (filter feeding near the cap-water interface) was evaluated to best understand cap effectiveness, relative to sheepshead minnows (confined to the surface water) and sandworms (which burrowed through the caps). All caps (sand and AC amended sand) provided isolation of native bedded PCBs (i.e., PCBs sourced from the bed), reducing uptake in organisms. Total PCB bioaccumulation in clams indicated that AC addition to the cap provided no benefit with spiked influx, or some benefit (56% reduction) with clean influx. Spiked input PCBs, when added to the depositional input sediment, were consistently detected in clams and passive samplers, with and without AC in the cap. PCB uptake by passive samplers located in the caps did not reflect the performance of the remedy, as defined by clam bioaccumulation. However, PCB uptake by passive samplers in the overlying water reasonably represented clam bioaccumulation results.

The effects of single macrofauna taxa on benthic nitrogen (N) cycling have been extensively studied, whereas how macrofaunal communities affect N-related processes remains poorly explored. In this study, we characterized benthic N-cycling in bioturbated sediments of the oligotrophic Öre Estuary (northern Baltic Sea). Solute fluxes and N transformations (N2 fixation, denitrification and dissimilative nitrate reduction to ammonium [DNRA]) were measured in sediments and macrofauna-associated microbes (holobionts) to partition the role of three dominant taxa (the filter feeder Limecola balthica, the deep deposit feeder Marenzelleria spp., and the surface deposit feeder Monoporeia affinis) in shaping N-cycling. In the studied area, benthic macrofauna comprised a low diversity community with dominance of the three taxa, which are widespread and dominant in the Baltic. The biomass of these taxa in macrofaunal community explained up to 30% of variation in measured biogeochemical processes, confirming their important role in ecosystem functioning. The results also show that these taxa significantly contributed to the benthic metabolism and N-cycling (direct effect) as well as to sediments bioturbation with positive feedback to dissimilative nitrate reduction (indirect effect). Taken together, these functions promoted a reuse of nutrients at the benthic level, limiting net losses (e.g. denitrification) and effluxes to bottom water. Finally, the detection of multiple N transformations in macrofauna holobionts suggested a community-associated versatile microbiome, however, its role was of minor importance as compared to the activity of sediment-associated microbial communities. The present study highlights hidden and interactive effects among microbes and macrofauna, which should be considered analysing benthic functioning.

This study integrates ichnological and sedimentological data to interpret depositional environments of the carbonate sediments of the Tirgan Formation (Lower Cretaceous) in the eastern Kopet-Dagh Basin, north-east Iran. Lithofacies analysis shows that these sediments were deposited in inner ramp, middle ramp and offshore (outer ramp) environments. Five ichnoassemblages are identified in the sediments that consist of Thalassinoides, Thalassinoides–Rhizocorallium, Planolites–Rhizocorallium, Arenicolites–Diplocraterion, and Arenicolites. Th, Th-Rh and Pl-Rh with low diversity and abundance of the trace fossils formed during waning phase of storms in a predominantly medium to high-energy hydrodynamic regime. High sedimentation rate and mobile substrate condition featuring a shallow-marine setting. Ar–Di ichnoassemblage, consisting of horizontal and vertical traces of deposit and suspension feeders, respectively, portray two different phases. A predominantly high energy phase with instable substrate is displayed by the vertical traces, while a minor omission phase, associated with a decrease in sedimentation rate or non-deposition, is indicated by the horizontal structures. Arenicolites ichnoassemblage with low bioturbation index and low ichnodiversity is related to a semi-sheltered area of lagoon environments with periodically marine water circulation. The study of the ichnological attributes in the studied successions indicates the presence of a shallowing up-ward trend in the storm‒tide-dominated ramp sequence. Ichnoassemblage development is largely controlled by depositional and ecological conditions, e.g., the stability of substrate, hydrodynamic regime (wave and tide), and food abundance, which altogether control the substrate colonization. Based on an integrated ichnological and sedimentological approach, we characterize the depositional environment, deciphering allogenic and autogenic environmental controls on the trace fossil distribution on a passive margin depositional setting.

Sea cucumbers play an important role in sediment bioturbation in coral reef and rocky intertidal ecosystems, and bacteria were a commonly-reported component of holothuroid diets. Bacterial community composition in the foregut and hindgut of two common tropical sea cucumbers (Holothuria atra and H. leucospilota) and the ambient surface sediment were investigated using high throughput sequencing based on 16S rRNA gene analysis. A total of 5 584 operational taxonomic units (OTUs) were obtained from 25 samples based on a 97% threshold, and more than half of the OTUs (n=3 694, 66.2%) were shared by the gut contents of two species of sea cucumbers and surrounding sediments. Bacterial richness and diversity in sediment samples were significantly higher than those in the gut content samples (P

Different conceptions of disturbance differ in the degree to which they appeal to mechanisms that are general and equivalent, or species‐, functional group‐, or interaction‐specific. Some concepts of disturbance, for example, predict that soil disturbances and herbivory have identical impacts on species richness via identical mechanisms (reduction in biomass and in competition). An alternative hypothesis is that the specific traits of disturbance agents (small mammals) and plants differentially affect the richness or abundance of different plant groups. We tested these hypotheses on a degu (Octodon degus) colony in central Chile. We ask whether native and non‐native forbs respond differently to degu bioturbation on runways versus herbivory on grazing lawns. We ask whether this can explain the increase in non‐native plants on degu colonies. We found that biopedturbation did not explain the locations of non‐native plants. We did not find direct evidence of grazing increasing non‐native herbs either, but a grazing effect appears to be mediated by grass, which is the dominant cover. Further, we provide supplementary evidence to support our interpretation that a key mechanism of non‐native spread is the formation of dry soil conditions on grazing lawns. Thus, ecosystem engineering (alteration of soil qualities) may be an outcome of disturbances, in which each interacts with specific plant traits, to create the observed pattern of non‐native spread in the colony. Based on these results, we propose to extend Jentsch and White (Ecology, 100, 2019, e02734) concept of combined pulse/ disturbance events to the long‐term process duality of ecosystem engineering/ disturbance., Non‐native plant species accumulate on the centers of native degu (Octodon degus) colonies. We show that this is the result of the interaction and accumulation of two kinds of disturbances (biopedturbation and herbivory) with different effects on plant species over time. Although disturbance is usually represented as different from, or indeed opposite to, ecosystem engineering, we show that ecosystem engineering best explains the outcome of these two disturbances over time.

Hydrologic dysfunction associated with desertification of grazing lands likely depends on two opposing biophysical drivers, compaction by livestock and bioturbation by plant roots and soil biota. To understand which is most important, we conducted a long-term field experiment. We tested the effects of phytobiomass (control vs. herbicide treated) and three ungulate disturbance treatments (none, once, and twice disturbed) on soil water transport in northern mixed-grass prairie. Field-saturated hydraulic conductivity (i.e., infiltration) was primarily reduced by the most severe (twice disturbed) ungulate disturbance treatment. To a lesser degree, ungulate disturbance and phytobiomass interacted, and similar levels of hydrologic dysfunction were detected for plots annually treated with herbicide and disturbed by a single livestock disturbance event (and while soils were dry and resistant to compaction) and naturally vegetated plots that had been twice disturbed (including while soils were wet and susceptible to compaction). Our findings suggest hydrologic dysfunction in grazing lands is mainly due to compaction by ungulates, especially when grazing at high stocking rates and while areas are vulnerable to compaction (e.g., fine soils, wet soils, not well vegetated).

The spiny water flea (Bythotrephes cederströmii), a freshwater crustacean considered to be the world’s best-studied invasive zooplankter, was first recorded in North America in the Laurentian Great Lakes during the 1980s. Its arrival is widely considered to be the result of ocean-going cargo ships that translocated contaminated ballast water from Eurasia to the Great Lakes during the 1970–1980s. The subsequent first discovery of the species in inland lakes is consistent with the hypothesis that propagules dispersed initially from established Great Lakes populations. Here we present evidence of exoskeletal remains, including mandibles, tail spines, and resting eggs, in 210Pb-dated lake sediment cores, which suggests that B. cederströmii was already resident in four inland North American lakes (two in Minnesota, USA; two in Ontario, Canada) by at least the early 1900s. Densities of exoskeletal remains were low and relatively steady from first appearance until about 1990, after which time they increased in all cores. The earliest evidence that we found was a mandible at 33-cm depth (pre-1650) in the sediments of Three Mile Lake, Ontario, Canada. These unexpected findings challenge the current paradigm of B. cederströmii invasion, renew uncertainty about the timing and sequence of its colonization of North American lakes, and potentially question our ability to detect invasive species with traditional sampling methods. We attempted to eliminate errors in the dated stratigraphies of the exoskeletal remains that might have been introduced either methodologically (e.g., core-wall smearing) or naturally (e.g., bioturbation). Nonetheless, given the very low numbers of subfossils encountered, questions remain about the possible artifactual nature of our observations and therefore we regard our results as ‘preliminary findings’ at this time.

As an extended comment on the paper by Sarnthein et al. (2020), we express strong reservations about the methodology of the so-called 14C plateau tuning (PT) technique used to date marine sediment records and its implications on the determination of 14C marine reservoir ages (MRA). The main problems are linked to: the assumption of constant MRA during 14C-age plateaus; the lack of consideration of foraminifera abundance changes coupled to bioturbation that can create spurious plateaus in marine sediments; the assumption that plateaus have the same shapes and durations in atmospheric and oceanic records; the implication that atmospheric 14C/12C peaked instantaneously from one plateau to the next; that the 14C plateaus represent 82 % of the total time spent between 14,000 and 29,000 cal yr BP, whereas during the remaining 18 % of the time, the radiocarbon clock was running almost 5 times too fast; that the sparsity, combined with the level of analytical uncertainties and additional noise, in both atmospheric and marine data do not currently allow one to reliably or robustly identify plateaus (should they exist) beyond 15,000 cal yr BP; and that the determination and identification of plateaus is reliant upon significant changes in sedimentation rate within the marine sediments which are, a priori, unknown and are not verified with an independent method. The concerns we raise are supported and strengthened with carbon cycle box-model experiments and statistical simulations of pseudo-atmospheric and pseudo-marine records, allowing us to test the ability to identify and tune 14C-age plateaus, in the context of noisy and sparse data.

Cable bacteria are multicellular filamentous bacteria that conduct electrons nonlocally between anoxic and oxic sediment regions, creating characteristic electrogenic pH fingerprints. These microbes aggregate in 3D patterns near biogenic structures, and filament fragments are also dispersed throughout deposits. Utilizing pH-sensitive planar optodes to investigate the dynamic response of electrogenic pH fingerprints to sediment reworking, we found that mobile bioturbators like nereid polychaetes (ragworms) can disturb the pH signatures. Sudden sediment disturbance associated with burrows at sub- to multi-centimeter scales eliminates detection of pH signatures. However, electrogenic pH fingerprints can recover in as little as 13 h near abandoned, closed burrows. Sequential collapse and regeneration of electrogenic pH fingerprints are associated with occupied and dynamic burrow structures, with the response time positively related to the scale of disturbance. In the case of relatively stable tube structures, built by benthos like spionid polychaetes and extending mm to cm into deposits, the electrogenic pH fingerprint is evident around the subsurface tubes. Cable filaments clearly associate with subsurface regions of enhanced solute exchange (oxidant supply) and relatively stable biogenic structures, including individual tubes and patches of tubes (e.g. made by Sabaco, a bamboo worm). Physically stable environments, favorable redox gradients, and enhanced organic/inorganic substrate availability promote the activity of cable bacteria in the vicinity of tubes and burrows. These findings suggest complex interactions between electrogenic activity fingerprints and species-specific patterns of bioturbation at multiple spatial and temporal scales, and a substantial impact of electrogenic metabolism on subsurface pH and early diagenetic reaction distributions in bioturbated deposits.

Beetles (Coleoptera) are a critical component of terrestrial ecosystems filling numerous ecological roles. Soil-dwelling beetles play an important role in pedogenesis through the production of biog...

In this artice, we studied the bioturbation and dung removal activity of dung beetle Catharsius molossus (Linnaeus, 1758) (Coleoptera: Scarabaeidae: Scarabaeinae) in different elevations in the Great Himalayan National Park Conservation Area for the first time to understand the capability of the species in providing such ecosystem services with an experimental approach in six different elevations in the area. We found that the weight of dung buried and bioturbation had significant difference between the elevations, and they had significant linear relationship with the elevations. Differences in such activities along the elevation can cause a low amount of nutrient transfer from the dung to the soil which can adversely affect the surrounding habitats.

Earthworm activity modifies soil structure and promotes important hydrological ecosystem functions for agricultural systems. Earthworms use their flexible hydroskeleton to burrow and expand biopores. Hence, their activity is constrained by soil hydromechanical conditions that permit deformation at earthworm’s maximal hydroskeletal pressure (≈200kPa). A mechanistic biophysical model is developed here to link the biomechanical limits of earthworm burrowing with soil moisture and texture to predict soil conditions that permit bioturbation across biomes. We include additional constraints that exclude earthworm activity such as freezing temperatures, low soil pH, and high sand content to develop the first predictive global map of earthworm habitats in good agreement with observed earthworm occurrence patterns. Earthworm activity is strongly constrained by seasonal dynamics that vary across latitudes largely due to soil hydromechanical status. The mechanistic model delineates the potential for earthworm migration via connectivity of hospitable sites and highlights regions sensitive to climate., Here, the authors present a mechanistic model of how soil bioturbation and climate interact to predict the global distribution of habitats and associated temporal windows of earthworms. Their models show that seasonal activity windows are predicted by soil mechanical states governed by precipitation level and distribution estimates are affected by habitat fragmentation, and highlights areas for potential earthworm migration and regions sensitive to climate.

Soil micromorphology, by means of the description and analysis of soil thin sections, provides information about soil microstructure, which includes, among other features, morphological data on the aggregates and the porosity derived from structure formation. Soil porosity may be due to both abiotic factors and biological activity (biopores). The aim of this study is to validate a methodology for the quantification of bioporosity in thin sections of Luvic Phaeozems of Argentina, for its use as soil quality indicator. Soil samples were taken from the surface horizon in plots with different uses: reserve (R), agricultural (A), Eucalyptus globulus forest plantation (E), and Pinus radiata forest plantation (P). In each site, bulk density, penetration resistance, structural stability, organic matter, and pH were determined. Three undisturbed samples were taken, impregnated with resin, and treated using routine techniques to obtain soil thin sections. Volume percentages of total porosity and biopores were determined in the thin sections using two methodologies (I: irregular polygon on the outline of the biopore and II point counting), in order to obtain an estimation of the biological activity under the different land uses. Plots R, E, and P showed greater porosity and higher bioturbation compared to plot A. In addition, the percentage of biopores in soils of R, E, and P plots reaches almost 80% of the total porosity, while in soil of plot A plot, it is two times lower (40%). This indicates greater biological activity in the natural and forested plots as compared with the cultivated plot. This activity is linked to the high content of organic matter, high structural stability, low bulk density, and low penetration resistance. These results show that the estimation of the bioturbated volume would be a good indicator of soil quality and, in addition, the methodologies used in this study constitute an easy-to-use tool for the determination of bioporosity in soil. However, methodology II is preferred, because it requires a shorter time of image edition.

The Upper Emsian to Frasnian Ia-Ib strata of the Marhouma area (or “km 30” outcrop), exposed in the Ougarta Range (SW Algeria) belong to the Chefar El Ahmar Formation. On the basis of distinct lithological and palaeontological features, this formation is subdivided into three members (Lower Marly Limestones Member, Middle Marly Limestones Member, and Upper Marly Limestones Member). The studied beds show low to moderate diversity of trace fossil assemblage which contains thirteen ichnotaxa: Chondrites intricatus, Chondrites isp., Chondrites cf. targionii, Circulichnis cf. montanus, Cochlichnus isp., Neonereites biserialis, Neonereites multiserialis, Nereites isp., Palaeophycus isp., Planolites isp., Thalassinoides isp., Zoophycos aff. cauda-galli, and Zoophycos isp. A. The two latter ichnotaxa are the most common trace fossils in the assemblage and occur at three different levels showing different bioturbation intensities. The first Zoophycos-bearing level (Zl 1) is characterised by an overall high bioturbation intensity reflecting a very high oxygenation rate and nutrient supply, allowing the development of large and dense Zoophycos specimens. The second Zoophycos-bearing level (Zl 2) has a considerable reduction of bioturbation intensity as compared to the previous level, with an abundance of Chondrites, which is probably due to radical palaeoecological changes that suggests dysoxic and stressful conditions. The third Zoophycos-bearing level (Zl 3) is characterised by an overall moderate bioturbation intensity. The distribution of trace fossils was influenced by lithology, sedimentation rate, energy level (storm events), bottom oxygenation, and nutrient supply. The lithofacies and trace fossils of the Chefar El Ahmar Formation both indicate a depositional environment fluctuating from the lower shoreface to lower offshore zone.

Bioturbation of reef sediments aerates the upper sediment layers and releases organic material to benthic communities. Despite being the larger and more conspicuous bioturbators on coral reefs, the value of holothurians (sea cucumbers) to reef ecosystems is less often attributed to their ecosystem services than their value for fisheries. This may be because they are considered to have an insignificant effect on reef health relative to other animals. Here, we ground-truthed remote sensing data obtained from drone and satellite imagery to estimate the bioturbation rates of holothurians across the 19 km2 Heron Island Reef in Queensland, Australia. Ex situ bioturbation rates of the most abundant holothurian, Holothuria atra, were assessed during 24-h feeding experiments. Using density measurements of holothurians across reef flat zones in a 27,000 m2 map produced from drone imagery, we extrapolated bioturbation across the reef using satellite remote sensing data. Individual H. atra were estimated to produce approximately 14 kg of bioturbated sediment per year. On a reef scale (excluding the reef lagoon) and accounting for varying densities of holothurians across different reef zones, total bioturbation from holothurians at Heron Reef was estimated at over 64,000 metric tonnes per year, slightly more than the mass of five Eiffel Towers. These results highlight the scale of structural and biochemical impacts that holothurians have on reef flats and their importance to ecosystem functioning and services. Management of these animals on reefs is imperative as overharvesting would likely cause substantial negative effects on sedimentary ecosystems and their biogeochemistry in corals reefs.

A new ichnospecies, Glossifungites gingrasi n. isp., is described from multiple locations in basal sand-filled coastal plain distributary channels of the Turonian (Upper Cretaceous) Ferron Sandstone (central Utah). Glossifungites gingrasi n. isp. is attributed to the ichnogenus Glossifungites based on the presence of scratch imprints, passive fill, and a tongue-shaped structure, yet the new ichnospecies is distinct because it displays transverse bioglyphs that run perpendicular to the planiform structure, which contrasts to the axis parallel bioglyphs present in the ichnospecies G. saxicava. The transverse arrangement of ornamentation exhibited by G. gingrasi n. isp. is observed in modern subaqueous insect burrows produced by mayfly and chironomid larvae, and constitutes a way to differentiate insect-generated burrows from structures produced by crustaceans that are known to create other Glossifungites ichnospecies. Differentiating insect- from crustacean-generated burrows is significant because it provides a way to distinguish bioturbation by marine-recruited fauna from that produced by freshwater fauna in the rock record, making G. gingrasi n. isp. a valuable ichnological tool for paleoenvironmental and stratigraphic interpretation. While G. gingrasi n. isp. may represent a burrow created by a variety of filter-feeding subaqueous insects, the large size of G. gingrasi n. isp. in the Ferron Sandstone suggests that the largest specimens are probable mayfly burrows and supports the assertion that burrowing mayflies (e.g., Polymitarcyidae and Ephemeridae) adapted to domicile filter-feeding during or prior to the Turonian.UUID: http://zoobank.org/a033b22f-bf09-481a-975e-3a1b096154cc

Bioturbation plays a critical role in sediment mixing and biogeochemical cycling between sediment and seawater. An abundance of bioturbation structures, dominated by Thalassinoides, occurs in carbonate rocks of the Cambrian Series 2 Zhushadong Formation in the Dengfeng area of western Henan Province, North China. Determination of elemental geochemistry can help to establish the influence of burrowing activities on sediment biogeochemical cycling, especially on changes in oxygen concentration and nutrient regeneration. Results show that there is a dramatic difference in the bioturbation intensity between the bioturbated limestone and laminated dolostone of the Zhushadong Formation in terms of productivity proxies (Baex, Cu, Ni, Sr/Ca) and redox proxies (V/Cr, V/Sc, Ni/Co). These changes may be related to the presence of Thalassinoides bioturbators, which alter the particle size and permeability of sediments, while also increase the oxygen concentration and capacity for nutrient regeneration. Comparison with modern studies shows that the sediment mixing and reworking induced by Thalassinoides bioturbators significantly changed the primary physical and chemical characteristics of the Cambrian sediment, triggering the substrate revolution and promoting biogeochemical cycling between sediment and seawater.

Pedologists generally pay less attention to bioturbation than other soil-forming processes since morphological descriptions and/or soil analytical methods often exclude the characterization of biogenic structures. For example, bioaggregates are not even considered in the Brazilian Soil Classification System. Here, we aimed to address this shortcoming by describing and analyzing biogenic features (e.g., channels, pedotubes, and casts) produced by earthworm activity in soils. Annelid structures in Brazilian Atlantic rain forest soils were collected, measured, and photographed. The bioaggregates were organized by type (cylindrical, irregular blocks) and class (very small, small, medium, large, and very large). Physical and chemical characterization of these structures was also performed, including analyses of soil texture, organic carbon, and exchangeable bases (Ca2+, Mg2+, K+, P). Some biogenic features were filled with revolved soil (i.e. krotovinas or paleoburrows), while others were not (intact channels). Redoximorphic features were very common on the channel walls and casts, likely because these biogenic pores contribute to soil O2 diffusion and CO2 removal. The casts were found to have a sandy texture and organic carbon contents were three times greater – as also exemplified by their darker color – than the surrounding soil matrix. These factors collectively suggest the efficiency with which certain ecological groups of annelids incorporate organic matter into forest soils. Earthworm casts also contained higher quantities of phosphorus, calcium, and magnesium (exchangeable bases) than the surrounding soil. Earthworms are a fundamental part of soil functioning, contributing to essential processes such as aeration, aggregation, organic matter incorporation, and fertility enhancement. Therefore, earthworms and the biogenic structures they are responsible for can be considered to strongly influence pedogenesis, especially in tropical regions.

Nitrogen fixation and methane production in surface sediments of a long bioturbated beach at the northeast coast of Bay of Bengal were quantified in vitro through gas chromatography. The beach was ...

Arsenic (As), iron (Fe), and manganese (Mn) contents were measured in sediment nodules and associated pore waters obtained from sediment cores collected from a salt marsh on Polvora Island (southern Brazil). Sediment cores were obtained when brackish water dominated the estuary, at two different environments: an unvegetated mudflat colonized by crabs (Neohelice granulata), and a low intertidal stand vegetated by Spartina alterniflora. We determined the percentage of nodules in each depth interval of the cores, along with redox potential, and As, Fe, and Mn contents of the nodules. The mineralogy of the nodules was investigated, and results showed they are mainly composed by quartz, phyllosilicates, and amorphous Fe–Mn oxides/oxyhydroxides. Pore water results showed that bioturbation by local crabs supports oxygen penetration to depths of ca. 25 cm below the salt marsh surface, with lower Fe contents in pore water associated with the brackish period. However, S. alterniflora growth appears to have a greater impact on sediment geochemistry of Fe, Mn, and possibly As due to sulfate reduction and the associated decrease in pore water pH. Higher Fe concentrations were observed in the pore waters during the period of brackish water dominance, which also corresponded to the S. alterniflora growth season. The study demonstrates that differences in geochemical conditions (e.g., Fe content) that can develop in salt marsh sediments owing to different types of bioirrigation processes (i.e., bioirrigation driven by crabs versus that related to the growth of S. alterniflora) play important roles in the biogeochemical cycling of As.

Significance Human disturbances, climate change, and their combined effects on species distributions and environmental conditions are increasingly modifying the organization of our world’s oceans, forests, grasslands, wetlands, tundras, and reefs. Here, we reveal that these contemporary conditions can trigger the emergence of novel keystone species. Across the southeastern US coastal plain, sea-level rise is outpacing salt marsh vertical accretion, causing these grasslands to be tidally inundated for longer and softening marsh substrates to levels optimal for crab burrowing. Using field experiments, measurements, surveys, and models, we show that these conditions amplify the burrowing and grazing effects of a previously inconspicuous crab, enabling it to redefine predator–prey interactions, eco-geomorphic feedbacks, and the mechanisms by which salt marshes are responding to climate change., Keystone species have large ecological effects relative to their abundance and have been identified in many ecosystems. However, global change is pervasively altering environmental conditions, potentially elevating new species to keystone roles. Here, we reveal that a historically innocuous grazer—the marsh crab Sesarma reticulatum—is rapidly reshaping the geomorphic evolution and ecological organization of southeastern US salt marshes now burdened by rising sea levels. Our analyses indicate that sea-level rise in recent decades has widely outpaced marsh vertical accretion, increasing tidal submergence of marsh surfaces, particularly where creeks exhibit morphologies that are unable to efficiently drain adjacent marsh platforms. In these increasingly submerged areas, cordgrass decreases belowground root:rhizome ratios, causing substrate hardness to decrease to within the optimal range for Sesarma burrowing. Together, these bio-physical changes provoke Sesarma to aggregate in high-density grazing and burrowing fronts at the heads of tidal creeks (hereafter, creekheads). Aerial-image analyses reveal that resulting “Sesarma-grazed” creekheads increased in prevalence from 10 ± 2% to 29 ± 5% over the past

The Rio Negro Formation (late Miocene-early Pliocene) mainly consists of continental deposits, but it contains a middle member of marine origin. It represents a transgressive-regressive sequence that can be seen at several outcrops along the N Patagonian coast. The taphonomical approach to the El Espigon marine deposits permits the identification of four main layers containing different kinds of skeletal accumulation, which mainly consists of oyster shells [Crassostrea patagonica (d'Orbigny, 1842)]. These concentrations display three different morphologies (pouches, pavements and bouquets) with a different taphonomic signature. These deposits were formed in shallow marine environments influenced by wave activity that produced valve concentrations of different entities. They contain several shell beds that represent event, composite, hiatal to lag skeletal concentrations. Trace of bioturbation in the sediment (Thalassinoides, Teichichnus) and bioerosion on the shells (Entobia, Gastrochaenolites, Caulostrepsis), and encrusters (cirripeds, bryozoans), are also abundant in the outcroup and constitute common components of these Miocene materials. Layers 1 and 2 of the sequence were deposited in shoreface(foreshore environments at the beginning of a highstand systems tract, while layers 3 and 4 were deposited at the end, or at the beginning of a forced regression, in foreshore environments, A final erosional episode cut the top of layer 4, which truncated the abundant bioturbation developed there

The foreshore at Redcar hosts the oldest Jurassic succession exposed on the Yorkshire-Cleveland Coast but has received little attention since the late nineteenth century. Temporary removal of beach sands by winter storms early in 2018 allowed for a sedimentological and palaeontological study of a nearly 60 m-thick foreshore section. The rocks are latest Hettangian to Early Sinemurian in age (Early Jurassic) and comprise five coarsening-upward cycles (parasequences) that grade from mudstones through siltstones into Gryphaea-rich shell beds. Ammonites are reasonably common along with a diverse benthos that includes abundant bivalves (e.g. Gryphaea, Cardinia, Luciniola, Plagiostoma and Oxytoma) and rarer serpulids, gastropods, foraminifera and solitary corals. In the upper part of the section thicker-shelled taxa are commonly bored by cirripedes and bryozoans. Despite relatively high benthic diversity and intense bioturbation, pyrite framboids are common with size distributions suggesting deposition under a moderately oxygen-restricted water column. The Redcar succession post-dates the end-Triassic mass extinction by as much as 4 Ma and the diverse marine assemblages indicate that recovery was substantially complete by this time.

We studied how soils vary between cohune palm and non-cohune forests and assessed whether the forests differed in soil fertility. We sampled soil profiles from six cohune palm forests and eleven non-cohune forests. Our laboratory analyses included soil organic matter (SOM), extractable phosphorous, and the total concentration of 10 elements. Each soil characteristic was subjected to a mixed-effects model with depth, forest type, and the interaction between the two as factors that were grouped by excavation. Total phosphorous, sulfur, and SOM differed significantly between the two forest types, with higher values in non-cohune forests, on average. SOM, extractable phosphorous, and nine elements showed statistically significant changes with depth. The interaction between depth and forest type was significant for eight elements and SOM. The elemental concentrations were consistently maintained with depth in the cohune forests. Meanwhile, the elemental concentrations in non-cohune forest soils decreased with depth for all elements except calcium and magnesium, which increased concentration with depth. Cohune forest soils and non-cohune forest soils differ in distinct ways but these differences do not relate to key measures of soil fertility. Cohune palm forest soils exhibit consistent elemental concentrations with depth, which suggests bioturbation or another phenomenon that redistributes nutrients.

The Cenozoic genusTerebratulaseems to be an exception to the post-Permian trend in brachiopod retreat to offshore habitats, because it was species rich and numerically abundant in warm-temperate shallow-water environments in the Mediterranean and the Paratethys realms. This was so despite the general dominance of bivalves and the pervasive bioturbation and predation pressure during the Neogene.Terebratula, however, went extinct in the Calabrian (Pleistocene). The optimal environmental conditions forTerebratuladuring its prime are poorly known. The Águilas Basin (SE Spain) is an ideal study area to investigate the habitat ofTerebratula, because shell beds of this brachiopod occur there cyclically in early Pliocene deposits. We evaluate the paleoecological boundary conditions controlling the distribution ofTerebratulaby estimating its environmental tolerances using benthic and planktic foraminiferal and nannoplanktic assemblages and oxygen isotopes of the secondary layer brachiopod calcite. Our results suggest thatTerebratulain the Águilas Basin favored oligotrophic to mesotrophic, well-oxygenated environments at water depths of 60–90 m. Planktic foraminiferal assemblages and oxygen isotopes point to sea-surface temperatures between ~16°C and 22°C, and bottom-water temperatures between 17°C and 24°C. The analyzed proxies indicate thatTerebratulatolerated local variations in water depth, bottom temperature, oxygenation, productivity, and organic enrichment.Terebratulawas probably excluded by grazing pressure from well-lit environments and preferentially occupied sediment-starved, current-swept upper offshore habitats where coralline red algae were absent. Narrow temperature ranges ofTerebratulaspecies might have been a disadvantage during the high-amplitude seawater temperature fluctuations that started about 1 Ma, when the genus went extinct.

The current geochronological state of the art for applying the radiocarbon (14C) method to deep-sea sediment archives lacks key information on sediment bioturbation. Here, we apply a sediment accumulation model that simulates the sedimentation and bioturbation of millions of foraminifera, whereby realistic 14C activities (i.e. from a 14C calibration curve) are assigned to each single foraminifera based on its simulation time step. We find that the normal distribution of 14C age typically used to represent discrete-depth sediment intervals (based on the reported laboratory 14C age and measurement error) is unlikely to be a faithful reflection of the actual 14C age distribution for a specific depth interval. We also find that this deviation from the actual 14C age distribution is greatly amplified during the calibration process. Specifically, we find a systematic underestimation of total geochronological error in many cases (by up to thousands of years), as well as the generation of age–depth artefacts in downcore calibrated median age. Even in the case of “perfect” simulated sediment archive scenarios, whereby sediment accumulation rate (SAR), bioturbation depth, reservoir age and species abundance are all kept constant, the 14C measurement and calibration processes generate temporally dynamic median age–depth artefacts on the order of hundreds of years – whereby even high SAR scenarios (40 and 60 cm kyr−1) are susceptible. Such age–depth artefacts can be especially pronounced during periods corresponding to dynamic changes in the Earth's Δ14C history, when single foraminifera of varying 14C activity can be incorporated into single discrete-depth sediment intervals. For certain lower-SAR scenarios, we find that downcore discrete-depth true median age can systematically fall outside the calibrated age range predicted by the 14C measurement and calibration processes, thus leading to systematically inaccurate age estimations. In short, our findings suggest the possibility of 14C-derived age–depth artefacts in the literature. Furthermore, since such age–depth artefacts are likely to coincide with large-scale changes in global Δ14C, which themselves can coincide with large-scale changes in global climate (such as the last deglaciation), 14C-derived age–depth artefacts may have been previously incorrectly attributed to changes in SAR coinciding with global climate. Our study highlights the need for the development of improved deep-sea sediment 14C calibration techniques that include an a priori representation of bioturbation for multi-specimen samples.

To study the effects of snail (Bellamya aeruginosa) bioturbation on phosphorus (P) mobility in sediment and the relevant mechanisms behind them. A microcosm simulation experiment was carried out at millimeter resolution with an 89 days culture of homogeneous sediments. High-resolution dialysis (HR-Peeper) and diffusive gradient in thin films (DGT) techniques were utilized to simultaneously acquire the vertical distribution of soluble and labile P/iron (Fe) in bioturbation sediments. Snail bioturbation significantly enhanced soluble reactive P (SRP) and labile P concentrations, with the maximum increment to 306% and 1133% of the control sediments within the influence depths from 0 to − 30 mm and to − 20 mm, respectively. The P fluxes released from the sediment–water interfaces in snail treatments were correspondingly enhanced with the maximum increments to 218% of the control. Also, snail bioturbation significantly enhanced the soluble Fe(II) and labile Fe concentrations by maximum increment of 218% and 199% of the control within 0 to −24 mm and − 19 mm, respectively. The high correlation between soluble/labile P and Fe suggested that P release from the sediment under snail bioturbation was due to the reduction and dissolution of Fe(III) oxyhydroxide.

Magadiite, a rare hydrous sodium-silicate mineral [NaSi7O13(OH)3·4(H2O)], was discovered about 50 years ago in sediments around Lake Magadi, a hypersaline alkaline lake fed by hot springs in the semi-arid southern Kenya Rift Valley. Today this harsh lacustrine environment excludes most organisms except microbial extremophiles, a few invertebrates (mostly insects), highly adapted fish (Alcolapia sp.), and birds including flamingos. Burrows discovered in outcrops of the High Magadi Beds (~25–9 ka) that predate the modern saline (trona) pan show that beetles and other invertebrates inhabit this extreme environment when conditions become more favourable. Burrows (cm-scale) preserved in magadiite in the High Magadi Beds are filled with mud, silt and sand from overlying sediments. Their stratigraphic context reveals upward-shallowing cycles from mud to interlaminated mud-magadiite to magadiite in dm-scale units. The burrows were formed when the lake floor became fresher and oxygenated, after a period when magadiite precipitated in shallow saline waters. The burrows, probably produced by beetles, show that trace fossils can provide evidence for short-term (possibly years to decades) changes in the contemporary environment that might not otherwise be recognised or preserved physically or chemically in the sediment record.

Crabs use burrows to prevent predation, environmental interference and shelter. The present study investigated the excavation behavior of the trichodactylid crab Dilocarcinus pagei, considering the biometric aspects of the burrows, the excavation time, the amount of bioturbation and the excavation behavior of the two sexes. The burrows of males had a mean diameter larger than the females, although the depth was similar for both sexes. Females had higher bioturbation than males, and showed enlargement in a camera format at the bottom, even closing the entrance of the burrows with a “plug” after their construction. Both the camera and the presence of the “plug” in the burrows of the females may be associated with reproduction. The presence of pellets observed at the entrance of burrows is associated with the cleaning of the pereiopods by crabs after the excavation. The sequence of behaviors for the construction of the burrows is described in detail, contributing to the knowledge about the biology and ecology of freshwater crabs of the Amazon.

Filter-feeding shellfish are common benthos and significantly affect the biogeochemical cycle in the shallow coastal ecosystems. Ark clam Scapharca subcrenata is one of the widely cultured bivalve species in many coastal areas owing to its tremendous economic value. However, there is little information regarding the effects of the bioturbation of S. subcrenata on the fluxes of nutrient exchange in the sediment-water interface (SWI). In this regard, S subcrenata was sampled during October 2016 to determine the effects of its bioturbation activity on the nutrient exchange flux of the SWI. The results showed that the biological activity of S. subcrenata could increase the diffusion depth and the rate of the nutrients exchange in the sediments. The bioturbation of S. subcrenata could allow the nutrients to permeate into the surface sediments at 6−10 cm and increase the release rate of nutrients at the SWI. The releasing fluxes of DIN and PO43−-P in the culture area were found to be around three times higher than that in the non-cultured region. The culture of S subcrenata has been proved to be an important contributor to nutrient exchange across the SWI in the farming area of Haizhou Bay. Nutrients exchange in the SWI contributes a part of 86% DIN, 71% PO43−-P and 18% SiO32−-Si for the aquaculture farm.

Several aquatic species use beach foreshores to lay their eggs. Understanding the dynamics of egg entrainment versus egg retention in foreshore sediment is important to delivering eggs to foraging species, and to predicting fecundity and population responses of beach nesting species to harvest and habitat management. Exhumation of these eggs is primarily by bioturbation and wave action. This study isolates effects of wave and swash processes on exhumation, entrainment, and transport of horseshoe crab eggs by conducting a 1-day field study designed to avoid effects of bioturbation by spawning and migratory shorebird predation. Dyed sand and horseshoe crab (Limulus polyphemus) eggs were injected into the foreshore of an estuarine beach in Delaware Bay, USA and sampled during 110 swash events using streamer traps. Significant wave heights ranged from 0.30 to 0.47 m. The quantity of eggs exhumed from the mid-foreshore by waves and swash was 3.8 times greater than from the upper foreshore where activation was by swash alone. Swash flows were skewed offshore, but egg transport was predominantly onshore from bore collapse. Egg release was greatest in early rising tide, making this the most productive time for shorebird foraging. Release of eggs from mid-foreshore may be dominated by wave action during high energy days with little spawning or by bioturbation by horseshoe crabs during intensive spawning. Activation depths in the swash were low, indicating that eggs buried on the upper foreshore can reach later stages of development after spawning ceases.

Research was funded by Projects CGL2015-66835-P, PID2019104624RB-I00 and PID2019-104625RB-100 (Secretaria de Estado de I + D + I, Spain), and B-RNM-072-UGR18, P18-RT-3804 and P18-RT4074 (Junta de Andalucia), and the Scientific Excellence Unit UCE2016-05 (Universidad de Granada). The research of SC-A is funded through a pre-doctoral grant, FPU, from the Ministerio de Educacion, Cultura y Deporte (Gobierno de Espana). The authors thank the Editor (Dr Rebesco) and both anonymous reviewers, whose comments helped improve the quality of this article., Organic rich layers (ORLs), deposited in the westernmost Mediterranean over the Last Glacial Cycle, have been studied integrating sedimentological and ichnological information from sediment records recovered at Ocean Drilling Program Leg 161 Sites 976 and 977. The conducted study has served to redefine the ORLs initially differentiated in sediment records from Sites 977 and 976, with seven new ORLs recognized, as well as extensions and subtraction of some parts in the ORLs previously defined. In addition, three different ORL types are distinguished according to sedimentological and ichnological features. Type 1 with intermediate thickness is highly bioturbated, mainly consisting of abundant Scolicia and Planolites, frequent Chondrites, and possible Thalassinoides in the base, which are interpreted as supporting dysoxic conditions during deposition. Type 2, corresponding to thicker intervals, shows alternance of highly to moderately bioturbated parts, revealing variable oxygen conditions -from moderate to extreme dysoxic or even suboxic. Type 3 consists of short, laminated intervals characterized by the absence of bioturbation, indicating anoxic or suboxic conditions and determining unfavourable macro benthic habitat. The amended ORLs show a correlation between the Sea Surface Temperatures and established climatic events over the Last Glacial Cycle in the Western Mediterranean., Junta de Andalucia B-RNM-072-UGR18 / P18-RT-3804 / P18-RT4074, Secretaria de Estado de I + D + I, Spain CGL2015-66835-P / PID2019104624RB-I00 / PID2019-104625RB-100, Universidad de Granada UCE2016-05, Ministerio de Educacion, Cultura y Deporte (Gobierno de Espana)

Highlights: • Temperature, dung mass and beetle density affected dung utilisation services. • Dung utilisation increased significantly with temperature and density. • Largest Khepher prodigiosus exhibited highest dung utilisation among species. • Emergent effects suggest species respond differently to warming and beetle density. • Ecosystem services provision requires surveillance under global climate change. Abstract: Increases in the frequency and magnitude of suboptimal temperatures as a result of climate change are subjecting insects to unprecedented stresses. This may negatively affect their fitness and the efficiency of their ecosystem service provision. Dung beetles are ecosystem service providers: through feeding on and burying dung, they facilitate nutrient recycling, secondary seed dispersal, parasite control, soil bioturbation and dung decomposition. As such, prediction of how dung beetles respond to multiple anthropogenic environmental changes is critical for the conservation of ecosystem services. Here, we quantified ecosystem services via dung utilisation and dung ball production in three telecoprid species: Allogymnopleurus indigaceous, Scarabaeus zambezianus and Khepher prodigiosus. We examined ecosystem service efficiency factorially under different beetle densities towards different dung masses and under three temperature treatments (21 °C, 28 °C and 35 °C). Khepher prodigiosus, exhibited greatest dung utilisation efficiency overall across dung masses, compared to both S. zambezianus and A. indigaceous. Dung removal was exhibited under all the tested temperatures by all tested species, and therefore the sub-optimal temperatures employed here did not fully inhibit ecosystem service delivery. However, emergent effects among temperatures, beetle species and beetle density further affected removal efficiency: S. zambezianus and A. indigaceous utilisation increased with both warming and beetle density, whereas K. prodigiosus performance was less temperature- and density-dependent. Beetles also tended to exhibit positive density-dependence as dung supply increased. The numbers of dung balls produced differed across species, and increased with temperature and densities, with S. zambezianus producing significantly most balls overall. Our study provides novel evidence for differential density-dependent ecosystem service delivery among species across stressful temperature regimes and emergent effects for dung mass utilisation. This information is essential for biodiversity-ecosystem-function and is critical for the conservation of functionally efficacious species, with implications for natural capital conservation policy in rapidly changing environments.

Seagrass meadows provide important and valuable ecosystem services. They are affected by several natural and human-induced stressors, but a combination of natural recovery and management actions have recently inverted the worldwide reduction. The main objectives of this study were to provide science-based knowledge on ecology and restoration, framed on environmental-related policies. By coupling the general guidelines with practical experience, obtained from sequential in situ experiments carried out for several months in a show-case study area, this study provides guidelines useful for restoration practitioners. A decision-making approach is proposed to answer the following questions: 1) What is the best Zostera noltei transplanting method? 2) What is the best technique to reduce the bioturbation activity of Arenicola spp.?, 3) Do bioturbation reduction techniques affect the survival rate of Z. noltei transplants?, and finally, 4) What are the key steps to maximize the success of a Z. noltei transplant and increase the species’ resilience? Having a Portuguese coastal lagoon as show-case (Mira Channel, Ria de Aveiro), different transplant and restoration methodologies were tested (i.e. metal frames, nails, bamboo sticks, shoots inserted unanchored into the sediment, and intact units of sediment with seagrasses, named as SODs) to assure low environmental impact on donor meadows, high survival rate of transplanted shoots and the recovery of fragmented or lost meadows. Moreover, to potentially reverse a degraded Arenicola spp. colonized seagrass habitat, different types of natural membranes were tested. Results showed that the best transplanting method is the use of SODs as the self-facilitation process of Z. noltei is enhanced, while being the least invasive for the donor population. The use of a natural membrane can significantly decrease the bioturbation stress caused by Arenicola spp., with jute membrane being the best option, given its cost-handling-benefit trade-offs. Enhancing the success of seagrass restoration requires the implementation of effective measures by environmental restoration practitioners. We defined a three-step process to improve the resilience of Z. noltei. This stepwise approach consists on 1) Characterization of the donor population, 2) Identification of the constraints and implementation of measures to prevent them, and 3) Scale-up the restoration plan. The application of this stepwise approach in intertidal coastal and estuarine systems management will, therefore, facilitate the success of Z. noltei restoration plans.

Holocene Ostracoda, the species fluctuation and habitual adaptations from the mangrove ecosystem implying the environmental condition are the focus of the present study. Mangrove Ostracoda are salinity tolerant species which thrives in nutrient-rich sediments. Bioturbation in mangrove environment mix up the Holocene sediments, however correlating adjacent marine Ostracoda clarifies the ambiguity. Mangrove Ostracoda from the Red Sea margin have a close generic affinity to Indian Ostracoda. Xestolebris, Loxoconcha, Paranesidea, Tanella, and Neonesidea are the Afro-Indian Ostracod genera. Loxoconcha, Parakrithella, Hemicytherura, etc. are common Indo-Australian genera. Detailed study elucidates that substrate nature, salinity, and calcium carbonate percentage controls the distribution of Ostracoda distribution from Indian mangroves. Generally and most commonly completely preserved carapace outnumber open valve in mangrove environment implies a nominal sedimentation rate. Mangrove Ostracoda species responds diversely to the environmental fluctuations. Dominance of highly ornamented forms with complex hinge pattern explains the tidal influence and wave turbidity. Precipitation and runoff from the land aids in less distribution of Ostracoda, however further studies are required whether the minimal production of Ostracoda is due to erosion or bioturbation.

This review covers more than twenty-five years of research listing and discussing the biogeochemical, mineralogical, and physical impacts of fungus-growing termites (or FGT, Macrotermitinae sub-family) on savanna sediments and landscapes. The main mechanisms by which FGT transform the surficial geological formations in tropical and sub-tropical environments is investigated from a geological perspective and the potential FGT legacies in the sedimentary facies are identified. In order to sustain a twenty million-year symbiosis with the fungus, in which fungi provide digestible food to termites, FGT must optimize the living conditions of the fungus for it to thrive. To do so, they build a biogenic structure maintaining a constant humidity of 80% and a temperature of 30 °C in any kind of environment and all year long. Indeed, FGT adapt to their environment by (i) modifying the grain-size distributions of sediments and soils where they develop, (ii) forming clay horizons below their mounds enabling water to be stored for long period of time in dry environments, (iii) increasing the alkalinity by an order of magnitude of two to three, (iv) mineralizing around 20% of all organic carbon in dry savannas, thus making them the predominant decomposing organisms and crucial actors in the carbon cycle, and (v) concentrating vital nutrients for plants and animals, creating patches of fertile land in sandy semi-deserts. Through their mound-building activities, termites substantially increase the clay fraction compared to the adjacent soil and alter 2:1 clay properties, particularly after the removal of potassium, leading to the formation of smectite layers, demonstrating their biogeochemical effects on silicate mineralogy. Through the binding of aggregates, FGT increase the strength of the mound by a factor of ten and provide exceptional weathering resistance to their mounds. Therefore, termites impact their environment from sub-millimetric transformations to solid voluminous landmarks. The water-holding capacity of a FGT mound leads to an array of positive feedbacks to the savanna landscape by enhancing protection from fires, delaying desertification, supporting rebounds by seedlings and reinforcing dryland resistance and recovery from drought. Termite bioturbation allows sediments to accumulate at a rate averaging 1 mm.y−1.ha−1, and tends to mitigate physical and chemical processes of soil degradation, boosting the heterogeneity at the landscape scale, providing it more resilience. Some of the modifications brought by FGT will remain in the landscape for long periods, testifying to past environmental conditions, and making these mounds potential proxies for paleoenvironmental reconstructions. To conclude, FGT are not only biological actors of the savanna ecosystem, but they act as a geological force by their impact on landscapes as well as by their major role in biogeochemical cycles. Finally, further research is recommended regarding the role of termite's saliva as a binding agent, as well as the age and the evolution of mounds over time.

Invasive wild pigs (Sus scrofa) have been spread by humans outside of their native range and are now established on every continent except Antarctica. Through their uprooting of soil, they affect societal and environmental values. Our recent article explored another threat from their soil disturbance: greenhouse gas emissions (O'Bryan et al., Global Change Biology, 2021). In response to our paper, Don (Global Change Biology, 2021) claims there is no threat to global soil carbon stocks by wild pigs. While we did not investigate soil carbon stocks, we examine uncertainties regarding soil carbon emissions from wild pig uprooting and their implications for management and future research.

Trypaea australiensis Dana, 1852 is the predominant bioturbating thalassinidean shrimp on the east coast of Australia. It is, like other large bioturbators, generally considered an important ecosystem engineer. The sediment particle reworking rate of thalassinideans, a key parameter in benthic biogeochemical modelling, nevertheless remains unknown. We have for the first time quantified particle reworking by a population of T. australiensis living in fine estuarine sand. The particle reworking rate was monitored for 18 days using coarse sand as a new tracer approach followed by analyses of grain-size distribution in the sediment to a depth of 24 cm. Burial depth (BD, cm) over time (t, days) followed the relationship BD = 0.3002 × t for an average population density of 96 individuals m–2, equivalent to a sediment displacement of 1.1 m3 m–2 yr–1 (11.4 liters individual–1 yr–1). The individual-specific particle reworking by this thalassinidean is higher than that reported for most other key bioturbators, and its engineering impact on estuarine sediments therefore has potentially large consequences for biodiversity and ecosystem functioning.

Abundant research has shown that macrobenthic species are able to increase sediment erodibility through bioturbation. So far, however, this has been at the level of individual species. Consequently, we lack understanding on how such species effects act on the level of bioturbator communities. We assessed the isolated and combined effects of three behaviorally contrasting macrobenthic species, i.e., Corophium volutator, Hediste diversicolor, and Limecola balthica, at varying densities on the critical bed shear stress for sediment resuspension (τcr). Overall, the effect of a single species on sediment erodibility could be described by a power function, indicating a relatively large effect of small bioturbator densities which diminishes toward higher individual density. In contrast to previous studies, our results could not be generalized between species using total metabolic rate, indicating that metabolic rate may be only suitable to integrate bioturbation effects within and between closely related species; highly contrasting species require consideration of species-specific bioturbation strategies. Experiments at the benthic community level revealed that the ability of a benthic community to reduce τcr is mainly determined by the species that has the largest individual effect in reducing τcr, as opposed to the species that is dominant in terms of metabolic rate. Hence, to predict and accurately model the net effect of bioturbator communities on the evolution of tidal flats and estuaries, identification of the key bioturbating species with largest effects on τcr and their spatial distribution is imperative. Metabolic laws may be used to describe their actual activity.

Tidal flats are biogeomorphic landscapes, shaped by physical forces and interaction with benthic biota. We used a metabolic approach to assess the overarching effect of bioturbators on tidal landscapes. The benthic bivalve common cockle (Cerastoderma edule) was used as model organism. The effect of C. edule on sediment resuspension was approximated as a function of the overall population metabolic rate per unit of area. We combined i) laboratory observations on how C. edule affect sediment resuspension along gradients of bioturbation activity, sediment cohesiveness and hydrodynamic force with ii) spatial data on on the natural distribution of intertidal C. edule populations. This allowed us to build an integrated model of the C. edule effect on sediment resuspension along the tidal gradient. Owing to the temperature dependence of metabolic rate, the model also accounted for seasonal variation in bioturbators activity. Laboratory experiments indicated that sediment resuspension is positively related to the metabolic rate of the C. edule population especially in cohesive sediments. Based on this observation, we predicted a clear spatial and seasonal pattern in the relative importance of C. edule contribution to sediment resuspension along a tidal transect. At lower elevations, our model indicates that hydrodynamics overrules biotic effects; at higher elevations, inter-tidal hydrodynamics should be too low to suspend bioturbated sediments. The influence of C. edule on sediment resuspension is expected to be maximal at the intermediate elevation of a mudflat, owing to the combination of moderate hydrodynamic stress and high bioturbator activity. Also, bio-mediated sediment resuspension is predicted to be particularly high in the warm season. Research into metabolic dependency of bio-mediated sediment resuspension may help to place phenomenological observations in the broader framework of metabolic theories in ecology and to formulate general expectations on the coastal ecosystem functioning.

During cruise 43 of the R/V Akademik Nikolaj Strakhov (September 21–October 9, 2019), new data were obtained on the bottom relief, sedimentation, and hydrological regime of the Discovery Gap (eastern North Atlantic). It was shown that the upper limit of the Antarctic Bottom Water in the study area follows the 2.05°C isotherm and 34.91 PSU isohaline at depths of 4400–4700 m. A digital elevation model of the Discovery Gap relief was obtained. Three acoustic facies have been identified, which characterize dense bottom sediments and low sedimentation rates. Sediment cores ANS-43003, ANS-43004, and ANS-43006 are represented by light brown silty clays with foraminiferal sands and bioturbation. Strong dissolution of foraminifera was found in core ANS-43006, which indicates the formation of sediments below the calcium carbonate compensation depth.

We use a single foraminifera enabled, holistic hydroclimate-to-sediment transient modelling approach to fundamentally evaluate the efficacy of discrete-depth individual foraminifera analysis (IFA) for reconstructing past sea surface temperature (SST) variability from deep-sea sediment archives, a method that has been used for, amongst other applications, reconstructing El Niño Southern Oscillation (ENSO). The computer model environment allows us to strictly control for variables such as sea surface temperature (SST), foraminifera species abundance response to SST, as well as depositional processes such as sediment accumulation rate (SAR) and bioturbation depth (BD), and subsequent laboratory processes such as sample size and machine error. Examining a number of best-case scenarios, we find that IFA-derived reconstructions of past SST variability are sensitive to all of the aforementioned variables. Running 100 ensembles for each scenario, we find that the influence of bioturbation upon IFA-derived SST reconstructions, combined with typical samples sizes employed in the field, produces noisy SST reconstructions with poor correlation to the original SST distribution in the water. This noise is especially apparent for values near the edge of the SST distribution, which is the distribution region of particular interest for, e.g., ENSO. The noise is further increased in the case of increasing machine error, decreasing SAR and decreasing sample size. We also find poor agreement between ensembles, underscoring the need for replication studies in the field to confirm findings at particular sites and time periods. Furthermore, we show that a species’ abundance response to SST could in theory bias IFA-derived SST reconstructions, which can have consequences when comparing IFA-derived SST from markedly different mean climate states. We provide a number of idealised simulations spanning a number of SAR, sample size, machine error and species abundance scenarios, which can help assist researchers in the field to determine under which conditions they could expect to retrieve significant results.

Particle mixing and irrigation of the seabed by benthic fauna (bioturbation) have major impacts on ecosystem functions such as remineralization of organic matter and sediment-water exchange. As a tribute to Prof. Gaston Desrosiers by the Nereis Park association, eighteen laboratories carried out a collaborative experiment to acquire a global snapshot of particle reworking by the polychaete Hediste diversicolor at 16 sites surrounding the Northern Atlantic. Organisms and soft sediments were collected during May – July at different geographical locations and, using a common laboratory protocol, particulate fluorescent tracers (‘luminophores’) were used to quantify particle transport over a 10-day period. Particle mixing was quantified using the maximum penetration depth of tracers (MPD), particle diffusive coefficients (Db), and non-local transport coefficients (r). Non-local coefficients (reflecting centimeter scale transport steps) ranged from 0.4 to 15 yr−1, and were not correlated across sites with any measured biological (biomass, biovolume) or environmental parameters (temperature, grain size, organic matter). Maximum penetration depths (MPD) averaged ~10.7 cm (6.5–14.5 cm), and were similar to the global average bioturbation depth inferred from short-lived radiochemical tracers. MPD was also not correlated with measures of size (individual biomass), but increased with grain size and decreased with temperature. Biodiffusion (Db) correlated inversely with individual biomass (size) and directly with temperature over the environmental range (Q10 ~ 1.7; 5–21 °C). The transport data were comparable in magnitude to rates reported for localized H. diversicolor populations of similar size, and confirmed some but not all correlations between sediment reworking and biological and environmental variables found in previous studies. The results imply that measures of particle reworking activities of a species from a single location can be generally extrapolated to different populations at similar conditions.

This study analysed the distribution and abundance of dead and live (Rose Bengal stained) infaunal foraminifera from three short cores taken at three locations in the mangrove swamps of Kemaman-Chukai, Terengganu, Malaysia. Eighteen agglutinated taxa were recorded in assemblages dominated by 'Arenoparrella mexicana', 'Haplophragmoides wilberti' and 'Miliammina fusca'; and of these, only two taxa were recorded as live. The distribution of subsurface and infaunal foraminifera varied from core to core, as did their depth of occurrence. Core 1 (seaward core) was dominated by sandy deposits, relatively high salinity (32 ppt), and extensive crab mounds, displayed very low numbers of dead foraminifera inconsistently throughout the core, while no infaunal foraminifera were observed, indicating intense bioturbation by mangrove crabs. In Core 2 (middle core), even though the numbers of live foraminifera decreased down-core, the number of dead or subsurface foraminifera were inconsistent, indicating taphonomic loss of the tests. Core 3 (landward core) however, displayed ideal foraminiferal distribution patterns required in the palaeo sea-level reconstruction (with less taphonomic loss and decreasing number of infaunal foraminifera downcore). Because of the similarity displayed in the foraminiferal assemblages in the 0–1 cm and 10–11 cm intervals, the surface sample (0–1 cm) should be an acceptable basis for down-core reconstructions in this study. Live (Rose Bengal stained) infaunal foraminifera, though observed at 40–41 cm depth, are not considered abundant enough to influence the dead assemblage in the subsurface sediment and its applicability for palaeoenvironmental and sea-level reconstructions. Therefore, it is possible for palaeo sea-level to be reconstructed based on foraminiferal assemblages preserved in the Kemaman-Chukai mangrove swamps.

The paucity of data on non-indigenous marine species is a particular challenge for understanding the ecology of invasions and prioritising conservation and research efforts in marine ecosystems. Marenzelleria spp. are amongst the most successful non-native benthic species in the Baltic Sea during recent decades. We used stable isotope analysis (SIA) to test the hypothesis that the dominance of polychaete worm Marenzelleria arctia in the zoobenthos of the Neva Estuary after its invasion in the late 2000s is related to the position of this species in the benthic food webs. The trend towards a gradual decrease in the biomass of Marenzelleria worms was observed during 2014–2020, probably due to significant negative relationships between the biomass of oligochaetes and polychaetes, both of which, according to SIA, primarily use allochthonous organic carbon for their production. The biomass of benthic crustaceans practically did not change and remained very low. The SIA showed that, in contrast to the native crustacean Monoporeia affinis, polychates are practically not consumed either by the main invertebrate predator Saduria entomon, which preys on M. affinis, oligochaetes and larvae of chironomids or by benthivorous fish that prefer native benthic crustaceans. A hypothetical model for the position and functional role of M. arctia in the bottom food web is presented and discussed. According the model, the invasion of M. arctia has created an offshoot food chain in the Estuary food webs. The former dominant food webs, associated with native crustaceans, are now poorly developed. The lack of top-down control obviously contributes to the significant development of the Marenzelleria food chain, which, unlike native food chains, does not provide energy transfer from autochthonous and allochthonous organic matter to the upper trophic levels. The study showed that an alien species, without displacing native species, can significantly change the structure of food webs, creating blind offshoots of the food chain.

Marine sedimentary records are a key archive when reconstructing past climate; however, mixing at the seabed (bioturbation) can strongly influence climate records, especially when sedimentation rates are low. By commingling the climate signal from different time periods, bioturbation both smooths climate records, by damping fast climate variations, and creates noise when measurements are made on samples containing small numbers of individual proxy carriers, such as foraminifera. Bioturbation also influences radiocarbon-based age-depth models, as sample ages may not represent the true ages of the sediment layers from which they were picked. While these effects were first described several decades ago, the advent of ultra-small-sample $^{14}$C dating now allows samples containing very small numbers of foraminifera to be measured, thus enabling us to directly measure the age-heterogeneity of sediment for the first time. Here, we use radiocarbon dates measured on replicated samples of 3-30 foraminifera to estimate age-heterogeneity for five marine sediment cores with sedimentation rates ranging from 2-30 cm kyr$^{-1}$. From their age-heterogeneities and sedimentation rates we infer mixing depths of 10-20 cm for our core sites. Our results show that when accounting for age-heterogeneity, the true error of radiocarbon dating can be several times larger than the reported measurement. We present estimates of this uncertainty as a function of sedimentation rate and the number of individuals per radiocarbon date. A better understanding of this uncertainty will help us to optimise radiocarbon measurements, construct age models with appropriate uncertainties and better interpret marine paleo records.

The Lower Globigerina Limestone Member, the oldest member of the Globigerina Lime- stone Formation, outcrops over most of the Maltese archipelago, notably Malta. It has provided the islands’ main building material since the Neolithic period. This paper makes available a corpus of findings relating to the geochemistry, mineralogy and textural properties of this limestone—mostly unpublished and undertaken nearly three decades ago—which provide a useful source to understand its behavior. Bulk chemistry and mineralogy showed that non-carbonate and clay content is higher in limestone of inferior quality. Textural analyses gave insight into the fabric of the matrix, including inter- and intra-particle porosity. These analyses were supplemented by an array of petrophysical tests, including color (a parameter which has a correlation with density and Fe2O3 content), ultrasonic pulse velocity and compressive strength. The findings not only give insight into the composition of the limestone, using insoluble residue content of ≥5% as the threshold of inferior quality lithotype, but provided an insight into the physico-mechanical bonding present, a characteristic which has a bearing on the deterioration of this limestone., peer-reviewed

Trematode parasites are distributed worldwide and can severely impact host populations. However, their influence on ecosystem functioning through the alteration of host engineering behaviours remains largely unexplored. This study focuses on a common host parasite system in marine coastal environments, i.e., the trematode Himasthla elongata, infecting the edible cockle Cerastoderma edule as second intermediate host. A laboratory experiment was conducted to investigate the indirect effects of metacercarial infection on sediment bioturbation and biogeochemical fluxes at the sediment water interface. Our results revealed that, despite high parasite intensity, the sediment reworking and bioirrigation rates, as well as nutrient fluxes, were not impacted. This finding was unexpected since previous studies showed that metacercarial infection impairs the physiological condition of cockles and induces a mechanical obstruction of their feet, thus altering their burrowing capacity. There are several explanations for such contrasting results. Firstly, the alteration of cockle behavior could arise over a longer time period following parasite infection. Secondly, the modulation of cockle bioturbation by parasites could be more pronounced in older specimens burying deeper. Thirdly, the intensity of the deleterious impacts of metacercariae could strongly vary across parasite species. Lastly, metacercarial infection alters cockle fitness through an interaction with other biotic and abiotic environmental stressors.