Macrofaunal Community Composition Research Articles

Broad-scale spatial distribution patterns of soft-sediment macrobenthic communities in the Red Sea

In sub-tropical and tropical regions, the diversity patterns of soft-sediment macrobenthic communities are still poorly understood, particularly when compared to temperate shelf environments. The present study investigates spatial patterns of variability in macrobenthic distribution along the eastern Red Sea margin, and the role of sediment composition and other explanatory variables in determining such patterns. This study has two main objectives: (i) to produce a baseline characterization of the Saudi Arabian Red Sea macrobenthic infauna, particularly along the central and southern regions, (ii) to assess the relative contribution of two major processes driving macrobenthic communities (i.e., dispersal-based and environmental filtering), based on changes on beta-diversity components (turnover and nestedness) across multiple scales (up to ~600km), using relevant modeling methodologies. Shallow soft-sediment macrobenthic communities in the Red Sea showed extremely high small-scale variability, highlighted by the percentage of rare species (44% of species present at a single sample) and the dominance of turnover (species replacement) over nestedness. Our results also suggest a strong influence of broad- over fine-scale variation in the species composition. However, sedimentary characteristics, particularly grain-size, played a critical role governing the distribution patterns of soft-sediment macrobenthic communities in the Red Sea. Our findings highlight the importance of regional factors in shaping the macrofaunal community composition whilst also highlighting the role of high species diversity at local scales. The current results suggest the need for conservation measures from regional levels (to maintain genetic diversity) to local levels (to preserve the high occurrence of rare species). To our knowledge, no other study investigated the distribution of Red Sea marine species over large spatial scales combining modeling methods and the partitioning of beta-diversity. The current approach applied to soft-sediment macroinvertebrates can be extended to other marine communities since conservation strategies can be more effective when mechanisms governing species distribution are considered.

Enhancing multiple scales of seafloor biodiversity with mussel restoration

Restoration projects are underway internationally in response to global declines in shellfish beds. As diverse biological assemblages underpin a variety of ecosystem services, understanding broader changes in biodiversity associated with mussel restoration becomes increasingly valuable to scientists and restoration practitioners. Studies generally show bivalve beds increase species richness and abundance, but results are scale-dependent and conditional on the mobility of specific communities observed. We examined biodiversity at multiple scales to determine how communities with varying levels of mobility are influenced by subtidal mussel restoration. Significant changes in assemblage structure were observed in both mobile fish and epifaunal communities, with enhanced species richness and total abundance of associated individuals. In contrast, we observed site-dependent effects of bivalve restoration on macrofaunal community structure and composition, with sheltered, harbour mussel bed communities numerically dominated by detritivores accustomed to organically enriched, muddy sediments. Sediment organic matter significantly increased within mussel beds, and distance-based linear models showed that sediment organic matter was an important predictor of macrofaunal assemblage structure on mussel beds, highlighting the significance of benthic-pelagic coupling and biodeposition to soft-sediment communities. This study contributes novel methods and ecological insights on the role of species mobility and site selection in structuring restoration outcomes, better informing future mussel restoration efforts aimed at emphasising functionally-driven ecosystem services.

Sea pens as indicators of macrofaunal communities in deep-sea sediments: Evidence from the Laurentian Channel Marine Protected Area

Pennatulacean octocorals (sea pens), one of the primary conservation targets of the Laurentian Channel Marine Protected Area (MPA) in eastern Canada, occur at high densities in some deep-sea sedimentary habitats. Considered important habitat-forming organisms for many megafaunal organisms, the effect of sea pens on nearby sedimentary macrofaunal communities remains unexplored. During two cruises in September 2017 and July 2018, we sampled 9 stations within the MPA (336-445 m depth), including sea pen fields and bare sedimentary habitats, targeting individual sea pens in a subset of the cores to assess small-scale effects. We evaluated macrofaunal density, taxonomic diversity, vertical distribution, community composition, and biological trait expression, and investigated variation between sea pen fields and other (bare) sedimentary habitats, as well as between cores with and without sea pen specimens. Using multivariate analyses, we identified abiotic and biotic drivers of macrofaunal community composition and biological trait expression. Enhancement of macrofaunal density and taxonomic diversity and higher percentages of organisms in the upper sediment layers characterized sea pen fields in autumn, with more variable results in summer. Community composition and biological trait expression consistently differed in sea pen fields compared to bare sedimentary habitats, with Pennatula sea pen density as one of the primary drivers of variation especially for community composition, along with other environmental drivers (depth, grain size, and organic matter quantity and quality). We also detected small-scale enhancement of macrofaunal diversity in cores containing sea pens at stations characterized by predominantly bare sediments. Our results indicate that macrofaunal communities within sea pen fields differ from those in bare sediments and we propose sea pens play a role in influencing those patterns by increasing food availability, stability, and small-scale heterogeneity in sedimentary habitats, acknowledging that other environmental factors might also play a role in determining the observed patterns. Characteristics of macrofaunal communities within sea pen fields also suggested potentially higher sensitivity to disturbance, which amplifies the need for protection of sea pen fields in deep-sea sedimentary environments.

Anthropogenic effects on the marine environment adjacent to Palmer Station, Antarctica

AbstractLocalized contamination from research-related activities and its effects on macrofauna communities in the marine environment were investigated at Palmer Station, a medium-sized Antarctic research station. Relatively low concentrations of polycyclic aromatic hydrocarbons (PAHs; 32–302 ng g-1) and total petroleum hydrocarbons (TPHs; 0.9–8.9 μg g-1) were detected in sediments adjacent to the sewage outfall and pier, where most human activities were expected to have occurred, and at even lower concentrations at two seemingly reference areas (PAHs 6–30 ng g-1, TPHs 0.03–5.1 μg g-1). Elevated concentrations of PAHs in one sample taken in one reference area (816 ng g-1) and polychlorinated biphenyls (353 ng g-1) and dichloro-diphenyl-trichloroethane (3.2 and 25.3 ng g-1) in two samples taken adjacent to the sewage outfall indicate spatial heterogeneity of localized sediment contamination. Limpet (Nacella concinna) tissues collected adjacent to Palmer Station had high concentrations of PAHs, copper, lead, zinc and several other metals relative to outlying islands. Sediment and limpet tissue contaminant concentrations have decreased since the early 1990s following theBahía Paraísospill. Natural sediment characteristics affected macrofaunal community composition more than contamination adjacent to Palmer Station, presumably because of the low overall contamination levels.

Sedimentary Organic Matter Shapes Macrofaunal Communities but Not Benthic Nutrient Fluxes in Contrasting Habitats Along the Northwest Atlantic Continental Margin

The heterogeneous topography of continental margins can influence patterns of resource availability and biodiversity in deep-sea sediments, potentially altering ecosystem functioning (e.g., organic matter remineralization). Noting a lack of studies that address the latter, we contrasted spatial patterns and drivers of benthic nutrient fluxes and multiple characteristics of macrofaunal communities in shelf, slope, canyon and inter-canyon sedimentary habitats along the Northwest Atlantic continental margin. Replicate sediment push cores were collected from 10 stations (229–996 m depth), incubated for ∼48 h to estimate fluxes of nitrate, nitrite, ammonium, phosphate, and silicate (as a measure of organic matter remineralization) and subsequently analyzed to characterize macrofaunal communities. We also considered various environmental factors, including sedimentary organic matter quantity and quality, and assessed their influence on fluxes and macrofauna. Comparatively high macrofaunal density and distinct community composition and trait expression characterized Georges Canyon, where elevated sedimentary organic matter suggested important lateral transport mechanisms along this canyon axis, with deposition of organic matter strongly affecting biological communities but not benthic nutrient fluxes. Lower penetration of macrofauna into the sediments, distinct community composition, biological traits, and higher nutrient flux rates characterized inter-canyon habitats compared to slope habitats at similar depths. Within inter-canyons, intermediate to low organic matter suggested hydrodynamic forces inhibiting organic matter deposition, affecting biological and functional processes. The input of fresh phytodetritus to the seafloor was the best predictor of macrofaunal density and diversity and contributed to variation in macrofaunal community composition and biological trait expression, together with latitude, depth, and other measures of organic matter quantity and quality. Benthic nutrient fluxes revealed complex variation, with disproportionate effects of few key macrofaunal taxa, together with bottom water oxygen concentration, and sediment granulometry. Our results suggest a relationship between resource availability and macrofaunal density, diversity, and taxonomic and trait composition, whereas organic matter remineralization exhibited a more complex response, which we suggest reflected variation in hydrodynamics and/or physical disturbance in heterogeneous continental margin habitats.

Shade tree identity rather than diversity influences soil macrofauna in cacao-based agroforestry systems

Humanity is facing a rapid decline in global biodiversity, caused mainly by tropical deforestation through industrial and smallholder agriculture. However, smallholder agriculture landscapes host areas containing home gardens and other agroforestry systems (AFS) proved highly relevant for soil and biodiversity conservation. The positive interactions between aboveground and belowground biodiversity probably constitute a key element to promote the efficiency of these agro-ecosystems. To determine whether a relationship exists between tree and soil macrofauna diversity and composition, we compared cacao AFS with contrasted tree diversity along a topography and forest cover gradient in Talamanca, Costa Rica. To determine which components of the shade tree species, community structure (density, richness, Shannon, Pielou), and agroforest floor best explain the macrofauna community composition and structure, we constructed the “best models” based on the tree composition, tree structure, and agroforest floor as explanatory matrices in redundancy analyses. Macrofauna composition was best explained by a mix of tree species and litter attributes (R2=26.5 %), whereas macrofauna and vegetation co-vary significantly with topography (R2=12 %). Macrofauna structure is best explained by a selection of seven tree species (R2=41.2 %). The co-variation with topography remained low (R2=10.9 %). Tree evenness (Pielou index) explained only 7 % of macrofauna community structure while other diversity indices were not correlated with macrofauna composition or structure. The soil macrofauna was therefore more influenced by tree identity and litter composition than by the overall diversity of the tree community. This information is important for designing the optimal combinations of species for the intensification of production and provision of ecosystem services in cacao-based AFS.

A General-Purpose Biotic Index to Measure Changes in Benthic Habitat Quality across Several Pressure Gradients

Realistic assessments of the ecological status of benthic habitats, as requested by European directives such as the Water Framework Directive and the European Marine Strategy Framework Directive, require biotic indices capable of detecting anthropogenic impact without having preliminary knowledge of the occurring pressures. In this context, a new general-purpose biotic index (GPBI) based on the deviation of benthic macrofauna community composition and structure from a valid reference (i.e., good ecological status) is proposed. GPBI is based on the assumption that as a site becomes impacted by a pressure, the most sensitive species are the first to disappear, and that stronger impacts lead to more important losses. Thus, it explicitly uses the within-species loss of individuals in the tested station in comparison to one or several reference stations as the basis of ecological status assessment. In this study, GPBI is successfully used in four case studies considering the impact of diversified pressures on benthic fauna: (1) maerl extraction in the northern Bay of Biscay, (2–3) dredging and trawling in the North Sea, and (4) hypoxic events at the seafloor in the Gullmarfjord. Our results show that GPBI was able to efficiently detect the impact of the different physical disturbances as well as that of hypoxia and that it performs better than commonly used pressure-specific indices (M-AMBI and TDI). Signal detection theory was used to propose a sound good/moderate ecological quality status boundary, and recommendations for future monitoring are also provided based on the reported performance of GPBI.

Winter cover crops and no-till promote soil macrofauna communities in irrigated, Mediterranean cropland in California, USA

Cover crops and reduced tillage are two elements of conservation agriculture with potential to support larger and more diverse soil biological communities. Soil macrofauna can be indicators of soil quality and can regulate multiple soil functions, but their response to cover crop adoption in temperate regions is not well studied. We evaluated soil macrofauna communities and related soil quality metrics in response to a 16-year winter cover crop and tillage trial located in the San Joaquin Valley of California, USA. The most abundant taxa were Coleoptera (beetles) and Lumbricidae (earthworms), with average densities ranging between 5 and 318 beetles m−2 and 65–480 earthworms m−2 depending on sample date and treatments. Overall macrofauna abundance increased by 93% with the addition of cover crops in rotation, and 50% with the elimination of tillage. Taxonomic richness increased by 48% with cover crops in treatments managed without tillage, though there was no effect of cover crops under standard tillage. Macrofauna abundance was positively related to total soil carbon, water infiltration, and soil aggregate stability. Macrofauna community composition was best explained by soil carbon, water stable aggregate fraction, and cover crop usage. Agricultural management practices that foster soil biological communities may support biodiversity and improve environmental outcomes critical for sustainable food production.

Relative importance of tree species richness, tree functional type, and microenvironment for soil macrofauna communities in European forests.

Soil fauna communities are major drivers of many forest ecosystem processes. Tree species diversity and composition shape soil fauna communities, but their relationships are poorly understood, notably whether or not soil fauna diversity depends on tree species diversity. Here, we characterized soil macrofauna communities from forests composed of either one or three tree species, located in four different climate zones and growing on different soil types. Using multivariate analysis and model averaging we investigated the relative importance of tree species richness, tree functional type (deciduous vs. evergreen), litter quality, microhabitat and microclimatic characteristics as drivers of soil macrofauna community composition and structure. We found that macrofauna communities in mixed forest stands were represented by a higher number of broad taxonomic groups that were more diverse and more evenly represented. We also observed a switch from earthworm-dominated to predator-dominated communities with increasing evergreen proportion in forest stands, which we interpreted as a result of a lower litter quality and a higher forest floor mass. Finally, canopy openness was positively related to detritivore abundance and biomass, leading to higher predator species richness and diversity probably through trophic cascade effects. Interestingly, considering different levels of taxonomic resolution in the analyses highlighted different facets of macrofauna response to tree species richness, likely a result of both different ecological niche range and methodological constraints. Overall, our study supports the positive effects of tree species richness on macrofauna diversity and abundance through multiple changes in resource quality and availability, microhabitat, and microclimate modifications.

Small‐scale macrobenthic community structure along asymmetrical sand waves in an underwater seascape

AbstractSand waves are dynamic and regular bedforms that are ubiquitous in sandy shelf seas. However, information about the ecological characteristics (e.g., benthic community structure) and their spatial variability within these habitats is very limited. To address this knowledge gap, we undertook a field campaign in summer 2017 to investigate the macrofaunal community composition of a sand wave area off Texel (Dutch part of the North Sea). Sand waves in this area were asymmetrical, with longer gentle slopes that were approximately double in length to the shorter steep slopes. The benthic distribution along the different parts of these sand waves was assessed by collecting a large number of box cores within a transect line (~1 km). We show considerable variability in the individual, biomass and taxon densities, which were all significantly higher on the steeper slopes of the sand waves. These results are consistent with the trends observed in both the abiotic parameters and video analysis that were measured in two recent studies at the same study area. Our results provide valuable insight into the small‐scale patterns of variability in asymmetrical dynamic bedform environments, where gentle slopes seem to be primarily controlled by physical forces, while steep slopes are more under biotic control.

Polycyclic Aromatic Hydrocarbons Have Adverse Effects on Benthic Communities in the Baltic Sea: Implications for Environmental Status Assessment

Changes in benthic macrofaunal communities are indicative of environmental stressors, including eutrophication and hypoxia. However, some species are sensitive not only to hypoxia but also to various environmental contaminants. We tested which of the environmental predictors (sediment organic carbon, sediment concentrations of metals and polyaromatic hydrocarbons [PAHs], bottom water oxygen, salinity, temperature, and surface chlorophyll-a concentration) that best explained the following response variables: (1) macrofauna community composition, (2) abundance of a benthic sentinel species, the amphipod Monoporeia affinis; and (3) the Benthic Quality Index (BQI). All data originated from 29 reference monitoring stations in the Baltic Sea and the statistical tests included both uni- and multivariate analyses. The community composition and BQI were best explained by the same combination of salinity, depth, temperature and PAH concentrations. The abundance of M. affinis, which is sensitive to hypoxia and chemical exposure, was best explained by PAHs as a single predictor. Our findings suggest that benthic communities in the Baltic Sea are influenced by anthropogenic contaminants, which should be taken into account when benthos is used for eutrophication status assessment.

A threefold perspective on the role of a pockmark in benthic faunal communities and biodiversity patterns

Pockmarks are circular-shaped depressions that increase seabed heterogeneity and are characterized by discontinuous fluid emissions. To understand how environmental conditions of pockmarks affect the structure of macro- and meiofauna, we investigated two sites in a pockmark field in the northwestern Madagascar margin. In a comparative approach, we explored the community structure of the dominant taxa (Polychaeta, Nematoda and hyaline foraminifera) in each component (macro-, metazoan meiofauna and foraminifera, respectively). The investigated active pockmark showed approximately two times higher meiofauna abundance compared to in a site away from another pockmark field, but macrofauna showed the opposite trend, with almost half density at the pockmark site. However, at both sites, macro- and meiofauna showed higher richness and abundance values in the top well-oxygenated layers of the sediment than in the underlaying ones. Polychaeta and Nematoda showed lower richness in the pockmark, opposed to hyaline foraminiferans, but lower evenness in the pockmark was found for the three groups. The detection of gas flares in the water column attests of the recent activity within the pockmark. High amount of sulfur-bearing minerals (mainly pyrite) evidences a production of dissolved free sulfides (not detected at the time of sampling) by sulfate reduction process driven by organic matter degradation and anaerobic oxidation of methane. Furthermore, recent increase in sedimentation rates in the past 70 years and organic matter inputs could have led to higher organic matter degradation rates resulting in reduced conditions and a high oxygen consumption. All this together seem to act as key factors in the determination of variation in richness, abundance and community composition of macrofauna and meiofauna. Additionally, some taxa seem to be more tolerant to these extreme conditions, such as species belonging to the Nematoda genus Desmodora and the phylum Kinorhyncha, which are highly abundant in the pockmark, and hence, may be considered as potential bioindicators of pockmark activity in this area. Further studies are required for a better assessment.

Shorebirds Affect Ecosystem Functioning on an Intertidal Mudflat

Ecosystem functioning and services have provided a rationale for conservation over the past decades. Intertidal muddy sediments, and the microphytobenthic biofilms that inhabit them, perform crucial ecosystem functions including erosion protection, nutrient cycling and carbon sequestration. It has been suggested that predation on sediment macrofauna by shorebirds may impact biofilms, and shorebirds are known to consume biofilm, potentially causing significant top-down effects on mudflat ecosystem functioning. We carried out an exclusion experiment on the Colne Estuary, Essex, to examine whether shorebird presence significantly affects sediment erodibility measured with a Cohesive Strength Meter (CSM) and microphytobenthos biomass measured using PAM fluorescence (Fo) and chlorophyll a content. We also tested for treatment effects on sediment-water nutrient fluxes [nitrate, nitrite, ammonia, phosphate and dissolved organic carbon (DOC)] during periods of both dark and light incubation. Excluding shorebirds caused statistically significant changes in regulating and provisioning ecosystem functions, including mudflat erodibility and nutrient fluxes. The presence of shorebirds lowered the sediment critical erosion threshold τcr, reduced nitrate fluxes into the sediment under illumination, lowered nitrate efflux, and reduced phosphate uptake, compared to sediments where birds were excluded. There were no significant differences in macrofauna community composition within the sediment between treatments after 45 days of bird exclusion, suggesting a direct link between shorebird presence or absence and the significant differences in biofilm-related variables. This study introduces previously unknown effects of shorebird presence on ecosystem functions within this system and highlights an area of shorebird science that could aid joint conservation and human provisioning action.

Impeded Macrofaunal Colonization and Recovery Following Marine Deposition of Inert and Organically Modified Mine-Tailings

Fine-grained, waste rock (or tailings) produced during mining processes are the main waste product following the extraction of valuable minerals and metals from ores. The proximity of mineral resources to coastal regions in some countries has meant that the organically inert mine tailings are often deposited into the marine environment as a submarine tailings placement or STP. This creates a real environmental challenge since the deposition of tailings at the seafloor can completely smother the benthic environment and reduce benthic biodiversity and alter ecosystem function. A limited number of studies have attempted to quantify the speed of seafloor recovery following tailings disposal and have suggested that one of the main factors limiting seafloor colonisation is the lack of organic matter of the tailings deposited. In this experimental study, we used hydrodynamically unbiased settlement trays within a complete randomised block design to test whether macrofaunal colonisation of mine tailings, and resemblance towards ambient assemblages, is enhanced when tailings become more enriched in organic C (Corg). Our experiment showed that tailings with Corg contents 1% exhibited lower faunal abundance and biomass and different macrofaunal community composition after one year compared to background sediments. Macrofaunal species richness (defined as the total number of different taxa) in the 0% and 0.5% Corg tailings treatments, however, was statistically indistinguishable from ambient intertidal sediments after one year. Furthermore, macrofaunal community structure was more similar to that of the background intertidal sediments after one year, which collectively suggest partial recovery of seafloor biodiversity in tailings with zero to low Corg levels. Nevertheless, macrofaunal abundance and biomass in these treatments remained significantly less than the background community after one year suggesting factors other than the Corg content of tailings may be structuring macrofaunal colonisation and impeding seafloor recovery of tailings deposits. We propose that the non-marine physical structure of the tailings particles, which show great angularity is predominantly responsible for the observed delayed recovery.

Recent change in benthic macrofaunal community composition in relation to physical forcing in the Pacific Arctic

There is growing evidence that increased Pacific water transport into the Arctic affects the marine ecosystem. One of the theoretical predictions for a future Arctic characterized by such environmental change is that subarctic taxa will expand northward and invade the native Arctic ecosystem. This study focuses on variation in macrofaunal community composition and the influence of changing physical drivers at known benthic hotspots in the Pacific Arctic. The average number of macrofaunal family-level taxa has increased significantly south of St. Lawrence Island and in the Chirikov Basin, whereas the number of macrofaunal taxa in the southeastern Chukchi Sea showed no significant trend over the 2000–2013 time period. However, the Shannon–Weaver diversity index, based on abundance, did not mirror these regional changes in the number of macrofaunal taxa, indicating that the abundance of newly present taxa was negligible compared to the entire abundance already present. We also investigated temporal variations in meridional sea level gradient and local winds, which contribute 2/3 and 1/3 of the variation in northward volume transport at Bering Strait, respectively. There were significant increasing trends in the meridional sea level gradient and local winds, suggesting the increased northward seawater volume transports over the benthic hotspots could contribute to the expansion of subarctic taxa into these northern Arctic regions. Our data suggest an increase in macrofaunal taxa type with increasing current transport northward into the Pacific Arctic region that could have a strong influence in restructuring the benthic ecosystem in this region in the future.

The development of a national approach to monitoring estuarine health based on multivariate analysis.

New Zealand has a complex coastal environment spanning a large latitudinal gradient and three water masses. Here we assess whether multivariate analyses of benthic macrofaunal community composition can be a sensitive approach to assessing relative estuarine health across the country, negating the need for regional indices and reducing reliance on reference sites. Community data were used in separate canonical analyses of principal coordinates to create multivariate models of community responses to gradients in mud content and heavy metal contamination. Both models performed well (R2 = 0.81, 0.71), and were unaffected by regional and estuarine typology differences. The models demonstrate a sensitive and standardized approach to assessing estuarine health that allowed separation of the two stressors. This approach could be applied to other stressors, countries or regions.

Patterns and environmental drivers of diversity and community composition of macrofauna in the Kveithola Trough (NW Barents Sea)

The Kveithola Trough located in the NW Barents Sea is a peculiar system characterized by distinct geomorphological and environmental features which are expected to exert an important role on the distribution of benthic assemblages. In the present study we investigated for the first time the distribution of macrofaunal abundance, biomass and diversity along the Kveithola Trough. Our analysis reveals major differences of the macrofaunal assemblages along the Kveithola Trough related not only to the different morpho-depositional features but also to differences in trophic conditions. The inner part of the Kveithola Trough was characterized by the presence of opportunistic species such as Levinsenia gracilis and Maldane sarsi among polychaetas, Mendicula cf. pygmea and Yoldiella sp. among bivalves, which are known to inhabit oxygen-depleted environments and organic-enriched sediments. Results reported in this study suggest that the peculiar environmental conditions of the Kveithola Trough along with the occurrence of methane seepage in the neighbouring Storfjorden Trough in association to the Knølegga fault may exert a major selective effect on macrofaunal organisms.

Tree species identity governs the soil macrofauna community composition and soil development at reclaimed post-mining sites on calcium-rich clays

We tested the effect of main soil characteristics and tree species on earthworm community composition and abundance in reclaimed spoil heaps planted with five different tree species. Earthworm and soil macroarthropod abundance and biomass were highest in alder plantations, followed by oak plantations. The numbers of soil macrofauna were positively correlated with the total soil N content, which was highest in alder plantation. The correlation was strongest for endogeic earthworms (genus Aporrectodea and Octolasion). Soil moisture, measured in top 10 cm, affected only endogeic species. Other soil variables (pH, Ca) did not have a strong effect on earthworms. The earthworm community composition was similar in alder and oak, with most species occurring at both types of forest; however, in alder forest the epigeic species Dendrobaena octaedra was more common, whilst in oak forest the epigeic earthworms form genus Lumbricus were more abundant (L. rubellus and L. castaneus). The anecic species Aporrectodea longa was more abundant at alder sites, but L. terrestris was more abundant under oak. The alder forest was characteristic by a thick humus layer (10–15 cm), which at oak and larch sites was thinner (4–7 cm) and at pine and spruce stands was absent. Soil compaction was lower under the deciduous trees (alder, oak, larch), than under spruce and pine. We conclude that the alder plantations have most palatable litter and lowest C/N ratio and therefore support the highest numbers of soil macrofauna, which affects the humus layer thickness and soil compaction in the surface layers.

Replanting of first-cycle oil palm results in a second wave of biodiversity loss.

Conversion of forest to oil palm plantations results in a significant loss of biodiversity. Despite this, first‐cycle oil palm plantations can sustain relatively high biodiversity compared to other crops. However, the long‐term effects of oil palm agriculture on flora and fauna are unknown. Oil palm has a 25‐year commercial lifespan before it must be replanted, due to reduced productivity and difficulty of harvesting. Loss of the complex vegetation structure of oil palm plantations during the replanting process will likely have impacts on the ecosystem at a local and landscape scale. However, the effect of replanting on biodiversity is poorly understood.Here, we investigate the effects of replanting oil palm on soil macrofauna communities. We assessed ordinal richness, abundance, and community composition of soil macrofauna in first‐ (25‐ to 27‐year‐old) and second‐cycle oil palm (freshly cleared, 1‐year‐old, 3‐year‐old, and 7‐year‐old mature).Macrofauna abundance and richness drastically declined immediately after replanting. Macrofauna richness showed some recovery 7 years after replanting, but was still 19% lower than first‐cycle oil palm. Macrofauna abundance recovered to similar levels to that of first‐cycle oil palm plantations, 1 year after replanting. This was mainly due to high ant abundance, possibly due to the increased understory vegetation as herbicides are not used at this age. However, there were subsequent declines in macrofauna abundance 3 and 7 years after replanting, resulting in a 59% drop in macrofauna abundance compared to first‐cycle levels. Furthermore, soil macrofauna community composition in all ages of second‐cycle oil palm was different to first‐cycle plantations, with decomposers suffering particular declines.After considerable biodiversity loss due to forest conversion for oil palm, belowground invertebrate communities suffer a second wave of biodiversity loss due to replanting. This is likely to have serious implications for soil invertebrate diversity and agricultural sustainability in oil palm landscapes, due to the vital ecosystem functions that soil macrofauna provide.

Hyperdiverse Macrofauna Communities Associated with a Common Sponge, Stylissa carteri, Shift across Ecological Gradients in the Central Red Sea

Sponges act as important microhabitats in the marine environment and promote biodiversity by harboring a wide variety of macrofauna, but little is known about the magnitude and patterns of diversity of sponge-associated communities. This study uses DNA barcoding to examine the macrofaunal communities associated with Stylissa carteri in the central Saudi Arabian Red Sea, an understudied ecosystem with high biodiversity and endemism. In total, 146 operational taxonomic units (OTUs) were distinguished from 938 successfully-sequenced macrofauna individuals from 99 sponges. A significant difference was found in the macrofaunal community composition of S. carteri along a cross-shelf gradient using OTU abundance (Bray–Curtis dissimilarity index), with more amphipods associated with offshore sponges and more brittle stars and fishes associated with inshore sponges. The abundance of S. carteri also showed a gradient, increasing with proximity to shore. However, no significant differences in macrofaunal community composition or total macrofauna abundance were observed between exposed and sheltered sides of the reefs and there was no significant change in total macrofauna abundance along the inshore–offshore gradient. As climate change and ocean acidification continue to impact coral reef ecosystems, understanding the ecology of sponges and their role as microhabitats may become more important for understanding their full ramifications for biodiversity.