Ecosystem Engineers Research Articles

Central Argentina vegetation characteristics linked to extinct megafauna and some implications on human populations

In this paper we study the relationships between plants and extinct megafauna by examining the characteristics of the vegetation in the central region of Argentina (i.e. Espinal, Monte, and Chaco phytogeographic regions). First, we study the size, shape, quantity, and characteristics of fruits and seeds. We also evaluate the presence of mechanical (spinescence and wood density) and chemical (secondary metabolic compounds) defenses against high rates of herbivory. Complementarily, we assess the importance these plants had for human populations, using archeological, ethnographic, and current data. A high percentage of the analyzed plants met the criteria proposed for fruits and seeds dispersed by megafauna, together with a high frequency of spinescence, high density woods, and secondary metabolites. We propose that these traits cannot be explained by the herbivory pressure of extant fauna in the area, but rather developed in interaction with currently extinct fauna. We suggest that Pleistocene megafaunal extinction had important consequences in the region due to their role as ecosystem engineers and to vegetation’s characteristics, which were probably strongly shaped by megafauna activities. Among these consequences, we discuss the loss of certain interactions between these animals and vegetation, such as loss of seed dispersal mechanisms, shrub invasion, and increased susceptibility of vegetation to fire. Other effects for hunter-gatherer groups were the generation of highly regulated mobility patterns and the formation of barriers for the dispersal of prey. Finally, we also discuss the importance of these plants for human populations as food, construction material, medicines and firewood. Likewise, the role of humans as “heirs” of the megafauna in the propagation of tree and shrub species is highlighted.

The interplay of co-occurring ecosystem engineers shapes the structure of benthic communities – a mesocosm experiment

IntroductionEcosystem engineers play a pivotal role in shaping habitats through their activities and presence. In shallow Baltic waters, seagrasses, patch-forming mussels, and infaunal clams modify soft bottom habitats, impacting benthic community structure. While the individual effects of these ecosystem engineers are well studied, interactions among co-occurring engineers are poorly understood. MethodsWe conducted a mesocosm experiment to assess the independent and combined impacts of seagrass (Zostera marina), epifaunal mussels (Mytilus spp.), and infaunal clams (Macoma balthica) on invertebrate colonization in soft sediments. ResultsOur findings reveal significant engineer-driven alterations in macrofaunal community structure. Combined engineer effects diverged from individual impacts, indicating potential synergies or antagonisms in sediment (re)colonization. Notably, a higher number of engineer species positively affected the diversity of settled macrofauna, with the lowest macrofaunal abundance and biomass but the highest Shannon diversity found in the presence of all three engineers. DiscussionResults suggest that seagrass, mussels, and clams influence benthos through larval settlement and sediment biogeochemistry, providing insights into the distinct roles of habitat-forming organisms in shaping the benthic communities in coastal ecosystems of the Baltic Sea.

Changes in Microbial Composition During the Succession of Biological Soil Crusts in Alpine Hulun Buir Sandy Land, China

Biological soil crusts (biocrusts) are considered “desert ecosystem engineers” because they play a vital role in the restoration and stability maintenance of deserts, including those cold sandy land ecosystems at high latitudes, which are especially understudied. Microorganisms participate in the formation and succession of biocrusts, contributing to soil properties’ improvement and the stability of soil aggregates, and thus vegetation development. Accordingly, understanding the composition and successional characteristics of microorganisms is a prerequisite for analyzing the ecological functions of biocrusts and related applications. Here, the Hulun Buir Sandy Land region in northeastern China—lying at the highest latitude of any sandy land in the country—was selected for study. Through a field investigation and next-generation sequencing (Illumina MiSeq PE300 Platform), our goal was to assess the shifts in diversity and community composition of soil bacteria and fungi across different stages during the succession of biocrusts in this region, and to uncover the main factors involved in shaping their soil microbial community. The results revealed that the nutrient enrichment capacity of biocrusts for available nitrogen, total nitrogen, total phosphorus, total content of water-soluble salt, available potassium, soil organic matter, and available phosphorus was progressively enhanced by the succession of cyanobacterial crusts to lichen crusts and then to moss crusts. In tandem, soil bacterial diversity increased as biocrust succession proceeded but fungal diversity decreased. A total of 32 bacterial phyla and 11 fungal phyla were identified, these also known to occur in other desert ecosystems. Among those taxa, the relative abundance of Proteobacteria and Cyanobacteria significantly increased and decreased, respectively, along the cyanobacterial crust–lichen–moss crust successional gradient. However, for Actinobacteria, Chloroflexi, and Acidobacteria their changed relative abundance was significantly hump-shaped, increasing in the shift from cyanobacterial crust to lichen crust, and then decreasing as lichen crust shifted to moss crust. In this process, the improved soil properties effectively enhanced soil bacterial and fungal community composition. Altogether, these findings broaden our understanding about how soil microbial properties can change during the succession of biocrusts in high-latitude, cold sandy land ecosystems.

Can Exclusion of Feral Ecosystem Engineers Improve Coastal Floodplain Resilience to Climate Change? Insight from a Case Study in North East Arnhem Land, Australia

Global climate change can interact with local drivers, such as ecosystem engineers, to exacerbate changes in ecosystem structure and function, with socio-ecological consequences. For regions of Indigenous interest, there may also be cultural consequences if species and areas affected are culturally significant. Here we describe a participatory approach between the Indigenous (Yolngu) Yirralka Rangers and non-Indigenous researchers that explored the interaction between sea level rise and feral ungulate ecosystem engineers on culturally significant floodplains in the Laynhapuy Indigenous Protected Area (IPA), northern Australia. A feral ungulate exclusion fence array (12 fenced and 12 unfenced plots) was stratified by elevation/salinity to disentangle the effects of salinity and ungulates on floodplain soil and vegetation. We found that exclusion of feral ungulates improved ground cover vegetation, which, according to our literature-derived ecosystem process model, may enhance soil trapping and reduce evapotranspiration to provide the antecedent conditions needed to improve floodplain resilience to sea level rise. The mid-zone of the supratidal floodplain study site was suggested as the region where the benefits of fencing were most pronounced after two years and ground cover species diversity was highest. Ongoing monitoring is required to investigate whether removal of feral ungulates can increase resilience against sea level rise and recruitment of eco-culturally significant Melaleuca species. An interview with a key Yolngu Traditional Owner of the study site demonstrated the importance and effectiveness of the partnership. Yolngu land owners and rangers were active co-researchers and will decide if, when and how to integrate results into feral ungulate management and climate adaptation responses, highlighting the importance of industry-university partnerships in maximising biocultural conservation outcomes.

A drying climate and habitat availability drive extirpations of a southward advancing ground squirrel

Abstract Ground squirrels act as important members of grassland ecosystems by serving as both ecosystem engineers and as a prey base for carnivores. There is mounting evidence that climate change is driving ground squirrel population declines. We resurveyed 54 historical localities throughout the Wyoming Basin and western Colorado where Wyoming Ground Squirrel (Urocitellus elegans) specimens were collected to investigate if climate change was driving extirpations at these historically occupied sites. We detected extirpations at 12 sites and used binomial generalized linear models in an information-theoretic framework to investigate if climate change was associated with these extirpations. Additionally, we investigated if land cover change was associated with persistence and if land cover ameliorated or exacerbated the effects of climate change. We found that changes in climate, especially increasingly dry summer air and increasing mean summer temperatures, were associated with a reduced probability that U. elegans persisted at a historically occupied site. In addition, we found that current forest cover at a site and increasing rangeland cover at the regional level were associated with reduced probability that U. elegans persisted, although these associations were weaker than the climate associations. The effects of climate change and land cover change did not interact. Our findings build on mounting evidence that montane-associated ground squirrels throughout the Western United States are negatively impacted by climate change. The reduction in ground squirrel abundance or their extirpation due to climate change could lead to changes in ecosystem structure or reductions in trophic complexity.

Beneath the surface: Decoding the impact of Chironomus riparius bioturbation on microplastic dispersion in sedimentary matrix

A detailed understanding of microplastics (MPs) behaviour in freshwater ecosystems is crucial for a proper ecological assessment. This includes the identification of significant transport pathways and net accumulation zones, considering their inherent, and already proven influence on aquatic ecosystems. Bioavailability of toxic agents is significantly influenced by macroinvertebrates' behaviour, such as bioturbation and burrowing, and their prior exposure history. This study investigates the effect of bioturbation activity of Chironomus riparius Meigen, 1804 on the vertical transfer of polyethylene MPs ex-situ. The experimental setup exposes larvae to a scenario of 10× the environmentally relevant high concentration of MPs (80 g m−2). Bioturbation activity was estimated using sediment profile imaging with luminophore tracers. This study demonstrated that spherical MPs are vertically transferred in the sediment due to the bioturbation activity of C. riparius larvae and that their presence influences the intensity of the bioturbation activity over time. The present findings provide a noteworthy contribution to the understanding of the relationship between ecosystem engineers and the dispersion and accumulation of MPs within freshwater ecosystems.

Density‐dependent effects of parasitism on the activity of a benthic engineer species: potential impact on ecosystem functioning

While parasitism is a common lifestyle on Earth, its importance for the functioning of marine ecosystems has been overlooked for a long time. In particular, parasites have significant potential to influence central ecological processes through their impacts on hosts that serve as ecosystem engineers. Using an ex situ experimental approach, we explored the effects of trematode parasites on the engineering bioturbation activity of a common and abundant bivalve along European Atlantic soft‐bottom coastlines, the peppery furrow shell Scrobicularia plana, as well as knock‐on effects for nutrient exchanges at the sediment–water interface (SWI). Trematodes negatively impacted the host's ability to transport sediment particles and solutes in a density‐dependent way, with parasite burden explaining 22–31% of the inter‐individual variability. This could be explained by parasitism impairing the bivalve physiological state and ability to burrow, as we observed a decrease in the condition index and the burrowing depth of the bivalves with an increase in the number of parasites they host. In contrast, the influence of S. plana on benthic biogeochemical fluxes did not vary significantly according to parasitic burden over a short time scale. Here, we focused on the effects of trematode parasites on the behaviour of S. plana alone, and thus excluded other macrofaunal organisms. We should next test whether trematodes modulate the structure and functioning of benthic communities dominated by S. plana to better understand and quantify the engineering role of parasites in soft‐bottom coastal environments.

Effects of Hemiparasites in Grassland Restorations Are Not Universal

Root hemiparasites infiltrate the vascular tissue of host roots to acquire water and nutrients, which often reduces host growth. Hemiparasites are postulated to be keystone species in grassland communities if they suppress dominant species and increase plant community biodiversity, and ecosystem engineers if they increase nutrient accessibility for surrounding species. We examined keystone effects by evaluating species richness and evenness in 1 m2 plots in a recent prairie restoration where Castilleja sessiliflora was naturally present or absent, and in a longer-established prairie restoration with or without Pedicularis canadensis. We examined ecosystem engineer effects by determining nitrate and phosphate concentrations under, 25 cm from, and 50 cm from hemiparasites, and in the center of hemiparasite-free plots. On the C. sessiliflora site, plots with the hemiparasites had higher species richness due to more forbs and higher floristic quality, consistent with the keystone species hypothesis. Soil phosphate levels were also greater in plots with C. sessiliflora present, consistent with the hypothesis of ecosystem engineering by this hemiparasite. In contrast, plots with/without P. canadensis showed no associations of any community metrics with the hemiparasite, and no correspondence between the presence of hemiparasites and soil nutrients. Although hemiparasites can increase grassland community heterogeneity, the effect is not universal, and the direction and strength of effects likely depends on local conditions.

Land use drives differential resource selection by African elephants in the Greater Mara Ecosystem, Kenya

Understanding drivers of space use by African elephants is critical to their conservation and management, particularly given their large home-ranges, extensive resource requirements, ecological role as ecosystem engineers, involvement in human-elephant conflict and as a target species for ivory poaching. In this study we investigated resource selection by elephants inhabiting the Greater Mara Ecosystem in Southwestern Kenya in relation to three distinct but spatially contiguous management zones: (i) the government protected Maasai Mara National Reserve (ii) community-owned wildlife conservancies, and (iii) elephant range outside any formal wildlife protected area. We combined GPS tracking data from 49 elephants with spatial covariate information to compare elephant selection across these management zones using a hierarchical Bayesian framework, providing insight regarding how human activities structure elephant spatial behavior. We also contrasted differences in selection by zone across several data strata: sex, season and time-of-day. Our results showed that the strongest selection by elephants was for closed-canopy forest and the strongest avoidance was for open-cover, but that selection behavior varied significantly by management zone and selection for cover was accentuated in human-dominated areas. When contrasting selection parameters according to strata, variability in selection parameter values reduced along a protection gradient whereby elephants tended to behave more similarly (limited plasticity) in the human dominated, unprotected zone and more variably (greater plasticity) in the protected reserve. However, avoidance of slope was consistent across all zones. Differences in selection behavior was greatest between sexes, followed by time-of-day, then management zone and finally season (where seasonal selection showed the least differentiation of the contrasts assessed). By contrasting selection coefficients across strata, our analysis quantifies behavioural switching related to human presence and impact displayed by a cognitively advanced megaherbivore. Our study broadens the knowledge base about the movement ecology of African elephants and builds our capacity for both management and conservation.

The role of large mammalian herbivores in shaping and maintaining soil microbial communities of natural mineral licks: A case study on sika deer at the firebreak adjacent to the Sino-Russian border.

Mineral licks are indispensable habitats to the life history of large mammal herbivores (LMH). Geophagy at licks may provide the necessary minerals for LMH, while LMH may be ecosystem engineers of licks by altering vegetation cover and soil physicochemical properties (SPCP). However, the precise relationship between the LMH and licks remains unclear. To clarify the geophagy function of licks for LMH and their influence on soil at licks, we recorded visitation patterns of sika deer around licks and compared SPCP and microbial communities with the surrounding matrix in a firebreak adjacent to the Sino-Russian border. Our study indirectly supports the "sodium supplementation" hypothesis. Proofs included (1) a significantly higher sodium, iron, and aluminum contents than the matrix, while lower carbon, nitrogen, and moisture contents; (2) significantly higher deer visitation during sodium-demand season (growing season), along with an avoidance of licks with high iron contents, which is toxic when overdose. The microbes at the licks differed from those at the matrix, mainly driven by low soil carbon and nitrogen and altered biogeochemical cycles. The microbial communities of licks are vulnerable because of their unstable state and susceptibility to SPCP changes. Structural equation modeling (SEM) clearly showed a much stronger indirect effect of deer on microbes at licks than at the matrix, especially for bacteria. Multiple deer behaviors at licks, such as grazing, trampling, and excretion, can indirectly shape and stabilize microbes by altering carbon and nitrogen input. Our study is the first to characterize soil microbial communities at mineral licks and demonstrate the processes by which LMH shapes those communities. More studies are required to establish a general relationship between the LMH and licks to promote the conservation of natural licks for wildlife.

A synthetic microbial Daisyworld: planetary regulation in the test tube.

The idea that the Earth system self-regulates in a habitable state was proposed in the 1970s by James Lovelock, who conjectured that life plays a self-regulatory role on a planetary-level scale. A formal approach to such hypothesis was presented afterwards under a toy model known as the Daisyworld. The model showed how such life-geosphere homeostasis was an emergent property of the system, where two species with different properties adjusted their populations to the changing external environment. So far, this ideal world exists only as a mathematical or computational construct, but it would be desirable to have a real, biological implementation of Lovelock's picture beyond our one biosphere. Inspired by the exploration of synthetic ecosystems using genetic engineering and recent cell factory designs, here we propose a possible implementation for a microbial Daisyworld. This includes: (i) an explicit proposal for an engineered design of a two-strain consortia, using pH as the external, abiotic control parameter and (ii) several theoretical and computational case studies including two, three and multiple species assemblies. The special alternative implementations and their implications in other synthetic biology scenarios, including ecosystem engineering, are outlined.

A global synthesis of predation on bivalves.

Predation is a dominant structuring force in ecological communities. In aquatic environments, predation on bivalves has long been an important focal interaction for ecological study because bivalves have central roles as ecosystem engineers, basal components of food webs, and commercial commodities. Studies of bivalves are common, not only because of bivalves' central roles, but also due to the relative ease of studying predatory effects on this taxonomic group. To understand patterns in the interactions of bivalves and their predators we synthesised data from 52 years of peer-reviewed studies on bivalve predation. Using a systematic search, we compiled 1334 studies from 75 countries, comprising 61 bivalve families (N = 2259), dominated by Mytilidae (29% of bivalves), Veneridae (14%), Ostreidae (8%), Unionidae (7%), and Dreissenidae and Tellinidae (6% each). A total of 2036 predators were studied, with crustaceans the most studied predator group (34% of predators), followed by fishes (24%), molluscs (17%), echinoderms (10%) and birds (6%). The majority of studies (86%) were conducted in marine systems, in part driven by the high commercial value of marine bivalves. Studies in freshwater ecosystems were dominated by non-native bivalves and non-native predator species, which probably reflects the important role of biological invasions affecting freshwater biodiversity. In fact, while 81% of the studied marine bivalve species were native, only 50% of the freshwater species were native to the system. In terms of approach, most studies used predation trials, visual analysis of digested contents and exclusion experiments to assess the effects of predation. These studies reflect that many factors influence bivalve predation depending on the species studied, including (i) species traits (e.g. behaviour, morphology, defence mechanisms), (ii) other biotic interactions (e.g. presence of competitors, parasites or diseases), and (iii) environmental context (e.g. temperature, current velocity, beach exposure, habitat complexity). There is a lack of research on the effects of bivalve predation at the population and community and ecosystem levels (only 7% and 0.5% of studies respectively examined impacts at these levels). At the population level, the available studies demonstrate that predation can decrease bivalve density through consumption or the reduction of recruitment. At the community and ecosystem level, predation can trigger effects that cascade through trophic levels or effects that alter the ecological functions bivalves perform. Given the conservation and commercial importance of many bivalve species, studies of predation should be pursued in the context of global change, particularly climate change, acidification and biological invasions.

Does restoring apex predators to food webs restore ecosystems? Large carnivores in Yellowstone as a model system

AbstractModification of food webs is a frequent cause of shifts in ecosystem states that resist reversal when the food web is restored to its original condition. We used the restoration of the large carnivore guild including gray wolves (Canis lupis), cougars (Felis concolor), and grizzly bears (Ursus arctos horribilis) to the northern range of Yellowstone National Park as a model system to understand how ecosystems might resist reconfiguration after the restoration of apex predators to the food web. The absence of wolves, cougars, and grizzly bears for nearly a century from the northern range was the primary cause of dramatic changes in riparian plant communities. Willows (Salix spp.) were suppressed in height by intense browsing by the dominant herbivore, elk (Cervus canadensis). The loss of activity by beavers (Castor canadensis) coincided with the loss of tall willows. We hypothesized that intense elk browsing interrupted the mutualism between willow and beavers: ecosystem engineering by beavers was a critical component of willow habitat and tall willows were a critical component of habitat for beavers. This interruption made riparian communities resilient to the disturbance caused by the restoration of apex predators. We hypothesized further that reductions in elk browsing attributable to reductions in elk population size were not sufficient to prevent the suppression of willow growth. To test these hypotheses, we conducted a 20‐year, factorial experiment that crossed simulated beaver dams with the exclusion of browsing. We found that willows grew to heights expected for restored communities only in the presence of dams and reduced browsing. Willows experiencing ambient conditions remained well below this expectation. We found no difference in heights or growth rates of willows in experimental controls and willows in 21 randomly chosen sites, confirming that the results of the experiment were representative of range‐wide conditions. A reorganized community of large herbivores was implicated in the suppression of willow growth. We conclude that the restoration of large carnivores to the food web failed to restore riparian plant communities on Yellowstone's northern range, supporting the hypothesis that this ecosystem is in an alternative stable state caused primarily by the extirpation of apex predators during the early 20th century.

Review of the Role of Bees as Ecosystem Engineers in Nature

Bees are a highly important group, providing a multitude of services to ecosystems, most notably through pollination. While much of the research on bees has traditionally focused on their role in pollinating a variety of wild and cultivated crops, this review paper expands the discourse by examining their functions as ecosystem engineers. Traditional definitions of ecosystem engineers exclude pollinators due to their nonphysical modifications of habitats for other species. However, contemporary studies challenge this perspective, recognizing pollinators as integral ecosystem engineers who offer a range of direct and indirect ecological services. For instance, bees’ pollination activities lead to the formation of dry fruits that subsequently serve as shelters for various organisms. In addition, ground-nesting bees modify soil composition through mechanisms such as aeration and bioturbation. This review aims to elucidate the transformative impact bees have as ecosystem engineers, thereby enhancing our understanding of their ecological importance.

Expanding and invading plant species in sagebrush steppe affect multiple aspects of small‐mammal ecology

AbstractInvasion and expansion of non‐native and native plants have altered vegetation structure in many terrestrial ecosystems. Small mammals influence multiple ecosystem processes through their roles as ecosystem engineers, predators, and prey, and changes to vegetation structure can affect habitat use, community composition, and predator‐prey interactions for this assemblage of wildlife. In the sagebrush (Artemisia spp.) shrublands of the western United States, invasion by non‐native grasses and expansion of native conifer trees beyond their historical range has altered vegetation structure. These changes may potentially affect distributions and interactions of deer mice (Peromyscus maniculatus), which are generalist omnivores, and Columbia Plateau pocket mice (Perognathus parvus), more specialized granivores. To assess the extent to which altered habitat affects small‐mammal density, survival, and home‐range size, we examined these aspects of small‐mammal ecology along a gradient of cheatgrass (Bromus tectorum) invasion and western juniper (Juniperus occidentalis) establishment in sagebrush shrublands in southwestern Idaho, USA. From 2017–2019, we used a spatially explicit mark‐recapture design to examine attributes of small‐mammal ecology along an invasion gradient. We did not find support for an effect of cheatgrass cover on density or survival of either species. Home‐range size of deer mice was 2.3 times smaller in heavier cheatgrass cover (60%) compared to areas with little or no cheatgrass cover. Density of deer mice was highest (5 individuals/ha) in areas with 10% juniper cover and decreased with increasing juniper cover, whereas density of pocket mice was positively influenced by shrub cover. Survival of deer mice declined as juniper stem density increased. Conversely, survival of pocket mice increased with increasing juniper stem density. We found evidence for interspecific interactions between these 2 species, in the form of a density‐dependent effect of deer mice on pocket mouse home‐range size. Home‐range size for pocket mice was 2 times smaller in areas with the highest estimated density of deer mice compared to areas with low densities of deer mice. Our data provides unique information about how small mammals in the sagebrush steppe are affected by expanding and invasive plant species and potential ways that habitat restoration efforts, in the form of conifer removal, may influence small mammals. Understanding the response of small mammals to conifer expansion or removal may shed light on the demographic and numerical responses of other wildlife associated with the sagebrush biome, including predators.

Testing the impacts of invasive jumping worms at their northern range limit

Earthworms can act as ecosystem engineers by altering soil structure, which impacts other organisms and ecosystem functioning. Jumping worms (family Megascolecidae) originating in Asia have been spreading in North America, extending their northern range limits to Ontario, Canada in the last decade and to New Brunswick in 2021. At the northern limits of their current range, little research has been done to examine the effects of jumping worms in these new habitats since their recent establishment. Our objectives were to evaluate: (1) how jumping worms impact soil nitrogen and soil carbon; (2) how their presence impacts the abundance of non-native European earthworms (family Lumbricidae); and (3) whether two sampling methods (i.e., mustard solution and wooden discs) are equally effective at detecting jumping worms. We sampled a residential property in Oromocto, New Brunswick, which was the first location where jumping worms were found in the province. Jumping worms did not have significant impacts on the abundance and biomass of European earthworms or soil carbon content in the top 5 cm of the soil, but they did significantly affect soil nitrogen levels. Both sampling methods were equally effective at detecting the presence of jumping worms. Further research is needed in managed landscapes, urban areas, and forests to determine the ecosystem impacts and invasion dynamics of jumping worms in Canada as this invasion progresses.

Exploring the impact of spatial patterns on restoration efforts: promoting self‐facilitating feedback mechanisms with an innovative biodegradable seed mussel collector

Transplantations of organisms in aquatic ecosystems play an important role in ecological restoration and commercial practices. However, success rates of these transplantations, especially when ecosystem engineers are involved, are often low. To enhance transplantation success, the promotion of self‐facilitation between transplants that mitigate environmental stressors is crucial. Besides, spatial patterns resulting from self‐facilitation can enhance ecosystem resilience. Using blue mussels as a model organism, we explored the possibility of increasing transplantation success in a subtidal ecosystem. We used biodegradable structures (“BioShell‐SMCs”) to ameliorate self‐facilitating feedback mechanisms to overcome environmental stressors in the initial post‐transplantation phase, and to increase transplantation success by implementing large‐scale spatial configurations, mimicking natural mussel bed patterns. The structures are an innovation of traditional seed mussel collectors (SMCs) used in mussel cultivation. They consist of a biodegradable net based on a compound of aliphatic polyesters, filled with empty cockle shells around a coconut fiber rope. We tested whether different spatial configurations could increase transplantation success of mussel seed: low versus high density labyrinth pattern and banded pattern. The results of this experiment showed high losses (approximately 75%), with no significant variation between configurations. The lack of migration due to unexpected retention of the biodegradable net hindered the initiation of natural aggregations, resulting in increased competition among mussels. Besides, factors such as hydrodynamic dislodgement, burial and interannual variation likely contributed to the observed losses. While the BioShell‐SMC has not demonstrated large‐scale success, this research contributes to understanding the mechanisms that underlie successful transplantation strategies in aquatic ecosystems.

High densities of large tuaki, the New Zealand cockle Austrovenus stutchburyi, provide a post-settlement predation refuge for conspecific juveniles

Bivalves are ecosystem engineers, and their effective management relies on a full understanding of the mechanisms that influence population dynamics. Juvenile tuaki (New Zealand cockle) Austrovenus stutchburyi, a numerically dominant and ecologically important bivalve in New Zealand estuaries, were found at higher densities when surrounded by high densities of large adults within Waitati Inlet, in southern New Zealand. Consequently, we hypothesised that adults provided a refuge from predation for juveniles, resulting in higher juvenile survival and retention in dense beds. The observed pattern was consistent with post-settlement Allee effects, where declines in density and truncated size distributions may have resulted in unsuccessful recruitment if a density threshold was reached. Field experiments were undertaken in 2020 and 2021 to test the potential sheltering effect of adults on retention and survival of juveniles, with and without the addition of organic loading of sediments. Presence of adults had significant effects on juvenile retention and interaction with organic loading in 2020, but not in 2021. To isolate the effects of adult presence on predation of juveniles, a series of laboratory experiments were carried out using the predatory crab Ovalipes catharus. Juvenile survivorship from crab predation was enhanced in the presence of large adults, consistent with the hypothesised sheltering effect. Further, predation rates increased significantly from winter to summer, which correlated with increasing water temperatures and the breeding and moult cycle of crabs. These findings across surveys, field and laboratory manipulations have significant implications for effective fisheries management and restoration of bed-forming bivalves.

Characterizing the bacterial communities associated with Mediterranean sponges: a metataxonomic analysis.

The oceans cover over 70% of our planet, hosting a biodiversity of tremendous wealth. Sponges are one of the major ecosystem engineers on the seafloor, providing a habitat for a wide variety of species to be considered a good source of bioactive compounds. In this study, a metataxonomic approach was employed to describe the bacterial communities of the sponges collected from Faro Lake (Sicily) and Porto Paone (Gulf of Naples). Morphological analysis and amplification of the conserved molecular markers, including 18S and 28S (RNA ribosomal genes), CO1 (mitochondrial cytochrome oxidase subunit 1), and ITS (internal transcribed spacer), allowed the identification of four sponges. Metataxonomic analysis of sponges revealed a large number of amplicon sequence variants (ASVs) belonging to the phyla Proteobacteria, Cloroflexi, Dadabacteria, and Poribacteria. In particular, Myxilla (Myxilla) rosacea and Clathria (Clathria) toxivaria displayed several classes such as Alphaproteobacteria, Dehalococcoidia, Gammaproteobacteria, Cyanobacteria, and Bacteroidia. On the other hand, the sponges Ircinia oros and Cacospongia mollior hosted bacteria belonging to the classes Dadabacteriia, Anaerolineae, Acidimicrobiia, Nitrospiria, and Poribacteria. Moreover, for the first time, the presence of Rhizobiaceae bacteria was revealed in the sponge M. (Myxilla) rosacea, which was mainly associated with soil and plants and involved in biological nitrogen fixation.

Furry Engineers: How Beavers Can Change an Entire Ecosystem

Every living being plays an important role on our planet. Some species create and modify the environment for others. These species can be called ecosystem engineers. By interacting with the environment and altering it, ecosystem engineers create favorable conditions for many other species. Beavers are excellent examples of ecosystem engineers. Just by building their homes and dams, these rodents modify the environment and allow other plants and animals to live in rivers and lakes. In this article, we will understand some of the ecological functions that bevers develop, how they help other species and ecosystems, and despite how helpful they are, why we should not place them everywhere.