Higher Trophic Levels Research Articles

Bioaccumulation of novel brominated flame retardants in a marine food web: A comprehensive analysis of occurrence, trophic transfer, and interfering factors.

Although the concept of bioaccumulation for novel brominated flame retardants (NBFRs) is clear, the process and interfering factors of bioaccumulation are still not fully understood. The present study comprehensively evaluated the occurrence, transfer and interfering factors of NBFRs in a marine food web to provide new thought and perspective for the bioaccumulation of these compounds. The occurrence of 17 NBFRs were determined from 8 water, 8 sediment and 303 organism samples collected from Dalian Bay, China. The trophic magnification factor (TMF), the bioaccumulation factor (BAF) and the biota sediment accumulation factor (BSAF) were calculated in a plankton-mollusk-crustacean-fish based food webs. Results showed that among the 17 target NBFRs, 11 compounds appeared the significant trophic magnification and 2 compounds of decabromodiphenylethane (DBDPE) and octabromotrimethylphenylindane (OBIND) presented the significant trophic dilution. The significant positive correlation was found between the value of BAFs and the trophic level for 15 NBFRs (except DBDPE and OBIND), indicating that the species with high BAFs values were all at high trophic levels. The stable and rapid metabolic rates of DBDPE and OBIND constitute the main reason why they hardly accumulate in high trophic level organisms. The BSAFs of NBFRs in swimming organisms were much higher than that in mollusks and crustaceans, indicating that a large part of NBFRs accumulated from food webs. The significant positive correlation between TMF and BAF was observed in high trophic level organisms, which demonstrates the important role of high trophic level organisms in evaluating the bioaccumulation effect of NBFRs.

Urbanization Impacts Top Predators and Alters Biotic Interactions in Predator-Prey-Mutualistic Communities of Urban Dry Grasslands.

Urbanization as a major driver of global change modifies biodiversity patterns and the abundance and interactions among species or functional species groups. For example, urbanization can negatively impact both predator-prey and mutualistic relationships. However, empirical studies on how urbanization modifies biotic, particularly multitrophic, interactions are still limited. In this study, we applied a framework focused on a predator-prey-mutualistic relationship involving communities of insect-pollinated vascular plants, pollinators (bees and hoverflies), predatory spiders, and sand lizards as top predators to test (i) the effect of urbanization on abundance and species richness at different trophic levels and (ii) the effect of urbanization on the regulation of biotic interactions using correlations between species abundances as a proxy. By assessing 56 dry grassland patches in Berlin, Germany, we found that higher trophic levels (sand lizard abundance as well as predatory spider species richness and abundance) were significantly impacted by urbanization whereas pollinators were affected to a lesser degree (only abundance, but not species richness). In contrast, insect-pollinated vascular plants were not impacted by urbanization. Path analyses revealed significant relationships in low-urbanized areas. In these areas, we observed significant bottom-up-regulated mutualistic and predator-prey interactions (plants-pollinators, and pollinators-predatory spiders), as well as top-down-regulated predator-prey interactions (sand lizards-pollinators, and predatory spiders-pollinators). In contrast, no significant interactions were found in highly urbanized sites. Our results suggest that bottom-up regulation is stronger than top-down regulation in low-urbanized areas. To our knowledge, this is the first study to examine the effects of urbanization on predator-prey-mutualistic interactions and to determine whether these interactions are regulated by bottom-up or top-down processes. These findings enhance our understanding of multitrophic interactions in urban environments and their associated ecosystem services, such as pollination, thereby supporting efforts in urban biodiversity conservation.

Trophic Web Structure and Ecosystem Attributes of a Coastal Lagoon System in the Southwest Atlantic

A comparative study of the lagoons that form the coastal lagoon system of Maricá-Guarapina (Southeast Atlantic, Brazil) was carried out based on the results of trophic models that describe the structure and functioning of each system. Two models were constructed using ECOPATH program to differentiate the main biomass fluxes in the systems. The model developed for Guarapina Lagoon considered 32 functional groups while that of Maricá Lagoon was developed with 29 that included primary producers to top predators, in addition to artisanal lagoon fisheries. The results indicated that biomass and production are concentrated at trophic levels 2 and 3 and the detritivore is more relevant than the grazing chain in both lagoons. This highlights the bottom-up control of our food webs despite the high trophic level of key groups. Otherwise, the increasing detritus could also reduce oxygen and influence most fish species, including mortality mass events reducing the fishery and the water quality. Ecosystem attributes suggest that both lagoons are in the intermediate stages of development. The low value of the Finn cycling index shows that Maricá Lagoon cannot recycle the organic matter, mainly because of the high input of nutrients. The importance of an ecosystem-based assessment, as presented here, constitutes an important tool for anticipating possible impacts from environmental disturbances on ecosystem functions, including the associated socio-economic challenges.

Model‐based impact analysis of climate change and land‐use intensification on trophic networks

There is well‐established evidence that land use is the main driver of terrestrial biodiversity loss. In contrast, the combined effects of land‐use and climate changes on food webs, particularly on terrestrial trophic networks, are understudied. In this study, we investigate the combined effects of climate change (temperature, precipitation) and land‐use intensification on food webs using a process‐based general mechanistic ecosystem model (‘MadingleyR'). We simulated the ecosystem dynamics of four regions in different climatic zones (Brazil, Namibia, Finland and France) according to trait‐based functional groups of species (ectothermic and endothermic herbivores, carnivores and omnivores). The simulation results were consistent across the selected regions, with land‐use intensification negatively affecting endotherms, whereas ectotherms were under increased pressure from rising temperatures. Land‐use intensification led to the downsizing of endotherms, and thus, to smaller organisms in the food web. In combination with climate change, land‐use intensification had the greatest effect on higher trophic levels, culminating in the extinction of endothermic carnivores in Namibia and Finland and endothermic omnivores in Namibia. Arid and tropical regions showed a slightly higher response of total biomass to climate change under a high‐emissions scenario with rising temperatures, whereas areas with low net primary productivity showed the most negative response to land‐use intensification. Our results suggest that 1) further land‐use intensification will significantly affect larger organisms and predators, leading to a major restructuring of global food webs. 2) Arid low‐productivity regions will experience significant changes in community composition due to global change. 3) Climate changes appear to have slightly greater effects in tropical and arid climates, whereas land‐use intensification tends to affect less productive environments. This paper shows how general ecosystem models deepen our understanding of multitrophic interactions and how climate change or land‐use drivers affect ecosystems in different biomes.

Climate warming drives population trajectories of freshwater fish

Climate change has emerged as a key threat to biodiversity, leading to broad-scale shifts in distributions of marine and terrestrial species as they attempt to track thermally suitable habitat. By contrast, our understanding of climate responses of freshwater species is relatively undeveloped, limiting our knowledge of whether projected warming will lead to freshwater biodiversity loss. Here, we linked a multicontinental database of riverine fish population abundance time series collected from 1958 to 2019 to temperature data from the same period. Across the sampled localities, waters warmed by 0.21 °C per decade (annual maximum of monthly temperatures). We tested whether fish responded to this change by i) increasing abundance at the cooler poleward limit of species distributions-predicted if warming has opened new opportunities-and ii) decreasing abundance toward the equatorward limit of distributions-predicted if temperatures have exceeded tolerance thresholds. We found that observed population trends were consistent with both of these expected patterns from climatic warming and that the trends were more pronounced in time series covering the longer time periods of 30+ y. The responses consistent with climate change were most evident in species with larger body sizes, higher trophic levels, river-sea migratory behavior, and more widespread distributions. Moreover, positive abundance responses to warming were more likely at higher altitudes where conditions tend to be cooler. These findings indicate that projected future warming will likely lead to widespread shifts in riverine community structure, including abundance declines at the trailing edge of species distributions.

Do microplastics dramatically shape the homogeneity of protozoan colonization in marine environments?

The impacts of microplastics (MPs) on the marine ecosystem have remained the focus of global attention. The microbial colonization plays an important role in driving the functional process of entire marine ecosystems, during which protozoa employ primary contributors for transferring the energy flow from the low to high trophic levels. To investigate the effects of MPs on microbial colonization, the protozoan assemblages were used as test organisms and exposed to a gradient of MP concentrations. With the increase of MP stress, the homogeneity of the test organisms was significantly altered: (1) the α- and γ-diversity indices decreased; (2) both univariate β-diversity and multivariate dispersions in species composition with weighted relative abundance increased; and (3) the traditional β-diversity showed a close linear relationship with multivariate dispersions in both the species composition and weighted relative abundance. Therefore, the results suggest that microplastics may dramatically impact the homogeneity of protozoan colonization in marine ecosystems.

Modelling global mesozooplankton biomass using machine learning

Mesozooplankton are a crucial link between primary producers and higher trophic levels and play a vital role in marine food webs, biological carbon pumps, and sustaining fishery resources. However, the global distribution of mesozooplankton biomass and the relevant controlling mechanisms remain elusive. We compared four machine learning algorithms (Boosted Regression Trees, Random Forest, Artificial Neural Network, and Support Vector Machine) to model the spatiotemporal distributions of global mesozooplankton biomass. These algorithms were trained on a compiled dataset of published mesozooplankton biomass observations with corresponding environmental predictors from contemporaneous satellite observations (temperature, chlorophyll, salinity, and mixed layer depth). We found that Random Forest achieved the best predictive accuracy with R2 and RMSE (Root Mean Standard Error) of 0.57 and 0.39, respectively. Also, the global distribution of mesozooplankton biomass predicted by the Random Forest model was more consistent with the observational data than other models. We used the Random Forest model to create a global map of mesozooplankton biomass which serves as a reference for validating process-based ecosystem models. The model outputs confirm that environmental factors, especially surface Chl a, a proxy for prey availability, significantly correlate with the spatiotemporal distribution of mesozooplankton biomass. The scaling relationship between the mesozooplankton biomass and Chl a can be used as an emergent constraint for model validation and development. Moreover, our model predicts that the global mesozooplankton biomass will decrease by 3% by the end of this century under the “business-as-usual” scenarios, potentially reducing fishery production and carbon sequestration. Our study contributes to predicting global mesozooplankton biomass and provides deep insights into the underlying environmental impacts on the distribution of mesozooplankton biomass.

Insect-flower interactions, ecosystem functions, and restoration ecology in the northern Sahel: current knowledge and perspectives.

Actions for ecological restoration under the Great Green Wall (GGW) initiative in the northern Sahel have been plant focused, paying scant attention to plant-animal interactions that are essential to ecosystem functioning. Calls to accelerate implementation of the GGW make it timely to develop a more solid conceptual foundation for restoration actions. As a step towards this goal, we review what is known in this region about an important class of plant-animal interactions, those between plants and flower-visiting insects. Essential for pollination, floral resources also support insects that play important roles in many other ecosystem processes. Extensive pastoralism is the principal subsistence mode in the region, and while recent analyses downplay the impact of livestock on vegetation dynamics compared to climatic factors, they focus primarily on rangeland productivity, neglecting biodiversity, which is critical for long-term sustainability. We summarise current knowledge on insect-flower interactions, identify information gaps, and suggest research priorities. Most insect-pollinated plants in the region have open-access flowers exploitable by diverse insects, an advantageous strategy in environments with low productivity and seasonal and highly variable rainfall. Other plant species have diverse traits that constrain the range of visitors, and several distinct flower types are represented, some of which have been postulated to match classical "pollination syndromes". As in most ecosystems, bees are among the most important pollinators. The bee fauna is dominated by ground-nesting solitary bees, almost all of which are polylectic. Many non-bee flower visitors also perform various ecosystem services such as decomposition and pest control. Many floral visitors occupy high trophic levels, and are indicators of continued functioning of the food webs on which they depend. The resilience of insect-flower networks in this region largely depends on trees, which flower year-round and are less affected by drought than forbs. However, the limited number of abundant tree species presents a potential fragility. Flowering failure of a crucial "hub" species during exceptionally dry years could jeopardise populations of some flower-visiting insects. Furthermore, across Sahelian drylands, browsers are increasingly predominant over grazers. Although better suited to changing climates, browsers exert more pressure on trees, potentially weakening insect-flower interaction networks. Understanding the separate and combined effects of climate change and land-use change on biotic interactions will be key to building a solid foundation to facilitate effective restoration of Sahelian ecosystems.

Acute Ecotoxicity and Bioconcentration Tests for Se(IV) in Nile tilapia (Oreochromis niloticus).

Selenium is one of the most important trace element micronutrients for the global biota, mainly due to its role in protecting against oxidative stress. However, this element can become toxic when present at concentrations slightly higher than those needed for metabolic purposes. It can be transferred through the food chain toward higher trophic levels, with bioaccumulation and biomagnification leading to possible toxicity. This study investigates the bioconcentration and toxicity potential of Se(IV) in Nile tilapia (Oreochromis niloticus). After 7 days of exposure, Se concentrations in the fish tissues were in the order: liver ≫ stomach > gills > muscle. In bioconcentration tests, the uptake constant (k a) ranged from 0.34 to 4.68 mL g-1 d-1, while the clearance rate constant (k d) ranged from 0.12 to 0.36 d-1. The tissues presented high bioconcentration factors (BCF) ranging from 2.67 to 12.73, demonstrating the ability of Se(IV) to concentrate in muscle, gills, and stomach. Although the data for the liver could not be fitted by the model used, the measured Se(IV) concentrations were approximately six times higher than those found for the stomach, indicating that the k a, k d, and BCF values were very high. Estimated LC50 values lower than 10 mg L-1 suggested that Se(IV) could be considered very toxic to the fish.

Graph neural networks and transfer entropy enhance forecasting of mesozooplankton community dynamics

Mesozooplankton are critical components of marine ecosystems, acting as key intermediaries between primary producers and higher trophic levels by grazing on phytoplankton and influencing fish populations. They play pivotal roles in the pelagic food web and export production, affecting the biogeochemical cycling of carbon and nutrients. Therefore, accurately modeling and visualizing mesozooplankton community dynamics is essential for understanding marine ecosystem patterns and informing effective management strategies. However, modeling these dynamics remains challenging due to the complex interplay among physical, chemical, and biological factors, and the detailed parameterization and feedback mechanisms are not fully understood in theory-driven models. Graph neural network (GNN) models offer a promising approach to forecast multivariate features and define correlations among input variables. The high interpretive power of GNNs provides deep insights into the structural relationships among variables, serving as a connection matrix in deep learning algorithms. However, there is insufficient understanding of how interactions between input variables affect model outputs during training. Here we investigate how the graph structure of ecosystem dynamics used to train GNN models affects their forecasting accuracy for mesozooplankton species. We find that forecasting accuracy is closely related to interactions within ecosystem dynamics. Notably, increasing the number of nodes does not always enhance model performance; closely connected species tend to produce similar forecasting outputs in terms of trend and peak timing. Therefore, we demonstrate that incorporating the graph structure of ecosystem dynamics can improve the accuracy of mesozooplankton modeling by providing influential information about species of interest. These findings will provide insights into the influential factors affecting mesozooplankton species and emphasize the importance of constructing appropriate graphs for forecasting these species.

Isotopic evidence of diet breadth hunter-gatherers changes during the Holocene in the Central Pampean Dunefields (Argentina, South America).

Based on the analysis of stable carbon and nitrogen isotopes of bone collagen, stable carbon isotopes of bone apatite and an extensive AMS dating series (~10,000-299 years cal BP), the human paleodiets of 34 individuals from the Central Pampean Dunefields (Argentina, South America) are evaluated. These data are interpreted from the isotopic ecology of animals with archaeofaunal evidence of consumption and isotopic models of human diet. Multivariate carbon and nitrogen stable isotope model and Bayesian stable isotope ellipses were used to interpret human diets. Analysis of isotopic values indicates intake of enriched lipids and/or carbohydrates in relation to the proteins consumed throughout the Holocene. The isotopic values of Middle Holocene humans in relation to the values of exploited resources point out that individuals obtained protein mainly from guanaco. Subsequently, there was an increase in the human breadth diet during the Late Holocene, with a greater relevance of small prey of high trophic levels and vegetables. This contrasts with zooarchaeological information indicating generalist human diets during the Middle Holocene and specialized human diets in guanaco during the Late Holocene. It is proposed that during the Middle Holocene arid period, the combination of low human population density and high residential mobility in wide foraging ranges allowed the guanaco to be the main source of protein. During the Late Holocene humid period, there was an increase in human population density and a decrease in residential mobility, which caused greater pressure on foraging territories and increased dietary breadth.

Monitoring bay-scale ecosystem changes in bivalve aquaculture embayments using flow cytometry.

Bay-scale empirical evaluations of how bivalve aquaculture alters plankton composition, and subsequently ecological functioning and higher trophic levels, are lacking. Temporal, inter- and within-bay variation in hydrodynamic, environmental, and aquaculture pressure complicate plankton monitoring design to detect bay-scale changes and inform aquaculture ecosystem interactions. Here, we used flow cytometry to investigate spatio-temporal variations in bacteria and phytoplankton (< 20 μm) composition in four bivalve aquaculture embayments. We observed higher abundances of bacteria and phytoplankton in shallow embayments that experienced greater freshwater and nutrient inputs. Depleted nutrient conditions may have led to the dominance of picophytoplankton cells, which showed strong within-bay variation as a function of riverine vs marine influence and nutrient availability. Although environmental forcings appeared to be a strong driver of spatio-temporal trends, results showed that bivalve aquaculture may reduce near-lease phytoplankton abundance and favor bacterial growth. We discuss confounding environmental factors that must be accounted for when interpreting aquaculture effects such as grazing, benthic-pelagic coupling processes, and microbial biogeochemical cycling. Conclusions provide guidance on sampling considerations using flow cytometry in aquaculture sites based on embayment geomorphology and hydrodynamics.

Coral reef condition at different trophic status in marginal waters of Bone Bay, South Sulawesi, Indonesia

AbstractCoral reef ecosystems are best suited to live in clear water conditions and oligotrophic trophic status, but marginal waters with high trophic levels in Bone Bay also have coral reef ecosystems living in them. This study was conducted in August 2023 with the aim of determining the percentage of live coral cover and its condition at different trophic status in marginal waters. Based on the processing of water quality data at 16 observation stations using the TRIX Index, four categories of water trophic status were identified, namely very high (hypertrophic), high (eutrophic), medium (mesotrophic), and low (oligotrophic) categories. Water conditions in areas close to the coastline have a higher trophic status compared to distant areas. The percentage of hard coral cover in eutrophic waters is 59.08%, in mesotrophic waters 63.63% and oligotrophic waters 43.15%. Based on PCA analysis, environmental conditions that correlate with hard corals are temperature, chlorophyll-a, TSS, pH, phosphate, nitrate and turbidity. It is anticipated that the results of this study can be a consideration for coastal area managers to protect coral reefs in marginal waters as the world’s future reef area.

Assessment of Heavy Metal (Zinc, Copper, Lead and Cadmium) Contamination in Common Edible Shellfish Species of the Hooghly River and Sunderbans, India

The content of four heavy metals (Zinc, Copper, Lead and Cadmium) in muscles of three shell fish species - prawns -Penaeus monodon and Penaeus indicus and crabs-Scylla serrata, the most prime shellfish food resources of human in the domestic and international market were studied at four stations in the estuarine belt near Bay-of-Bengal which receives wastes of various types from industries and various anthropogenic activities. The samples were digested by acid digestion. The metal contents were quantified using an AAS (Atomic absorption spectrophotometer). The distribution of trace metals accumulated in the muscle tissues of the above mentioned species was in the order- Zn &gt; Cu&gt; Pb&gt; Cd. In the present study, levels of Zinc in the shell fishes ranged from 07.44±0.65 to 128.10 ±2.96 ; Cu ranged from 5 ±0.15 to 99.14 ±1.31; Pb varied from 1.67± 0.14 to 23.99 ± 0.79 and Cd ranged from 1.29± 0.35 to 7.09 ± 0.80.The concentration of the four metals exhibited spatial variation as station 1 &gt;station 2 &gt; station 3 &gt; station 4, which could be a reflection of different bioavailability of metal concentrations in the water body at different stations. The results obtained showed that the metal concentrations in most of the cases were above the threshold value recommended by WHO. Metals such as Cu, Zn, Pb, Cd, can affect various aquatic organisms as well as human being either directly or indirectly as they can enter into the food chain and may be biomagnified at higher trophic levels which is one of the top concerns for human health. Essential heavy metals such as Zinc and Copper are relatively less harmful at low concentration while non-essential metals such as Cd and Pb are highly toxic even at low concentrations.

What is happening to the European Union aquaculture production? Investigating its stagnation and sustainability

While global aquaculture production has been highly successful in terms of production growth in recent decades, most developed countries including the European Union (EU) have not participated in this development to a significant extent. As recently as the 1970s, several EU countries were global leaders in aquaculture production, primarily focusing on filter feeders such as mussels and oysters. However, aquaculture production in the EU has largely stagnated over the past few decades. Despite political support, investment and research efforts over the last three decades, environmental regulations and competition with other activities have slowed down or even halted production growth in many cases. Recent EU legislation aimed at boosting food security and sustainable food systems, recognise aquaculture as a major potential contributor, focusing for example on sustainable or low environmental impact aquaculture, e.g. the production of low trophic level species. In this context, this article aims to contribute to the understanding of the EU aquaculture sector by examining the stagnation in production and its causes. We investigate the evolution of the EU aquaculture production in weight and value, as well as its average trophic level, length and diversity of the species produced. Results indicate an increase in the diversity of species produced, but a decline in the production of low trophic level species over the last two decades, and an increase in more challenging high trophic levels species, raising the overall average trophic level of the production. The decline in mussel and oyster production is mainly due to environmental and, to a lesser degree, economic factors. The rapid growth of carnivorous fish, such as seabream, seabass and salmon has slowed down since 2000, mainly due to regulations aiming at limiting environmental impacts.

Stress Response of Aphid Population Under Combined Stress of Cadmium and Lead and Its Effects on Development of Harmonia axyridis.

Heavy metal pollution is a serious global environmental issue. It threatens human and ecological health. Heavy metals can accumulate in the soil over extended periods and inevitably transfer through the food chain to herbivorous insects and their natural enemies, leading to various adverse effects. This study aimed to investigate the stress responses and biochemical metabolic changes of aphids and one of aphids' predators, ladybugs, under cadmium (Cd) and lead (Pb) stress by constructing a food chain of Vicia faba L., Megoura crassicauda, and Harmonia axyridis. The results showed that aphids and ladybugs had a notable accumulation of Cd2+ and Pb2+. Insects can adapt to heavy metal stress by regulating their energy metabolism pathways. Glycogen content in the first filial generation (F1) aphids decreased significantly, glucose content in the second filial generation (F2) to the fourth filial generation (F4) adult aphids significantly increased, and trehalose content in the F1 adult aphids increased significantly. Moreover, the relative expression levels of trehalase (TRE) and trehalose-6-phosphate synthase (TPS) in the F1 adult aphids were significantly higher than those in the control group, and the expression levels of TPS genes in the second filial generation to the fifth filial generation (F2 to F5) aphids decreased, suggesting that insects can resist heavy metal stress by regulating trehalose metabolism. The fertility of female aphids in all treatment groups was reduced compared to the control group. Additionally, the relative expression level of vitellogenin (Vg) was down-regulated in all aphid generations except the F1 aphids. There was interaction between heavy metal concentration and aphid generation, and it significantly affected the number of aphids' offspring and the expression of the aphid Vg gene. The developmental duration of the ladybugs from the second to fourth instars was prolonged, and the weight decreased significantly from the prepupa to the adult stages. These results contribute to understanding the effects of Cd2+-Pb2+ accumulation on phytophagous insects and higher trophic levels' natural enemies, laying the foundation for protecting natural enemies and maintaining ecosystem stability.

Seasonal Distribution of Key Small-Sized Fish in the South Inshore of Zhejiang, China

Small-sized fish are a vital food source for large predatory commercial fish and play a key role in marine food webs, bridging lower and higher trophic levels. They are indispensable in maintaining the energy flow and material cycling within aquatic ecosystems. This study utilized bottom-trawl survey data from 2017 to 2020 along the south inshore of Zhejiang, China, complemented by concurrent environmental data, to examine the influence of environmental factors on the resource density and seasonal distribution patterns of four dominant small-sized fish species. The research findings indicated that SSH (sea surface height) and Chl (chlorophyll-a concentration) emerged as the key environmental factors influencing resource densities, with all four species exhibiting similar preferences toward these variables. However, significant disparities were observed in their preferences for SST (sea surface temperature), SSS (sea surface salinity), and DO (dissolved oxygen). The various species’ resource density and distribution patterns underwent significant seasonal variations. Additionally, the seasons and regions with the highest resource densities consistently aligned, occurring predominantly in autumn within the northern waters of the study area. This research further elucidated the environmental predilections and seasonal spatial distribution traits of small-sized fish in the south inshore of Zhejiang, an important feeding ground for economic fish species in the East China Sea. This provides scientific backing for forecasting alterations in coastal fishery resources under environmental and climate change scenarios and supports ecosystem-based fisheries management strategies.

The role of evolutionary processes in determining trophic structure

There are two contrasting hypotheses regarding the drivers of biomass‐distribution among trophic levels within ecosystems. Energetic or bottom–up models propose control by supply of energy, either from autotrophy or from the underlying trophic level. Dynamical or top–down models propose control by predators in the overlying trophic level. Although multiple approaches have been used to reconcile these hypotheses, they have rarely considered the evolutionary pressures created by different distributions of biomass. Here, we study the effects of these evolutionary processes using an agent‐based, spatially‐explicit, eco‐evolutionary model. We demonstrate that, when ecosystems are simple and predator–prey relationships between species are fixed and do not evolve, primary productivity limits the number of trophic levels. In this case, the abundance in the top trophic level is always limited by productivity. However, productivity‐limited trophic levels subject those below them to limitation by predation, and predation‐limited trophic levels allow trophic levels below them to grow until limited by productivity. These results match the expectations of the exploitation ecosystems hypothesis (EEH), which predicts the same pattern of alternating top–down and bottom–up control on trophic levels. When species are able to evolve to adaptively adjust their trophic levels, however, selection is liable to lead to collapse of the trophic pyramid through prey switching. Under these conditions, all trophic levels experience bottom–up control. When the evolution of prey switching is restricted, higher trophic levels are evolutionarily stable and the predictions of the EEH are once again met; the stability of long food chains is thus dependent on the difficulty associated with prey switching. These results suggest that, at least under the combinations of model parameters explored in this study, evolutionary limitation is key to maintaining trophic structure.

Identifying toxic elements in water, sediments, and roots of mangrove forest (Avicennia marina) in Chabahar Bay, Sea of Oman

Mangroves play a crucial role in filtering pollutants from water and sediments. However, excessive accumulation of potentially toxic elements (PTEs) has harmful effects on marine organisms. This article investigates the concentration and distribution of PTEs in water, sediment, and the roots of endangered mangrove species in Chabahar Bay, a subtropical coastal wetland. The relationship between PTE absorption and accumulation rates with flow rate, mangrove extent, and sedimentation was also explored. Water, sediments, and aerial roots samples were taken at four stations along the wetland from upstream fresh water toward outfall. According to the results, Cd had more distribution in sediment and water samples and plants did not play as adsorbent in the study area. The lowest and highest PTEs concentrations were detected in water and sediment media, respectively. The average concentrations of PTEs in the sediments in the Chabahar Bay were Fe > Cr > Zn > Ni > Cu > Pb > Co > As > Cd while in aerial roots of the mangroves were Fe > Zn > Ni > Cr > Cu > Co > As > Pb > Cd. Except Zn, As, and Cd, there was a good correlation between increasing PTEs content in the sediments with decreasing flow velocity and increasing vegetation density along stations 3 to 4. In addition, the amount of PTEs uptake by the mangroves was less than that of global wetlands. The results also demonstrated a greater uptake in aerial roots in saline water for Cr, Ni and Co. Since the absorption rate of PTEs by the aerial roots of pneumatophores is slower than that in sediments, elevated concentrations of PTEs in the sediment can disrupt the entire ecosystem, leading to a potential decline in biodiversity. These toxins can enter the food chain, affecting not only organisms directly interacting with the sediment but also higher trophic levels, such as fish and birds.

Ecometrics demonstrates that the functional dental traits of carnivoran communities are filtered by climate.

Terrestrial carnivorans, with their diverse diets and unique adaptations such as the carnassial tooth, offer insights into the connections between functional traits and the climatic and environmental conditions they inhabit. They shed light on functional trait-environment relationships at the highest trophic levels across a broad range of environmental conditions. In this study, we evaluate the relationship between relative blade length (RBL) of the lower carnassial tooth, a key dietary adaptation among terrestrial carnivorans for slicing and grinding food items, and climate. We propose RBL as an ecometric trait and test the hypothesis that community-level RBL is correlated with climate and mediated by environmental effects on food availability. Our findings show that communities with higher mean and broader variance of RBL are typically located in warmer and wetter climates, suggesting a relationship between carnivoran dietary diversity and climate. Conversely, communities with a lower mean and narrower variance of RBL predominantly occupy cooler, drier places. This indicates that community-level carnivoran dietary traits have the potential to serve as indicators of environmental conditions. Given the robust fossil record associated with carnivorans, we also show how RBL can be used as a proxy for reconstructing paleoclimates by examining trait change at seven sites in North America to estimate changes in temperature and precipitation over time in relation to changes in carnivoran community assembly. Understanding the nature of trait-environment relationships can help us anticipate biological impacts of ongoing environmental change and the geographic regions at the greatest risk of ecological disruption.