Higher Trophic Level Organisms Research Articles

Mercury monitoring in the coastal areas of the Republic of Korea using the black-tailed gull egg as an indicator

In the southeast and east coasts of the Republic of Korea, it is essential to monitor mercury accumulation in coastal organisms in view of the higher mercury distribution in sediments and human samples. However, mercury pollution monitoring in organisms, especially higher trophic-level organisms that can exhibit high mercury accumulation, is limited. Here, we examined the applicability of the eggs of the black-tailed gull (Larus crassirostris), which belongs to a high trophic level, for mercury monitoring in coastal areas. Breeding sites were selected in West, Southeast, and East Seas with different mercury concentrations in other matrices (sediment and biological samples of residents). The 5-year mean total mercury concentration in eggs collected during the breeding seasons from 2016 to 2020 was lower in Baengnyeongdo (705 ± 81 ng/g dry weight (dry), West Sea) than in Hongdo (1,207 ± 214 ng/g dry, Southeast Sea) and Ulleungdo (1,095 ± 95 ng/g dry, East Sea). The different patterns of mercury concentration in gull eggs among the breeding sites was consistent with those in the other matrices among the coastal areas. These results support the applicability of the black-tailed gull egg as an indicator for establishing a monitoring framework in the coastal areas of the Republic of Korea.

Spatiotemporal Protein Variations Based on VIIRS-Derived Regional Protein Algorithm in the Northern East China Sea

Over the past two decades, the environmental characteristics of the northern East China Sea (NECS) that make it a crucial spawning ground for commercially significant species have faced substantial impacts due to climate change. Protein (PRT) within phytoplankton, serving as a nitrogen-rich food for organisms of higher trophic levels, is a sensitive indicator to environmental shifts. This study aims to develop a regional PRT algorithm to characterize spatial and temporal variations in the NECS from 2012 to 2022. Employing switching chlorophyll-a and particulate organic nitrogen algorithms, the developed regional PRT algorithm demonstrates enhanced accuracy. Satellite-estimated PRT concentrations, utilizing data from the Visible Infrared Imaging Radiometer Suite (VIIRS), generally align with the 1:1 line when compared to in situ data. Seasonal patterns and spatial distributions of PRT in both the western and eastern parts of the NECS from 2012 to 2022 were discerned, revealing notable differences in the spatial distribution and major controlling factors between these two areas. In conclusion, the regional PRT algorithm significantly improves estimation precision, advancing our understanding of PRT dynamics in the NECS concerning PRT concentration and environmental changes. This research underscores the importance of tailored algorithms in elucidating the intricate relationships between environmental variables and PRT variations in the NECS.

Poison in the water: Arsenic's silent assault on fish health.

Arsenic occurs across the world in freshwater and marine environments, menacing the survival of aquatic organisms. Organic and inorganic forms of this substance can be found, in which the inorganic form is more hazardous than the organic form. Most aquatic bodies contain inorganic arsenic species, but organic species are believed to be the dominant form of arsenic in the majority of fish. Natural and anthropogenic both are the sources of water contamination with arsenic. Its bioaccumulation and transfer from one trophic level to another in the aquatic food chain make arsenic a vital environmental issue. Continuous exposure to low concentrations of arsenic in aquatic organisms including fish leads to its bioaccumulation, which may affect organisms of higher trophic levels including large fishes or humans. Humans can be exposed to arsenic through the consumption of fish contaminated with arsenic. Hence, the present review facilitates our understanding about sources of arsenic, its bioaccumulation, food chain transfer, and its effect on the fish health. Also, "Poison in the Water: Arsenic's Silent Assault on Fish Health" serves as a wake-up call to recognize the pressing need to address arsenic contamination in water bodies. By understanding its devastating impact on fish health, we can strive to implement sustainable practices and policies that safeguard our precious aquatic environments and ensure the well-being of both wildlife and human communities that depend on them.

Trophic Transfer of Cd, Cu, Pb, Zn, P and Se in Dutch Storage Water Reservoirs.

Heavy metals are naturally omnipresent in aquatic systems. Excess amounts of heavy metals can accumulate in organisms of pollution impacted systems and transfer across a food web. Analysing the food web structure and metal contents of the organisms can help unravel the pathways of biomagnification or biodilution and gain insight in trophic linkages. We measured heavy metals and other elements in mussel bank detritus and organisms of the Biesbosch reservoirs (the Netherlands) and linked those to stable isotopic signatures. The heavy metal contents (cadmium, copper, lead, and zinc) were often lowest in benthivorous, omnivorous and piscivorous species (mainly fish); whereas, phosphorus contents were lower in the autotrophs. Mussel bank detritus contained the highest amounts of heavy metals. The heavy metals were negatively correlated with δ15N values. For selenium no clear trend was observed. Furthermore, there was a negative correlation between fish length and some heavy metals. Based on all 20 analysed elemental contents, similarities between species became apparent, related to niche or habitat. This study confirms that elemental contents of species can differ between feeding guilds and/or species, which can be attributed to metabolic and physiological processes. The organisms in higher trophic levels have adaptations preventing metal accumulation, resulting in lower contents. Within the fish species biodilution occurs, as most metal contents were lowest in bigger fish. Overall, the metals did not seem to biomagnify, but biodilute in the food web. Metal analyses combined with isotopic signatures could thus provide insights in metal transfer and possible trophic linkages within a system.

High trophic level organisms and the complexity of soil micro-food webs at aggregate scale regulate carbon accumulation in cropland soils

Enhancing soil organic carbon (SOC) levels via improved fertilization strategies can promote soil health and support sustainable crop production. While bacteria and fungi play a key role in SOC accumulation, the effects of soil micro-food webs that include organisms from higher trophic levels remain uncertain. We sought to narrow this knowledge gap by clarifying the associations between SOC accumulation and soil micro-food webs at the aggregate scale under long-term (18 years) fertilization treatments, which included a no-fertilizer control (Ctrl), synthetic fertilizers (NPK), and partial synthetic nitrogen replacement with pig slurry (OMNPK) or crop straw (RSDNPK). The concentration of SOC was significantly increased by fertilization following the order RSDNPK (13.1 g kg−1) > OMNPK (11.4 g kg−1) > NPK (9.1 g kg−1) > Ctrl (6.4 g kg−1). Nematodes and protists accounted for approximately 20% of all nodes in the multitrophic networks. Fertilization increased network complexity at the aggregate scale by 1–4 times across different sampling dates (P < 0.05). In all aggregate classes, the functionally important (FI) nematodes, protists, and bacterial taxa involved in soil carbon cycle had higher relative abundances under the fertilization treatments than under the Ctrl (P < 0.05). Structural equation modeling further indicated that besides soil microbes, network complexity, FI nematodes and protists were important to SOC accumulation. Compared with NPK, the key moments during which these soil biological attributes strongly regulated SOC under OMNPK and RSDNPK were delayed to late growth stages of maize. In conclusion, the increased network complexity and relative abundance of functionally important organisms from higher trophic levels of the soil micro-food webs at certain periods are vital contributors to effective SOC accumulation under fertilization regimes that include organic amendments.

Ecology and environmental characteristics influence methylmercury bioaccumulation in coastal invertebrates

Quantifying mercury (Hg) concentrations in invertebrates is fundamental to determining risk for bioaccumulation in higher trophic level organisms in coastal food webs. Bioaccumulation is influenced by local mercury concentrations, site geochemistry, individual feeding ecologies, and trophic position. We sampled seven species of invertebrates from five coastal sites in the Minas Basin, Bay of Fundy, and determined body concentrations of methylmercury (MeHg), total mercury (THg), and stable isotopes of nitrogen (δ15N) and carbon (δ13C). To evaluate the effects of environmental chemistry on Hg production and bioaccumulation, bulk sediments from all sites were analysed for THg, %Loss on ignition (LOI) (carbon), and sulfur isotopes (δ34S), and concentrations of MeHg, Total Organic Carbon (TOC), sulfate, and sulfide were measured in porewaters. The mean concentration of MeHg in tissues for all invertebrates sampled was 10.03 ± 7.04 ng g−1). MeHg in porewater (mean = 0.22–1.59 ng L−1) was the strongest predictor of invertebrate MeHg, but sediment δ34S (−0.80–14.1‰) was also a relatively strong predictor. δ34S in tissues (measured in three species; Corophium volutator, Ilyanassa obsoleta, and Littorina littorea) were positively related to MeHg in invertebrates (r = 0.55, 0.22, and 0.71 respectively), and when used in combination with δ15N and δ13C values improved predictions of Hg concentrations in biota. Hg concentrations in the amphipod Corophium volutator (mean MeHg = 10.60 ± 1.90 ng g−1) were particularly well predicted using porewater and sediment chemistry, highlighting this species as a useful bioindicator of Hg contamination in sediments of the Bay of Fundy.

Concentration of mercury and other metals in an Arctic planktonic food web under a climate warming scenario

Arctic marine ecosystems act as a global sink of mercury (Hg) and other metals, and high concentrations of these have been measured in higher trophic-level organisms. Nevertheless, the concentrations of metals at the basis of the marine food web in the Arctic is less known despite the likelihood of biomagnification from dietary sources. We investigated the concentrations of mercury (Hg) and other metals in different size fractions of plankton in West Greenland. All size fractions contained detectable levels of Hg (ranging from 4.8 to 241.3 ng g dw−1) at all stations, although with high geographic variability, likely reflecting the sources of mercury (e.g., meltwater). In many cases, the concentrations in the larger-size fractions were lower than in the smaller-size fractions, suggesting depuration through the metabolic activity of mesozooplankton. Concentrations of Cd, Pb, V, Ni, and Cr were higher than previously reported elsewhere in the Arctic.

Seasonal Changes in Vertical Distribution and Population Structure of the Dominant Hydrozoan Aglantha digitale in the Western Subarctic Pacific

Hydrozoans are numerically dominant taxa in gelatinous zooplankton communities of the worldwide oceans and play an energy transfer role connecting primary producers and higher trophic level organisms. In the western subarctic Pacific, St. K2 has been established as a long-term time-series monitoring station. Various studies on zooplankton have been conducted, while hydrozoans have not been treated. This study presents the abundance, vertical distribution, and population structure of the dominant hydrozoan species (Aglantha digitale) at St. K2. Samples collected by vertical stratification samplings from eight layers of 0–1000 m both day and night during four seasons in one year. Hydrozoans occur throughout the year. The annual mean abundance of A. digitale was 198.4 ind. m−2 and composed of 91.9% of hydrozoans. The vertical distribution of A. digitale was concentrated for the epipelagic layer (0–200 m), both day and night of the most season. The bell height (BH) of A. digitale ranged between 2.4–18.9 mm. Most of the mature individuals, with gonad length larger than 10% of BH, occurred only in July. The BH of mature individuals ranged from 4.7 to 17.6 mm, with the BH of most mature individuals were larger than &gt;10 mm. Through observation on BH at each sampling layer, small individuals with BH &lt; 6 mm were distributed below 300 m depths throughout the seasons, expanding their vertical distribution to the deeper layers. Inter-region comparison of abundance, maturation body size, and generation length of A. digitale revealed that these parameters are varied with the region and depend on the marine ecosystem structures.

Nematode biomass changes along an elevational gradient are trophic group dependent but independent of body size.

Aboveground, large and higher trophic-level organisms often respond more strongly to environmental changes than small and lower trophic-level organisms. However, whether this trophic or size-dependent sensitivity also applies to the most abundant animals, microscopic soil-borne nematodes, remains largely unknown. Here, we sampled an altitudinal transect across the Tibetan Plateau and applied a community-weighted mean (CWM) approach to test how differences in climatic and edaphic properties affect nematode CWM biomass at the level ofcommunity, trophic group and taxon mean biomass within trophic groups. We found that climatic and edaphic properties, particularly soil water-related properties, positively affected nematode CWM biomass, with no overall impact of altitude on nematode CWM biomass. Higher trophic-level omnivorous and predatory nematodes responded more strongly to climatic and edaphic properties, particularly to temperature, soil pH, and soil water content than lower trophic-level bacterivorous and fungivorous nematodes. However, these differences were likely not (only) driven by size, as we did not observe significant interactions between climatic and edaphic properties and mean biomasses within trophic groups. Together, our research implies a stronger, size-independent trophic sensitivity of higher trophic-level nematodes compared with lower trophic-level ones. Therefore, our findings provide new insights into the mechanisms underlying nematode body size structure in alpine grasslands and highlight that traits independent of size need to be found to explain increased sensitivity of higher trophic-level nematodes to climatic and edaphic properties, which might affect soil functioning.

Evaluating impacts of non‐native submerged aquatic vegetation on native nekton

AbstractThe introduction and spread of non‐native species restructure native ecosystems and can be particularly impactful when invaders are ecosystem engineers or habitat‐forming species. In coastal, estuarine, and marine systems, submerged aquatic vegetation (SAV), like macroalgae and seagrasses, form key habitats for nekton, serving as nurseries, foraging grounds, and reproduction sites. If non‐native ecosystem engineers can provide sufficient structure and/or resources, they may exert a neutral or positive effect on organisms occupying higher trophic positions. As such, we hypothesized that nekton response to non‐native SAV species may be neutral or positive. We performed a quantitative meta‐analysis to quantify impacts of non‐native SAV on native crabs, fishes, and shrimps. We extracted data from 35 studies and evaluated 11 response metrics related to facilitation (e.g., habitat use and foraging), restricting our analysis to studies that compared at least one of these metrics in nekton from co‐occurring native and non‐native SAV habitats in marine, coastal, or estuarine systems. We found that nekton abundance, species richness, and biomass were the most assessed metrics of nekton performance. Our pooled data revealed differential results among response metrics, with nekton growth and reproduction enhanced in non‐native habitats and species richness enhanced in a native setting. The mean effect sizes for all other nekton response metrics, including abundance, had 95% CIs that overlapped zero, indicating no difference in response between native and non‐native SAV. For many endpoints, limited sample sizes prevented robust inferences, but they also highlighted areas where more research is needed in future studies. Non‐native species have the potential to restructure the systems they invade. Our results lend support to the relative trophic position hypothesis, indicating that non‐native habitat formers may facilitate native organisms in higher trophic levels. We identify research gaps that may guide future studies and allow for a more comprehensive understanding of responses to non‐native ecosystem engineers.

Trophic level and proteobacteria abundance drive antibiotic resistance levels in fish from coastal New England

BackgroundThe natural marine environment represents a vast reservoir of antimicrobial resistant bacteria. The wildlife that inhabits this environment plays an important role as the host to these bacteria and in the dissemination of resistance. The relationship between host diet, phylogeny, and trophic level and the microbiome/resistome in marine fish is not fully understood. To further explore this relationship, we utilize shotgun metagenomic sequencing to define the gastrointestinal tract microbiomes of seven different marine vertebrates collected in coastal New England waters.ResultsWe identify inter and intraspecies differences in the gut microbiota of these wild marine fish populations. Furthermore, we find an association between antibiotic resistance genes and host dietary guild, which suggests that higher trophic level organisms have a greater abundance of resistance genes. Additionally, we demonstrate that antibiotic resistance gene burden is positively correlated with Proteobacteria abundance in the microbiome. Lastly, we identify dietary signatures within the gut of these fish and find evidence of possible dietary selection for bacteria with specific carbohydrate utilization potential.ConclusionsThis work establishes a link between host lifestyle/dietary guild, and microbiome composition and the abundance of antibiotic resistance genes within the gastrointestinal tract of marine organisms. We expand the current understanding of marine organism-associated microbial communities and their role as reservoirs of antimicrobial resistance genes.

Role of ZnCl2 in the Uptake and Translocation of Cd to Different Parts of Wheat Plant and Risk Assessments for Cow and Human

ABSTRACT In this study, we assessed the effect of zinc (Zn) when present in form of zinc chloride (ZnCl2) on translocation and accumulation of cadmium (Cd) in different parts of wheat plants (Triticum aestivum). Along with that, health risks to organisms of higher trophic levels (cows and humans) that consume these polluted wheat plants were also calculated. For the experiments, the soil was spiked with CdCl2 at rate of 3, 6, 12, 24, and 48 mg Cd kg−1 soil and ZnCl2 at a rate of 50, 100, 200, and 300 mg Zn kg−1 soil. In the combination treatment, all Cd concentrations used in single exposure were mixed in the soil that spiked with 200 mg kg−1 of Zn. According to the data, concentration of Zn and Cd in all parts of wheat plants increase with the increase of their concentration in the soil. However, soil application of Zn reduced Cd concentration in all parts of wheat plants (approximately two-fold in root and shoot, and more than 13-fold in the grains). The highest bioaccumulation of both metals was recorded in the roots and least in grains and leaves. The translocation factor also showed that roots store most of the metals and did not translocate them to the grains. The data showed that Zn application in the soil did not decrease ecological risk factor. However, daily intake metal (DIM) and health risk index (HRI) of cows showed that the Cd intake was higher than the permissible limit, but this quantity was not a health risk for cows. In humans, DIM values were higher than the permissible limit and caused severe health risk. However, a two-fold decrease in health risk of human due to Cd was recorded in the presence of Zn. This study revealed that ZnCl2 can be used to suppress the Cd uptake in wheat even at high pollution levels. It may decrease the risk of toxicity to higher tropic levels that consume different parts of wheat plants. In future further investigation about the role of ZnCl2 in the mitigation of other metals phytotoxicity is required to use it in agroecosystem.

Mercury bioaccumulation and speciation in coastal invertebrates: Implications for trophic magnification in a marine food web

Studies on mercury bioaccumulation and biomagnification in coastal invertebrates in eastern Canada are limited, but these data are necessary to determine risk of mercury exposure effects in upper trophic level organisms. We quantified methylmercury (MeHg), total mercury (THg), and stable isotopes of δ13C and δ15N in 14 species of invertebrates in the Minas Basin. The overall mean concentration of MeHg (12.78 ± 11.23 ng/g dw) was approximately 10 times below the Canadian guideline for the protection of wildlife consumers like fish and birds of 157.20 ng/g dry weight (dw). Invertebrates at higher trophic positions (δ15N) had greater THg and particularly MeHg. The Trophic Magnification Factors (TMF) for MeHg and THg (1.59 and 1.21 respectively) were similar to others reported in studies of food webs containing higher trophic level organisms.

The Complex Interactions Between Sediment Geochemistry, Methylmercury Production, and Bioaccumulation in Intertidal Estuarine Ecosystems: A Focused Review.

Due to their natural geochemistry, intertidal estuarine ecosystems are vulnerable to bioaccumulation of methylmercury (MeHg), a neurotoxin that readily bioaccumulates in organisms. Determining MeHg concentrations in intertidal invertebrates at the base of the food web is crucial in determining MeHg exposure in higher trophic level organisms like fish and birds. The processes that govern the production of MeHg in coastal ecosystems are influenced by many geochemical factors including sulfur species, organic matter, and salinity. The interactions of these factors with mercury are complex, and a wide variety of results have been reported in the literature. This paper reviews conceptual models to better clarify the various geochemical and physical factors that impact MeHg production and bioavailability in intertidal ecosystems.

Vulnerability to climate change increases with trophic level in terrestrial organisms

The resilience of ecosystem function under global climate change is governed by individual species vulnerabilities and the functional groups they contribute to (e.g. decomposition, primary production, pollination, primary, secondary and tertiary consumption). Yet it remains unclear whether species that contribute to different functional groups, which underpin ecosystem function, differ in their vulnerability to climate change. We used existing upper thermal limit data across a range of terrestrial species (N = 1701) to calculate species warming margins (degrees distance between a species upper thermal limit and the maximum environmental temperature they inhabit), as a metric of climate change vulnerability. We examined whether species that comprise different functional groups exhibit differential vulnerability to climate change, and if vulnerability trends change across geographic space while considering evolutionary history. Primary producers had the broadest warming margins across the globe (μ = 18.72 °C) and tertiary consumers had the narrowest warming margins (μ = 9.64 °C), where vulnerability tended to increase with trophic level. Warming margins had a nonlinear relationship (second-degree polynomial) with absolute latitude, where warming margins were narrowest at about 33°, and were broader at lower and higher absolute latitudes. Evolutionary history explained significant variation in species warming margins, as did the methodology used to estimate species upper thermal limits. We investigated if variation in body mass across the trophic levels could explain why higher trophic level organisms had narrower warming margins than lower trophic level organisms, however, we did not find support for this hypothesis. This study provides a critical first step in linking individual species vulnerabilities with whole ecosystem responses to climate change.

Bioaccumulation of silver nanoparticles in marine copepod Tigriopus japonicus under waterborne and dietary exposure

At present, the emission of silver nanoparticles (AgNPs) will affect a variety of aquatic organisms. AgNPs may be transferred to the food web through the bioaccumulation or biomagnification of the food chain, which is harmful to at higher trophic level organisms, and even threatens human health. Therefore, in this study, we tested the acute toxicity effect of AgNPs to marine copepod Tigriopus japonicus, and analyzed the Ag bioaccumulation in T. japonicus under short-term waterborne (exposure of AgNPs to T. japonicus) and dietary exposure (AgNP-accumulated algae cells of Isochrysis galbana are used to feed T. japonicus). The results showed that, after 48 h exposure, significant effects of AgNPs on the mortalities were observed (LC50=6.330 mg·L−1). The bioaccumulation of Ag by T. japonicus under different exposure modes was positively correlated with exposure concentration and time, and the bioaccumulation level under waterborne exposure was significantly higher. The biomagnification of T. japonicus was not observed under 24 h dietary exposure of different AgNP concentrations (BMFs<1), but the transfer efficiency was higher under low exposure concentration (BMFlow concentration>BMFhigh concentration). This study is helpful to understand the toxicity mechanism and effect of AgNPs on aquatic organisms.

Evidence of Spatial Stability in Core Fauna Community Structure of Holopelagic Sargassum

As Sargassum biomass continues to increase globally, it is critical to develop a better understanding of how it functions as habitat, therefore, community structure of Sargassum-associated organisms was examined from 11 sampling locations spanning the tropical Florida Straits to the more temperate Gulf Stream off the coast of Savannah, Georgia from May to September 2018 using a combination of modified shrimp trawls and dip nets. A total of 5413 organisms were collected from Sargassum habitat representing 14 species from 10 families. A core group of organisms (Platynereis dumerilii, Litiopa melanostoma, Portunus sayi, Portunus spinimanus, Leander tenuicornis, and Latreutes fucorum) were found throughout the entirety of the geographic range surveyed. This core community did not vary significantly with increasing distance to shore or latitude, nor did it correlate with environmental variables such as salinity and temperature. However, community structure did vary with clump size, with larger clumps harboring more speciose communities. The Sargassum community in the Florida Straits and Gulf Stream appear to provide habitat for a consistent group of epifaunal organisms. In turn, this stable group offers a consistent prey source for a variety of important, higher trophic level organisms.

Trophic Transfer and Toxicity of (Mixtures of) Ag and TiO2 Nanoparticles in the Lettuce-Terrestrial Snail Food Chain.

The increasing application of biosolids and agrochemicals containing silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiO2NPs) results in their inevitable accumulation in soil, with unknown implications along terrestrial food chains. Here, the trophic transfer of single NPs and a mixture of AgNPs and TiO2NPs from lettuce to snails and their associated impacts on snails were investigated. Both AgNPs and TiO2NPs were transferred from lettuce to snails with trophic transfer factors (defined as the ratio of the Ag/Ti concentration in snail tissues to the Ag/Ti concentration in lettuce leaves) of 0.2–1.1 for Ag and 3.8–47 for Ti. Moreover, the majority of Ag captured by snails in the AgNP-containing treatments was excreted via feces, whereas more than 70% of Ti was distributed in the digestive gland of snails in the TiO2NP-containing treatments. Additionally, AgNP-containing treatments significantly inhibited the activity of snails, while TiO2NP-containing treatments significantly reduced feces excretion of snails. Furthermore, the concurrent application of AgNPs and TiO2NPs did not affect the biomagnification and distribution patterns of Ag and Ti in snails, whereas their co-existence exhibited more severe inhibition of the growth and activity of snails than in the case of applying AgNPs or TiO2NPs alone. This highlights the possibility of nanoparticle transfer to organisms of higher trophic levels via food chains and the associated risks to ecosystem health.

Rolling pits of Hartmann's mountain zebra (Zebra equus hartmannae) increase vegetation diversity and landscape heterogeneity in the Pre-Namib.

Microsites created by soil‐disturbing animals are important landscape elements in arid environments. In the Pre‐Namib, dust‐bathing behavior of the near‐endemic Hartmann's mountain zebra creates unique rolling pits that persist in the landscape. However, the ecohydrological characteristics and the effects of those microsites on the vegetation and on organisms of higher trophic levels are still unknown. In our study, we characterized the soil grain size composition and infiltration properties of rolling pits and reference sites and recorded vegetation and arthropod assemblages during the rainy season of five consecutive years with different amounts of seasonal rainfall. We further used the excess green vegetation index derived from drone imagery to demonstrate the different green up and wilting of pits and references after a rainfall event. In contrast to the surrounding grassland, rolling pits had finer soil with higher nutrient content, collected runoff, showed a higher infiltration, and kept soil moisture longer. Vegetation in the rolling pits was denser, dominated by annual forbs and remained green for longer periods. The denser vegetation resulted in a slightly higher activity density of herbivorous arthropods, which in turn increased the activity density of omnivorous and predatory arthropods. In times of drought, the rolling pits could act as safe sites and refuges for forbs and arthropods. With their rolling pits, Hartmann's mountain zebras act as ecosystem engineers, contributing to the diversity of forb communities and heterogeneity of the landscape in the Pre‐Namib.

Microplastic characteristics in organisms of different trophic levels from Liaohe Estuary, China

Microplastics are a growing concern globally due to their small size and easy ingestion by terrestrial and aquatic organisms, resulting in potential adverse impacts on wildlife. However, current data regarding microplastics in wild organisms in different trophic levels is limited. This study investigated microplastic characteristics, including their abundance, size, shape and polymer type, in estuarine invertebrates and vertebrates. Resultantly, polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) were the predominant microplastics found, as confirmed by a Fourier transform infrared spectrometer (FT-IR). An average microplastic abundance of 0.83 ± 0.99 to 3.87 ± 2.18 items/individual was detected across all species, including sandworm, mollusks, crustacean and fish, but they were not found in all individuals. Microplastics ranged from 52 μm to 5392 μm in size, and the shapes were consisted of fiber, fragment, and pellet. Moreover, the detection ratio (91.95%) and abundance (3.34 ± 2.17 items/individual) of microplastics in fish were significantly higher than in sandworm (42.86%, 0.88 ± 1.04 items/individual), mollusks (66.97%, 1.42 ± 1.41 items/individual) and crustaceans (66.66%, 1.33 ± 1.32 items/individual) (p < 0.05). Furthermore, a positive relationship was identified between microplastic abundance and the trophic level of organisms. These findings imply that microplastics might transfer along the food chain and accumulate at organisms in higher trophic levels.