Round Goby Research Articles

Suitability of invasive gobies as paratenic hosts for acanthocephalans of the genus Pomphorhynchus sp.

Ponto-Caspian gobies became highly abundant in many regions outside their native distribution range (e.g. in the Rhine River system). In the newly invaded habitats, the parasite communities of the invasive gobies are characterized by a lower species richness compared to their native range. Interestingly, acanthocephalans of the genus Pomphorhynchus are highly abundant, although they do not become mature and mostly remain encapsulated in the abdominal cavity as preadults. Thus, gobiids could either represent a dead-end host for Pomphorhynchus sp. declining its population (dilution effect) or act as a paratenic host that could increase the infection pressure if the infected gobies are preyed upon by appropriate definitive hosts (spill back). To determine which of the 2 scenarios the gobiids contribute to, we conducted 2 infection experiments using smaller and larger individuals of the definitive host chub (Squalius cephalus), infected with preadults of Pomphorhynchus sp. collected from the abdominal cavity of Neogobius melanostomus. The results showed that preadults were able to complete their development and mature in the definitive host with mean recovery rates of 17.9% in smaller and 27.0% in larger chubs. Successful infections were observed in 62.0% and 80.0% of the smaller and larger chubs, respectively. Our study demonstrated that gobies can theoretically serve as a paratenic host for acanthocephalans of the genus Pomphorhynchus, and that infection might spill back into the local fish community if infected gobies are preyed upon by suitable definitive hosts of Pomphorhynchus sp. such as large barbel or chub.

Contrasting the role of historic factors in phylogeograpic patterns in the native Johnny darter (Etheostoma nigrum) and invasive round goby (Neogobius melanostomus) in lower michigan.

Round goby (Neogobius melanostomus) is an invasive fish present in all five Great Lakes and is becoming increasingly common in their tributaries. Johnny darter (Etheostoma nigrum) is a native species that often coexists with N. melanostomus. In this work, historic factors are addressed as a source of genomic variation in study populations of these species. To do this, patterns of variation in the mitochondrial gene NADH dehydrogenase subunit 2 (ND2) were characterized for both species throughout Lower Michigan. Populations of N. melanostomus and E. nigrum were sampled from 17 localities representing both eastern and western basins of Lower Michigan to test the hypothesis that populations differ between the eastern and western basins of the Great Lakes. Neogobius melanostomus populations were largely homogenous with no significant differences detected among populations or between the eastern and western basins. Additionally, N. melanostomus exhibited no evidence of overarching historical genetic structure, consistent with the recent invasion and rapid expansion of this species. Etheostoma nigrum exhibited significant differentiation among local populations; however, similarity among mtDNA haplotypes indicated that differences among populations are recent, suggesting that local forces are a more important factor in shaping patterns of variation than historical factors. Contrary to predictions, there were no significant differences detected between the eastern and western basins of the Great Lakes; however, construction of a neighbor-joining tree with F ST estimates revealed clustering of populations by basin with some anomalies. These anomalies may be the result of recent stream capture events facilitating gene flow between the two basins.

Quantifying Invasiveness Risk of Non‐Native Freshwater Fishes in South Korea Under a Changing Climate

ABSTRACTBiological invasions pose a serious threat to native biodiversity, and climate change intensifies the risk of non‐native species invasion in human‐altered environments, particularly in freshwater ecosystems. In South Korean freshwaters, the number of non‐native fish species increased significantly since the early 1950s. We screened risk of invasion by 43 freshwater fish species in South Korea using the Aquatic Species Invasiveness Screening Kit (AS‐ISK). Of these species, 26 (~ 61%) posed a high to very high risk of invasiveness. Black bullhead Ameiurus melas, brown bullhead Ameiurus nebulosus, North African catfish Clarias gariepinus, green sunfish Lepomis cyanellus, black carp Mylopharyngodon piceus, round goby Neogobius melanostomus, and Chinese sleeper Perccottus glenii were very high risk under current and predicted climate conditions. Striped snakehead Channa striata, longear sunfish Lepomis megalotis, smallmouth bass Micropterus dolomieu, white perch Morone americana, Eurasian perch Perca fluviatilis, and rudd Scardinius erythrophthalmus were high risk only under predicted climate conditions. Present risks were generally consistent with previous qualitative assessment, with some discrepancies, likely due to unobserved or under‐reported invasive traits of some species or a better ability of the present semi‐quantitative approach to estimate potential risks. Our results will inform South Korean decision‐making to potentially enhance regional cooperation across East Asia against transboundary introductions of aquatic invasive species.

Characterization of the reproductive strategy of invasive Round Goby (Neogobius melanostomus) in the Upper DanubeRiver.

Originating from the Black and Caspian seas, the Round Goby (Neogobius melanostomus) has become one of the most successful invaders of freshwater ecosystems. In this study, we provide a characterization of the reproductive strategy of an established population of Round Gobies in the Upper Danube river including sex ratio, fluctuations of gonadosomatic index (GSI), analysis of timing of spawning as well as of clutch and egg size. We compare these results to other studies from the native and invaded range. In the Danube, the Round Goby population was found to be female dominated, however fluctuations in magnitude of female bias were observed between months. Monitoring of the population across 1.5 years revealed that GSI was highest from April to June, while lowest values were observed in August and September. Using time-series analysis, a delayed effect of temperature on GSI was found for females and males, while a quicker response of GSI levels to photoperiod and discharge was observed for females. GSI increased with body size for females and eggs were found to be significantly larger in May, however clutch sizes did not differ between months. Results of a literature review revealed great differences in timing and length of spawning season as well as sex ratio between populations throughout the distribution range, which can probably be explained by climatic and photoperiodic conditions together with the time since invasion and the high plasticity of Round Gobies.

Limited Migration From Physiological Refugia Constrains the Rescue of Native Gastropods Facing an Invasive Predator.

Biological invasions have caused the loss of freshwater biodiversity worldwide. The interplay between adaptive responses and demographic characteristics of populations impacted by invasions is expected to be important for their resilience, but the interaction between these factors is poorly understood. The freshwater gastropod Amnicola limosus is native to the Upper St. Lawrence River and distributed along a water calcium concentration gradient within which high-calcium habitats are impacted by an invasive predator fish (Neogobius melanostomus, round goby), whereas low-calcium habitats provide refuges for the gastropods from the invasive predator. Our objectives were to (1) test for adaptation of A. limosus to the invasive predator and the low-calcium habitats, and (2) investigate if migrant gastropods could move from refuge populations to declining invaded populations (i.e., demographic rescue), which could also help maintain genetic diversity through gene flow (i.e., genetic rescue). We conducted a laboratory reciprocal transplant of wild F0 A. limosus sourced from the two habitat types (high calcium/invaded and low calcium/refuge) to measure adult survival and fecundity in home and transplant treatments of water calcium concentration (low/high) and round goby cue (present/absent). We then applied pooled whole-genome sequencing of 12 gastropod populations from across the calcium/invasion gradient. We identified patterns of life-history traits and genetic differentiation across the habitats that are consistent with local adaptation to low-calcium concentrations in refuge populations and to round goby predation in invaded populations. We also detected restricted gene flow from the low-calcium refugia towards high-calcium invaded populations, implying that the potential for demographic and genetic rescue is limited by natural dispersal. Our study highlights the importance of considering the potentially conflicting effects of local adaptation and gene flow for the resilience of populations coping with invasive predators.

Which Fish Predators Can Tell Us the Most about Changes in the Ecosystem of the Pomeranian Bay in the Southwest Baltic Proper?

The results of our preliminary studies indicated that the diets of predatory fishes can be bioindicators of faunistic changes in ecosystems and indirectly of changes taking place in aquatic environments in the Pomeranian Bay. We examined the diet composition of top predators Gadus morhua, Sander lucioperca, Perca fluviatilis, and the mesopredator Neogobius melanostomus. The diet composition of the perch, pikeperch, and round goby in the Pomeranian Bay was analyzed for the first time. Our findings indicated that perch, an euryphagous species, is the best potential bioindicator because it is present in the area studied most of the year and has a low to moderate feeding index (FI). Baltic cod, also an euryphagous species, could be a good bioindicator in the areas where it is abundant and occurs frequently, but not in the Pomeranian Bay, where it is caught mainly in the fall. Round goby, which is present in the area studied and had a low FI, is a stenophagous species that preys mainly on benthic species, while pikeperch had a very high FI and the least number of prey species in its diet. The results of trophic interaction analysis among the predators analyzed and their non-native/invasive prey are also provided.

Round gobies (Neogobius melanostomus) in the River Rhine: Population genetic support for invasion via two different routes

The round goby, Neogobius melanostomus, is a successful invasive fish species. Originating from the Caspian and Black Sea, it is now distributed widely within European fresh- and brackish waters. The River Rhine was colonized in 2008 only a few years after the opening of the Rhine-Main-Danube canal and only four years after N. melanostomus was first reported in the upper Danube River. Its invasion history of the River Rhine was unclear because the species was first detected close to the Rhine river delta which would suggest a route of invasion other than via the Rhine-Main-Danube canal. To investigate the colonization history of N. melanostomus in the Rhine, we combined abundance estimates with molecular analysis. Abundance estimates found N. melanostomus to be dominant in the Lower Rhine (> 90% of all catches). Molecular analysis was done on 286 individuals from four different sites. Using the mitochondrial control region (d-loop), we found three different haplotypes in both Rhine sites. None of the potential invasive source populations in the rivers Danube and Trave exhibited all three haplotypes. The molecular data therefore supported a scenario of two different colonization directions. Our results show that the invasion history of the River Rhine is complex and warrants further investigation.

Disentangling the effects of abiotic and biotic processes on non-indigenous species dominance

Relatively little attention has been paid to the underlying mechanisms determining the dominance of non-indigenous species (NIS) once established, despite being regarded as a proxy of invasion success and potential impacts in recipient communities. To bridge this knowledge gap, here we evaluate the potential direct and indirect effects of community filters on the dominance of two widespread NIS in the Baltic Sea: Marenzelleria spp. and the round goby (Neogobius melanostomus) within their corresponding communities. We applied a structural equation modelling approach to assess the direct and indirect effects amongst multiple abiotic and biotic variables on the relative biomass (as proxy of dominance) of NIS. The biotic variables represented the taxonomic- and functional diversity of the recipient communities, as well as the trait similarity between NIS and native species. We observed a comparable influence of abiotic and biotic drivers on the dominance of both NIS, with biotic variables having a somewhat stronger overall direct effect. Specifically, the dominance of both NIS was similarly affected negatively by the richness and positively by the evenness of the native communities. However, we also detected that both NIS might need different ecological strategies to become dominant in their recipient communities, which underwent similar assembly processes. Such strategies were partly highlighted by the different degrees of trait similarity between each NIS and their respective co-occurring native species. A better understanding of the underlying processes affecting NIS dominance is of high relevance to mitigate potential impacts of NIS once established. Furthermore, the provided approach could be further applied to unveil the potential strategies that NIS might follow in other regions and ecosystem types.

Physiological responses of invasive round goby (Neogobius melanostomus) to environmental stressors across a latitudinal span

Ecosystems worldwide are struggling with increasingly high levels of human-induced stressors, impacting their ecological health at local, regional, and global scales. Among the factors affecting freshwater organisms, temperature stands out, especially given the recent escalation of global warming, with possible adverse effects. In this study, we examined the basal levels of oxidative stress parameters in the round goby Neogobius melanostomus, spanning its native and non-native ranges of occurrence. We aimed to assess five populations across transcontinental scale (Turkey, Croatia, Slovakia, Poland, Finland) to determine whether individuals already experiencing conditions other than their thermal optimum (such as those in Turkey and Finland) would display elevated non-enzymatic indicators (level of lipid peroxidation and reduced glutathione levels) and enzymatic indicators (activity of glutathione peroxidase and catalase activity) of oxidative stress compared to those inhabiting milder ecosystems. The results obtained did not align with our initial predictions. The native Turkish population exhibited the lowest values for both antioxidants and oxidative damage, indicating an efficient redox system in this species. All tested parameters showed variation among populations, as well as between tissues and sexes. Temperature did not emerge as significant factor in any of the parameters tested, while for glutathione peroxidase, our analysis indicated a positive relationship with enzyme activity and salinity. The lack of a continuous latitudinal pattern in the non-native populations suggests the species’ potential for adaptive shifts, indicating superior adaptive abilities, especially in human affected ecosystems, rather than strictly adhering to environmental gradients.

Multi-decadal trophic shifts in Lake Erie yellow perch Perca flavescens

In Lake Erie, yellow perch Perca flavescens support vast commercial and recreational fisheries, yet populations have recently declined. Using N = 5889 yellow perch stomachs collected from 1997 to 2021, we explored trends in the feeding ecology and trophic level of yellow perch with generalized additive models. Models revealed a significant decrease in yellow perch trophic level (−0.15 trophic levels in the last decade), and significant dietary shifts. Yellow perch have shifted away from feeding on piscine prey and round goby Neogobius melanostomus over the 25-year period, and now feed on invertebrates more frequently—including invasive waterfleas ( Bythotrephes longimanus and Cercopagis pengoi) and chironomids. Dietary patterns appear to reflect broad ecological changes—invasive waterfleas have proliferated while populations of forage fish and round goby have declined. Furthermore, hypoxia events have increased in duration and severity, which may explain observed increases in chironomid consumption, which are hypoxia tolerant. This study demonstrates trophic adaptability in yellow perch, which have changed feeding behavior and trophic position in response to novel invaders and changing environmental conditions.

Methodological Aspects of using the frequency of occurrence Indicator for an analysis of Ichthyocenoses, the Ichthyofauna of the Baltic Sea Coastal zone Taken as an Example

The specificity of utilizing the frequency of occurrence indicator in relation to the study of the species structure of a fish community is considered. The coastal ichthyocenosis of the Baltic Sea within the Kaliningrad Region was used as a study object. Fishing was carried out at up to 20 m depths using a set of collection of gillnets with a mesh size of 12 to 80 mm in the period 2006–2022. In total, data on 894 catches were summarized, in which 11.8 thousand fish were caught. It is shown that the frequency of occurrence of a species can be presented in several ways: (1) as the average for the catches of the entire set of mesh, (2) as the maximum for the mesh size optimal for a given species, (3) as a structural characteristic that determines the nature of an ichthyocenosis’ species organization. In general, in the catches of a collection of gill nets the coastal ichthyocenosis was found to be represented by 29 species of fish, among which the river flounder, Baltic herring, round goby and smelt dominate in terms of occurrence. In the interannual aspect, the occurrence rate is demonstrated to show certain stability and is characterized by a confidence interval ranging within ±10–20%. Taking into account that the indicator of occurrence is quite simply determined just through the capture record of a species, it is recommended to use it in addition to the traditional indicators of the relative abundance and biomass of the species. Using multi-cell fishing gear for the assessment of the structure of a fish community is prerequisite.

Feeding of the caspian seal (Pusa caspica Gmelin, 1788) during haul out periods at the Kenderli rookery (Middle Caspian)

The Kendirli Haul-Out Site of the Caspian Seal served as the sole haul-out location in the Central Caspian Sea. Consequently, data obtained regarding the seal's diet at this site holds significant importance for the study and conservation of the Caspian Seal population. This study analyzed the diet of the Caspian Seal based on fecal collections from the Kendirli Haul-Out Site spanning from 2015 to 2019. Given the Caspian Seal's endangered status, a vital in vivo method of coprological analysis was employed to assess its diet. Comparative analysis of the seal's diet was conducted across seasons and years, and fish lengths consumed by seals were determined using otoliths extracted from feces. The study revealed that the Caspian Seal's diet at the Kendirli Haul-Out Site comprises 11 fish species, including species of the Cyprinidae family and Benthophilus genus, along with unidentified species of gobies. It was observed that the seal's diet varies seasonally; during autumn, the primary food source consists of gobies, whereas in spring, Atherina caspia predominates the diet. Additionally, carp species, Clupeonella caspia, and Alosa braschnikowi are present in the spring diet but absent in the autumn diet. Reconstruction of fish length ranges for three fish species — Neogobius melanostomus affinis, N. pallasi, and Alosa braschnikowi — demonstrated that seals consume fish ranging from 30 to 260 mm in length.

Invasive Round Goby (Neogobius melanostomus) Fish from the Southern Baltic as a Source of Arsenic and Selenium-Food Safety Aspects.

Minimizing human exposure to arsenic (As) and ensuring an adequate dietary intake of selenium (Se) are significant issues in research on food sources. This study measured the content of As and Se in the muscles, gills, liver, and gonads of the fish round goby (Neogobius melanostomus) to assess the benefits and risks associated with their consumption. This was achieved by using dietary reference intake (DRI), estimated daily intake (EDI), target hazard quotient (THQ), and carcinogenic risk (CR). The elements were analyzed by atomic absorption spectrometry. The mean concentrations of As and Se (in μg kg-1 wet weight) were 25.1 and 161.4 in muscle, 58.8 and 367.4 in liver, 47.4 and 635.3 in gonads, and 16.4 and 228.5 in gills, respectively. Arsenic in the muscle portion of fish accounted for up to 0.5% of the DRI, while Se constituted approximately 30% of the DRI. The EDI values were below the reference oral dose (RfD). The THQ were much below the permissible levels (THQ < 1), and the CR were at least within the permissible limit (CR < 10-4). With regard to the As content, round goby muscles can be deemed safe for consumers. They may also be a valuable source of Se in the human diet. However, round goby consumption should be monitored for the proper and safe intake of these elements.

Risk Perception: Chemical Stimuli in Predator Detection and Feeding Behaviour of the Invasive Round Goby Neogobius melanostomus.

The round goby Neogobius melanostomus is a notoriously invasive fish originating from the Ponto-Caspian region that in recent decades has successfully spread across the globe. One of its primary impacts is direct predation; in addition, when entering new ecosystems, the round goby is likely to become a food resource for many higher native predators. However, little is known either about the indirect effects of predators on the round goby as prey or its feeding behaviour and activity. The non-consumptive effect of the presence of higher native predators presumably plays an important role in mitigating the impact of non-native round gobies as mesopredators on benthic invertebrate communities, especially when both higher- and mesopredators occupy the same habitat. We tested the food consumption probability and gut evacuation rates in round gobies in response to chemical signals from a higher predator, the European eel Anguilla anguilla. Gobies were placed individually in experimental arenas equipped with shelters and exposed to water from a tank in which (a) the higher predator had actively preyed on a heterospecific prey, earthworms Lumbricus sp. (the heterospecific treatment; HS); (b) the higher predator had fed on round gobies (the conspecific treatment; CS); or (c) the water was provided as a control treatment (C). To ensure exposure to the chemical stimuli, this study incorporated the application of skin extracts containing damaged-released alarm cues from the CS treatment; distilled water was used for the remaining treatments. No significant differences were observed in either the food consumption probability or gut evacuation rate in the tested treatments. Despite the lack of reaction to the chemical stimuli, round gobies did exhibit high evacuation rates (R = 0.2323 ± 0.011 h-1; mean ± SE) in which complete gut clearance occurred within 16 h regardless of the applied treatment. This rapid food processing suggests high efficiency and great pressure on resources regardless of the presence or not of a higher predator. These findings hint at the boldness of round gobies, which did not exhibit any pronounced threat sensitivity. This would seem to suggest great efficiency in food processing and a potential competitive advantage over local native species when colonising new ecosystems, irrespective of the presence of native predators. Our study did not detect any non-consumptive effect attributable to the higher predator, given that the feeding activity of the invasive round goby was not altered.

The effects of intensive trapping on invasive round goby densities.

The round goby (Neogobius melanostomus) is an invasive benthic fish first introduced to the Laurentian Great Lakes in 1990 that has negatively impacted native fishes through increased competition for food and habitat, aggressive interactions, and egg predation. While complete eradication of the round goby is currently not possible, intensive trapping in designated areas during spawning seasons could potentially protect critical native fish spawning habitats. Baited minnow traps were spaced 10 meters apart in shallow water along a 100-meter stretch of shoreline within the Duluth-Superior Harbor during the round goby breeding period (June to October) with captured round gobies removed from interior traps (N = 10) every 48 hours. These traps were bracketed by two pairs of reference traps deployed weekly for 48 hours, from which round gobies were also tagged and released. The number of round gobies captured in the interior traps declined by 67% compared to reference traps over the course of the study, with extended periods of no captures. The tagged round gobies showed high site affinity, with 82.8% of tagged fish recaptured at the previous release site. The results indicate that even at open water sites, which allow natural migration of round gobies into the area, extensive trapping could reduce local population numbers.

Ecological impact of a generalist invader in the aquatic food web is mediated by environmental context

Abstract Freshwater ecosystems are threatened by the introduction of invasive species. Generalist invaders often compete with native species for shared resources, resulting in possible native species niche displacement. However, environmental heterogeneity may modulate the level of individual specialisation in invasive species, altering the outcome of interspecific competition between invasive and native species. The objectives of our study were to (1) evaluate the environmental context of dietary specialisation and trophic position of an invasive species according to the Environmental Matching Hypothesis (EMH), and (2) consider how the environmental context of invasive species dietary resource use may influence the dietary niche of native species competing for similar resources. Resource use, trophic position and dietary niche were determined using gut content and stable isotope analyses for the invasive round goby (Negobius melanostomus) and the native yellow perch (Perca flavescens), along environmental gradients in an invaded fluvial ecosystem. Our results were in support of EMH for the invader diet and resource specialisation, but not trophic position. Under environmental conditions of high water‐conductivity, round gobies were generalists feeding mostly on pelagic prey. Under more challenging environmental conditions of low water‐conductivity, the invader specialised on preferred high‐quality benthic prey. The ecological impact of the round goby was greatest at low water‐conductivity sites where the invader was a benthic specialist; there was a greater relative dietary niche overlap between the invader and the native species. Our study uniquely illustrates how invasive species’ resource specialisation can be modulated by spatial environmental heterogeneity within ecosystems, and how this can subsequently alter the ecological impact of the invader on native species in aquatic food webs.

Indications of reproductive disturbance by the invasive round goby on a native salmonid

Invasive species have a wide array of effects on species in their introduced ranges, including sub-lethal effects such as disruption of courtship or parental care, with potential negative influence on fitness of the native species. The invasive round goby (Neogobius melanostomus) is a door-knocker species to freshwater rivers and streams connected to the Baltic Sea. In the case of establishment of round goby in freshwater it may overlap spatially with native salmonids like Baltic Sea Atlantic salmon and sea trout, and we therefore experimentally studied interactions between round goby and salmon during salmon spawning. We found that salmon spawning behaviour was unaffected by the presence of round goby. However, salmon displayed aggression towards the round goby and the salmon male and female resided closer to each other in the presence of round goby at higher round goby densities, which we interpret to be a protective behaviour. In addition, salmon spawning was delayed in the presence of round goby. Altogether, our results imply that the reproductive success of vulnerable Baltic salmonids may be impaired under a scenario where round goby migrates upstream and establishes in Baltic rivers and streams. Consequently, we see the need for management actions to hinder spread and subsequent establishment of round goby in freshwaters along the Baltic coastline.

New molecular evidence on the members of the genus Ortholinea (Cnidaria, Myxozoa) and the description of Ortholinea hamsiensis n. sp. infecting the urinary bladder of European anchovy Engraulis engrasicolus in the Black Sea.

Members of the genus Ortholinea are among the worldwide distributed myxozoan parasites that mainly infect marine fish. In this study, a new myxosporean species, Ortholinea hamsiensis n. sp., was isolated from the urinary bladder of European anchovy Engraulis engrasicolus collected from the Sinop coasts of the Black Sea. The prevalence and density values of infection were 1.4% and 1–5 individuals in the field of view (1 + ), respectively. Mature myxospores are subspherical with slight tapering down to the less pronounced tip in the frontal view and subspherical in the sutural view. Myxospores measured 9.1 ± 0.25 (8.8–9.9) μm in length, 9.2 ± 0.11 (8.9–9.4) μm in thickness, and 8.4 ± 0.33 (8.2-9.1) μm in width. Two polar capsules equal in size measured 3.1 ± 0.11 (3.0–3.3) μm in length and 2.7 ± 0.11 (2.6–2.9) μm in width. The polar tubule had 3–4 coils. Along with morphological peculiarities, the results of the 18S rDNA also revealed it to be a new species for science compared to the other species of the genus. In this study, another myxosporean species O. gobiusi was also detected in round goby Neogobius melanostomus with a prevalence of infection value of 4.8% and a density of 1–5 individuals in the field of view (1 + ). The present study also provided the first data of 18S rDNA of O. gobiusi from N. melanostomus and type species of the genus O. divergens from Gobius niger and the phylogenetic relationships of these species with other Ortholinea species have been revealed.

Exploring the potential of extreme citizen science with Danish high school students using environmental DNA for marine monitoring

Citizen science involves non-professionals assisting with scientific research, contributing data, and conducting experiments under professional guidance. In this paper, we describe the citizen science project DNA &amp;amp; life, based at the Natural History Museum of Denmark, which actively engages high school students in both fieldwork and advanced laboratory analyses by collecting and analyzing eDNA samples from marine environments across Denmark. The analysis is performed via species-specific real-time PCR and in a case study we present data gathered in the project from 2017-2023 with focus on the potential of eDNA detecting in use for species monitoring. The results include seasonal occurrence of Mnemiopsis leidyi and national distributions of selected species of particular ecological interest Perca fluviatilis, Anguilla anguilla, Neogobius melanostomus and Alexandrium ostenfeldii. In addition to the eDNA case study, we present a new way of conducting citizen science and eDNA analysis, as a development of the established DNA &amp;amp; life project. Local DNA laboratories are created to shorten the path from sampling site to laboratory facility, creating the possibility for Danish high schools to participate in a new version of the project. In close collaboration with the academic staff of the DNA &amp;amp; life project both teachers and students help develop facilities, protocols and laboratory analyses in an extreme citizen science and co-creation approach, where the participants are involved in a higher level of laboratory work and data analysis. Allowing high school students to perform intricate molecular lab analyzes through an extreme citizen science approach has demonstrated encouraging outcomes and potential for data of high quality in terms of sampling and analyzing eDNA with the purpose of species monitoring and conservation.

Background levels of heavy metals in the water of Khadzhibey estuary

In the Odesa region, heavy metal contamination of fishery water bodies is a pressing problem. The accumulation of heavy metals in fish depends on the physiological and biochemical activity of the organism and the physical and chemical parameters of the water body. Most heavy metals enter the fish's body through the gills, skin, and digestive organs. Copper, zinc, and plumbum accumulate in the skin, gills, and liver, while cadmium and mercury accumulate in the kidneys. The level of heavy metal pollution in the water of the Khadzhibey estuary was measured and determined in 2022–2023. The following methods were used to determine the content of heavy metals in water: atomic emission spectroscopy using an EMAS-200 CCD instrument to determine cadmium, copper, zinc, and plumbum; cold vapor atomic absorption spectroscopy using the “Julia-2M” method to determine the content of mercury. Toxicological studies of water were carried out in the water hygiene and ecology laboratory of the Ukrainian Research Institute of Transport Medicine and at the Department of Veterinary Hygiene, Sanitation, and Expertise of Odesa State Agrarian University. The study found that the content of heavy metals in the water of the Khadzhibey estuary is not constant and fluctuates depending on the season. The maximum levels of heavy metals are observed in summer (plumbum and cadmium) and autumn (zinc, copper and mercury). It was found that cadmium, plumbum, copper, and mercury content does not exceed the maximum permissible levels for marine fisheries. The zinc content in the water of the Khadzhibey estuary exceeds the maximum permitted concentration by 2.65%. The zinc content in the studied water samples is a stress factor affecting the meat quality of common carp (Cyprinus carpio) and round goby (Neogobius melanostomus).