Patricia Burkhardt-Holm

Microplastics affect assimilation efficiency in the freshwater amphipod Gammarus fossarum

An important issue in assessing microplastics is whether this newly emerging type of pollution affects freshwater invertebrates. This study was designed to examine the interactions between the amphipod Gammarus fossarum and two types of microplastics. To determine the ingestion and egestion of polyamide (PA) fibres (500xa0×xa020xa0μm), amphipods were exposed to four concentrations (100, 540, 2680, 13,380 PA fibresxa0cm−2 base area of glass beakers) and four exposure times (0.5, 2, 8, 32xa0h) as well as four post-exposure times (1, 2, 4, 16xa0h). We demonstrate a positive correlation between concentration and ingestion of PA fibres. Fibres were found in the gut after 0.5xa0h of exposure. Egestion was rapid and the digestive tract was empty 16xa0h after exposure ended. To investigate whether polystyrene (PS) beads (1.6xa0μm) can be taken up in the epithelial cells of the gut and the midgut glands, four concentrations (500, 2500, 12,500, 60,000 PS beadsxa0mL−1) were tested. Cryosections exhibited fluorescent PS beads only within the gut lumen. In a 28-day feeding experiment with both, fibres and beads, we studied the amphipod’s feeding rate, assimilation efficiency and wet weight change. The exposure to PA fibres (2680 PA fibresxa0cm−2 base area of glass beakers) significantly reduced the assimilation efficiency of the animals. While both tested polymer types are ingested and egested, PA fibres can impair the health and ecological functions of freshwater amphipods under continuous exposure.

An eDNA Assay to Monitor a Globally Invasive Fish Species from Flowing Freshwater

Ponto-Caspian gobies are a flock of five invasive fish species that have colonized freshwaters and brackish waters in Europe and North America. One of them, the round goby Neogobius melanostomus, figures among the 100 worst invaders in Europe. Current methods to detect the presence of Ponto-Caspian gobies involve catching or sighting the fish. These approaches are labor intense and not very sensitive. Consequently, populations are usually detected only when they have reached high densities and when management or containment efforts are futile. To improve monitoring, we developed an assay based on the detection of DNA traces (environmental DNA, or eDNA) of Ponto-Caspian gobies in river water. The assay specifically detects invasive goby DNA and does not react to any native fish species. We apply the assay to environmental samples and demonstrate that parameters such as sampling depth, sampling location, extraction protocol, PCR protocol and PCR inhibition greatly impact detection. We further successfully outline the invasion front of Ponto-Caspian gobies in a large river, the High Rhine in Switzerland, and thus demonstrate the applicability of the assay to lotic environments. The eDNA assay requires less time, equipment, manpower, skills, and financial resources than the conventional monitoring methods such as electrofishing, angling or diving. Samples can be taken by untrained individuals, and the assay can be performed by any molecular biologist on a conventional PCR machine. Therefore, this assay enables environment managers to map invaded areas independently of fishermen’s’ reports and fish community monitorings.

Natural Mineral Particles Are Cytotoxic to Rainbow Trout Gill Epithelial Cells In Vitro

Worldwide increases in fluvial fine sediment are a threat to aquatic animal health. Fluvial fine sediment is always a mixture of particles whose mineralogical composition differs depending on the sediment source and catchment area geology. Nonetheless, whether particle impact in aquatic organisms differs between mineral species remains to be investigated. This study applied an in vitro approach to evaluate cytotoxicity and uptake of four common fluvial mineral particles (quartz, feldspar, mica, and kaolin; concentrations: 10, 50, 250 mg L−1) in the rainbow trout epithelial gill cell line RTgill-W1. Cells were exposed for 24, 48, 72, and 96 h. Cytotoxicity assays for cell membrane integrity (propidium iodide assay), oxidative stress (H2DCF-DA assay), and metabolic activity (MTT assay) were applied. These assays were complemented with cell counts and transmission electron microscopy. Regardless of mineral species, particles ≤2 µm in diameter were taken up by the cells, suggesting that particles of all mineral species came into contact and interacted with the cells. Not all particles, however, caused strong cytotoxicity: Among all assays the tectosilicates quartz and feldspar caused sporadic maximum changes of 0.8–1.2-fold compared to controls. In contrast, cytotoxicity of the clay particles was distinctly stronger and even differed between the two particle types: mica induced concentration-dependent increases in free radicals, with consistent 1.6–1.8-fold-changes at the 250 mg L−1 concentration, and a dilated endoplasmic reticulum. Kaolin caused concentration-dependent increases in cell membrane damage, with consistent 1.3–1.6-fold increases at the 250 mg L−1 concentration. All effects occurred in the presence or absence of 10% fetal bovine serum. Cell numbers per se were marginally affected. Results indicate that (i.) natural mineral particles can be cytotoxic to gill epithelial cells, (ii.) their cytotoxic potential differs between mineral species, with clay particles being more cytotoxic, and (iii.) some clays might induce effects comparable to engineered nanoparticles.

A tough egg to crack: recreational boats as vectors for invasive goby eggs and transdisciplinary management approaches.

Abstract Non‐native invasive species are a major threat to biodiversity, especially in freshwater ecosystems. Freshwater ecosystems are naturally rather isolated from one another. Nonetheless, invasive species often spread rapidly across water sheds. This spread is to a large extent realized by human activities that provide vectors. For example, recreational boats can carry invasive species propagules as “aquatic hitch‐hikers” within and across water sheds. We used invasive gobies in Switzerland as a case study to test the plausibility that recreational boats can serve as vectors for invasive fish and that fish eggs can serve as propagules. We found that the peak season of boat movements across Switzerland and the goby spawning season overlap temporally. It is thus plausible that goby eggs attached to boats, anchors, or gear may be transported across watersheds. In experimental trials, we found that goby eggs show resistance to physical removal (90 mN attachment strength of individual eggs) and stay attached if exposed to rapid water flow (2.8 m·s−1for 1 h). When exposing the eggs to air, we found that hatching success remained high (>95%) even after eggs had been out of water for up to 24 h. It is thus plausible that eggs survive pick up, within‐water and overland transport by boats. We complemented the experimental plausibility tests with a survey on how decision makers from inside and outside academia rate the feasibility of managing recreational boats as vectors. We found consensus that an installation of a preventive boat vector management is considered an effective and urgent measure. This study advances our understanding of the potential of recreational boats to serve as vectors for invasive vertebrate species and demonstrates that preventive management of recreational boats is considered feasible by relevant decision makers inside and outside academia.

What do we really know about the impacts of one of the 100 worst invaders in Europe? A reality check

Invasive species are one of the greatest threats to biodiversity worldwide, and to successfully manage their introductions is a major challenge for society. Knowledge on the impacts of an invasive species is essential for motivating decision makers and optimally allocating management resources. We use a prominent invasive fish species, the round goby (Neogobius melanostomus) to objectively quantify the state of scientific knowledge on its impacts. Focusing on how native fish species are affected by round goby invasions, we analyzed 113 peer-reviewed papers and found that impacts are highly ecosystem and time scale dependent. We discovered round goby impacts to be profound, but surprisingly complex. Even if identical native species were affected, the impacts remained less comparable across ecosystems than expected. Acknowledging the breadth but also limitations in scientific knowledge on round goby impacts would greatly improve scientists’ ability to conduct further research and inform management measures.

Unraveling the mechanisms involved in zearalenone-mediated toxicity in permanent fish cell cultures

The world-wide occurrence of zearalenone (ZEN) as a contaminant in feed for farm animals and fish requires the evaluation of toxicity mechanisms of action of ZEN. The present study investigates possible metabolization of ZEN in fish cell lines suggesting that mainly glucuronidation takes place. It demonstrates that concentrations up to 20,000xa0ngxa0ml(-1) ZEN are capable of influencing cell viability in permanent fish cell cultures in a dose-response manner with different response patterns between the five tested cell lines, whereby lysosomes appeared to be the main target of ZEN. ZEN toxicity is often discussed in the context of oxidative stress. Our study shows a biphasic response of the cell lines when reactive oxygen species (ROS) production is monitored. Damage in cells was observed by measuring lipid peroxidation, DNA strand breaks, and alterations of intracellular glutathione levels. Metabolization of ZEN, especially at concentrations above 7500xa0ngxa0ml(-1) ZEN, does not prevent cytotoxicity. ZEN as an estrogenic compound may involve processes mediated by binding to estrogen receptors (ER). Since one cell line showed no detectable expression of ER, an ER-mediated pathway seems to be unlikely in these cells. This confirms a lysosomal pathway as a main target of ZEN in fish cells.

A hydro-economic model for water level fluctuations: combining limnology with economics for sustainable development of hydropower.

Water level fluctuations in lakes lead to shoreline displacement. The seasonality of flooding or beaching of the littoral area affects nutrient cycling, redox gradients in sediments, and life cycles of aquatic organisms. Despite the ecological importance of water level fluctuations, we still lack a method that assesses water levels in the context of hydropower operations. Water levels in reservoirs are influenced by the operator of a hydropower plant, who discharges water through the turbines or stores water in the reservoir, in a fashion that maximizes profit. This rationale governs the seasonal operation scheme and hence determines the water levels within the boundaries of the reservoirs water balance. For progress towards a sustainable development of hydropower, the benefits of this form of electricity generation have to be weighed against the possible detrimental effects of the anthropogenic water level fluctuations. We developed a hydro-economic model that combines an economic optimization function with hydrological estimators of the water balance of a reservoir. Applying this model allowed us to accurately predict water level fluctuations in a reservoir. The hydro-economic model also allowed for scenario calculation of how water levels change with climate change scenarios and with a change in operating scheme of the reservoir (increase in turbine capacity). Further model development will enable the consideration of a variety of additional parameters, such as water withdrawal for irrigation, drinking water supply, or altered energy policies. This advances our ability to sustainably manage water resources that must meet both economic and environmental demands.

Improving invasive species management by integrating priorities and contributions of scientists and decision makers

Managing invasive species is a major challenge for society. In the case of newly established invaders, rapid action is key for a successful management. Here, we develop, describe and recommend a three-step transdisciplinary process (the “butterfly model”) to rapidly initiate action for invasion management. In the framing of a case study, we present results from the first of these steps: assessing priorities and contributions of both scientists and decision makers. Both scientists and decision makers prioritise research on prevention. The available scientific knowledge contributions, however, are publications on impacts rather than prevention of the invasive species. The contribution of scientific knowledge does thus not reflect scientists’ perception of what is essentially needed. We argue that a more objective assessment and transparent communication of not only decision makers’ but also scientists’ priorities is an essential basis for a successful cooperation. Our three-step model can help achieve objectivity via transdisciplinary communication.

Cytotoxic effects of pentachlorophenol (PCP) and its metabolite tetrachlorohydroquinone (TCHQ) on liver cells are modulated by antioxidants

The worldwide distribution and high bioaccumulation potential of pentachlorophenol (PCP) in aquatic organisms imply a high toxicological impact in aquatic systems. Firstly, our investigations show that, similar to mammalian cell lines, PCP can be metabolized to tetrachlorohydroquinone (TCHQ) in the permanent cell line derived from rainbow trout liver cells (RTL-W1). Moreover, we demonstrate that PCP as well as its metabolite TCHQ is capable of influencing the viability of these cells. Three cell viability assays were performed to assess possible cellular targets of these substances. Thus, the cytotoxicity of the PCP-derivative TCHQ was shown for the first time in a fish cell line. Further investigations revealed the involvement of ROS in the cytotoxicity of PCP and its metabolite TCHQ. The observation of oxidative stress provides a plausible explanation for the increased cytotoxicity at higher concentrations especially for PCP and implies possible mechanisms underlying these observations. In addition, antioxidants such as ascorbic acid and quercetin modulate the detrimental effects of PCP and TCHQ whereby both compounds exacerbate the cytotoxic effects of high PCP and TCHQ concentrations.

The invasive bighead goby Ponticola kessleri displays large-scale genetic similarities and small-scale genetic differentiation in relation to shipping patterns.

Colonization events, range expansions and species invasions leave genetic signatures in the genomes of invasive organisms and produce intricate special patterns. Predictions have been made as to how those patterns arise, but only very rarely, genetic processes can be monitored in real time during range expansions. In an attempt to change that, we track a very recently established invasive population of a fish species, the bighead goby Ponticola kessleri, with high temporal and spatial resolution through 2 years to identify patterns over time. We then compare Swiss and German samples of bighead goby along the river Rhine using microsatellites, mitochondrial D‐loop sequences and geometric morphometrics to investigate geographic patterns. We detect weak temporal and strong geographic patterns in the data, which are inconsistent with isolation by distance and indicate long range transport. In search of an explanation for our observations, we analyse the vector properties and travel patterns of commercial vessels on the river Rhine. We present evidence that freshwater cargo ships and tankers are plausible vectors for larvae of invasive goby species. We also present indications that cargo ships and tankers act as differential vectors for this species. In summary, we present genetic data at unique temporal resolution from a vertebrate invasion front and substantiate the paramount role of commercial shipping in freshwater fish translocations.