Living in potentially burdened waters and prey on loaded species, marine mammals are sentinels for microplastic (MP) pollution. Here, seven different species of cetaceans were investigated covering baleen (Mysticeti) and toothed (Odontoceti) whales stranded along the German coast between 2016 and 2021. Intestinal and faecal samples of 12 sperm whales, three minke whales, two dolphin species, one long-finned pilot whale, one fin whale and one neonate orca were analysed. The concentrations of 11 phthalates were assessed in blubber and muscle samples. MPs were detected with Nile Red staining, polymer identification was conducted using μFTIR spectroscopy. Four individuals showed no MP burden. An average of 4.6 MPs (Odontocetes) and 3.25 MPs (Mysticetes) were found. A share of 0 and 19 MPs was found per 10 g of faeces. Polyamide, polyolefin and polyester were detected. No significant differences between baleen or toothed whales were identified. In individuals which revealed macro debris inside their stomach also showed MPs in their faeces. Individuals with an empty stomach (N = 3) still showed MP presence. Nine compounds of PAEs were quantified in both muscle and blubber of seven species in different concentrations. DEHP was the most abundant compound. The results cannot be linked to the burden in the North - or Baltic Sea, since not all investigated specimens are regularly occurring here. Evidence is given that both baleen and toothed whales from the northern hemisphere are similarly burdened with MPs, and that not only ingested macro-debris can be assumed as a source for MP.

Plastic forms, including plastiglomerate, pyroplastic, plasticrusts, anthropoquinas, plastistone and plastitar, were recorded worldwide. These plastic forms derive from geochemical or geophysical interactions such as heat-induced plastic fusion with rock in campfires, incomplete plastic combustion, water motion-driven plastic abrasion in the rocky intertidal zone, plastic deposition in hardened sediments and plastic bonding with tar. Thereby, these interactions can profoundly influence the fate of plastics in the environment. This study characterized three novel plastic forms (plasticoncrete, plastimetal and plastisessiles) discovered on Helgoland island (North Sea). Plasticoncrete consisted of common polyethylene (PE) and polypropylene (PP) fibers hardened in concrete. Plastimetal included PE fibers rusted with metal. Plastisessiles consisted of PE fibers attached to benthic substrates by sessile invertebrates (oysters and polychaetes). Plasticoncrete and plastimetal are the first plastic forms composed of two man-made materials. Plastisessiles show that plastic forms not only result from human- or environment-mediated interactions but also from biological interactions between invertebrates and plastic. All plastic forms (bulk density ≥ 1.4 g/cm3) sunk during floating tests and hardly changed their positions during a 13-day field experiment and 153- to 306-day field monitorings, indicating their local formation, limited mobility and longevity. Still, experimentally detached plastic fibers floated, confirming that the formation of these plastic forms influences the fate of plastic fibers in the environment. Furthermore, the experiment showed that plasticoncrete got deposited in beach sand under wavy and windy conditions, indicating that coastal waves and onshore winds drive plasticoncrete deposition in coastal sediments. We also provide first records of plasticoncrete on Mallorca island (Mediterranean Sea) and plastimetal on Hikoshima island (Sea of Japan), respectively, which show that these plastic forms are no local phenomena. Thereby, our study contributes to the growing fundamental knowledge of plastic forms that is essential to understand the role and fate of these pollutants in coastal habitats worldwide.

Microplastics (<5 mm) are emerging pollutants in oceans worldwide. As such small particles are easily ingested, microplastics are found in numerous pelagic and benthic organisms. However, information on microplastics in rocky intertidal organisms and habitats is relatively scant. Therefore, we examined snails and water samples from wave-sheltered and wave-exposed rocky intertidal habitats in Helgoland (North Sea), Cap Ferrat and Giglio (Mediterranean) and Madeira (Atlantic Ocean) in 2019-2020 for microplastics. Furthermore, we examined snails from the same habitats in Helgoland, Cap Ferrat and Giglio in 2007-2009. In total, we performed 362 individual micro-Fourier-transform infrared spectroscopy (mu FTIR) measurements on the snails and water samples. While the snails contained 50 microplastics (composed of nine polymer types), the water samples contained 24 microplastics (comprising six polymer types). Microplastic load and polymer type composition in the snails were rather similar across locations, wave exposure and years. Also, microplastic load and polymer composition in the water samples were similar across locations and wave exposure. Moreover, snail and water microplastic loads were significantly correlated which indicates that snails are useful bioindicators for microplastic loads in rocky intertidal habitats. Interestingly, the majority of the microplastics consisted of paint chips that likely derived from ships. Overall, our study provides the first comprehensive microplastic record in rocky intertidal organisms across locations, wave exposure and years that can serve as a baseline to examine historic and future microplastic dynamics in rocky intertidal systems.

Assessment of fish assemblage structure depends on representative sampling. In contrast to lotic water bodies, recommendations for a general study design are sparse for lentic water bodies. Therefore, we evaluated the fish assemblages in different littoral structure types (e.g. macrophytes and riprap stone) and the impact of these structure types on the minimum distance required to obtain samples representative of fish species number in oxbow lakes. Boat-based electrofishing was used at 88 sections, each 200-m long within five oxbow lakes connected to the Upper River Rhine in southwest Germany. Submerged macrophytes and riprap stones were important littoral structures for determining fish community structure. Littoral structure was related to species accumulation, which illustrates the importance of littoral structure to define the minimum length of sampling. Our findings suggest that at least 200-m stretches should be sampled to describe fish assemblages in oxbow lakes.

Microplastic ingestion by lower trophic level organisms is well known, whereas information on microplastic ingestion, egestion and accumulation by top predators such as cetaceans is still lacking. This study investigates microplastics in intestinal samples from harbour porpoises (Phocoena phocoena) found along the coastline of Schleswig-Holstein (Germany) between 2014 and 2018. Out of 30 individuals found along the North Sea (NS) and the Baltic Sea (BS) coast, 28 specimens contained microplastic. This study found a relationship between the nutritional status of cetaceans and the amount of found microplastics. Harbour porpoises with a good or moderate nutritional status contained a higher number of microplastics, when compared with specimens in a poor nutritional status. In addition, when individuals died accidently due to suspected bycatch in gillnets, where a feeding event is highly assumed or a pharyngeal entrapment happened, the microplastic burden was higher. In total, 401 microplastics (≥100 μm), including 202 fibres and 199 fragments were found. Intestines of the specimens of the BS contained more microplastics than the ones from the NS. Differences in the share of fibres could be revealed: for BS fibres constituted 51.44% and for NS, fibres constituted 47.97%. The polymers polyester, polyethylene, polypropylene, polyamide, acrylic (with nitrile component) and an acrylic/alkyd paint chip (with styrene and kaolin components) were identified. This is the first study investigating the occurrence of microplastics in harbour porpoises from German waters and will, thus, provide valuable information on the actual burden of microplastics in cetaceans from the North and Baltic Seas.

Plastic is a versatile material appreciated for its durability and wide applicability in everyday products like food containers, beverage bottles, and medical devices. However, mismanaged plastic waste frequently washes into streams and rivers, where it is consumed by various organisms. To help avoid mortality from potentially crushing predators such as juvenile dragonflies (Odonata) and brown trout (Salmo trutta), the aquatic larvae of caddisflies (Trichoptera) build protective cases. Interestingly, we recently discovered that caddisfly (Lepidostoma basale) larvae use plastic waste as a material for case-building (Aquat Biol 2019; doi.org/10.3354/ab00711). During a laboratory experiment, the caddisfly larva shown here was offered blue microplastic particles (<5 mm) of polyethylene terephthalate (PET, a plastic type commonly used in beverage bottles), along with gray sand grains. After having been removed from its original case composed of natural materials, the larva immediately started building a new case using the PET particles, and then later incorporated the sand grains into its case. The experiment revealed that caddisfly case stability decreased with increasing PET particle load (Environ Sci Pollut R 2020; doi.org/10.1007/s11356-020-08790-5), suggesting that plastic waste incorporation in caddisfly cases may reduce protection from predators and, thereby, influence predator–prey interactions. Fish often consume caddisfly larvae along with their cases, and microplastics are known to cause inflammatory responses in fish. The question that remains unanswered is how microplastics in caddisfly larval cases may affect predatory fish.

Microplastics are pollutants threatening the health of marine, freshwater and terrestrial organisms. To analyze whether an organism is able to ingest microplastics, the organism is usually fed with expensive fluorescent microbeads and placed under a fluorescence microscope for microplastic detection. However, such equipment cannot be afforded by many laboratories. Therefore, we developed a low-cost method to study the ingestion and egestion of low-cost, fluorescent microplastic fragments and fibers by aquatic invertebrates. During our feeding experiments, we exposed the freshwater snail Radix balthica to artificial biofilms containing 15% microplastic fragments and fibers, respectively. We then used an ultraviolet (UV) flashlight to irradiate the microplastics. Hence, we could directly observe the microplastics in the food, during ingestion and egestion as well as in the snail feces. Our method, thereby, allowed us to analyze the snails' behavior (during ingestion and egestion), the microplastics' distribution in the snail feces and the microplastics' shape after the snails' digestion. Furthermore, we observed that the snails ceased to egest microplastics after 76 hr following microplastic ingestion. However, chemical digestion of the snails 6 days after microplastic exposure revealed that microplastics were still present in R. balthica, emphasizing the microplastics' persistence in the animals' bodies. This is the first study combining the usage of low-cost fluorescent microplastics with an inexpensive UV flashlight for microplastic detection during microplastic ingestion and egestion by living organisms. Our new method is not only cost-effective, but also fast and can be performed by a wide range of researchers without special previous training.

Caddisfly larvae occur in streams and rivers, and many caddisfly species build protective cases using material from their habitat such as sand grains. At the same time, microplastics (MPs) are regularly deposited in aquatic sediments and are incorporated into caddisfly (Lepidostoma basale) cases in the field. However, it is unknown what the effects of MP incorporation into cases might be on the health of the caddisfly larvae. Hence, we offered two commonly used MPs (polyvinyl chloride (PVC) and polyethylene terephthalate (PET)) to L. basale larvae during a laboratory experiment. Both plastic types have a high density and co-occur with L. basale larvae in benthic habitats. In our experiment, L. basale actively used sand, PET and PVC MPs for building tube-like portable or emergency cases. The latter is a temporary shelter under which the larva can hide for immediate protection. Furthermore, case stability decreased with increasing PVC and PET particle content in the cases, suggesting that MPs may threaten caddisflies by destabilising cases. When case stability is reduced, the protective function of the cases is limited and the larvae may be more prone to predation. Additionally, larvae may be washed away by the current as plastic is lighter than sand. Both effects could limit the caddisfly's survival, which could have far-reaching consequences as caddisfly larvae are important primary consumers in aquatic ecosystems.

Plastic pollution is present in aquatic systems worldwide. While numerous studies have investigated microplastic interactions with marine organisms, microplastic effects on freshwater organisms, especially insects, have been rarely studied. Previous studies have mainly focused on dietary uptake of microplastics, but the presence of microplastics in animal constructions is largely unknown. To date, microplastics have only been observed in the tubes of a marine polychaete species. In freshwater systems, common caddisfly (Trichoptera) larvae build cases by using larval silk and mineral grains from benthic sediments, which are known microplastic sinks. Therefore, we examined caddisfly cases for microplastic presence. We collected caddisfly Lepidostoma basale cases in the field, disintegrated them using hydrogen peroxide, and determined microplastic polymer type through micro-Fourier-transform infrared spectroscopy. We found primary and secondary microplastics of different shapes, colors, sizes and chemical compositions (e.g. polypropylene, polyethylene, polyvinyl chloride). Thus, this is the first study to show that microplastics are present in the biological construction of a freshwater organism. Larval stages are usually more vulnerable than adult individuals, and microplastics can transport persistent organic pollutants and emit toxic leachates. In the caddisfly larval case, those substances are in close proximity to the sensitive larval body, which may be harmful for the larva and may eventually impede its development. We discuss the potential of caddisfly larval cases to act as microplastic bioindicators in freshwater habitats.

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Freshwater environments are the route through which inland plastics are transported to the ocean, explaining why the number of freshwater microplastic (MP) studies has recently been increasing. Despite the lack of recycling and the presence of severe plastic pollution in many African countries, MPs have been scarcely reported in African freshwaters and the current study gives the first empirical account for West Africa. The study investigates MP pollution in an important West African river system (Osun River system, Nigeria) and gives an insight into microplastic contamination in a main European river (Rhine River), using gastropods which are potential consumers of MPs, from both systems. From the Osun River system, the most common gastropods (Lanistes varicus and Melanoides tuberculata) were analysed for MP contamination. Two MP types (fibre and film) were recorded in L. varicus, whereas only fibre was recorded in M. tuberculata. Micro-Fourier-transform infrared spectroscopy (μFTIR) revealed that the MP films in the African gastropods were made of polyethylene and strongly resembled black polyethylene bags that covered the Osun River banks. From the Rhine River, the gastropod Theodoxus fluviatilis was analysed and nylon as well as polypropylene fibres were found. In both systems (Osun River and Rhine River), fibre was the dominant MP type. In conclusion, the study shows that MP contamination in Nigeria, a West African country with a lack of recycling and poor waste management practice, is reflected in two different local gastropod species. Furthermore, the comparison with a European gastropod species shows that fibres are the dominant MP type in gastropods from both freshwater systems. In both systems, MPs ingested by the gastropods could be transferred to higher trophic levels following predation. We therefore recommend that more empirical studies should be carried out along different feeding guilds of African freshwater invertebrates and fish. When MPs are transferred to fish, MPs may reach humans through fish consumption.

Riverbanks hold a key position on functionality of floodplains as they constitute the gradual transition between aquatic and terrestrial ecosystems. However, due to technical constructions the majority of riverbanks in temperate regions are far from their ecological potential. This results in the loss of valuable habitats and biodiversity. The need for restoration is high but hardly compatible with economic interests. Bioengineering methods could help to increase the ecological potential of river banks. A comparative investigation on bioengineering bank protection techniques was conducted along two watercourses of different characters of navigation and hydrology (Rhine, Weser). We measured the response of four organism groups to different bioengineering methods. Our results indicate an ecological enhancement of riparian zones by re-establishing of valuable floodplain habitats. The number of terrestrial riparian species increased at both rivers. However, habitat quality for aquatic communities remained limited at due to insufficient extension of measures below mean water level.

The Ponto-Caspian amphipod Dikerogammarus villosus is one of the most successful invaders in Central European rivers. Contrary to studies on its ecology, ecophysiological studies comparing the species' physiological traits are scarce. In this context, in particular the metabolic activity of the invasive species has rarely been considered and, moreover, the few existing studies on this species report strongly deviating results. The purpose of this study was to assess the metabolic activity and behavior of D. villosus and other common European amphipod species (Gammarus fossarum, Gammarus roeselii) in relation to temperatures covering the thermal regime of the invaded habitats. Based on direct calorimetric measurements of metabolic heat dissipation at three temperature levels (5°C, 15°C and 25°C), we found the routine metabolic rate of D. villosus to be significantly lower than that of the other studied gammarid species at the medium temperature level. The estimated resting metabolic rate indicated a similar trend. At 5°C and 25°C, both routine and resting metabolic rate did not differ between species. Compared to G. fossarum and G. roeselii, D. villosus exhibited lower locomotor activity at the low and medium temperatures (5°C and 15°C). In contrast, its locomotor activity increased at the high experimental temperature (25°C). G. fossarum and G. roeselii were apparently more active than D. villosus at all studied temperatures. We conclude that D. villosus has both physiological and behavioral adaptations that lead to a reduction in metabolic energy expenditure, which is assumed to be beneficial and might contribute to its invasive success.

Summary 1. We assessed sex‐specific seasonal changes in major energy storage compounds (triglycerides, glycogen) in Gammarus fossarum and Gammarus pulex collected from the field, with respect to their reproductive activity. 2. The dynamics of stored energy followed a seasonal pattern in both species and sexes. Moreover, over a 4‐year period, these changes were independent of the year in which they were investigated. Stored energy reached a peak in late winter, but was depleted in late summer and early autumn, coinciding with the reproductive periods. 3. Triglyceride (annual mean ± SD) accounted for 79.7 ± 11.9% of the total stored energy and was responsible for the seasonal pattern. In contrast, glycogen contributed a lesser percentage (20.3 ± 11.9%). Over the study period, the amount of stored energy ranged between 0.39 and 4.08 kJ g −1 dry mass (triglyceride: 0.19–3.69 kJ g −1 dry mass; glycogen: 0.14–0.80 kJ g −1 dry mass). 4. In both species, the energy reserves of males were drastically depleted shortly before the cessation of precopulatory mate guarding in the field, thus offering a bioenergetic explanation for the reproductive period in these two widespread species.

While terrestrial insects can usually attach directly to a substrate, for aquatic insects the situation is more complicated owing to the presence of a biofilm on the primary substrates. This important fact has been neither the subject of investigation nor commonly taken into account in the interpretation of functional aspects of attachment in mobile freshwater animals. In this study, we investigate the impact of a biofilm on the attachment of living mayfly larvae. We performed in vivo attachment experiments in a flow channel using different substrates with defined surface roughness. Additionally, we measured friction forces directly generated by dissected tarsal claws on the same substrates. On substrates with smooth or slightly rough surfaces, which have little or no surface irregularities large enough for the claws to grasp, the presence of a biofilm significantly increases the friction force of claws. Consequently, larvae can endure higher flow velocities on these smooth substrates. The opposite effect takes place on rough substrates, where the friction force of claws decreases in the presence of a biofilm. Consequently, a biofilm is a critical ecological structure for these larvae, and other aquatic organisms, not only as a food source but also as a factor influencing attachment ability.

Indices to assess the ecological status of water bodies according to the European Water Framework Directive (WFD) frequently produce widely differing results when applied to estuarine systems. Although several ecological indices have been employed to coastal environments and in estuaries in particular, there is still a lack of knowledge about their suitability for assessing the ecological status of heavily modified water bodies. Thus, we evaluated the performances of indices and fauna parameters (AMBI, M-AMBI, BOPA, BO2A, W-value, Shannon diversity, species richness, abundance) that have been discussed in the WFD context using data on invertebrates dwelling in two typical morphological units: the navigation channel and the river bank habitats of Elbe estuary (Germany). In addition, we tested their ability to identify several environmental factors (grain size distribution and chemical sediment contamination). All indices were able to detect major changes in macrofauna composition along the estuarine salinity gradient and were able to differentiate between navigation channel and shallow bank habitats. A strong significant correlation was found with most indices with the exceptions of the W-value and the BOPA with mean grain size. Almost all indices signaled poor ecological quality in the coarser fairway sediments against the finer sublitoral bank sediments. However, AMBI and BOPA showed the opposite: both indicators classified the invertebrate assemblages from the navigation channel better compare than the shallower habitats. The correlation of ecological indices and parameters with sediment contaminants and the toxicity of the sediment calculated as toxic units showed a diverse picture: all indices, except species richness and the BOPA, had a certain significant correlation with several individual sediment pollutants, however, only one index, the W-value, was correlated significant with the majority of chemical pollutants (Pb, Cd, Cu, Ni, Hg, Zn, β-HCH, pp′-DDD, and TBT) and the toxic units. Our results show clearly that ecological quality classification of heavily modified estuaries depends strongly on both the index and the habitat. Thus, we conclude that no index should be used on its own to estimate the ecological quality of estuaries. Further investigations and the improvement or development of such indices should place emphasis on their independence from the grain size spectrum of the sediments and on their good correlation with its pollution status.

Tarsal claws, which are common attachment devices in arthropods, interlock with the surface irregularities of the substrata. Most insects have two tarsal claws, but the larvae of some aquatic insects, such as Ephemeroptera and Trichoptera, bear only one claw on their tarsi. The range of surface roughness that is sufficient for the function of the single claws of aquatic invertebrates has not yet been investigated. In the present study, we investigated the surface texture required for the function of the claws of larvae of the mayfly, Epeorus assimilis. We conducted attachment experiments using replications with defined surface roughness, white light profilometry, videotaping and scanning electron microscopy. The results demonstrate that the choice of an appropriate roughness order is very important. A setting resulting in a cut-off length of approximately thirty times the diameter of the claw tip proved most appropriate for describing the roughness order that is relevant for the functioning of the claws of E. assimilis larvae. Common technical roughness parameters such as Ra, Rq or Rz supplied sufficient differentiation between the tested substrata. E. assimilis larvae require a minimum surface roughness (Ra∼6.0μm) for their claws to grip. At lesser surface roughness, the larvae left the substratum. This was surprising because E. assimilis larvae have been observed to attach even to smooth surfaces. Based on the use of sterile substrata in this experiment, we assume that coverage with biofilm considerably influences the attachment of the larvae.