International audience | Sound emissions from human activities represent a pervasive environmental stressor. Individual responses in terms of behaviour, physiology or anatomy are well documented but whether they propagate through nested ecological interactions to alter complex communities needs to be better understood. This is even more relevant for freshwater ecosystems that harbour a disproportionate fraction of biodiversity but receive less attention than marine and terrestrial systems. We conducted a mesocosm investigation to study the effect of chronic exposure to motorboat noise on the dynamics of a freshwater community including phytoplankton, zooplankton, and roach as a planktivorous fish. In addition, we performed a microcosm investigation to test whether roach’s feeding behaviour was influenced by the noise condition they experienced in the mesocosms. Indeed, compared to other freshwater fish, the response of roach to motorboat noise apparently does not weaken with repeated exposure, suggesting the absence of habituation. As expected under the trophic cascade hypothesis, predation by roach induced structural changes in the planktonic communities with a decrease in the main grazing zooplankton that slightly benefited green algae. Surprisingly, although the microcosm investigation revealed persistent alterations in the feeding behaviour of the roach exposed to chronic noise, the dynamics of the roach-dominated planktonic communities did not differ between the noisy and noiseless mesocosms. It might be that roach’s individual response to noise was not strong enough to cascade or that the biological cues coming from the conspecifics and the many planktonic organisms have diverted each fish’s attention from noise. Our work suggests that the top-down structuring influence of roach on planktonic communities might be resilient to noise and highlights how extrapolating impacts from individual responses to complex communities can be tricky.

The present study investigated temporal influences on metal distribution in gudgeon (Gobio gobio) and roach (Rutilus rutilus), and its relation to condition metrics and fish community structure. Fish communities were sampled in two seasons (autumn and spring) during two successive years and the Index of Biotic Integrity (IBI) was calculated. Cadmium, Cu, Pb, Zn and As concentrations were measured in gill, liver, kidney and muscle, and condition factor (CF) and hepatosomatic index (HSI) were measured. Cadmium (max. 39.0 μg g−1 dw) and Zn (max 2502 μg g−1 dw) were most strongly stored in kidney and liver and periodical influences on metal accumulation were observed. CF appeared to be a stable metric related to accumulated metal-mixtures and was best related to hepatic levels, while the HSI was less useful. Relations between single metal accumulation and IBI were influenced by sample period, however, when taking into account multiple metals periodical influences disappeared.

A large variety of anthropogenic chemicals present in the aquatic environment have been shown to be able to alter the endocrine system of exposed organisms, potentially impacting their reproductive function. The aim of this study was to assess the effects of environmental pollution on the reproductive system of wild female roach (Rutilus rutilus) from the Seine River (Normandy, France). A suite of biomarkers of endocrine disruption including gonado-somatic index, plasmatic vitellogenin, gonadal aromatase activity and histological parameters (oocyte diameter and gonad maturation) were studied. Female fish from the polluted sites showed a number of reproductive alterations, including inhibited gonad maturation, reduced oocyte growth, reduced levels of plasmatic vitellogenin and 3-fold lower gonadal aromatase activity than females collected in the reference site. Overall, these results highlight the presence of endocrine disruption in female roach from the Seine River.

Organochlorine pollutants in the major fish species (pike Esox lucius, perch Perca fluviatilis, and roach Rutilus rutilus) of Lake Årungen, Norway, were investigated after an extensive removal of large pike in 2004. The organochlorine pollutants detected in fish liver samples in 2005 were dichlorodiphenyltrichloroethane (DDTs), polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), and heptachlor epoxide (HCE). DDTs were the dominant among all analyzed OCs. ΣPCB and HCB, detected in fish from two clearly distinct trophic levels (prey and predators), give an indication of biomagnification. All OC concentrations in female pike were significantly lower compared to males, which might be due to the removal of high concentrations of pollutants in roe during spawning. Organochlorine pollutants in fish tissues tend to magnify up the food chain.

Microplastics are widespread throughout aquatic environments. However, there is currently insufficient understanding of the factors influencing ingestion of microplastics by organisms, especially higher predators such as fish. In this study we link ingestion of microplastics by the roach Rutilus rutilus, within the non-tidal part of the River Thames, to exposure and physiological factors. Microplastics were found within the gut contents of roach from six out of seven sampling sites. Of sampled fish, 33% contained at least one microplastic particle. The majority of particles were fibres (75%), with fragments and films also seen (22.7% and 2.3% respectively). Polymers identified were polyethylene, polypropylene and polyester, in addition to a synthetic dye. The maximum number of ingested microplastic particles for individual fish was strongly correlated to exposure (based on distance from the source of the river). Additionally, at a given exposure, the size of fish correlated with the actual quantity of microplastics in the gut. Larger (mainly female) fish were more likely to ingest the maximum possible number of particles than smaller (mainly male) fish. This study is the first to show microplastic ingestion within freshwater fish in the UK and provides valuable new evidence of the factors influencing ingestion that can be used to inform future studies on exposure and hazard of microplastics to fish.

It is a common method to analyse physiological mechanisms of organisms – commonly referred to as biomarkers – to indicate the presence of environmental pollutants. However, as biomarkers respond to a wide range of stressors we want to direct the attention on natural stressors, i.e. on parasites. After two years maintenance under controlled conditions, roach (Rutilus rutilus) revealed no influence on levels of metallothionein by the parasite Ligula intestinalis. The same was found for Gammarus fossarum infected with Polymorphus minutus. However, the heat shock protein (HSP70) response was affected in both host-parasite systems. While the infection of roach resulted in reduced levels of HSP70 compared to uninfected roach, the infection in G. fossarum led to higher levels of HSP70. We also analysed the effect of a 14 days Cd exposure (4 μg/L) on the uninfected and infected gammarids. The exposure resulted in induced levels for both, metallothionein and HSP70 whereas the combination of stressors, parasite and exposure, revealed a decrease for levels of HSP70 in comparison to the metal exposure only. Accordingly, parasites as natural parts of aquatic ecosystems have to be considered in ecotoxicological research.

Concerns about the negative effects of microplastics (MPs) on human health have led to increasing attention to the occurrence of MPs in the aquatic environment. Recent studies have focus on the spatio-temporal distribution of MPs in rivers for residential and agricultural areas. Qarasu River Basin, watershed to Gorgan Bay, is the site of many permanent rivers and the levels of MP pollution in those rivers are unknown. This research was conducted in three different types of land use: forest, residential, and agricultural along 8 different rivers. A total of 9 fish species were identified and the presence of MPs in 87% of fish was confirmed. The prevalence of MP among species was Liza sp. > Carassius gibelio > Gambusia holbrooki > Rutilus rutilus > Neogobius melanostomus > Cyprinus carpio = Vimba vimba > Rutilus frisii > Barbus sp. The highest frequency of MPs was observed in Qarasu River (1880 ± 251 n/kg) and Mohammadabad River (184 ± 1340 n/kg) in agricultural land use, and the lowest frequency was related to Baghu and Ziarat Rivers with 660 ± 77 and 600 ± 91 n/kg found in forest land use respectively. The highest type, color, and size of MP sediments were fragment, black, and 1–2 mm, respectively. The highest type, color, and size of MP in fishes were fiber, black, and 0.5–0.1 mm respectively. Overall according to the source tracing result, agricultural land use was the main source of MP pollution of Gorgan Bay. The Bay is strongly affected by the incoming rivers, the Qarasu River Basin as the most important river supplying water.

Aluminium is used in diverse anthropogenic processes at the origin of pollution events in aquatic ecosystems. In the Champagne region (France), high concentrations of aluminium (Al) are detected due to vine-growing practices. In fish, little is known about the possible immune-related effects at relevant environmental concentrations. The present study analyzes the simultaneous effects of aluminium and bacterial lipopolysaccharide (LPS), alone and in combination, on toxicological biomarkers in the freshwater fish species Rutilus rutilus. For this purpose, roach treated or not with LPS were exposed to environmental concentrations of aluminium (100 μg/L) under laboratory-controlled conditions for 2, 7, 14 and 21 days. After each exposure time, we assessed hepatic lipoperoxidation, catalase activity, glutathione reductase activity and total glutathione content. We also analyzed cellular components related to the LPS-induced inflammatory response in possible target tissues, i.e. head kidney and spleen. Our results revealed a significant prooxidant effect in the liver cells and head kidney leukocytes of roach exposed to 100 μg of Al/L for 2 days. In liver, we observed more lipoperoxidation products and lower endogenous antioxidant activity levels such as glutathione reductase activity and total glutathione content. These prooxidant effects were associated with a higher oxidative burst in head kidney leukocytes, and they were all the more important in fish stimulated by LPS injection. These findings demonstrate that environmental concentrations of Al induce oxidative and immunotoxic effects in fish and are associated to an immunomodulatory process related to the inflammatory response.

The reproduction of vertebrates is regulated by endocrine and neuro-endocrine signaling molecules acting along the brain-pituitary-gonad (BPG) axis. The understanding of the neuroendocrine role played in reproductive function has been recently revolutionized since the KiSS1/GPR54 (KiSS1r) system was discovered in 2003 in human and mice. Kisspeptins, neuropeptides that are encoded by the KiSS genes, have been recognized as essential in the regulation of the gonadotropic axis. They have been shown to play key roles in puberty onset and reproduction by regulating the gonadotropin secretion in mammals while physiological roles in vertebrates are still poorly known. In order to provide new knowledge on basic reproductive physiology in fish as well as new tools to assess impacts of endocrine disrupting compounds (EDCs), the neurotransmitter system, i.e., gene/receptor, KISS/GPR54 might constitute an appropriate biomarker. This study provides new understandings on the neuroendocrine regulation of roach reproduction as well as new molecular tools to be used as biomarkers of endocrine disruption. This work completes the set of biomarkers already validated in this species.