Ponds, as small freshwater ecosystems, are particularly vulnerable due to their limited size. Yet they are often overlooked in research, possibly because they are considered less important (Biggs et al., 2017). Shallow water bodies support higher biodiversity than larger aquatic ecosystems. Peri-urban areas, characterized by a blend of agricultural and urban land uses, are dynamic and constantly evolving landscapes with diverse activities and stakeholders (Zoomers et al., 2017); as such, they are referred to as "restless landscapes" or zones of continual transformation (Zoomers et al., 2017). They often harbor neglected ecosystems, and despite their ecological importance, ponds and wetlands in peri-urban areas remain relatively underexplored (Wanek et al., 2021). Furthermore, these areas may experience increased contaminant inputs, which are regarded as one of the 12 major threats to freshwater biodiversity (Reid et al., 2019).

In this context, Hulot et al. (2025) monitored 12 peri-urban ponds in the Île-de-France region (near Paris, France) to investigate the relationships between land use, pollutant concentrations in water and sediment, and macroinvertebrate distribution. The originality of this work lies in its multidisciplinary and integrated approach, combining ecological and chemical analyses. While assessing agricultural, urban, grassland, and forest landscapes surrounding each pond, this study aimed to understand how contaminants constrain macroinvertebrate communities. The authors hypothesized that i) ponds in grassland and forest environments support higher local diversity than those in agricultural or urban areas, ii) rare and pollution-sensitive species significantly contribute to regional diversity, and iii) contaminants in water and sediment influence the distribution of macroinvertebrate morphotaxa.

This study provides numerous novel results. Specifically, it demonstrates that fluctuations in morphotaxa composition are predominantly driven by species replacement rather than by disparities in species richness. This pattern was largely attributed to the high prevalence of pollutant-tolerant species in certain ponds. In addition, community compositions appeared to be influenced by sediment levels of pharmaceuticals, water conductivity, and ammonium concentrations. In summary, ponds located in peri-urban areas are subject to a range of human-induced disturbances, and these results suggest that these disturbances lead to chronic and varied contamination, which in turn affects the composition of morphotaxa communities.

These findings establish a clear connection between local pollution and ecological composition, a crucial aspect for effective conservation and restoration efforts on peri-urban ponds.

References

Biggs, J., S. von Fumetti, Kelly-Quinn M. (2017). The importance of small waterbodies for biodiversity and ecosystem services: implications for policy makers. Hydrobiologia 793(1): 3-39 625. https://doi.org/10.1007/s10750-016-3007-0

Hulot, F.D., Hanot, C., Nélieu, S., Lamy, I., Karolak, S., Delarue, G., Baudry E., (2024) Do macroinvertebrate abundance and community structure depend on the quality of ponds located in peri-urban areas? ver.3 peer-reviewed and recommended by PCI Ecotoxicology and Environmental Chemistry. https://hal.science/hal-04850220v1

Reid, A. J., A. K. Carlson, I. F. Creed, E. J. Eliason, P. A. Gell, P. T. J. Johnson, 712 K. A. Kidd, T. J. MacCormack, J. D. Olden, S. J. Ormerod, J. P. Smol, W. W. Taylor, K. Tockner, J. C. Vermaire, D. Dudgeon, Cooke, S. J. 2019. Emerging threats and persistent conservation challenges for freshwater biodiversity. Biological Reviews 94(3):849-873. https://doi.org/10.1111/brv.12480

Wanek, A., C. L. M. Hargiss, J. Norland, Ellingson, N. 2021. Assessment of water quality in ponds across the rural, peri-urban, and urban gradient. Environmental Monitoring and Assessment 193: 694. https://doi.org/10.1007/s10661-021-09471-7

Zoomers, A., F. van Noorloos, K. Otsuki, G. Steel, van Westen, G. 2017. The Rush for Land in anUrbanizing World: From Land Grabbing Toward Developing Safe, Resilient, and Sustainable Cities and Landscapes. World Dev 92:242-252. https://doi.org/10.1016/j.worlddev.2016.11.016

Our ability to anticipate and estimate how pollution affects biota is intrumental in the field of ecotoxicology. Impact of chemical pollution by metals, drugs or pesticides was widely studied in different species using acute and chronic scenarios. Since the ban on tributyltin in antifouling paints, other copper (Cu)-based paints are on the market, including a new generation of booster biocides:metal pyrithiones such as Cu pyrithione (CuPT). Pyrithione acts as a Cu ionophore facilitating Cu transport across the membranes. Although some data show their occurrence in aquatic ecosystems and few studies on the toxicity of CuPT in fish are published, major gaps in knowledge remain about their toxicity and toxic pathway. Few studies were previously conducted in animals exposed to CuPT pointing to reprotoxicity, developmental malformation and mortality (Li et al. 2021, Mochida et al., 2011; Mohamat-Yusuff et al., 2018, Shin et al., 2022). However, its toxicokinetic and toxicodynamic remain to be characterized in details. 

In this context, Bourdon et al. (2023) compared in juveniles of rainbow trout (Oncorhynchus mykiss), the effects of exposure to CuPT and ionic Cu2+ at equivalent Cu2+ molar concentrations. Presented data allow to compare the toxicity threshold, the accumulation of Cu and mechanisms of toxicity of both compounds. Acute and chronic exposures showed a higher bioaccumulation of Cu in the gills, and a higher toxicity of CuPT than that of ionic Cu2+, e.g. mortality , transcription levels of genes related to oxidative stress, detoxification and Cu transport. Intriguingly, the activities of enzymatic biomarkers used as proxy of antioxidant capacity were not significantly altered, although Cu is generally expected to trigger oxidative stress. In conlusion, this study brings new knowledge pointing that the presence of CuPT in the environment could induce toxic effects in non-target species. Moreover, it support the need to study in detail the toxicity of Cu-based paints to adapt regulations concerning their use and release in aquatic environments. Because of its low solubility in water, CuPT is expected to adsorb to suspended matter and food pellets. Future research should study this route of exposure.

References

Bourdon, C., Cachot, J., Gonzalez, P., Couture, P., 2023. Characterization of the bioaccumulation and toxicity of copper pyrithione, an antifouling compound, on juveniles of rainbow trout,  bioRxiv  ver. 3 peer-reviewed and recommended by Peer Community in Ecotoxicology and Environmental Chemistry. https://doi.org/10.1101/2023.01.31.526498

Li, X., S. Ru, H. Tian, S. Zhang, Z. Lin, M. Gao and J. Wang, 2021. Combined exposure to environmentally relevant copper and 2,2′-dithiobis-pyridine induces significant reproductive toxicity in male guppy (Poecilia reticulata). Science of the Total Environment 797, https://doi.org/10.1016/j.scitotenv.2021.149131

Mochida, K., Amano, H., Onduka, T., Kakuno, A., Fujii, K., 2011. Toxicity and metabolism of copper pyrithione and its degradation product, 2,2’-dipyridyldisulfide in a marine polychaete. Chemosphere 82, 390–397, https://doi.org/10.1016/j.chemosphere.2010.09.074

Mohamat-Yusuff, F., Sarah-Nabila, Ab.G., Zulkifli, S.Z., Azmai, M.N.A., Ibrahim, W.N.W., Yusof, S., Ismail, A., 2018. Acute toxicity test of copper pyrithione on Javanese medaka and the behavioural stress symptoms. Marine Pollution Bulletin 127, 150–153, https://doi.org/10.1016/j.marpolbul.2017.11.046

Shin, D., Y. Choi, Z. Y. Soon, M. Kim, D. J. Kim and J. H. Jung, 2022. Comparative toxicity study of waterborne two booster biocides (CuPT and ZnPT) on embryonic flounder (Paralichthys olivaceus). Ecotoxicology and Environmental Safety 233, https://doi.org/10.1016/j.ecoenv.2022.113337

In recent years, the use of environmental DNA (eDNA) to investigate biodiversity has gained considerable interest (Thomsen and Willerslev, 2015; Mauvisseau et al., 2022). It allows for the indirect detection of species but it requires a sound understanding of eDNA behaviour and persistence in the environment. This is, however, a complex task because eDNA may be found in several states (e.g., dissolved, adsorbed, intracellular or intraorganellar), which display specific decay rates controlled by environmental factors (Harrisson et al., 2019; Mauvisseau et al. 2022). In the environment, dissolved DNA may interact with the surfaces of various sorbents, including mineral and organic particles/colloids. Current knowledge on eDNA sorption suggests that eDNA–sorbent interactions are controlled by electrostatics as well as inner-sphere complex formation (Mauvisseau et al., 2022). 

In this context, the work undertaken by Jelavic et al. (2022), focused on the adsorption of eDNA by lesser-investigated carbonaceous materials (CMs), namely soot and charcoal, as common non-mineral environmental surfaces. 

The authors aimed to study the adsorption capacity of soot and charcoal surfaces with respect to eDNA, in relation to solution parameters (i.e., pH, ionic strength, concentration/type of cations), time and eDNA length, under both non‐equilibrium and equilibrium conditions. Using such an approach, Jelavic et al. demonstrated the large adsorption capacities of CMs and the strong binding of DNA to these sorbents. The authors did not provide definitive conclusions on the mechanisms of eDNA sorption onto CMs. However, they provided new elements suggesting that, along with electrostatic interactions, hydrophobic interactions might play an important role in the adsorption of eDNA to CMs such as soot and charcoal. 

Altogether, the results presented in this paper highlight the relevance of CMs as sources of biodiversity information. In addition, it is likely that those results will also prove useful for the community to improve protocols for eDNA extraction from environmental samples that contain high fractions of CMs, e.g. urban soils. 

References

Harrison JB, Sunday JM, Rogers SM (2019) Predicting the fate of eDNA in the environment and implications for studying biodiversity. Proceedings of the Royal Society B: Biological Sciences, 286, 20191409. https://doi.org/10.1098/rspb.2019.1409

Jelavic S, Thygesen LG, Magnin V, Findling N, Müller S, Meklesh V, Sand KK (2022) Soot and charcoal as reservoirs of extracellular DNA. ChemRxiv, ver. 5 peer-reviewed and recommended by Peer Community in Ecotoxicology and Environmental Chemistry. https://doi.org/10.26434/chemrxiv-2021-9pz8c-v5

Mauvisseau Q, Harper LR, Sander M, Hanner RH, Kleyer H, Deiner K (2022) The Multiple States of Environmental DNA and What Is Known about Their Persistence in Aquatic Environments. Environmental Science & Technology, 56, 5322–5333. https://doi.org/10.1021/acs.est.1c07638

Thomsen PF, Willerslev E (2015) Environmental DNA – An emerging tool in conservation for monitoring past and present biodiversity. Biological Conservation, 183, 4–18. https://doi.org/10.1016/j.biocon.2014.11.019