Aquatic publication review (25)

Poor these waters of ours, oh poor! From whichever side you look, we see the negative effects of anthropogenic pressure everywhere. Much has already been said about the anthropogenic salinity of rivers, but recent studies show that unnatural changes in the salinity of waters can significantly modify the thermal tolerance of the organisms that inhabit them. This means that salinity and climate warming affect ecosystems interactively. We have more examples of the synergistic effect of different pressures. Studies of water samples from the Oder River indicate that a chemical cocktail of micropollutants in that river’s waters in the summer of 2022. may have increased the negative effects of prymnesins produced by the familiar golden haptophyte.

Another problem is antibiotics – there are more and more of them in the waters, and their effects on organisms are varied and difficult to predict. If the waters are so degraded, how do we know what they should be? Paleoecological methods can come to the rescue in determining the target (reference) state when taking corrective measures. As an example, we cite the study of phosyllous remains from cores taken in the oxbow lakes of Drava (the Croatian one). And finally, a humorous touch, that is, what the study of a dead trout will tell us about swimming fish. The answer in an article by this year’s Ig Nobel laureate.

1 Influence of salinity on the thermal tolerance of aquatic organisms

Farias L., Beszteri B., Castellanos A. M. B. et al. (2024). Influence of salinity on the thermal tolerance of aquatic organisms. Science of The Total Environment, 953, 176120.

It has not been known for a long time that nature is an interconnected system of vessels, and various anthropogenic pressures can affect ecosystems in complex ways, showing mutual interactions. We have already written about the fact that salinity in surface waters promotes their eutrophication, but it turns out that it also affects the thermal tolerance of organisms. Based on a meta-analysis of more than 10,000. literature reports (including 90 with the required range of data), the researchers compared the thermal tolerance (optimal temperatures, lower and upper limits, and thermal ranges) of freshwater, brackish-water and marine organisms (including algae, macrophytes, heterotrophic protists, parasites, invertebrates and fish) at different ranges of water salinity.

In the brackish and marine ecosystems that dominated the database, decreases in salinity led to significant increases in lower and decreases in upper temperature limits, regardless of the group of organisms analyzed. Although the number of studies on freshwater species was limited, they showed a negative, though statistically insignificant, effect of increased salinity on the thermal tolerance of species. The overall sensitivity of thermal tolerance to salinity changes followed the order of algae > invertebrates > fish, although differences in response between the two were found to be statistically insignificant. The authors also showed that the temperature tolerance of aquatic invertebrates and fish is modified by parasitic infections. These results support the hypothesis that energetically costly osmoregulation in response to salinity changes can reduce the thermal tolerance of aquatic organisms.

2. Mixtures of organic micropollutants exacerbated in vitro neurotoxicity of primnesins and contributed to aquatic toxicity during a toxic algal bloom

Escher B.I., Ahlheim J., Böhme A. et al. (2024). Mixtures of organic micropollutants exacerbated in vitro neurotoxicity of primnesins and contributed to aquatic toxicity during a toxic algal bloom. Nat Water.

Confirmation of the complex and interactive effects of water pollution on organisms is also provided by another study, conducted by scientists at Berlin’s Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB). Its goal was to determine the effects of polluted water, taken from the Oder River during the August 2022 mass fish die-off, on aquatic organisms (i.e., algae, daphnia and fish embryos without developed functional gills) and human cell lines. The researchers aimed to study the interaction of complex mixtures of prymnesins and micropollutants extracted from water, fish biomass and particulate matter, and to determine how micropollutants can exacerbate the toxic effects of algal metabolites.

More than 120 organic micropollutants were found in the samples analyzed, in addition to B-type primenazines. They occurred at concentrations at which the predicted risk factor for aquatic life would exceed acceptable thresholds. Water, biomass and particulate extracts produced moderate in vivo effects in algae, daphnia and zebrafish embryos, but large effects on human neuronal cells, indicating the presence of neurotoxins. Modeling of the toxicity of the mixtures showed that the in vitro neurotoxic effects were mainly due to B-type primnesins with a minor contribution from organic micropollutants. An inadequate understanding of the complex interactions between natural and anthropogenic toxins can lead to a significant underestimation of their actual risks to aquatic ecosystems.

3 Assessment of ecological risks posed by veterinary antibiotics in European aquatic environments: A comprehensive review and analysis

Albarano L., Suarez E.G.P., Maggio Ch. et al. (2024). Assessment of ecological risks posed by veterinary antibiotics in European aquatic environments: A comprehensive review and analysis. Science of The Total Environment, 954, 176280,

The widespread use of antibiotics in medical treatment has led to an increase in environmental pollution by these substances, which generates serious risks to human health and ecosystems. Antibiotics enter the aquatic environment mainly through human and animal excretions, improper drug disposal, inadequate wastewater treatment, and the influx of waste from manufacturing plants. Since these compounds are only partially removed by conventional wastewater treatment plants, they continuously enter the environment.

Despite a growing body of research, understanding of the ecological and health effects of these contaminants remains inadequate. A review of the issue prepared by a team of Italian scientists presents a comprehensive analysis of the risk assessment of veterinary antibiotics in aquatic environments in Europe, where concentrations of these substances range from micrograms to milligrams per liter. An analysis of the toxicity of antibiotics from more than a dozen classes revealed varying degrees of harm and different effects on various fresh- and saltwater organisms. Antibiotics from the group of aminoglycosides, β-lactams, fluoroquinolones, macrolides and tetracyclines show elevated levels of toxicity to some autotrophic microorganisms.

Macrolides and fluoroquinolones showed particularly high toxicological risks in various aquatic environments. The study’s authors identify tetracyclines, fluoroquinolones, sulfonamides and macrolides as priority compounds due to their prevalence and potential negative effects on organisms. In conclusion, each class of antibiotics creates its own set of ecological challenges, which significantly complicates taking mitigation measures and means that managing the risks associated with their presence in the aquatic environment requires a comprehensive and multifaceted approach.

4. Long-term ecological studies on the oxbow ecosystems development and fire history in the Drava river valley (Central Europe): Implications for ecological restoration

Galka M., Apolinarska K., Bubak I. et al. (2024). Long-term ecological studies on the oxbow ecosystems development and fire history in the Drava river valley (Central Europe): Implications for ecological restoration. Progress in Physical Geography: Earth and Environment, 0(0).

Old riverbeds are an important part of the landscape and hydrographic network, provide habitat for many rare and protected aquatic and marsh organisms, and play an important role as floodplain pollution stores. Unfortunately, as a result of land reclamation works and modification of river channels, many oxbow lakes have been destroyed. Thanks to the use of paleoecological analyses, it becomes possible to identify the succession of the fauna and flora of these valuable ecosystems over the centuries and millennia, as well as to determine their reference conditions, i.e. the state untransformed by human activities.

An interdisciplinary team of Polish scientists, in cooperation with experts from Hungary, Germany and Egypt, examined fossil remains (plant macrofossils, pollen, mollusks, oligochaetes, diatoms, traces of charcoal as traces of fires) from profiles taken from two oxbow lakes of the Drava River (not to be confused with our native Drava, here it is a tributary of the Danube), located in Croatia. Paleoecological analyses, supported by radioactive carbon dating, allowed us to determine a reference taxonomic composition of organism assemblages, which should serve as a reference for the restoration of oxbow lakes in the region.

They also allowed tracing their history, including in the context of human impacts, i.e. indicating periods of transformation into peatlands as a result of the process of landforms in the warm phases of climate (Roman period, medieval period), anthropogenic changes in the taxonomic composition of riverine forests in the medieval period, or the intensity of fires resulting from the history of colonization of the Drava River valley. Paleoecological studies provide important support in understanding the functioning of aquatic ecosystems, reconstructing their history and restoring them to their pre-destructive human impact.

5. neuromuscular control of trout swimming in a vortex street: implications for energy economy during the Kármán gait

Liao J.C. (2004). Neuromuscular control of trout swimming in a vortex street: implications for energy economy during the Kármán gait. J Exp Biol., 207 (20): 3495-3506.

Let me warn you right away that the year of publication of the last item in today’s list is not a mistake at all. For those who wonder why we are presenting the results of a study from 20 years ago, I hasten to explain. Well, the author of this study, American biologist James C. Liao, has just been awarded the IG Nobel Prize in Physics for demonstrating and explaining the ability of dead trout to swim. The ceremony for these unique awards was held on the night of September 12-13 this year. for the 34th time. Of the research in the 10 award-winning fields, this is the one we thought was most interesting from the perspective of the hydrophilic reader.

In his work, Liao analyzed how fish behave in turbulent waters. Comparing the kinetic characteristics of living and dead individuals of rainbow trout(Oncorhynchus mykiss), he showed that living fish can temporarily adopt a Kármán gait (a way of moving fish that adjusts their body wavelength and lateral translation to the frequency of the von Kármán vortex) without activating their axial muscles. This means that (like dead fish) they have the ability to move passively against the turbulent flow. Thus, the winner of this year’s IG Nobel Prize proved that in a current full of eddies, the bodies of living and dead fish arrange themselves in the same way.