Aquatic publication review (30)

The current review of aquatic scientific publications includes several works from our backyard. After all, Poles are not geese. In an article published in Ecohydrology & Hydrobiology, scientists from Silesia present the results of an intriguing study, which is another piece of the complicated puzzle on the ecology of Prymnesium parvum. The Lodz center, on the other hand, proves that the use of nature-based solutions to reduce nutrients and suspended solids in the waters of urban rivers is sensible and effective in urban areas as well, even with the surface limitations present there. Unfortunately, in addition to nutrients, chemical pollutants are a major problem for urban watercourses. Portuguese scientists point to more than 100 pharmaceuticals detected in urban streams that can have significant negative effects on aquatic organisms.

Did you know that the experience of flooding significantly increases the risk of infant mortality, and this effect can persist up to 4 years after the disaster? This is confirmed by the results of studies conducted on African countries. We also ask whether, in the face of climate change, we have an impact on the increased risk of algal blooms in lakes. Dutch scientists prove that yes. We just need to prioritize nutrient and climate management on political agendas. And we can’t forget about hydromorphology, because lakes with reduced buffer capacity will be subject to eutrophication faster, as studies of lakes from the Polish lake districts prove.

1. the reaction of Prymnesium parvum to a sudden salinity decrease

Woznica A., Karczewski J., Lipowczan M. et al. (2024). The reaction of Prymnesium parvum to a sudden salinity decrease, Ecohydrology & Hydrobiology.

A lot of water has passed since the catastrophe in the Oder River in the summer of 2022, but the problem of the presence of Prymnesium parvum in this river ecosystem does not give peace of mind. The haptophyte, known as the “golden alga,” is a mysterious organism whose mechanisms of functioning, ecology and physiology are still very poorly understood. The alga produces many cytotoxic metabolites, which is why large-scale die-offs of fish and other gill-bearing organisms are observed during its massive blooms. Unfortunately, so far we do not know what causes the sudden release of toxins from algal cells.

The team of Silesian scientists hypothesized that osmotic pressure was the key, and conducted an experiment, exposing P. parvum cells to water of decreasing salinity, in the range of specific electrolytic conductivity from 2970 to 250 µS/cm (the value recorded in the Gliwice Canal during the intake of P. parvum for the experiment).

At a practical salinity value of 0.68 (corresponding to a conductivity of 1330 µS/cm), an increase in osmotic pressure to 360 hPa after just 10 minutes of exposure caused an average doubling of cell volume, as well as cell rupture and the release of huge quantities of small particles into the water. These particles are probably responsible for the mass death of gill-breathing organisms. The study’s authors conclude from this that the survival of P. parvum depends on the homeostasis of water salinity, which is considered to be satisfied above a practical salinity value of 0.88 (1,700 µS/cm).

2. stormwater treatment in constrained urban spaces through a hybrid Sequential Sedimentation Biofiltration System

Jarosiewicz P., Font-Najera A., Mankiewicz-Boczek J. et al. (2024). Stormwater treatment in constrained urban spaces through a hybrid Sequential Sedimentation Biofiltration System. Chemosphere; 367: 143696.

Surface runoff from urban areas carries a lot of dangerous pollutants and poses a serious threat to water quality. Their effective treatment remains a challenge. In addition to hard engineering methods, hydroecologists are looking to nature-based solutions (NbS) to solve this problem. But with limited space and the possibility of applying these solutions in urban areas, will their effectiveness in cleaning up water be enough to invest in them? Researchers from centers in Lodz and Rome tested this by testing the suspended solids and nutrient removal performance of a new hybrid sedimentation biofiltration system SSBS (Sequential Sedimentation Biofiltration Systems). The system was installed along the Mleczna River in Radom, which drains rainwater into the Radomka River.

The system was adapted to the existing stormwater infrastructure by integrating a sedimentation basin (SED), three permeable reactive barriers (PRB) and a biofiltration zone (BIO). Due to space limitations and a high hydraulic loading rate (HLR = 1.31 m/d), sediment removal in the SED and PRB was limited, yielding an average suspended solids reduction of 13.6 percent. However, the PRBs showed effective removal of ammonia (43.4 percent) and phosphate (59.3 percent). The BIO zone further increased nutrient retention (56 percent orthophosphate) and suspended solids (52 percent).

The study highlights the potential of integrating traditional urban infrastructure with NbS in a sequential rainwater treatment system, demonstrating its effectiveness in space-constrained urban environments. As our domestic scientists have been proving for years, all it takes is some limestone rock, dolomite, absorbent and macrophytic vegetation for biofiltration to help our waters. Also in the city.

3 Pharmaceuticals in urban streams: A review of their detection and effects in the ecosystem

Rodrigues Fernanda, Durães Luisa, Simões Nuno E.C et al(2025). Pharmaceuticals in urban streams: A review of their detection and effects in the ecosystem. Water Research, 268, 122657.

Biogens and suspended solids are only part of the problem for rivers, especially in cities. Based on a review of more than 200 publications on pharmaceutical pollution and the impact of these compounds in 49 urban streams and creeks located in 13 countries on four continents, the researchers found 139 pharmaceuticals from 10 therapeutic groups. Anti-inflammatory and anticonvulsant drugs proved to be the most common substances.

Of the substances identified, 17β-estradiol, estriol, estrone, acetaminophen, caffeine, carbamazepine, diltiazem, diphenhydramine, fluoxetine, norfluoxetine, sertraline, desmethylsertraline, methylphenidate and ciprofloxacin have the greatest effects on aquatic organisms. The effects ranged from bioaccumulation, endocrine disruption, impaired growth, reproductive inhibition, increased mortality and reproductive disorders to morphological changes and reduced gross primary production and biomass.

Despite a significant increase in the number of publications on pharmaceutical contamination of surface water in recent years (up 43 percent between 2019 and 2023), the problem – especially in urban streams – is still not well recognized. Contributing to this is the insufficient frequency of analysis of these metabolites, ineffective treatment of urban wastewater with respect to pharmaceuticals, and insufficient research on the effects of pharmaceuticals on aquatic communities/populations.

4 Burden of infant mortality associated with flood in 37 African countries

Zhu Y., He C., Bachwenkizi J. et al. (2024). Burden of infant mortality associated with flooding in 37 African countries. Nat Commun 15, 10171.

Floods are accompanied by many negative consequences, but the aspect that the authors of the article in Nature Communication analyzed and presented, I must admit, was quite surprising to me. Using an extensive database of demographic and health data from Africa from 1990-2020, they conducted a case-control study of the impact of floods on infant mortality (children under one year of age). Analysis of more than 500,000 data showed an increased risk of infant mortality associated with flood exposure at various time intervals, with the risk remaining elevated until four years after the disaster.

Overall, between 2000 and 2020 in Africa, 3.42 excess infant deaths per 1,000 births could be associated with an average 5-year flood exposure, a rate 1.7 times higher than the burden of lifetime flood exposure (2 deaths per 1,000 births). This study provides new evidence that flood events can increase the risk and burden of infant mortality, even for many years after the event. The relationship between the two can be explained in several ways. First and foremost will be drowning and severe injuries, but also potential water and soil pollution, as well as mental health problems, including post-traumatic stress disorder (PTSD) and depression, which can make it difficult for mothers to care for themselves, and consequently increase the risk of infant mortality.

The study is, admittedly, about African countries, but it is not excluded that similar correlations may be occurring in other areas of the world. For example, the great flood in Nepal in 1993 caused a nearly sixfold increase in the child mortality rate, as did the 2004 tsunami disaster in Sri Lanka, which significantly increased the mortality rate among children under the age of 5. A study in Fiji found that the mortality rate for children living in flooded areas is as high as 16.5 per 1,000 children.

5. the future of algal blooms in lakes globally is in our hands

Tigli M., Bak M. P., Janse J. H. et al. (2025). The future of algal blooms in lakes globally is in our hands. Water Research, 268, 122533.

We wrote about the impact of climate warming and the effects of the disappearance of ice phenomena on lakes in Water Matters quite recently. Whether the lack of ice on lakes is a beneficial phenomenon or not, and for whom, can be debated. However, it doesn’t change the fact that higher average temperatures lead to an increase in the likelihood and intensity of algal blooms, and this is already a definite disadvantage for everyone (except perhaps the algae themselves). Clear fluctuations in chlorophyll a (Chl-a) concentrations have been observed in recent decades, and numerous studies indicate that they are determined by two primary factors: increases in nutrient loads (nitrogen and phosphorus) and the effects of climate change. Despite this, we know little about the future trends of algal blooms in lakes around the world and the relative role of each of these factors.

The problem was tested by Dutch researchers at Wageningen University. Combining two models – the process-based PCLake model and the MARINA-Multi catchment model – they examined future trends of algal blooms for more than 3,500 representative lakes around the world, accounting for biogenes and climate variables. The authors tested two contrasting scenarios of climate and socioeconomic development through 2050: fossil fuel-based development (RCP8.5-SSP5) and sustainable development (RCP2.6-SSP1), taking the state in 2010 as a baseline. The risk of algal blooms was analyzed based on the Carlson Trophic State Index, calculated from chlorophyll-a (TSI-Chla).

The results show an increasing trend of algal blooms between 2010 and 2050 under the fossil fuel-based development scenario (TSI-Chla increase in 91 percent of lakes) and a decreasing trend under the sustainable development scenario (TSI-Chla decrease in 63 percent of lakes). These changes are largely related to nutrient availability, while climatic variables, although not always significant, favor the deterioration of lake water quality. The results of the study point to the need to prioritize responsible nutrient and climate management on policy agendas. They also confirm that the future of algal blooms in lakes is largely in our hands.

6. hydromorphological pressure explains the status of macrophytes and phytoplankton less effectively than eutrophication but contributes to water quality deterioration

Kutyła S., Kolada A., Ławniczak-Malińska A., (2025). Hydromorphological pressure explains the status of macrophytes and phytoplankton less effectively than eutrophication but contributes to water quality deterioration. Water Research, 268, 122669.

We are used to the idea that the main factor causing the deterioration of lake water quality is the excessive supply of nutrients leading to accelerated eutrophication. And this is true. However, it should be remembered that a whole range of other pressures, including hydromorphological transformations, add to the degradation of lake ecosystems. Admittedly, in the case of lakes (especially Polish lakes), these may seem insignificant compared to the hydromorphological transformation of rivers, yet it turns out that this is not such a marginal problem.

Analysis of biological (phytoplankton and macrophyte indices), physicochemical and hydromorphological data from 30 lowland lakes of Poland showed that both biological elements and water quality parameters significantly correlated with the hydromorphological index of lake transformation LHMS_PL. Admittedly, hydromorphological pressures explained only a small part (5.5 percent) of the variation in ecological status assessed using macrophytes and had no direct effect on ecological status assessed using phytoplankton, but the joint effect of physicochemistry and hydromorphology explained a significant part of the variation in ecological status indicators based on these two assemblages.

In addition, hydromorphological changes were usually associated with increased nutrient concentrations. This means that physical changes can affect the biological complexes of lakes not only directly, but primarily indirectly, reducing the natural buffering capacity of the ecosystem and thus contributing to the intensification of the eutrophication process.