Aquatic publication review (27)

Is climate warming affecting the spread of alien species? The results of research on the occurrence of alien aquatic plants in Poland seem to clearly support this hypothesis, at least for several of the 15 identified neophyte aquatic taxa. Hydrophytes deserve special attention because they are excellent at removing pollutants from waters. Of course, different species show varying effectiveness in removing particular substances, as we can read about in the paper by Scottish scientists. It is also interesting to read about the impact of climate change on the possibility of achieving environmental goals in accordance with the WFD.

In a changing climate, won’t they become a bunny that we won’t be able to catch up with? We also present an intriguing literature review that aims to verify the circulating view of the role of forests in preventing hydrological droughts. It turns out that the relationship between vegetation cover and water flows is not so simple, and everything depends on the specific conditions of a particular case.

1. Alien Aquatic Plants in Poland: Temporal and Spatial Distribution Patterns and Effects of Climate Changes.

Draga M., Szczęśniak E., Rosadziński S. et al. (2024). Alien Aquatic Plants in Poland: Temporal and Spatial Distribution Patterns and Effects of Climate Changes. Global Ecology and Conservation, 55, e03247

The distribution of alien aquatic plant species in European inland waters, as well as the influence of climatic factors on their expansion, are not yet well understood. Polish hydrobiologists from several academic centers have taken up the challenge of studying this problem in our country. On the basis of published and unpublished data from the last 70 years, they have inventoried alien macrophyte species, analyzed temporal and spatial changes in their distribution and the influence of climate on occurrence and diversity.

As a result of the search, 15 alien aquatic plant taxa (neophytes) were identified in Polish inland waters, including 14 species and one collective Nymphaea taxon (cultivars). The most frequently occurring species is the Canadian soak Elodea canadensis (more than 25,000 listings). Next in the ranking are the delicate soak E. nuttallii, the fern azolla Azolla filiculoides and the turion lash Lemna turionifera (a total of more than 300 listings). Ten species occurred only in isolated sites. Analyses showed a significant increase in the number of aquatic neophyte sites over the past 20 years, which can be linked to increased average monthly and annual air temperatures in Poland.

The authors showed a strong relationship between elevated average temperatures in Poland and the spread of some species, such as Azolla filiculoides, while others, such as Elodea nuttallii and Lemna turionifera, showed no dependence on this factor. Three species(Vallisneria spiralis, Pontederia crassipes and Hygrophila polysperma) occurred only in waters with anthropogenically elevated temperatures (thermally polluted), so their range was limited to specific areas or objects. The results of the study confirm the relationship between thermal conditions of freshwater ecosystems and the distribution of alien aquatic plants.

2. multi-pollutant removal dynamics by aquatic plants in monoculture or mixed communities

Fletcher J., Willby N.J., Oliver D.M., Quilliam R.S. (2024). Multi-pollutant removal dynamics by aquatic plants in monoculture or mixed communities. Environmental Research, 263, 120041

Research on the potential of aquatic and marsh vegetation to remove contaminants (phytoremediation) often focuses on single substances and single plant species. But how would it work in multi-species systems when contaminated with multiple substances? Scottish researchers at the University of Stirling studied the effectiveness of eleven pollutants (biogenes and trace metals) removal byfloating treatment wetlands(FTW) islands planted with three species of monocotyledonous marsh plants(Typha latifolia, Glyceria maxima and Phragmites australis) in varying proportions. FTW systems are a type of hydroponic cultivation, where macrophytes are planted on floating, artificial platforms. They are gaining popularity as an aesthetically pleasing and effective way to remove pollutants from standing water through uptake and sequestration of substances in plant tissues or degradation in the root zone.

The most effectively removed contaminants were total inorganic nitrogen (TIN), potassium (K) and manganese (Mn), while removal of phosphorus (P), zinc (Zn) and copper (Cu) was moderate. The weakest removal was of magnesium (Mg), calcium (Ca), sodium (Na), chromium (Cr) and iron (Fe). FTWs with broadleaf scabious showed the highest efficiency, although the taxonomic composition of the vegetation was most important for Zn removal, while it was less important for TIN, Mg, K and Na. Sequestration in plant tissues was significant for reducing concentrations of Mn, TIN, P and Fe.

Importantly, the removal efficiency of some contaminants (e.g. Cu) increased with water retention time. In general, FTWs show more effective performance in areas where water flow is slowed, such as in ponds or low-flow streams. This research demonstrates that multi-species and complex FTWs with different characteristics and removal mechanisms can enable simultaneous remediation of several pollutants.

3. climate change and ecological assessment in Europe under the WFD – Hitting moving targets with shifting baselines?

Free G., Poikane S., Lyche Solheim A. et al. (2024). Climate change and ecological assessment in Europe under the WFD – Hitting moving targets with shifting baselines? Journal of Environmental Management, 370, 122884

In a rapidly changing climate, the notion of a runaway target, or in free translation, a bunny to chase, is gaining popularity. The problem of being able to achieve the environmental objectives of the Water Framework Directive is no different. The main objective of the WFD is to ensure the good status of surface and groundwater. However, climate change can have a significant impact on ecological status by directly changing monitored parameters, modifying the interaction of various pressures and pressures and the ecosystem, or limiting the effectiveness of corrective measures.

In an article published in the Journal of Environmental Management, a group of scientists analyzes the implications of climate change for assessing the ecological status of European waters. Phenomena such as lowering of water levels, disruption of thermal stratification of lakes or occurrence of extreme droughts and floods will affect the values of ecological quality indicators. The authors present various aspects and solutions to this problem and advocate the inclusion of indicators that take into account climatic pressures in WFD-compliant water status assessment systems in the near future.

4. global freshwater distribution of Telonemia protists

Boukheloua R., Mukherjee I., Park H. et al. (2024), Global freshwater distribution of Telonemia protists, The ISME Journal, wrae177

Telonemia is a cluster of unicellular flagellates characterized by a unique combination of cellular structures not found in other eukaryotes. At the same time, it is one of the oldest identified marine protists, which for most of its history was considered a separate lineage incertae sedis. The evolutionary affinities of these flagellates with the SAR supergroup (Stramenopiles, Alveolates and Rhizaria) are now firmly established, but their occurrence and role in food webs, especially in freshwater ecosystems, still remain unrecognized.

The study, carried out by an international team of scientists based on the analysis of more than a thousand freshwater metagenomes from around the world and more than 400 water samples from lakes and reservoirs, showed that representatives of this cluster are widely distributed in freshwater ecosystems, although they exhibit a marked variation in habitat preferences. They are very sporadic in shallow and highly zeutrophic lakes, while they strongly prefer the cooler hypolimnion of lakes and reservoirs in the northern hemisphere, where they can make up as much as 10-20 percent of the total population of heterotrophic threadworms. These studies indicate that Telonemia may be important predatory flagellates in the food chain of some freshwater ecosystems, especially deep, cooler lakes.

5 Reforestation effects on low flows: Review of public perceptions and scientific evidence

Van Meerveld I., Seibert J., (2024). Reforestation effects on low flows: Review of public perceptions and scientific evidence. WIREs Water. 2024;e1760

I very much enjoy looking into WIREs Water journal. It mainly presents literature reviews, which may be considered less valuable than new findings, but the papers published there provide really solid, up-to-date and comprehensive knowledge on issues close to the heart of a hydrophile. A review article has just been published that focuses on the complex relationship between forests and water, and in particular on the effects of deforestation and reforestation on water status and flow during meteorological droughts.

The impact of forests on water resources has long been the subject of research, but there are many common beliefs in the public space that are based on selective scientific evidence or are not supported by any of it. Researchers at the University of Zurich have revised some of the circulating opinions by conducting an extensive review of available research on the effects of forests on precipitation, soil water dynamics, evaporation and water flow. In general, reforestation increases evaporation and reduces groundwater recharge, which can lead to a decrease in water flow, especially in low-flow situations.

These effects can be mitigated by increased infiltration as a result of improved hydrological properties of soils due to the emergence of vegetation cover, potentially offsetting some of the losses from evaporation and transpiration. Overall, the results of the review indicate that the view that forests prevent or reduce hydrological droughts turns out to be false in many cases. However, the authors stress that this finding should not be used as an argument for cutting down forests or not reforesting areas where forests occur naturally, as these ecosystems provide many other benefits (e.g., carbon sequestration, biodiversity, cooling), including important water quality enhancements.

Predicting the effects of forests on water flow is complicated because the effects are site-specific and depend on many factors, such as climate, forest and soil characteristics before and after afforestation, and the hydrogeological environment. A more accurate and detailed understanding of the role of forests in hydrology, and a better ability to predict where and when the effects of afforestation are positive or negative, are crucial for sustainable forest and water management. That is, with forests it’s like with everything in nature – each patient needs an individual diagnosis.