Aquatic publication review (21)

The European Union has just passed a Nature Restoration Law (NRL), so work on restoring damaged ecosystems should get into full swing. To what extent are our actions likely to succeed? This question is partly answered by an article by German ecologists on the restoration of trophic networks in rivers. Despite the urgent need to work on ecosystem restoration, the waters are still subject to strong anthropogenic pressure, including salinization. U.S. researchers have developed a biotic index to assess the effects of chlorides on benthic macroinvertebrate communities in U.S. rivers. Perhaps it would also find application in Europe?

Another global problem is foreign invasive species. We recommend to your attention an article published in Nature Ecology & Evolution, presenting the main conclusions of the report of the Intergovernmental Science-Policy Platform on the Future of Science. IPBES Biodiversity and Ecosystem Services on the challenges of biological invasions on a global scale. The problem of nitrogen from agricultural sources is not diminishing either, and it appears that its accumulated reserves in groundwater will continue to feed surface water for a long time to come. And degradation of groundwater resources is linked to threats to global food security, as mentioned in an article on scenarios analyzing the relationship between climate, water and food.

1. long-term recovery of benthic food webs after stream restoration

Schlenker A., Brauns M., Fink P. et al. (2024). Long-term recovery of benthic food webs after stream restoration. Science Of The Total Environment, 923, 171499.

The implementation of corrective measures in degraded ecosystems is aimed at restoring their structure and function and proper biodiversity. The effectiveness of such measures was analyzed by researchers using the example of renaturated rivers in the heavily urbanized catchment of the Boye River in West Germany. The authors used stable carbon and nitrogen isotope analysis (δ13C and δ15N) to trace the rate and direction of trophic network structure regeneration in benthic invertebrate assemblages at 12 river sites in the urbanized Boye River catchment, restored in different years (with different recovery periods, with a maximum of 28 years). Restoration activities were carried out between 1993 and 2011 and consisted of cutting off the flow of wastewater and morphological restoration of rivers.

Based on isotopic analysis of biological samples collected annually from 2012 to 2021, it was shown that at almost all restored sites, trophic similarity (percentage of coexisting species occupying similar trophic niches) increased over time and reached values of sites close to natural (reference) sites, suggesting an increase in food web stability and resilience. In general, restoration activities had a very pronounced effect on the trophic network structure of river ecosystems, with some effects, such as an increase in trophic similarity, consistent across almost all sites, and others, such as a change in food chain length, being context-dependent. The study demonstrates the potential of using trophic network indicators, particularly trophic similarity, in water restoration studies.

2. Salt Belt Index (SBI): A biotic index for streams within the North American “salt belt,” with proposed baseline chloride thresholds.

Miess S., Dzialowski A.R. (2024). Salt Belt Index (SBI): A biotic index for streams within the North American “salt belt,” with proposed baseline chloride thresholds. Science Of The Total Environment, 173726.

The use of road salt (most often sodium, calcium or magnesium chlorides) is one of the significant reasons for the increase in salinity of inland freshwater ecosystems in many countries around the world, including the United States. The goal of the study, conducted by two researchers at Oklahoma State University, was to determine optimal values and chloride tolerance ranges for benthic macroinvertebrates inhabiting rivers in different regions of the US. The authors used 2008-2009 and 2013-2014 U.S. Environmental Protection Agency (EPA) data from 23 North American states to develop a Salt Belt Index(SBI) to assess the effects of river salinity on aquatic invertebrate fauna.

The taxonomic richness of macroinvertebrate communities showed a significant negative relationship with increasing chloride concentrations. The paper also determined region-specific chloride concentration thresholds, which turned out to be much lower than those currently used. This means that for most rivers in the United States, environmental standards for chloride should be updated at the federal level. The approach presented in the article may inspire similar research in our country’s waters.

3. curbing the major and growing threats from invasive alien species is urgent and achievable

Roy H.E., Pauchard A., Stoett P.J. et al. (2024). Curbing the major and growing threats from invasive alien species is urgent and achievable. Nat Ecol Evol.

Invasive alien species have long been recognized as a major threat to nature and humans, so a comprehensive global review of the status, trends, causal factors, impacts and challenges of managing biological invasions is essential. Such a review was carried out by members of the intergovernmental science-policy platform on the issue. Biodiversity and Ecosystem Services (IPBES, or Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services) in a thematic report based on more than 13,000. scientific publications and national reports on all taxa, ecosystems and regions around the world.

The synthetic findings were published this month in Nature Ecology & Evolution. The work provides clear evidence of the serious and growing threat posed by invasive alien species, and identifies ambitious but realistic approaches to managing them. The authors of the IPBES assessment stress the urgent need for immediate action to prevent further loss of diversity.

4 Impact of groundwater nitrogen legacy on water quality

Liu X., Beusen A.H.W., van Grinsven H.J.M. et al. Impact of groundwater nitrogen legacy on water quality. Nat Sustain (2024).

Nitrogen (N) losses from agriculture are a major cause of global eutrophication of inland and coastal waters worldwide. Despite regulatory efforts, such as the EU Nitrates Directive, high N concentrations in freshwater persist. In groundwater, the circulation of nitrogen is much slower than in surface water, so it has become a kind of reservoir of this element. Dutch researchers have analyzed current and projected groundwater nitrogen dynamics for four major global river basins: Rhine, Mississippi, Yangtze and Pearl, presenting different trajectories of the element’s circulation.

Nitrogen has been accumulating in the Rhine and Mississippi river basins since the 1950s. and while strategies to reduce its supply from agriculture have yielded reductions in the case of the Rhine, it remains high in the latter river. The Yangtze and Pearl river basins entered a phase of N accumulation in the 1970s. In the 1970s. and there the authors forecast the continuation of this process until 2050.

Policies aimed at reducing water pollution from fertilizers have not stopped its accumulation in groundwater, and restoring concentrations to 1970 levels. will take longer than expected – 9 years for the Rhine, 15 years for the Mississippi and more than 35 years for the Yangtze and Pearl. It follows that sustainable water management requires not only long-term strategies, but also a lot of patience.

5. ending groundwater overdraft without affecting food security

Perez N., Singh V., Ringler C. et al. (2024). Ending groundwater overdraft without affecting food security. Nat Sustain.

In times of climate crisis, groundwater management is crucial for agriculture and ensuring food security. However, the rapid increase in their exploitation over the past four decades, especially in regions facing severe water shortages, has resulted in resource depletion and degradation. This could have irreversible consequences for food security and economic prosperity. In a paper published in Nature Sustainability, the researchers present operational scenarios of the relationship between climate, water and food, developed based on the IMPACT ( International Model for Policy Analysis of Agricultural Commodities and Trade) integrated biophysical-economic assessment model.

The models indicate that reducing groundwater use without complementary policy actions would adversely affect food production and trade, increase food prices and the number of people at risk of hunger by 26 million by 2050. To avoid such a scenario, interventions are needed to support food and water systems, such as increasing the efficient use of precipitation and investing in research and development of water-efficient agriculture. The authors also point out that reducing the amount of meat consumed in high-income countries would help curb the rise in food prices.

In order for groundwater to be sufficient to meet needs, comprehensive measures will be needed, including improved water management practices, advances in agricultural technologies and appropriate institutional management. Conclusions on the whole are trivial, but analysis of the scenarios themselves gives much food for thought.

6 Impact of heteroaggregation between microplastics and algae on particle vertical transport

Parrella F., Brizzolara S., Holzner M. et al. (2024). Impact of heteroaggregation between microplastics and algae on particle vertical transport. Nat Water.

The problem of microplastics (MPs) in aquatic ecosystems is still current and pressing, so it continues to be an object of intensive research and is often featured in the pages of professional scientific journals. This time, Nature Water published a paper on the rate of movement of MP particles in a column of water, from the surface toward deeper layers. The authors analyze the role of so-called “the Freshwater snow (FWS, or freshwater snow), which is a mixture of microorganisms (phyto- and zooplankton) and organic particles in the sedimentation of microplastics.

The researchers used a Plexiglas column equipped with a stereoscopic camera system to track the settling velocity of MPs of different composition, density and morphology, FWS flocs and MP-FWS agglomerates. Organic matter particles (FWS) in agglomerates with MP settled at least twice as fast as FWS alone, implying a much shorter residence time of organic matter in the water column for agglomerates with microplastic particles. This means that MP particles can influence biogeochemical cycles by altering the flux of nutrients contained in FWS from the surface to the sediment.