Aquatic publication review (23)

The previous winter is far behind us, and we still have a few months until the next one, but we can already learn how climate warming is affecting ice phenomena in southern Poland. We’re also considering whether it’s more effective to set up one large conservation area or a network of smaller but functionally linked ones. It turns out that for migratory birds, the key is the distance between refugia.

We also present the latest reports on carbon dioxide fixation by mangroves and atmospheric nitrogen fixation by heterotrophic diazotrophs, as well as the effect of the presence of polyester on intertidal sediment metabolism. In the latest report on the most famous recent alga Prymnesium parvum, we will learn about the newly discovered giant enzyme aptly named PKZILLA, which is involved in the synthesis of prymnesins. That is, the golden alga surprises again. And finally, we’ll find out what water has to do with building pyramids.

1. Analysis of changes in the occurrence of ice phenomena in upland and mountain rivers of Poland

Kochanek K., Rutkowska A., Baran-Gurgul K. et al. (2024). Analysis of changes in the occurrence of ice phenomena in upland and mountain rivers of Poland. PLoS ONE 19(7): e0307842.

In the rivers of temperate, continental and polar climate zones, ice phenomena are an integral part of the natural annual cycle. However, the increasing warming of the climate is leading to a decrease in snow cover on land and ice phenomena in water bodies, which is disrupting the stability of the hydrological cycle and the functioning of ecosystems. We also wrote about how snow conditions affect flow in rivers in the previous issue of Water Matters.

In order to see what the situation is in the upland and mountain rivers of our country, a team of Polish scientists analyzed changes in the annual number of days with ice phenomena (NDI, or number of days with ice) in rivers in southern Poland, where ice phenomena were observed every year for at least 30 years between 1951 and 2021. Based on the results of the Mann-Kendall test, statistically significant downward trends in annual NDI were found for most of the measurement stations. Correlation and regression analyses showed that the main driver of NDI decline is an increase in average winter air temperature, with a 1°C increase in temperature causing a 12-20 day decrease in NDI. The authors predict that if these negative trends continue, ice phenomena may disappear completely in the rivers of southern Poland within a few decades.

2. proximity among protected area networks promotes functional connectivity for wintering waterfowl

Masto N.M., Keever A.C., Highway C.J. et al. Proximity among protected area networks promotes functional connectivity for wintering waterfowl. Sci Rep 14, 17527 (2024).

Designing a network of protected areas requires decision-makers to consider whether conservation goals will be achieved more effectively by one large area or a complex of many smaller ones (the SLOSS dilemma, from single large or several small). Wetland birds, which, because of their mobility, are being used as model organisms to test island predictions in protected area networks, can help solve this dilemma. In a study using data on the movements of Anas platyrhynchos mallards wintering in wetland complexes of western Tennessee, western Kentucky, northeast Arkansas and southeast Missouri in the U.S. from 2019 to 2023, researchers tested whether the size and isolation of areas affect the functional connectivity of refugia (reserves, sanctuaries) within networks of such areas.

The proximity of refugia supported movements between network nodes to a greater extent than area size, even for birds that are theoretically not constrained by the quality of connecting areas (no barriers). The use of refugia increased the survival rate of wintering birds, meaning that access to refugia has direct consequences for population fitness. The results of this research can help improve protected area network design, including land acquisition, restoration and management practices, especially for wetland-dependent migratory game birds.

3. four decades of data indicate that planted mangroves stored up to 75% of the carbon stocks found in intact mature stands

Bourgeois C. F., MacKenzie R. A. Sharma S. et al. (2024). Four decades of data indicate that planted mangroves stored up to 75% of the carbon stocks found in intact mature stands. Sci. Adv.10, eadk5430.

Areas covered with vegetation play an important role in sequestering carbon dioxide from the atmosphere, and one way to mitigate greenhouse gas emissions is to introduce plantings in areas devoid of vegetation due to human activities. Such practices are currently being used, among others. in areas of mangrove forests, which over the past 50 years have lost more than 35 percent. of their area due to deforestation. These ecosystems, also known as mangrove forests, are extremely effective at trapping and sequestering carbon dioxide from the atmosphere, thus playing an important role in reducing the effects of greenhouse gas emissions.

The researchers asked whether, and over what time horizon, planted mangroves are similarly effective as natural, untransformed ecosystems. They analyzed data on aboveground biomass, belowground biomass and carbon stocks (to a depth of 1 m) from more than 800 sites from 24 countries where mangroves have been restored (planted) and compared them with data from 475 untransformed sites. Using Bayesian logistic models developed from 40 years of data, they showed that biomass carbon stocks reached 71-73 percent within about 20 years after planting. relative to natural sites.

In addition, they proved that higher accumulation values were achieved by species-mixed plantings (species from the genera Rhizophora, Candelia or Avicennia) than monocultures. Despite a 25%. increase in the first 5 years after planting, no significant changes were observed in soil carbon stocks, which remained constant at 75 percent. relative to carbon stocks on untransformed sites.

Mangroves are not found in our physical and geographic conditions, but the results of this study indicate that fast-growing (<10 years to peak biomass) pioneer plant species may find application in nature-based solutions for soil stabilization, ecological support and mitigation of adverse effects of human activities.

4. nitrogen fixation in the widely distributed marine γ-proteobacterial diazotroph Candidatus Thalassolituus haligoni

Rose S. A., Robicheau B. M., Tolman J. et al. (2024). Nitrogen fixation in the widely distributed marine γ-proteobacterial diazotroph Candidatus Thalassolituus haligoni. Sci. Adv. 10, eadn1476.

The oceans are colonized by a common and diverse group of heterotrophic bacterial diazotrophs (HBDs), that is, bacteria (and archaeons) that have the ability to fix molecular nitrogen (_N2), thanks to the enzyme nitrogenase. One such organism is Candidatus Thalassolituus haligoni, a member of the widely distributed HBD clade, belonging to the Oceanospirillales, which was isolated and characterized by Canadian biologists from the University of Halifax.

Analysis of the nifH gene of this organism by amplicon sequencing showed that it is common and found in the Pacific, Atlantic and Arctic Oceans. Analysis of the pangenome also indicated that the isolate shares >99 percent identity with an uncultured genome composed of a metagenome called Arc-Gamma-03, recently recovered from the Arctic Ocean. Based on genomic, proteomic and physiological studies, the researchers confirmed that the isolate binds molecular nitrogen, although the mechanisms that regulate nitrogenase in Cand. T. haligoni remain unclear. Cand. T. haligoni is the only known cultured representative of the _N2-binding Oceanospirillaceae family that is widely distributed throughout the open ocean.

The possibility of culturing it provides valuable information on the lifestyle of other uncultured HBDs, whose presence is detected only by metagenomic sequencing or nifH amplicon. The study authors postulate that the isolate should be considered a key model species for studying the ecophysiology of the diazotrophic Oceanospirillales clade under polar and temperate conditions.

5. giant polyketide synthase enzymes in the biosynthesis of giant marine polyether toxins

Fallon T.R., Shende V.V., Wierzbicki I.H. et al. (2024). Giant polyketide synthase enzymes in the biosynthesis of giant marine polyether toxins. Science 385, 671-678.

While we’re on the subject of genetic research, a very interesting report appeared in the pages of Science magazine in early August this year on the discovery of hitherto unknown genes in the alga Prymnesium parvum (the so-called golden alga), which has become famous in Poland in recent years. This organism has the ability to produce substances that are toxic to gillnetic animals, the so-called. prymnesins, which are among the largest non-polymeric compounds in nature. Nevertheless, their biosynthesis has remained a mystery to us for more than 40 years.

A team of American scientists led by Fallon at the University of California has identified P. parvum polyketide synthase (PKS) genes that encode proteins involved in the biosynthesis of prymnesins of unprecedented size. These proteins are among the giants in the natural world, being larger than thymine, the largest known human protein. Because of their size, the authors have given this gigasynthase the graceful name PKZILLA. The publication is another step toward understanding the workings of this mysterious and difficult-to-interpret alga. It also expands our expectations about genetic and enzymatic size limitations in biology.

6 Rapid effects of plastic pollution on coastal sediment metabolism in nature

Ladewig S.M., Bartl I., Rindelaub J.D. et al. (2024). Rapid effects of plastic pollution on coastal sediment metabolism in nature. Sci Rep 14, 17963.

The ubiquity of microplastic is a well-established fact, and we all know that there is basically no environment on the planet that is free of this pollution. In contrast, the impact of its presence on the functioning of ecosystems is still poorly studied. It turns out that the presence of plastic can significantly modify the metabolism of marine intertidal sediments, as demonstrated by a team of marine ecologists from the University of Auckland in New Zealand.

In an experiment lasting 72 days, the authors monitored the rate of oxygen consumption in sediments in which strips of polyester mesh, a commonly available plastic, were buried. The results showed a faster decline in oxygen consumption compared to the control sites, which was potentially linked to the loss of the additive di (2-ethylhexyl) phthalate (DEHP) from the polyester material, with DEHP concentrations dropping by 89 percent. within the first week of implementation. However, after just 22 days of the experiment, the effect of plastic on oxygen consumption disappeared, indicating a short-term impact and rapid recovery. This study confirms the direct consequences of plastic pollution in coastal sediments, contributing to a better understanding of the temporal variability of the multifaceted effects of this type of substance in the environment.

7. On the possible use of hydraulic force to assist with building the step pyramid of saqqara

Landreau X., Piton G., Morin G. et al. (2024) On the possible use of hydraulic force to assist with building the step pyramid of saqqara. PLoS ONE 19(8): e0306690.

And finally, a perverse question: what does water have to do with the pyramids? Well, it does, because research published in August in the journal PLOS ONE by Xavier Landreau of the CEA Paleotechnic Institute in France and his colleagues indicates that the oldest of Egypt’s iconic pyramids, the pyramid of Djeser (built around 2680 BC), may have been constructed using a unique hydraulic elevator system (hydraulic elevator).

Research suggests that water may have flowed into two shafts inside the structure, where it could have been used to raise and lower the float carrying the building stones. A series of chambers dug into the ground outside the pyramid may have served as a water treatment facility, allowing the water to be purified of sediment as it flowed through each successive chamber. The water could then flow into the shafts, where its force was used to carry the building stones.

The study’s authors suggest that even if other construction improvements, such as ramps, were used to erect the pyramid, a hydraulic system may have been used to support the process. A prerequisite for the use of such a solution was the availability of sufficient water, which during the period of pyramid construction, the so-called “Green Sahara. Green Sahara, was much more plentiful than it is today.