The use of more sedimentary DNA for Following long -term changes in the terrestrial and aquatic biota (fish) is a fast evolutionary field in Paleoecological research. Although it is applied on a large scale today, knowledge lacunes in this area continue to exist, so there is still research to guarantee the reliability of the sedimentary DNA signal.
Based on the most recent literature and seven original case studies have researchers Synthetized avant -garde analytical procedures For sampling, extraction, reinforcement, quantification and/or effective DNA inventory generation.
And they did this Old Sedimentary DNA (Sedadna) through high performance Sequencing technologiesfrom which they presented their recommendations based on current knowledge and best practices.
Re -introduced fish
The ancient DNA of the Redon Pyrenean Lake, located in Catalonia, reveals that people could deliberately add fish to the lake in the seventh century, perhaps to have food while they graze livestock. This would take a few hundred years before the first historical documents and Its discovery is revoluting the knowledge that was so far from the activity in the Pyrenees.
It is the conclusion of a study Led by creea -researcher Elena Fagín and the CSIC researcher at Creaf Jordi CatalanThat is published today in Nature communication. These results also coincide with a finding of archaeological remains in the area and reinforce the idea that the region had grass areas that the inhabitants of the Late-Roman and Visigotic times used for cattle.
To discover it, the team kept the history hidden A testimony of the sediment of the lake that is 3300 years old in just 30 centimeters. In general, the sediments do not retain the Fish -DNA and they can be lost, but the team used an innovative methodology: they analyzed the DNA of the fishing parasites, which was well preserved.
“Fish have no way to access high mountain lakes and can only come if someone takes them, so their presence is an indicator of intentionality and human activity,” he explains Elena Fagín, Creaf researcher and one of the most important authors of the study.
The historical documents began to register the existence of fish in the European lakes during the fourteenth and fifteenth centuries and most of them describe the rights of fish and act, “but thanks to the memory that the sediments we can go many years ago, when there was no documentation, and it places it on a more precise date,” the author adds.
The data suggests that the fish population remained constant over the years, despite the changes in the human population of the surrounding area, although however They could have had the impact of climatic trends, such as times of very cold or heat.
Apart from the parasites, during the investigation Other environmental indicators were also analyzed, such as photosynthetic pigmentsAlso present in the sediment, which give instructions about the number of photosynthetic organisms that inhabited more in the past.
It was observed that the The presence of fish parasites coincided with an increase in the productivity of the lake -more photosynthetic activity-. According to the team, the reason may be that the increase in cattle (mainly sheep) in the late Roman and Visigotic era caused a greater erosion of the soil and, when it rained or snowfall, some nutrients from the country were transmitted to the lake.
“It’s Nutrient contribution is in favor of the growth of Fytoplankton And it is reflected in the increase in photosynthetic pigments that are stored in sediments, “explains the creea -researcher and the Barcelona University Marisol Felip, also co -author of the study.
Parasitized gills
To enter the past of the mountain lakes, the so sent ‘Sediment witnesses’cylindrical samples that are extracted from the bottom of the lake by a perforation. Normally I know They observe certain parameters such as phosphorus and nitrogen feed substancesIf there are heavy metals or the remains of fossil organisms and environment -DNA.
This can, for example, help determine What was the climate and if there was a presence of certain types of life“To get an idea of the valuable of these sediments, every 3 centimeters contain about 100 years of history,” explains Elena Fagín.
With this study one step further and researchers went have used fragments of ectoparasites DNA for the first time -Organisms that in this case live on the outer surface of fish and depend on it to feed or complete your life cycle.
“Until now, the search for fish -DNA in the high mountain lakes was looking for a fish in an Olympic swimming pool, because it depends on where you died, you will find it or not in the sediment witness. Instead the Parasites are expanding by the lake, so they are good proof of the presence of PeceS ”, explains Jordi Catalan, CSIC researcher at Creaf and one of the most important authors of the study.
The parasites that were the easiest detected belonged to the genre IchthyobodoAnd Flagellated Protozoo that lives on the skin and gills of the fishAlthough others were also observed Kinetoplasta and other groups such as Unclecota” Ichthyospora y Ciliaofor.
“These findings show the Potential of old DNA of parasites to understand historical human activity and the impact of documentation Until now unclear of settlements in ecosystems with high mountain, ”adds Elena Fagín.
Redon Lake: 40 years of research
Lake Redon is located in the Catalan Pyrenees and currently has a population of around 60,000 trout, which is mainly used for recreational fishing. A special aspect of this lake is that, at a height of 2,240 meters in the Pyrenees, has Relatively isolated state of human activity for centuries. This means that any change that occurs in the ecosystem is easier to attribute to environmental or human factors, such as the introduction of fish or grazing.
The researcher Marisol Felip and Jordi Catalan are investigating this for more than 40 years and currently continue to study various processes. “It’s like having a natural historical archive, true We can discover what the ecosystems were from the past And also an outdoor laboratory where we can observe how climate change and human activity influence the ecosystem, “conclude these two researchers.
This research was led by Creaf and the University of Barcelona, the CSIC, the National Institute of Biology of Slovenia and the Edith Cowan University of Australia has also participated.