Huge variety of deep-water animal life revealed – sciencedaily

Ecologists at the Institute of Zoology at the University of Cologne have for the first time demonstrated the extremely high and very specific diversity of deep seabed species by comparing 20 deep basins in the Atlantic and Pacific Oceans. Over a period of 20 years, a research team led by Professor Dr Hartmut Arndt at the Institute of Zoology has compiled a body of data that makes it possible for the first time to compare the diversity of existing eukaryotes – organisms with a nucleus cellular. Samples of sediments 4,000 to 8,350 meters deep, the cultivation and sequencing of populations exclusively present in the high seas and finally molecular analysis using high-throughput techniques give a complete picture of biodiversity in high seas. Wed The research results were published in Communications biology under the title “High and specific diversity of protists in deep basins dominated by diplonemids, kinetoplastids, ciliates and foraminifera”.

The seabed at water depths of over 1,000 meters covers over 60% of the Earth’s surface, making it the largest part of the biosphere. Yet little is known about the diversity, distribution patterns, and functional importance of organisms in this extreme and gigantic habitat. What is certain is that climate change – for example through warming, acidification or oxygen depletion – is already having an impact on this sensitive ecosystem. In addition, the deep sea is under pressure from the growing interest in the extraction of raw materials.

Scientists previously assumed that deep-sea basins, which are all characterized by the same low temperature (0-4 ° C), the same salinity (about 3.6%), high pressure (300-500 bar depending on the depth ) and very similar sediments, have a relatively low – and also the same – species diversity. Additionally, most of the deep sea studies to date have focused on specific habitats such as hydrothermal vents and saltwater duckweed. Until now, there has been a lack of data on the diversity of the deep plains, which by far make up most of the seabed. “ Using a novel approach of combined molecular biology and culture-based studies, we found substantial and very specific local differences in communities of organisms with little overlap with communities of organisms in coastal regions’ ‘said Dr Alexandra Schönle, lead author of the study.

Among the life forms, single-celled organisms (protists), which have been mostly neglected in current models of deep-sea food webs, have dominated. In addition to the calcareous chambered organisms (foraminifera) traditionally considered in studies, whose deposits dominate large areas of the global ocean, tiny naked protists dominated, including bacterial and parasitic flagellates and ciliates, whose diversity exceeded largely that of multicellular animals. The high proportion of parasitic forms (10 to 20%), hitherto unknown on this scale, was also surprising. Many of them are susceptible to infecting animals such as crustaceans or fish, but others are susceptible to infecting protozoa.

“Our results show that organic matter from the seabed is recycled through different and hitherto insufficiently considered components of the microbial food web, then transmitted into the food web. This is crucial for our understanding of the global carbon flow, ”explains Professor Hartmut Arndt. “ Given the significant differences in the biodiversity of individual deep basins and their importance in the global context, the economic exploitation and foreseeable devastation of individual deep basins and the sparing of other deep basins seems absurd. ”

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