MICROBIAL COMMUNITIES IN OLIGOTROPHIC MARINE ECOSYSTEMS

doctoral thesis

• Title (croatian): MIKROBNE ZAJEDNICE U OLIGOTROFNIM MORSKIM EKOSUSTAVIMA
• Author: Katarina Kajan
• Mentor: Sandi Orlić (mentor)
• Committee member: Sunčica Bosak (predsjednik povjerenstva)
• Committee member: Neven Cukrov https://orcid.org/0000-0003-3920-6703 (član povjerenstva)
• Committee member: Jelena Godrijan (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Geology); Zagreb
• Defense date and country: 2023-11-22, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Interdisciplinary Natural Sciences; Marine Science
• Universal decimal classification (UDC): 55 - Geology. Meteorology. Hydrology

Abstract

Oligotrophic ecosystems are characterized by low nutrient concentration and low primary production. Climate change and anthropogenic nutrient loading affect the microbial communities of oligotrophic marine ecosystems, and therefore, understanding the essential functions of microbial communities is extremely important for understanding environmental changes. However, studying uncultured microorganisms and complex microbial communities in oligotrophic ecosystems remains a scientific challenge. This dissertation investigated the diversity and composition of microbial communities and their response to individual environmental conditions using modern molecular methods in an oligotrophic open ecosystem such as an ocean gyre and in semi-closed ecosystems such as coastal anchialine speleological objects. The results show that the physicochemical gradients, including light penetration, oxygen concentration, and salinity, along with nutrient limitation, play a crucial role in defining the microbial community composition and dynamics within the studied oligotrophic marine environments. Specifically, the protistan communities in the ultra-oligotrophic South Pacific Gyre are influenced by the depth of light penetration, while site-specific parameters influence the fungal communities. Additionally, the composition of protistan and prokaryotic communities in anchialine pits and caves undergoes changes along the salinity gradient within the water column, demonstrating a high degree of site-specificity in their diversity. Moreover, the diversity, activity, and function of the prokaryotic community in anchialine speleological object depends on the availability of oxygen and the stratification of the salinity gradient. The research provides insight into the microbial community's biodiversity and ecological role, expanding the knowledge of oligotrophic marine ecosystems.

Abstract (croatian)

Oligotrofne ekosustave karakterizira niska koncentracija nutrijenata i niska razina primarne produkcije. Klimatske promjene te antropogeno opterećenje hranjivim tvarima utječu na mikrobne zajednice morskih oligotrofnih ekosustava te je stoga poznavanje osnova njihovog funkcioniranja od iznimne važnosti za razumijevanje okolišnih promjena. Međutim, istraživanje raznolikosti nekultiviranih mikroorganizama i metaboličkog potencijala kompleksnih mikrobnih zajednica u oligotrofnim ekosustavima još uvijek predstavlja značajan znanstveni izazov. U ovom doktorskom radu istraživana je raznolikost i sastav mikrobnih zajednica i njihov odgovor na pojedinačne uvjete okoliša korištenjem suvremenih molekularnih metoda u oligotrofnom otvorenom ekosustavu kao što je oceanski vrtlog i u poluzatvorenim ekosustavima kao što su obalni anhijalini speleološki objekti. Rezultati pokazuju da fizikalno-kemijski gradijenti, uključujući dubinu prodora svjetlosti, koncentraciju kisika i salinitet, zajedno s ograničenjem hranjivih tvari, igraju ključnu ulogu u definiranju sastava i dinamike mikrobne zajednice u istraživanim oligotrofnim morskim ekosustavima. Na prisutnost zajednica protista u ultra-oligotrofnom vrtlogu južnog Tihog oceana utječe dubina prodora svjetlosti, dok obrasci specifični za mjesto također utječu na prisutnost zajednica gljiva. Sastav zajednica protista i prokariota u anhijalinim jamama i špiljama mijenja se duž gradijenta saliniteta unutar vodenog stupca, dodatno pokazujući visok stupanj specifičnosti lokacije u njihovoj raznolikosti. Štoviše, raznolikost, aktivnost i funkcija prokariotske zajednice u anhijalinom speleološkom objektu duž gradijent saliniteta, ovisi o dostupnosti kisika. Istraživanje pruža uvid u bioraznolikost i ekološku ulogu mikrobne zajednice, proširujući znanje o oligotrofnim morskim ekosustavima.

• Keywords: microbial community; ocean gyre; anchialine speleological object; metagenomics
• Keywords (croatian): mikrobna zajednica; oceanski vrtlog; anhijalni speleološki objekt; metagenomika
• Language: english
• URN:NBN: urn:nbn:hr:217:767270
• Promotion: 2024
• Project: Number: KK.01.1.1.01.0003; Title: STIM-REI (hrv. istraživanje, inovacija, edukacija); Title: STIM-REI (eng. Research, Education, Innovation); Acronym: STIM-REI; Leader: Vlasta Bonačić-Koutecky; Jurisdiction: eu; Funder: Europska unija; Funding stream: European Regional Development Fund
• Study programme: Title: DOCTORAL STUDY OF OCEANOLOGY; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti u području prirodnih znanosti (doktor/doktorica znanosti u području prirodnih znanosti)
• Type of resource: Text
• Extent: 106 str. ; 30 cm
• File origin: Born digital
• Access conditions: Open access; Embargo expiration date: 2024-11-23
• Created on: 2025-01-31 10:06:17