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Identifier

000449811

Title

Μελέτη του ημερήσιου κύκλου των πλαγκτονικών μικροβιακών κοινοτήτων σε περιβάλλον υδατοκαλλιεργειών

Alternative Title

Study of the diel cycle of planktonic microbial communities in the proximity of aquaculture farms

Author

Παπαχρήστου, Ηλέκτρα Κ.

Thesis advisor

Πήττα, Παρασκευή

Reviewer

Λαδουκάκης, Εμμανουήλ
Παφίλης, Ευάγγελος

Abstract

Microbial plankton exhibits diel fluctuations in composition and abundance. These fluctuations are related to the light cycle as well as the availability of nutrients, and are probably particularly important in the aquaculture environment where large amounts of such nutrients are added daily. In the present work, for the first time, the daily variability of the main microbial planktonic groups is studied (prokaryotes, eukaryotes and viruses) under the influence of aquaculture activity. For this purpose, DNA metabarcoding analysis was performed on multiple water samples from an aquaculture environment (Argolikos Gulf, Vourlias) that were collected at three time points of the day (morning, noon, evening). To test the repeatability of the results, sampling was repeated for three days in each station: a non-impacted site (control), a site with one fish cage (one farm) and a site with many fish cages (multiple farms). Specific regions of the 16S and 18S rRNA genes and the ITS region were amplified for the detection of prokaryotes, eukaryotes and fungi, respectively, and an attempt was made to amplify the DNA polymerase, g20, g23 and phosphatase genes of viruses. Our results show that the increase in aquaculture activity lead to changes in the composition of prokaryotic communities. In particular, there may be opportunistic strains that "replace" strains that are not adapted to high concentrations of nutrients in areas where fish cages exist. In addition, diurnal variability was found in particle-attached prokaryotes, possibly related to their direct dependence on particulate organic matter. Meso-zooplankton and pico- and nano-autotrophic and heterotrophic eukaryotes, including fungi, were affected by aquaculture. Sampling day, i.e. environmental parameters that change from day to day like water circulation and temperature, significantly affected eukaryotic communities too. The diurnal variability was observed in several zooplankton phyla that are known to perform diel vertical migration, having maximum contribution to the surface waters at night. Small diatoms were found to contribute less to aquaculture stations, while small Dinoflagellata contributed less to all stations at night. Results need further investigation in order to detect any other difference at lower taxonomic levels. In this first study of fungal diversity in the Eastern Mediterranean, a large percentage of uncharacterized species was found along with an association with inorganic and organic nutrients. Finally, the primers used to amplify the viral genes may not have been suitable for the studied environment.

Language

Greek

Subject

Aquacultures

DNA metabarcoding

DNA μετακωδικοποίηση

Diel variability

Eukaryotes

Fungi

Prokaryotes

Viruses

Ευκαρυώτες