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Identifier

000447593

Title

Απόκριση διαφορετικών πλαγκτονικών κοινοτήτων σε προσθήκη διαλελυμένου οργανικού άνθρακα

Alternative Title

Response of different plankton communities to a single addition of dissolved organic carbon (DOC)

Author

Κτιστάκη, Γεωργία Ξ.

Thesis advisor

Πήττα, Παρασκευή

Reviewer

Καρακάσης, Ιωάννης
Λύκα, Κωνσταντίνα

Abstract

The addition of dissolved organic carbon (DOC) from terrestrial to coastal, marine or freshwater ecosystems colors the water yellow-brown. This phenomenon is called “brownification” and causes shading, affecting primary production. In addition, increasing the concentration of organic carbon can lead to increased production and biomass of heterotrophic organisms, with potential consequences on the whole food web. The present study focused on the effect of this phenomenon on marine plankton groups. The effect was simulated in an mesocosm experiment by adding HuminFeed to seawater. The mesocosm experiment took place at CretaCosmos facility of H.C.M.R. in June 2021 and had 2 treatments: Control (C) and HuminFeed (HF) with 3 replicates for each treatment. No manipulation was performed in C while in HF, HuminFeed was added at a concentration of 2 mg L^-1 . The experiment lasted 15 days during which it was observed that the addition of HuminFeed caused brownification and reduced light penetration causing a decrease in the abundance of strictly autotrophic organisms (Synechococcus cyanobacteria and diatoms). However, no clear effect on nanoflagellates was recorded, possibly due to the mixotrophy observed in this group. In addition, HuminFeed was a source of DOC for the bacterial community. Although the abundance of bacteria was greater, mainly during the first days of the experiment, the abundance of HNA (High Nucleic Acid) bacteria was higher in the HF condition during the whole experiment, which is reflected in the increased bacterial production. In the HF treatment, an increased abundance of dinoflagellates was observed, which may be due to either a dominance of mixotrophic species or to a decrease in the abundance of their predators (copepods). However, the decrease in ciliate abundance recorded immediately after the addition of HuminFeed to the seawater probably indicates that its addition to the water was responsible for their number reduction and their altered form. Finally, HuminFeed seems to have had a negative effect on the copepods, as well.

Language

Greek

Subject

Brownification

Mesocosm

Microbial ecology

Διαλελυμένος οργανικός άνθρακας

Μεσόκοσμος

Μικροβιακή οικολογία

Πλακτόν

Χρωματισμός των νερών

Issue date