Αλλαγές στις θαλάσσιες βακτηριακές κοινότητες σε συνθήκες εμπλουτισμού με θρεπτικά

Abstract

Nutrient enrichment is a common source of disturbance for marineecosystems. A prerequisite for the prediction of the effects of nutrient enrichment atthe ecosystem level is the understanding of the ecological mechanisms governingbacterioplankton communities, due to their high affinity with nutrients. The aim ofthis thesis was to examine changes in the composition and structure ofbacterioplankton communities of the water column and coastal sediment undernutrient enrichment. Three studies were conducted for that purpose: two in closedexperimental conditions and one examining changes in situ. In the first two studies,changes in the water column bacterioplankton communities were examined after Paddition and in nutrient enriched habitats, respectively. In the third study, changes inthe communities of coastal sediment were examined with and without the additionof organic matter and aeration of the water column. The main conclusions from theresults of this thesis were:a) Bacterioplankton communities of the Eastern Mediterranean show a high degreeof resistance to short-term P addition, although their biomass and production islimited by P.b) Five abundant taxonomic groups showed a similar pattern of change across threedifferent nutrient enriched habitats. These groups could be potentially used asindicators for monitoring nutrient enrichment at the water column.c) After incubation under presence or absence of organic enrichment, sedimentbacterial communities originating from different habitats clustered based on theincubation conditions rather than on the area of origin. That occurred faster for twoout of the three areas, where the amount of organic matter in the sediment wasinitially higher and bacterial community diversity was lower. These results indirectlysupport the theory of Baas-Becking that "everything is everywhere but theenvironment selects" and the positive correlation between diversity and communitystability.