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Identifier uch.biology.phd//2001labadariou
Title Μελέτη του μειοβενθικού οικοσυστήματος του Αιγαίου με ιδιαίτερη έμφαση στους νηματώδεις
Alternative Title Study of the meiobenthic ecosystem of the Aegean sea with a special emphasis on nematodes
Author Λαμπαδαρίου, Νικόλαος
Thesis advisor Ελευθερίου Αναστάσιος
Abstract In order to describe the meiobenthic ecosystem of the Aegean, samples were taken monthly along a continental shelf transect and during two different seasons (Spring-Autumn) at selected deep-sea stations from the North and South Aegean Sea. Samples were taken by means of a Craib-corer, a Multicorer or a Box-corer, depending on the circumstances. Stations varied in depth from 20 to 1772 m. Additional sediment samples were taken for chloroplastic pigments, particulate organic carbon determination, redox potential, temperature measurements and sediment grain size analysis. For the faunal data analysis several numerical techniques were employed namely: classification (using Bray-Curtis similarity index), MDS ordination, Principal Component Analysis (PCA) and Canonical Correspondence Analysis (CCA) while the characteristic species were detected using the program SIMPER. The diversity estimations were based on various diversity indices which were weighted either for the number of species or for equitability. Almost all the sampling stations were characterized by silty substrate, whereas only at the very shallow stations significant proportions of sand were detected. Nematodes were the most dominant group, ranging from 78% of total meiofaunal abundance in March to 95% in August. Harpacticoid copepods were the second most abundant group ranging from 2% in August to 18% in April. In the Aegean Sea the average productivity of the system was considered to be very low whereas the south Aegean appeared to be one of the most oligotrophic areas in the world. After the onset of the spring bloom a marked increase in sedimentary chlorophyll a values (on average 1.6 μg/g) was observed. These values remained stable throughout the spring and summer period while during autumn and winter they dropped again to levels of 0.2 μg/g. Most meiobenthic taxa displayed significant seasonal changes within the euphotic zone with abundances rising during spring and autumn, while in deeper stations no seasonal variability was evident in terms of abundance. Total nematode abundance was significantly different between sampling periods, with highest numbers occurring in late spring and autumn (April-May and September-October), following the spring and autumn phytoplankton blooms. Along the continental shelf transect, epistrate feeders and selective deposit feeders were more abundant at the two shallower stations, displaying significantly higher abundances during late spring and autumn after the phytoplankton blooms. On the contrary, at the deeper stations no significant differences were displayed between feeding modes and sampling periods. Individual nematode species displayed various distributional patterns with peak abundances occurring once or several times during the year. Among the most dominant species, some represented as much as 18% of the total nematode abundance. The nematode community structure displayed a gradual transition with increasing depth being mostly influenced by the sedimentary characteristics of the environment as well as the overall productivity of the system. Diversity analyses on a local scale indicated that species diversity and equitability are lowest at the intermediate station (70 m) where physical disturbance was highest. Likewise, diversity analyses on a wider regional scale revealed that diversity is higher at sites of higher productivity and that nematode diversity in the Eastern Mediterranean is positively correlated to increasing water depth.
Language Greek
Subject Νηματώδεις; Οικολογία; Υφαλοκρηπίδα Κρήτης; Αιγαίο πέλαγος; Ανατολική Μεσόγειος; Βιοκοινωνίες; Βιομάζα; Βαθύαλο οικοσύστημα
Issue date 2001-06-27
Collection   School/Department--School of Sciences and Engineering--Department of Biology--Doctoral theses
  Type of Work--Doctoral theses
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