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Identifier uch.biology.phd//2004akoumianaki
Title Μακροβενθικές βιοκοινωνίες υποθαλάσσιων δελταϊκών αποθέσεων: παράδειγμα από έναν ημίκλειστο κόλπο της Ανατολικής Μεσογείου (Μαλιακός κόλπος, Αιγαίο πέλαγος)
Alternative Title Macrobenthic communities of subaqueous deltaic depositions: a case study from a semi-enclosed bay in the Eastern Mediterranean (Maliakos Bay, Aegean Sea).
Author Ακουμιανάκη, Ιωάννα
Thesis advisor Ελευθερίου, Αναστάσιος
Abstract Benthic communities at subaqueous deltaic depositions are subject to natural disturbance caused by erosional/depositional events, varying riverine sediment and suspended material discharges and unstable seabed. It is expected that 1. The community structure is physically controlled when intensity of sedimentation is high. 2. The community displays a spatial and temporal mosaic of species compositions when disturbance from sedimentation is mild and 3. Sedimentation disturbance leads to miniaturization of macrobenthic fauna due to high maintenance cost. The present study explores these hypotheses in the deltaic depositions of Sperchios River in Maliakos Bay, a shallow (max. depth 25 m) semi-enclosed embayment. The hypotheses were explored according to three sampling plans. The first investigated the environmental conditions including stations throughout the bay while the second and third plan focused on the delta front area to assess the riverine impact on benthic community structure and the sediment community oxygen consumption rates (SCOC). The study site was visited 6 times from January 2000 until May 2001. Samples for sediment analysis, chlorophyll α (Chl α), total organic and biopolymeric carbon in the sediment (three layers) as well as for suspended particulate mater (SPM) and chlorophyllous pigments in the water column were taken in association with CTD profiles. All macrofauna samples, 288 overall, were taken in triplicate with a Ponar grab (0.05m2) and retained in a 0.5mm sieve while SCOC were measured during dark incubation experiments on sediment cores. Macrofauna diversity and biomass size spectra (BSS) were calculated while production and respiration were estimated using empirical models. Statistical analyses included univariate and multivariate methods. The study showed that: 1. Due to high functional diversity, macrobenthic community displays resilient spatial and temporal structure and responds to environmental variability and disturbance with high numbers of species and individuals. 2. Macrobenthos is able to withstand the higher levels of environmental variability and disturbance in the delta front due to the continuous larval supply from adjacent sediments. Community structure resembles a spatiotemporal mosaic of species abundances which can be explained from organic suspended load, chloroplastic pigments equivalent, silt - clay % and depth. 3. Intermediate biomass size classes dominate macrofauna respiration as a response to high lability of sedimentary organic matter despite disturbance. BSS indicates that during mild levels of sedimentation the accumulation of biomass in a few large individuals of a few sensitive species is favored. Therefore, BSS is recommended as a riverine sedimentation impact monitoring tool. 4. It is estimated that under the sedimentation regime during the course of the study, carbon burial rate exceeds carbon uptake rate by macrofauna which provides indirect evidence of sedimentation induced disturbance. 5. The increase of SCOC coincides with elevated pigment levels in the water column and sediment in spring and coarser sediments near the river mouth. However, organic suspended load and the contribution of lipids in organic matter exert a negative influence, probably due to clogging of suspension feeding appendages of invertebrates and lipidic refractory terrigenous compounds, respectively. 6. There is no evidence of impacts due to organic pollution or eutrophication on macrozoobenthos in Maliakos Bay. Macrobenthos is however subject to natural disturbance. This situation is directly consistent with the climatic - geological conditions (wet winter, hot dry summer, subaqueous deltaic environment, semi-enclosed shallow embayment) and indirectly associated with manmade interventions in the catchment area and the coastal zone. The results of the present thesis, as part of the first integrated study of subaqueous deltaic benthic communities in Greece, are discussed in the light of scientific questions for the functioning of these ecosystems and practical considerations for the management of the mediterranean deltaic coastal zone.
Language Greek
Issue date 2004-03-01
Collection   School/Department--School of Sciences and Engineering--Department of Biology--Doctoral theses
  Type of Work--Doctoral theses
Permanent Link https://elocus.lib.uoc.gr//dlib/c/1/1/metadata-dlib-2004akoumianaki.tkl Bookmark and Share
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