Biomedical subjects

D Kitsiou

Publications and source records attributed to D Kitsiou.

4 recordsLinked to original sources

PubMed2001

Marine eutrophication: a proposed data analysis procedure for assessing spatial trends.

A methodology for the discrimination of the different trophic levels at a spatial scale in the marine environment is proposed using spatial analysis methods and non-parametric statistics. Phytoplankton cell number, being a representative parameter to express trophic trends in the marine ecosystem is selected for the methodology development; Saronicos Gulf, Greece is used for the case study. The proposed stepwise methodology includes interpolation for assessing the spatial distribution of phytoplankton cell number, division of the Gulf into a number of quadrates, development of a scale characterising trophic levels and finally characterisation of the trophic state of each quadrate using non-parametric statistics. The advantages of this methodology and the potential applications in coastal management studies are also discussed.

Cell Count↗

PubMed2001

Developing an optimal sampling design. A case study in a coastal marine ecosystem.

The development of a sampling design for optimising sampling site locations collected from a coastal marine environment has been the purpose of the present work; application of statistical analysis and spatial autocorrelation methods have been carried out. The dataset included data collected from 34 sampling sites spaced out in the Strait of Lesbos, Greece, arranged in a 1 x 1 NM grid. The coastal shallow ecosystem was subdivided into three zones, an inner one (7 stations), a middle one (16 stations) and an offshore zone (11 stations). The standard error of the chlorophyll-a concentrations in each zone has been used as the criterion for the sampling design optimisation, resulting into reallocation of the sampling sites into the three zones. The positions of the reallocated stations have been assessed by estimation of the spatial heterogeneity and anisotropy of chlorophyll-a concentrations using variograms. Study of the variance of the initial dataset of the inner zone taking into account spatial heterogeneity, revealed two different sub-areas and therefore, the number of the inner stations has been reassessed. The proposed methodology eliminates the number of sampling sites and maximises the information of spatial data from marine ecosystems. It is described as a step-by-step procedure and could be widely applied in sampling design concerning coastal pollution problems.

Chlorophyll↗

PubMed2000

Categorical mapping of marine eutrophication based on ecological indices.

The present work is concerned with the development of methodological procedures for studying the spatial distribution of eutrophication in the marine environment. Seven ecological indices (S, number of phytoplankton species; N, total number of individuals; D(Mg), Margalef's index; D(Mn), Menhinick's index; D(Od), Odum's species per thousand individuals; H', Shannon's Diversity index; E, Evenness index), based on phytoplankton community data collected from Saronicos Gulf, Greece were used for describing the eutrophication state of the sea environment. A representation of the spatial distribution for each ecological index was developed using the Inverse Distance Weighted (IDW) interpolation method. A eutrophication scale for each index was also developed for indicating four different trophic levels in the marine environment (eutrophic, upper-mesotrophic, lower-mesotrophic, oligotrophic); categorization of the interpolated values of each index resulted in a clear illustration of these trophic levels on seven thematic maps. Two methodological procedures were finally applied for synthesizing the information of these thematic maps. The purpose was the development of a final map illustrating the spatial distribution of eutrophication in the study area. The first procedure was based on the integration of unsupervised and supervised classification methods, widely used in the field of remote sensing, while the second one on the overlay technique, simply carried out within the frame of a Geographical Information System (GIS). The hybrid unsupervised/supervised classification method can assess the optimal number of classes in which data values from simultaneously considered parameters could be allocated, while the overlay technique is an additive procedure not taking into account existing trends in the dataset. The advantages and disadvantages of each procedure are further discussed.

Animals↗

PubMedDate not supplied

Development of a data visualization and analysis tool to study the particle dynamics in the coastal zone.

Developing a field experiment to study the different aspects of the marine system involves both the co-operation of research groups from distinct disciplines and the use of various meteorological and oceanographical sensors deployed simultaneously at different locations. The information obtained, stored in voluminous data sets and frequently in various formats, needs to be visualized and analysed in different ways to provide knowledge of the dynamics of the system examined. There is therefore need for tools to be able to: (i) access and retrieve data sets stored in various file formats, and (ii) to allow their visualization and analysis. In this work, a user-friendly visualization and analytical tool was developed for this purpose using the IDL (Interactive Data Language v.5.3). It allows the description, interpretation and analysis of the temporal and spatial variability of both scalar and vector variables. A description of the software is given and an application using data from the High Frequency Flux (HFF) experiment, part of the European MTP II-Mater research project, in the Gulf of Lions is presented.

Automation↗