Συμβολή στη μελέτη της βιοποικιλότητας των συνευρέσεων του σκληρού μεσοπαραλιακού και υπερπαραλιακού υποστρώματος

Abstract

The main aim of this study was to produce the main knowledge framework that will permit the creation of a model on the influence of key environmental factors on the formation of the hard substrate midlittoral and supralittoral assemblages in the Mediterranean. In order to achieve this goal the following hypothesis was made: The results of the examination of the qualitative and quantitative composition of a certain assemblage, in different locations with a graded influence of a certain factor, will determine the influence of this factor on the configuration of the certain assemblage’s biodiversity. The factors that were selected to examine their influence on the configuration of the assemblage biodiversity were: a) hydrodynamism, as a result of water flow, b) hydrodynamism, as a result of wave action, c) salinity, d) recent warm, sulfurous waters and e) pollution (mainly organic). After a thorough survey of coasts with hard substrate (artificial or natural) in a large part of the Greek coastline, the sampling stations network was selected. For each one of the studied factors,the network included three different locations in which this factor prevailed over the others having a graded intensity in each one of these three locations. Thus, for the examination of the hydrodynamism influence due to water flow, three neighboring stations were selected in the area of Evripos channel where a strong tidal current exists. The second group of stations was selected in the area of Chalkidiki in order to study the influence of hydrodynamism intensity due to wave action. For this purpose, three stations were selected with a graded exposure to wave action. For the examination of the influence of pollution, three stations were selected in the inner part of Thermaikos gulf. In Porto – Lagos, two stations were chosen in order to study the influence of salinity changes on the biodiversity of the hard substrate midlittoral and supralittoral assemblages. Finally, for the examination of the structure of these assemblages in locations with hydrothermal springs, one station was selected at the coast of Loutra Aidipsou (Evvoia). The sampling program was carried out from September to October, 1997 and included one sampling in all the selected stations. In the lower midlittoral zone of each station 5 samples were always taken, either with a quardat–sampler, 400 cm2 total surface, which had a net attached on its upper part, or with a subdivided quardat– sampler, 400 cm2 total surface, which had a grid on its upper part. In the upper midlittoral and supralittoral zone of each station 5 samples were also taken with the subdivided quardat–sampler. In each station, indicative measurements of water temperature, salinity and conductivity were carried out as well as an estimation of hydrodynamism intensity by the method of determining the weight loss of preweighted plaster discs.