Some observations on the maërl distribution in the northern Adriatic Sea
Abstract
This paper forms part of a wider research into changes among the deepest phytocoenoses of the Northern Adriatic Sea.
The area is featured by organogenous rocks rising from a sandy bottom and rather strong deep currents thus explaining the presence of adapted species such as: Lithophyllum racemus (Lamarck) Foslie, Lithothamnion corallioides Crouan et Crouan, Phymatolithon calcareum Pallas, Spongites (Lithothamnion) fruticulosa (Kuetzing) Foslie and Lithothamnion valens Foslie. These species are calcareous perennial structures which form a part of the sediment. This meant it was necessary to distinguish between living and dead algae during the mapping of the facies.
The area from Grado to Venice was investigated with 15 sampling sites each of which had 5 grab picks. In order to understand how the environment may act on the distribution of maerl, the samples were identified, then divided according to colour-vitality and finally dried and weighed. Data were analyzed by means of multivariate methods.
The results indicate trends similar to those already suggested by previous works since the elaborated data show one abundance gradient stretching from Grado to Venice and another located in-offshore near Venice. These gradients are further confirmed by a greater presence of living algae near Venice.