A. Zenetos, CLASSIFICATION AND INTERPRETATION OF THE ESTABLISHED MEDITERRANEAN BIOCOENOSES BASED SOLELY ON BIVALVE MOLLUSKS, Journal of the Marine Biological Association of the United Kingdom, 76(2), 1996, pp. 403-416
Based on the bivalve fauna known from an extensively studied zone, alo
ng the infralittoral in the Patras Gulf, a biotope approach was attemp
ted using numerical taxonomy methods. The efficiency of various combin
ations of similarity measures and clustering techniques is discussed f
or this type of data (single group - binary). Four main station groups
were delimited which were further assigned to the biotopes of known M
editerranean biocoenoses. The four groups correspond to: (a) the bioto
pe of the Posidonia beds (HP) and that of coarse sands and fine gravel
s under the influence of bottom currents (SGCF). The limits of these t
wo biocoenoses are not clear-cut. (b) The biotope of the coastal detri
tic bottoms (DC) usually occurring in deeper areas but met in the infr
alittoral under environmental stress. (c) A transitional zone where de
generating Posidonia meadows are gradually replaced by Cymodocea and Z
ostera, facies of the muddy sand in sheltered areas biocoenoses (SVMC)
. This degradation can be attributed to various disturbing factors inc
luding natural environmental changes. (d) The biotope of fine well-sor
ted sands (SFBC). A typical malacofauna is present with the addition o
f some species. Regardless of the differences, Peres & Picard's (1964)
scheme is more appropriate in the Mediterranean ecosystems than any o
ther northern European scheme.