Proceedings of the Second Mediterranean Symposium on Marine

PROCEEDINGS OF THE SECOND MEDITERRANEAN SYMPOSIUM ON MARINE VEGETATION (ATHENS, 12-13 DECEMBER 2003)
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MATERIALS AND METHODS
The indices were applied on existing data from <strong>the</strong> Maliakos Bay (Aegean Sea, Greece)
(Chryssovergis & Panayotidis, 1995). The data was quantitative and consisted <strong>of</strong> a set <strong>of</strong> five
stations along an eutr<strong>of</strong>ication gradient (Fig. 1) for two years (summer and winter months).
Fig 1: Map <strong>of</strong> Maliakos Bay (Greece) showing <strong>the</strong> five sampling stations along a eutr<strong>of</strong>ication gradient from
<strong>the</strong> Sperchios River mouth (stations A & B), from were <strong>the</strong>re is an important nutrient input, towards <strong>the</strong>
Aegean Sea (stations C & E).
The Ecological Evaluation Index
The EEI was calculated according to Orfanidis et al. (2001). The macrophyte species
were divided in two Ecological State Groups. In ESG I were grouped <strong>the</strong> thick lea<strong>the</strong>ry,
<strong>the</strong> articulate upright calcareous and <strong>the</strong> crustose calcareous species, most <strong>of</strong> <strong>the</strong>m being
k-selected species. In ESG II were grouped <strong>the</strong> foliose, <strong>the</strong> filamentous and <strong>the</strong> coarsely
branched upright species. Most <strong>of</strong> <strong>the</strong>m are r-selected species. Each sampling site was
classified in one <strong>of</strong> <strong>the</strong> five ESC after a cross-comparison <strong>of</strong> <strong>the</strong> mean abundance value
<strong>of</strong> <strong>the</strong> ESG I and II, on a matrix. Additionally to <strong>the</strong> mean abundance value, <strong>the</strong> relative
abundance value for <strong>the</strong> two groups was applied.
Taxonomic diversity indices
According to Warwick & Clarke (2001) <strong>the</strong> average taxonomic distinctness, ∆ + , is <strong>the</strong> mean
number <strong>of</strong> steps up <strong>the</strong> hierarchy that must be taken to reach a taxonomic rank common
to two species, computed across all possible pairs <strong>of</strong> species in an assemblage. The
species are placed within a taxonomic hierarchy, based on <strong>the</strong> Linnean classification
(phylum, class, order, family, and genus). Thus, if two species are congeneric, one step
(species-to-genus) is necessary to reach a common node in <strong>the</strong> taxonomic tree. If <strong>the</strong> two
species belong to different genera but <strong>the</strong> same family, two steps will be necessary
(species-to-genus, and genus-to-family); and so on, with <strong>the</strong>se numbers <strong>of</strong> steps averaged
across all species pairs. If ∆ + is <strong>the</strong> mean path length through <strong>the</strong> taxonomic tree
connecting each pair <strong>of</strong> species, Λ + is simply <strong>the</strong> variance <strong>of</strong> <strong>the</strong>se pairwise path lengths
and could be seen as an index <strong>of</strong> <strong>the</strong> “complexity” <strong>of</strong> <strong>the</strong> hierarchical tree (Fig. 2).