Marine benthic diatoms from Sardinia
(Tyrrhenian Sea, sublittoral zone)
Collection of the samples
samples were collected by schnorkelling between 3 and 5 meters deep, at
the end of October 2010, on the north-east littoral of the island
(between San Teodoro and Posada; 40°43'31.15" N, 9°42'53.18" E).
surface of the sediment was scraped on a thickness of 3-4 mm using 50
ml Falcon tubes. After dilution with 0,5 volume of sea water,
the samples were shaken deeply and the diatoms were separated from the
sediment by 2 or 3 differential sedimentations, then fixed with acidic
Lugol solution. The frustules were treated and prepared according to Loir
2004b; see Bibliography).
Composition of the diatom populations :
The analysis of the 4 samples has allowed to list a
total de 271 taxa, belonging to 46 genera (see list of taxa). Twenty four genera were represented by only one taxus. Sixty six taxa were not identified. The genus of 2 taxa was not determined.
The most represented genera are :
Genus Mastogloia : 46 taxa,
Genus Nitzschia : 34 taxa,
Genus Amphora (and Halamphora) : 31 taxa,
Genus Navicula : 29 taxa,
Genus Cocconeis: 27 taxa,
Genus Diploneis : 19 taxa,
Genus Lyrella : 9 taxa,
Genus Licmophora : 6 taxa.
The genus Mastogloia Thwaites ex WM Smith :
Many taxa have measurements near or below the inferior limit given by the diagnoses.
Pictures of some of the collected taxa are presented in :
Several non-identified taxa are presented in :
The 4 samples have allowed to list 46 taxa belonging to the genus Mastogloia (see list of taxa). One taxa has not been identified.
Thirty seven taxa are present in the French
The valves of an half of the identified taxa have measurements near or
below the inferior limit indicated by the diagnoses. Five taxa have a
size clearly below the inferior
Some of the Mastogloia taxa are presented in :
4 samples collected at the end of October in a very restricted area of
the sardinian littoral have allowed to establish a likely incomplete list of the diatom taxa present in the first meters of the
sub-littoral zone of this coast. Nevertheless, they have allowed to
evidence the occurence of a great specific diversity and the presence
of numerous Mastogloia taxa.
A total of 790 taxa (254 have not been identified) was listed in the samples collected in Sardegna, in Dalmatie, in Greece, in Crete, in Corfu and in Menorca (see list of diatoms from Mediterranean Sea). In these samples, we have listed a total of 102 taxa belonging to the genus Mastogloia (see A check-list of the Mastogloia species from the Mediterranean area and list Mastogloia from the Méditerranean Sea).
As we have already observed for the genus Cocconeis present in the sub-littoral zone of Brittany (Loir, 2007 ; see Bibliography) and of Guadeloupe (see Basse-Terre), as well as for several species present in the same zone in Martinique (see Martinique), two tens of Mastogloia taxa collected in Sardegna on the sandy sediments in the sub-littoral zone present measurements near or below the inferior limit indicated in the diagnoses.