Marine benthic diatoms from

the coast of Menorca

(Balears Islands, Mediterranean Sea, sublittoral zone)

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Collection of the samples

Five samples were collected by schnorkelling at the end of September 2015, at the following stations:
- Punta Prima beach,  2.5-4 meters deep,
- Benibecca beach, 2.5-3 meters,
- Cala'n Porter beach, 2.5-4 meters,
- Son Saura beach, 2.5-3 meters,
- Cala en Turqueta beach, 2.5-4 meters.

At the end of September 2016, two samples were collected, one at the Cala Macarella (southern coast) and one at the beach of Algaairens (northwestern coast).

At the end of september 2017, four samples were collected at the following stations:
         - Plage de Cala Rotja (au NE de la plage de Cavalleria), profondeur 2,5- 3,5 mètres,
         - Plage de Algaiarens, profondeur 3-4 mètres,
         - Plage de Sa Caleta (près de la plage de Santandria), 2,5-3 mètres,
         - Plage de Cala Blanca, 3-4 mètres.


On all stations, the diatomic populations were always insufficiently dense to show itself by one yellow-brown tint of the surface of the sand.

The 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 and stored in acidic Lugol solution. The frustules were treated and prepared according to Loir (2004a and 2004b ; see bibliography).

Composition of the collected diatom populations :

The analysis of the 11 collected samples has allowed to list 277 taxa belonging to 49 genera (see list of taxa ).
Twenty four genera are represented by only one taxus. Fifty five taxa were not determined. The genus of four taxa was not determined.

The most represented genera are :
Genus Mastogloia : 53 taxa,
Genus Navicula : 35 taxa,
Genera Amphora and Halamphora : 28 taxa,
Genus Cocconeis : 24 taxa,
Genus Diploneis : 21 taxa,
Genus Nitzschia : 14 taxa,
Genus Pleurosigma : 11 taxa,
Genus Lyrella : 9 taxa.


Pictures of some of the collected species are presented in  :
Genera Achnanthes to Amphora
Genera Ardissonia to Cocconeis
Genera Diploneis to Fogedia
Genera Grammatophora to Lyrella
Genre Navicula
Genera Nitzschia to Pleurosigma
Genera Podocystis to Triceratium

Some undetermined taxa are presented in :
Undetermined taxa
Undetermined Navicula taxa

The genus Mastogloia
Thwaites ex WM Smith :

The analysis of the eleven samples has allowed to list 53 taxa belonging to the genus Mastogloia (see list of taxa). Fourteen taxa were not determined.

Thirteen taxa among the 36 determined taxa are présent in the sublittoral zone of Corfou, Crete, Dalmatia, Greece and  Sardegna. Thirty four are also présent in the sublittoral zone of the French Lesser Antilles.
 
Five Mastogloia taxa among the 12 undetermined taxa (M. sp. 3, M. sp. 15, M. sp. 17, M. sp. 19 and M. sp. C ) are présent at the French Lesser Antilles. Seven were already observed in the Mediterranean Sea  (M. sp. 3, M. sp. 17, M. sp. C, M. sp. D, M. sp. E, M. sp. K  and M. sp. N; see list of taxa)
  
Pictures of some of the 53 Mastogloia taxa are presented in :

Genus Mastogloia 1
Genus Mastogloia 2
Genus Mastogloia 3


Conclusions :

The samples collected at the end of September, along the southern and northwestern seasides of Menorca have allowed to establish a first inventory of the diatoms present on the sandy bottoms, in the first meters of the sublittoral zone of this island. They highlight a global specific diversity on this coast lower than those observed in Corfou (298 taxa), in Crete (344 taxa) and in Dalmatia (299 taxa). It is the same thing for the specific diversity of the genus Mastogloia (respectively 63, 67 and 55 taxa). These moderate specific diversities go hand in hand with a weak density of the collected diatom populations. 

Fifty six among the 277 taxa present at Menorca were not observed in our samples previously collected in the Mediterranean Sea.

At the present time, a total of 790 taxa was observed in the samples that we have collected in the Mediterranean Sea (diatoms from the Mediterranean Sea). Among these taxa, 254 have not been determined. One hundred and twelve taxa belong to the genus Mastogloia (see list of Mastogloia from the Mediterranean Sea).


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