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Cocconeis subantarctica sp. nov. from Kerguelen Archipelago (Austral Ocean) and comparison with Cocconeis stauroneiformis (W.Smith) Okuno

Riaux-Gobin C., Witkowski A.

Oceanological and Hydrobiological Studies

2017

Vol. 46, No. 3

350--362

Cocconeis subantarctica sp. nov., a small monoraphid marine diatom, previously described as C. scutellum cf. var. parva Grunow, is reported from the Kerguelen Archipelago. Based on the careful re-examination of the material using SEM (scanning electron microscopy), both valves and the cingulum were described, which enabled a better classification of this small Subantarctic taxon. The shape of the frustule is widely rounded to subdiscoid, with uniseriate and radiate striae on both valves. The SV (sternum valve) areolae have rota-like hymenate pore occlusions, with larger marginal areolae separated by a hyaline rim. The RV (raphe valve) areolae are more complex than those of the SV, with several reniform concentric hymenate occlusions. This taxon has no real stauros, only one virga, which is larger on one side of each valve. The species is not a member of the Cocconeis scutellum ‘complex’, but is closely related to C. stauroneiformis despite several morphological differences.

Nutrient status in coral reefs of the Îles Eparses (Scattered Islands): comparison to nearby reefs subject to higher anthropogenic influences (Mozambique Channel and Mascarenes, Indian Ocean) [commun.]

Riaux-Gobin C., Witkowski A., Saenz-Agudelo P., Neveux J., Oriol L., Vétion G.

Oceanological and Hydrobiological Studies

2011

Vol. 40, No.3

84-90

Indian Ocean coral reef environments off Mascarenes (Réunion and Rodrigues Islands), Comores archipelago (Mayotte) and Eparses atolls (Europa, Glorieuses, Juan de Nova and Tromelin), were sampled in 2007 and 2009 for environmental parameters and benthic diatoms studies. This preliminary note documents the nutrient concentrations [NO_3-, NO_2-, PO_4- and Si(OH)_4] of coastal waters in diverse sites and examines the possible relationship between nutrient concentration and anthropogenic pressure. The pool of data is restricted, but the marine coastal environments of Réunion, Rodrigues and Mayotte exhibit, on average, higher levels of nutrient concentration, as compared to Eparses atolls, probably in relation to the degree of urbanisation. A project based on the study of benthic diatom assemblages will offer the opportunity to search for possible anthropogenic signatures.