Diatom distribution across a temperate microtidal marsh, Mar Chiquita coastal lagoon, Argentina

ESPINOSA, MARCELA A.; HASSAN, GABRIELA S.; ISLA, FEDERICO I.

Thalassas

Universidad de Vigo

Lugar: Santiago de Compostela; Año: 2006 vol. 22 p. 9 - 16

0212-5919

The distribution of surface diatom assemblages across a marsh was examined in a coastal lagoon of Buenos Aires Province. Mature marsh development within the lagoon is recognised as related the growing of spits and the infilling of the tidal flats comprised between these spits evolving to marshes, as the salt tolerant species colonise the sea environment. Five diatom zones were identified by cluster analysis. R-mode factor analysis was performed in order to define representative diatom assemblages. The first group (zone A) is associated to the flood plain environment, where tidal inundation is not frequent and of short duration (subject to floods or storms). The assemblage is dominated by brackish/epiphytic and aerophilous taxa adapted to irregular floods. The second group (zone B) is represented by brackish/freshwater epiphytic and  tychoplanktonic assemblages characterising the distant high marsh. In the high marsh closer to the lagoon environments. Zone D corresponds to the levee and chenier where the tidal flooding is frequent and dominated by marine planktonic, benthic and epiphytic taxa. The diatom assemblage of zone E is represented by marine epiphytic and benthic species (autochthonous) and freshwater plankton and tychoplankton, characterising the mudflat. Overall, the composition of diatom assemblages in this microtidal marsh is a direct function of morphology in relation to the duration and frequency of tidal exposure.