Fidelity of dead diatom assemblages in estuarine sediments...

HASSAN, G; ESPINOSA, M. A; FEDERICO IGNACIO ISLA

Palaios

SEPM

Año: 2008 vol. 23 p. 112 - 120

The main objective of this contribution is to evaluate the environ- mental fidelity of dead diatom assemblages along two microtidal es- tuarine systems from southeastern Buenos Aires Province (Argenti- na). Living communities (inferred from counting protoplasm- containing cells) were compared to dead diatom assemblages through several fidelity metrics. Gradient analysis (by canonical correspon- dence analysis) was applied in order to assess the quantitative rela- tionship between diatom assemblages and the environmental gradi- ent. The presence of allochthonous components in diatom assemblag- es was assessed by analyzing the distribution of the main ecological groups. Results indicated a good agreement between living commu- nities and total assemblages in surface sediments, as well as between total surface and subsurface assemblages from both estuaries. A high percentage of the variance in diatom assemblage composition was explained by the environmental gradient, particularly by sediment composition and salinity, indicating that taphonomic alterations play a minor role in structuring these assemblages. The good preservation of diatom thanatocoenoses in estuarine sediments makes them accu- rate indicators of the environmental conditions at the point of de- position, providing useful information for paleosalinity reconstruc- tions in coastal settings.