BIOLOGICAL-GEOCHEMICAL PROCESSES AFFECTING TIDAL FLAT SEDIMENTS

CUADRADO D.G.; PIZANI N.V

Paraty (Brasil)

Congreso; 10th Internacional Conference on Cohesive Sediment Transport Processes; 2009

universidad Federal de Rio de Janeiro

Intertidal sediments often support abundant populations of phototrophic microorganisms (Stal et al., 1985). Such populations may produce macroscopically recognisable microbial mats, often dominated by cyanobacteria or by visible biofilms of epipelic diatoms. On cohesive and noncohesive sediments, sedimentary structures are often embedded in a thick mucilaginous matrix of extracellularpolymeric substances (EPS). This EPS has been related with the adhesion of sediment particles, thereby influencing the stability of the sediment (Paterson, 1989). The presence of microorganisms in the sediment also produce geochemical changes as modification in pH which induce the mineral precipitation. The Bahía Blanca Estuary uncovers large tidal flats at low tide. In Puerto Rosales, these extend nearly 1000 m between the high and low tide line, revealing a low slope and isolated patches of vegetation. Semi-diurnal tides predominate and therefore, large areas are covered by water for only short periods at high tide and often left exposed for several days at neap tide. The objective of the study is to document field observation in a modern supratidal flat where microbial mats and biofilms are present. Also, the study try to know the role of organism activities in physical and geochemical processes in intertidal sediments.