Dredging impact on the epipelic diatom species composition on mudflat from the Bahía Blanca Estuary (Argentina)

PIZANI, N; PARODI, E.R.

Viena, Austria

Congreso; XXVII International Botanical Congress,; 2005

International Botanical Society

The dredging in areas of intense harbour activity is cause of considerable alterations in the conformation and dynamics of the biological communities. The aim of this work was to analyse its effects on the epipelic diatom species composition. The study was conducted in muddy tidal flats in Puerto Rosales (38° 53´S 62° 06´O) after 10 days from a dredging, in low tidal conditions. Observations were carried out parallel to the coastline from the dredging site (E3) and other two stations (E2 and E1) 200 m away. Diatom assemblages and density were sampled by the lens tissue method. The nearest station of the dredging zone (E3) showed only fine sediment particles and scarce frustules rest of phytoplanktonic diatoms that indicated the major disturbance due to deposition particles produced by nearby dredging. There were important taxonomic structural changes in the diatom-dominated and no differences in their density between the rest stations. E2 was dominated by Surirella minuta while in the farthest (E1) Cylindrotheca closterium and Gyrosigma spencerii were the most abundant. The presence of alive benthic diatom populations indicated an active biogenic process.