Benthic bacterial cells

The most obvious impact of sediment-associated pollutants on aquatic biota is direct acute toxicity and there is considerable literature on both laboratory and field effects of toxic substances on marine and freshwater invertebrates (Baker, 1980 Reynoldson, 1987). For example, Warwick (1980) and Wiederholm (1984) observed deformities in chironomid larvae mouthparts at polluted sites of lakes in Canada and Sweden Milbrink (1983) has shown setal deformities in oligochaetes exposed to high sediment mercury levels. Indirect effects resulting from sediment contamination oftenly include changes in benthic invertebrate community structure. For example, Lock et al. (1981) evidenced increased growth of bacterial flora and algal cells on oiled substrates and a consequent stimulation of macroinvertebrates. Chapman et al. (1982) have shown effects of life history alterations (e.g., impairment of reproduction and age selective toxicity) which have been linked to sediment contaminants. ... 

The role of bacteria. In a recent study on the activity of benthic bacteria in Amazonian rivers (22), microbial biofilms were collected off of submerged plants and sediment, and subsequently analyzed with transmission electron microscopy (TEM), coupled with energy dispersion X-ray spectroscopy (EDS) and selected area electron difiraction (SAED). th TEM, it was observed that bacterial biomineralization involved a complex interaction between metals in solution with the reactive components of the cell. The anionically-charged cell wall and the encompassing layers provided special microenvironments for the deposition of iron and other soluble cationic species. Ferric iron, which exhibits unstable aqueous chemistries, was bound in significant amoimts, and previous studies indicate that... 

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