Environmental impact of heavy metals from dredged and resuspended sediments on phytoplankton and bacteria assessed in in situ mesocosms

Some Metabolic, Diversity and Toxicity Aspects of Bacterial Communities Life in Aquatic Sediments

“…These results and those reported by Frostegård et al [21] seem to support this assumption since (i) an increase in the tolerance of the bacterial community and changes in the PLFA pattern were found at similar metal concentrations and (ii) similar effects of heavy metal additions were deduced after the bacterial communities were grouped on the basis of the results of a PLFA pattern analysis and tolerance pattern measurements [21]. Nayar et al [22] studied reactions of heterotrophic bacteria on heavy metals in mangrove sediment environment in Ponggol Estuary. This study revealed very high concentrations of heavy metals in suspended particulates and sediments compared to the levels in water.…”

“…This explains the enhanced rates of heterotrophic bacterial production and increased total bacterial biomass in treatments with high concentrations of metals. It was apparent that bacterial heterotrophs were not affected by the background concentrations of heavy metals that were biologically available from the sediments re-suspended by dredging [22].…”

“…Circumneutral to alkaline sediment pH creating good conditions for hydrogenotrophic methanogenesis. Other studies have shown that CH 4 production at low temperature (4 o C) in sediments was mainly from acetate, however, an increase in temperature (20)(21)(22)(23)(24)(25) o C) lead to an increase in contribution of CH 4 production from H 2 /CO 2 . Slightly higher temperature at the sediment-water surface (26.3-30.7 o C) creates good conditions for hydrogenotrophic methanogenesis.…”

Effects of sediment dredging on water quality and zooplankton community structure in a shallow of eutrophic lake

“…But most of the previous studies related to effects of dredging on water quality, release of nutrients and heavy metals, benthos, algal-periphyton, bacteria, larval zooplankton, birds and aquatic plants (Brookes, 1987;DeCoursey and Vernberg, 1975;Howarth et al, 1982;Lewis et al, 2001;Lohrer and Wetz, 2003;Nayar et al, 2004;Spencer et al, 2006). Information on the effects of dredging on zooplankton community structure is rare but also inconsistent (Wang et al, 2005;Li et al, 2007;Wu et al, 2008).…”

“…The increase in EC was partly due to the increasing NO 3 − -N concentration judged from their significant correlation (Pearson's correlation, P = 0.018, n = 24). The increases in EC and TDS levels might also indicate the re-suspension of particulate metals (e.g., Ca, Mg, Na, K, Ba, Fe, Sr (Zhang, unpublished data)) and their release from the sediment to the aqueous phase (Nayar et al, 2004).…”