Heavy metals level in the surficial sediment from Perai River of Penang, Malaysia

Perai river is one of the important rivers to Penang and Kedah states. Many industries are located along the river that flows to the Strait of Malacca. In order to gather the status of pollution along the river, a total of 47 stations were established to measure the heavy metals content and the sediment characteristics. Findings show that finer sediments had dominated all sampling sites as samples are mostly muddy sediment. The heavy metal concentration in the surficial sediment was analyzed using the Inductively Coupled Plasma Mass Spectrometer after the Teflon Bomb digestion method. The average concentration for Zn, Cr, Cu, Cd, Pb were 74.7±33.3, 66.0±28.1, 21.8±9.05, 0.42±0.32, and 28.6±6.84 μg/g dry weights, respectively. Generally, the concentration of metals studied seemed to be controlled by natural processes. This is proved by the enrichment factor, categorized as a deficiency to minimal enrichment, and can be concluded to be the main source from the lithogenous in origin. The sources of the heavy metals in some of the stations in the Perai river are speculated from the nearby urban runoff, industry activities along with the river, fishing and shipping activities, and land transportation emission may also accumulate for the pollution in the river.

Sediment underneath charophyte meadows is enriched in viable ephippia and enhances the benthic periphytic biofilm

We contribute to the knowledge of charophyte meadows as key components of aquatic systems by analysing how they affect wetland sediments. We performed a factorial-design experiment with limnocorrals (outdoor mesocosms) in a Mediterranean protected wetland with presence or absence of charophytes [Chara vulgaris (CV) and Chara hispida (CH), planted from cultures or recruited in situ from germination of their fructifications]. The first 1 cm-surficial and 2 cm-bottom sediment layers were analysed for cladoceran ephippia, ostracods valves, benthic community of bacteria and periphytic biofilm, and charophyte fructifications. In the surficial sediment, the ephippia density was fourfold higher in the conditions with charophytes than in sites with no-charophytes and higher apparent viability was found. The surficial sediment periphyton biofilm was composed mainly of diatoms, with tenfold higher biomass underneath charophytes, and a much diverse community. The specific microhabitat generated by each charophyte species was reflected in the different abundances and relationships between the analysed components, firstly establishing a divergence with the sediment without meadows and, secondly, a distinction between the meadows of CH and CV that exhibit particular morphology-architecture, might exudate different metabolites and might have different allelopathic capacities over microalgae and microinvertebrates. Thus, the charophyte–sediment tandem is relevant for biodiversity and habitat conservation.