Cadmium Toxicity and Uptake by Mats of the Freshwater Diatom: Navicula pelliculosa (Bréb) Hilse

Abstract

Contaminant uptake by algae, and its subsequent toxicity, has important ramifications for aquatic biomonitoring and environmental risk assessment. To study the effects of cadmium on diatom mats, a series of experiments was undertaken. These investigated the sensitivity of Navicula pelliculosa mats to cadmium, uptake of cadmium across a range of exposure concentrations, influence of mat biomass and thickness on uptake, and cadmium uptake by mats over time. Diatom mat formation proved to be sensitive to cadmium exposure, with a 96-h EC(50) of 31 microg/L. The rapid uptake of cadmium over 15 min was a linear function of exposure concentration and was not significantly affected by mat thickness. Cadmium uptake over time was also a linear function of exposure concentration for time periods up to 5 h. Linear uptake was likely due to the availability of algal binding sites as cadmium ions diffused through the diatom mats. Internal high-pH microenvironments may also have influenced uptake, through cadmium precipitation or enhanced adsorption within the mats. The lack of a significant relationship between mat biomass and uptake could be explained by the static water exposure conditions. Other studies have shown that cadmium uptake by algal mats was only significantly affected by biomass under flowing water conditions. Flowing water appeared to facilitate the diffusion of cadmium ions through the algal mats. Our research demonstrates the propensity of diatom mats to adsorb cadmium to achieve concentrations that could inhibit macroinvertebrate grazing. Overall, these findings contribute to a greater understanding of cadmium bioavailability in aquatic ecosystems and to the further development of benthic algae as an effective biomonitoring tool.

Larval aquatic insect responses to cadmium and zinc in experimental streams

“…Similarly, Kim et al [55] noted that Zn losses from solution to periphyton in static exposures were initially rapid, with 63% loss on the first day, increasing to 77% loss by day 2. Irving et al [58] similarly found that Cd uptake dynamics were rapid at moderate dissolved concentrations ($10 mg/L) and increased linearly over time up to approximately 1 wk. Irving et al [58] similarly found that Cd uptake dynamics were rapid at moderate dissolved concentrations ($10 mg/L) and increased linearly over time up to approximately 1 wk.…”

Recent views on river pollution and diatoms

“…These artificial substrates can, after several days of colonization, be transferred from an unpolluted to a metal-polluted site (Ivorra et al, 1999;Gold et al, 2002) to study the reactions of naive biofilms to contamination. Several studies have used cultures isolated in the field (Cohn & McGuire, 2000;Ivorra et al, 2002b;Debenest et al, 2008;Irving et al, 2009) to determine dose-effect responses in the laboratory.…”

“…One of the first questions studies should address is whether metals or pesticides are accumulated in the biofilms (Ivorra et al, 2000;Gold et al, 2003b;Morin et al, 2007Morin et al, , 2008Irving et al, 2009;Serra et al, 2009). Metal accumulation in biofilms follows three different mechanisms:…”

“…In rare cases measurements of mat thickness were conducted: it was shown by exposing cultures of Navicula pelliculosa to Cd contamination that this metal prevents formation of mats and reduces biomass (Irving et al, 2009).…”

Substratum‐Associated Microbiota

“…Copper and zinc addition in artificial stream channels significantly reduced chlorophyll a concentrations, dry mass and AFDM, and also changed benthic algal species diversity and relative abundances of benthic algal species (Atazadeh et al, 2009). Experiments investigated the uptake properties of cadmium by Navicula pelliculosa mats and found that diatom mats achieve concentrations that could inhibit macroinvertebrate grazing (Irving et al, 2009). The effects of sediment-associated toxins in the River Elbe basin on benthic algae were analyzed.…”