Copper and Zinc in Estuarine Water: Chemical Speciation in Relation to Bioavailability to the Marine Planktonic Diatom Dityl Um Brightwellii

Abstract

Availability of toxic trace metals in relation to phytoplankton growth was studied in water of the polluted Westerschelde (southwestern Netherlands). The prominent estuarine diatom Ditylum brightwellii was grown in bioassays with estuarine water (14%o salinity). Selective removal of Cu and Zn, and addition of a chelator (EDTA), had a positive effect on its cell division, whereas addition of Zn had an adverse effect, indicating an influence of in situ levels of Cu or Zn on estuarine phytoplankton growth. To study this in more detail, metal availability was manipulated in order to measure the responses of Ditylum brightwellii at different cellular levels of Cu and Zn. Metal speciation was approached with different metal‐adsorbing resins and compared with cellular metal concentrations. Optimum positive correlations between cellular and column‐adsorbed fractions of Cu and Zn were obtained, using an aluminum hydroxide‐coated sulfonic acid resin (ALSA). Both ALSA‐adsorbed and cellular Cu and Zn increased after a 4–h UV irradiation of Westerschelde water, whereas division rates and final cell numbers decreased. Opposite results were obtained after a partial removal of Cu and Zn with Chelex‐100®: ALSA‐adsorbed and cellular Cu and Zn were relatively lower, and this reduction caused a relative increase of final cell numbers. Addition of Cu caused a relative increase of both ALSA‐adsorbed and cellular Zn, probably due to Cu‐Zn exchange and a subsequent release of Zn from ligands in Westerschelde water. Increasing amounts of utile Zn or Cu may shorten the exponential‐growth phase of Ditylum brightwellii in the Westerschelde. This effect was stronger in a medium from Restronguet Creek (UK) containing micromoles of dissolved Cu and Zn, due to drainage of copper and tin mines.

Concentrations of Selected Heavy Metals in Benthic Diatoms and Sediment in the Westerschelde Estuary

“…Only at the Oosterschelde locations was the bioconcentration factor > 1. These concentrations are in the range that has been found for the pelagic species Dytilum brightwellii (Rijstenbil and Poortvliet 1992). The relationship with sediment concentrations was less obvious than for Pb or Zn.…”

Oxidative stress induced by copper: defense and damage in the marine planktonic diatom Ditylum brightwellii, grown in continuous cultures with high and low zinc levels

“…9 c), but cell division was suppressed in Zn+ cells (Fig. 6) (Stauber and Florence 1990;Rijstenbil and Poortvliet 1992). Chlorophyll a proved to be sensitive to Cu, and its decrease coincided with the decrease of photosynthetic activity.…”

“…At low values, both Cu and Zn stimulate phytoplankton growth (Brand et al 1983;Verweij et al 1992), but a slight excess of both metals binds SH sites, while Cu also oxidizes -SH to disulfur (-SS-) bridges in proteinaceous biomolecules, causing a cumulative, inhibitive Cu/Zn effect Florence 1987, 1990;French and Evans 1988;Rijstenbil and Poortvliet 1992). With speciation models it was calculated that for most algae, ion activities of Cu 2+ limit growth below 10 -13 M, and become sublethal above 10 -11 M (Brand et al 1986;Verweij et al 1992).…”

Evaluating the efficiency of sediment metal pollution indices in interpreting the pollution of Haraz River sediments, southern Caspian Sea basin

“…This study provides valuable information on the potential mobility and bioavailability of heavy metals in river sediments. As it is indicated in lots of studies, toxicities and bioavailabilities depend on heavy metal species, e.g., free ion and labile complexes are more toxic and bioavailable to aqueous organisms and plants (Ibrahim Korfali and Davies 2004;Murakami et al 2009;Degryse et al 2006;Rijstenbil and Poortvliet 1992). Accordingly, it may be concluded from the chemical partitioning data that there are significant differences in the distribution of the metals studied.…”