Physico-chemical form of trace metals accumulated by phytoplankton and their assimilation by filter-feeding invertebrates

Abstract

This study investigated whether the nature of the binding of the trace metals cadmium, silver and zinc accumulated by phytoplankton can affect their subsequent assimilation efficiencies (AE) in 3 filter-feeding benthic invertebrates, the green mussel Perna viridis, the clam Ruditapes philippinarum and the barnacle Balanus amphitrite. Seven phytoplankton species were chosen from a wide systematic range to ensure large differences in the partitioning of their accumulated trace metals into 3 fractions: (1) exchangeable metal adsorbed on the outside of the cells, as defined by extraction with the chelating agent 8-hydroxyquinoline-5-sulphonate; (2) incorporated metal that is in a soluble form; and (3) insoluble incorporated metal. There were few significant correlations between AE and the percentage of phytoplankton metal incorporated into any 1 fraction or combination of fractions. There is no support, therefore, for a generalised conclusion that any of the 3 fractions isolated represents the sole form of phytoplankton metal that is bioavailable for trophic transfer to a herbivore. Even trace metals bound to the insoluble fraction in phytoplankton may be bioavailable to herbivores. Furthermore, there were no consistent effects of phytoplankton concentration on metal AEs in 1 of the herbivores -P. viridis. There was no evidence that the AE of any of the 3 trace metals was changed when the herbivores were feeding on the phytoplankton species (Thalassiosira weissflogii) on which they were fed during acclimation. KEY WORDS: Trace metal assimilation · Phytoplankton · Filter-feeding invertebratesResale or republication not permitted without written consent of the publisher

Seasonal variation of metal contamination in the barnacles Pollicipes pollicipes in northwest coast of Portugal show clear correlation with levels in the surrounding water

“…These results mean that barnacle shells do not reflect adequately metal uptake from seawater and should not be used to biomonitor or predict metal contamination in the environment. The bioaccumulation of metals in barnacle hard tissues involves the metabolic mechanisms related with the equilibrium of metal assimilation from phytoplankton and zooplankton diets and metal efflux rates, but probably also the mineralization processes during shell plates formation, when replacement of Ca by other bioavailable metals in the seawater may occur (da Silva et al 2004Silva et al , 2005Silva et al , 2009aHockett et al,1995Hockett et al, , 1997Ng et al 2005;Rainbow 2007;Rainbow andWang 2001, 2005;Rainbow and White 1989;Rainbow et al 2003Rainbow et al , 2004bViarengo and Nott 1993;Wang and Rainbow 2000Wang et al 1999;Watson et al 1995). Thus, bioaccumulation of metals in barnacle hard tissues may be masked by mineralization (Fig.…”

Mercury and plankton in tropical marine ecosystems: A review

“…The total amount of trace elements accumulated by prokaryotes (microplankton) will affect the quantity of trace metals transferred trophically along the food chain, due to the fact that mesoplankton (copepods and cladocerans) grazing on microplankton (diatoms and dinoflagellates) and both of these plankton fractions served as food source for small fish (Fenchel 2008). The nature of metal binding in microplankton also possesses the potential to significantly affect trophic transfer (Ng et al 2005).…”

Trophic transfer of trace metals: subcellular compartmentalization in bivalve prey, assimilation by a gastropod predator and in vitro digestion simulations

“…It is therefore relevant to identify general principles that govern the trophic bioavailability of trace metals (Wang & Fisher 1999). The chemical form of trace metals accumulated by food organisms is one potential major factor controlling the assimilation of a trace metal from the diet (Reinfelder & Fisher 1991, Wallace & Lopez 1996, 1997, Wallace et al 1998, Ng et al 2005, Rainbow et al 2006a. Reinfelder & Fisher (1991) observed a linear 1:1 relationship between the metal assimilated by marine copepods from diatoms Thalassiosira pseudonana and various metals partitioned in the cytoplasm of the ingested phytoplankton, suggesting that only metal bound to the soluble fraction in diatoms is available to copepods.…”

“…This relationship is an oversimplification, however, for filter-feeding invertebrates in general (Wang & Fisher 1996, Decho & Luoma 1996, Xu & Wang, 2001, 2002. For example, Ng et al (2005) investigated whether the nature of the binding of Cd, Ag and Zn accumulated by phytoplankton (surface exchangeable metal, soluble incorporated metal, insoluble incorporated metal) could affect their subsequent assimilation efficiencies in 3 filter-feeding benthic invertebrates. None of the 3 fractions isolated represented the sole form of metal that is trophically available to a herbivore, and even trace metals bound to the insoluble fraction in phytoplankton were at least partly trophically available to the herbivores.…”