Contribution of dietary bacteria to metal accumulation in the slipper limpet

Abstract

Recent studies have shown that dietary ingestion can be an important source for metal accumulation in aquatic animals. Whether bacteria can contribute significantly to the overall metal accumulation in these animals remains little known. In this study, we used the kinetic modeling approach to examine the relative contribution of the aqueous phase, bacteria, and phytoplankton, as sources for Cd, Cr, and Zn accumulation by the slipper limpet Crepidula onyx, a suspension feeder that can capture bacteria efficiently. Metal uptake rate constants measured in C. onyx were 0.200, 1.232, and 1.294 l g -1 d -1 for Cd, Cr, and Zn, respectively. The assimilation efficiency (AE) of metals from ingested phytoplankton (11 to 44% for Cd, and 31 to 41% for Zn) was comparable to AEs of metals from ingested bacteria (21 to 42% for Cd, 35 to 47% for Zn), whereas the AEs of Cr from ingested phytoplankton (10 to 22%) were lower than from ingested bacteria (44 to 59%). The AEs of Cr from different phytoplankton and bacterial diets were related to its distribution in the cytoplasm of cells and its passage time across the animal's guts. The limpets filtered the bacteria at rates (17 l h -1 g -1 ) 1.3 to 1.9× lower than the filtration rate on different phytoplankton diets (22 to 33 l h -1 g -1). The estimated average bioconcentration factors of metals by 2 bacterial strains were 2 to 6 × 10 5 for Cd, 1 to 7 × 10 5 for Cr, and 1.5 to 7 × 10 5 for Zn. The kinetic model predicted that uptake from dietary phase dominated metal accumulation in the slipper limpets (87% for Cd, 72% for Cr, and 83% for Zn). Ingestion of bacteria contributed 23% for Cd, 27% for Cr, and 17% for Zn accumulation in the limpets under typical conditions for the limpets. Our study therefore highlights bacteria as a potentially important source of metal accumulation in this filter-feeding mollusc.

Metal and antibiotic-resistance in psychrotrophic bacteria from Antarctic Marine waters

“…This may be the reason for higher tolerance to Zn at 100 ppm. Bacteria are a potentially important source of metal accumulation in filter-feeding mollusk like limpets as ingestion of bacteria contributed up to 17% for Zn accumulation (Qiu et al 2001). Interestingly, about 29% of the isolates were resistant to 100 ppm of cadmium salt.…”

Brachidontes variabilis and Patella sp. as quantitative biological indicators for cadmium, lead and mercury in the Lebanese coastal waters

“…Cubadda et al (2001) and Davies and Cliff (1999) suggested that the feeding habits are involved in the process. Qiu et al (2001) demonstrated using kinetic modeling that the uptake from dietary phase (especially bacteria) dominated metal accumulation in the slipper limpets (87% for Cd).…”

The barnacle Balanus amphitrite as a biomonitor for Cd: Radiolabelled experiments

“…selected food items are of the organism's natural diet (Qiu et al, 2001), because each item may present a specific AE. Usually, two feasible options can be adopted on the determination of AE from laboratory experiments: (i) to select a small number of species (Wang et al, 1999b;Wang and Rainbow, 2000;Rainbow and Wang, 2001) or (ii) to work with the 'in situ' food Luoma et al, 1998;Ke and Wang, 2002).…”

“…Manipulative experiments using radioisotopes are among the best methods to obtain these (Wang and Fisher, 1999), and there have been many studies determining assimilation efficiency (AE), influx and efflux rates 1 for Cd and other metals by organisms Wang and Fisher, 1999;Wang et al, 1999a,b;Qiu et al, 2001;Rainbow and Wang, 2001;Ke and Wang, 2002;Rainbow et al, 2003).…”