Trophic transfer of seven trace metals in a four-step marine food chain

Abstract

There is increasing recognition of the importance of dietary pathways in determining metal body burdens in marine organisms. With a simple kinetic model that requires information about the ingestion rate of an animal and the assimilation efficiency (AE) and efflux rate constant (k e ) of a metal following dietary exposure, it is possible to quantitatively predict the trophic transfer and biomagnification potential of a metal between trophic levels. In this study, we used radiotracers to examine the trophic transfer of 7 metals (Am, Cd, Co, Cs, Mn, Se, and Zn) in a 4-step marine food chain from phytoplankton (Isochrysis galbana) to crustacean zooplankton (Artemia salina) to juvenile sea bream (Sparus auratus) and finally to piscivorous sea bass (Dicentrarchus labrax). AEs generally were highest for Cs (63-84%) and Se (60-77%), and lowest for Am (<10%) for all animals; differences in AEs for the other metals were comparatively small for all animals. There was no consistent pattern among the metal k e s; however, k e s for any given metal tended to decrease with increasing trophic level. At each trophic step, we calculated the trophic transfer factor (TTF), defined mathematically as the ratio of metal concentration in predatory animals to metal concentration in prey organisms at steady state, and found that this ratio consistently approached or exceeded 1 for only Cs, suggesting that Cs biomagnifies at every trophic step from phytoplankton to fish. TTF values were always <1 for Am, Cd, Mn, and Co, suggesting that these metals are not expected to biomagnify in marine food chains. Se and Zn did not consistently display TTF values >1 at every trophic level, but values were close enough to unity to suggest the possibility of biomagnification under certain environmental regimes. KEY WORDS: Trophic transfer · Biomagnification · Metals · Food chain Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 367: [23][24][25][26][27][28][29][30][31][32][33] 2008 fore the potential for bioaccumulation or biomagnification of dietary metals at different trophic levels, especially for animals at the top of the food chain. Biomagnification is defined here as the progressive bioconcentration of metals with increasing trophic level, and the potential for biomagnification can be mathematically described as the ratio of metal concentration in a predator organism to the metal concentration in its prey. If this ratio is >1, biomagnification is likely to occur (Reinfelder et al. 1998). This is analogous to the bioconcentration factor (BCF) used to describe bioconcentration of dissolved metals, but while BCFs have been characterized for many metals and many marine organisms, the biomagnification potential remains unknown for most predator-prey interactions and for most metals (Wang 2002).Here, we compare the trophic transfer of 7 metals (Am, Cd, Co, Cs, Mn, Se, Zn), which differ in chemical properties and biological functions, to assess their capacities for trophic transfer in a simplifi...

Intraspecific comparisons of metal bioaccumulation in the juvenile Atlantic silverside Menidia menidia

“…Our Am AE values (0.3 to 1.9%) are lower than other values noted in fish fed zooplankton prey (4 to 6%; Baines et al 2002, Mathews & Fisher 2008b). Nearly all Am had been lost from both silverside populations within the first 8 h of depuration, and if the fish were radioassayed more frequently during this time, Am could be used as a tracer to calculate an accurate gut passage time, as noted for copepods .…”

“…The AEs observed (15% for Nova Scotia, 39% for South Carolina) are within the range noted for other estuarine and marine fish fed zooplankton prey (21 to 28%; Baines et al 2002, Mathews & Fisher 2008b). However, our values were higher than those observed for killifish Fundulus heteroclitus (7%, Mathews & Fisher 2008a), grunt Terapon jarbua (6.3%, Zhang & Wang 2006), and mangrove snapper (9.8%, Xu & Wang 2002) fed zooplankton prey.…”

Ecosystem model-based approach for modeling the dynamics of &lt;sup&gt;137&lt;/sup&gt;Cs transfer to marine plankton populations: application to the western North Pacific Ocean after the Fukushima nuclear power plant accident

“…The phytoplankton elimination rates estimated from this calibration (0.5 d −1 ) were very similar to that calculated using the allometric relationship reported by Vives i Batlle et al (2007) The 137 Cs assimilation efficiency by zooplankton calibrated in this study was 0.75. This value is similar to that used by Brown et al (2006), and is slightly higher than the 0.63 observed by Mathews and Fisher (2008) for the crustacean zooplankton Artemia salina.…”

“…In our study, the modeled TTFs were generally higher than the unity for all zooplankton groups, showing evidence of biomagnification potential at this trophic level. Mathews and Fisher (2008) reached the same general conclusion for the crustacean zooplankton Artemia salina feeding on phytoplankton, and reported that TTFs are directly related to the food ingestion rates, and that a consistent capacity for biomagnification exists when the food ingestion rate is high.…”

“…This sensitivity analysis showed that the parameters related to the two groups of phytoplankton are very important for the estimation of the 137 Cs concentration in all plankton groups. Therefore, these parameters are key determinants Kaeriyama et al (2014) and (e) Kitamura et al (2013). of the radionuclide concentration in all marine animals of the pelagic food chain (Mathews and Fisher, 2008). Consequently, the experimental determination of these parameters, often neglected due to the difficulties characterizing the measurement of radionuclides in phytoplankton, is of the greatest importance.…”