Food Web Magnification of Persistent Organic Pollutants in Poikilotherms and Homeotherms from the Barents Sea

Abstract

Food web magnification of persistent organic pollutants (POPs) was determined for the Barents Sea food web using 615N as a continuous variable for assessing trophic levels (TL). The food web investigated comprised zooplankton, ice fauna and fish (poikilotherms, TL 1.7-3.3), and seabirds and seals (homeotherms, TL 3.3-4.2), with zooplankton representing the lowest and glaucous gull the highest trophic level. Concentrations of lipophilic and persistent organochlorines were orders of magnitude higher in homeotherms than in poikilotherms. These compounds had significantly higher rates of increase per trophic level in homeotherms relative to poikilotherms, with the highest food web magnification factors (FWMFs) for cischlordane and p,p'-DDE. Some compounds, such as transnonachlor and HCB, had similar rates of increase throughout the food web, whereas compounds that are more readily eliminated (gamma-HCH) showed no relationship with trophic level. It is preferable to calculate FWMFs with regard to thermal groups, because the different energy requirements and biotransformation abilities between poikilotherms and homeotherms may give different rates of contaminant increase with trophic level. When biomagnification is compared between ecosystems, FWMFs are preferable to single predator-prey biomagnification factors. FWMFs represent a trophic level increase of contaminants that is average for the food chain rather than an increase for a specific predator-prey relationship. The Barents Sea FWMFs were generally comparable to those determined for marine food webs with similar food chain lengths in the Canadian Arctic.

Bioaccumulation of PCBs in Arctic seabirds: influence of dietary exposure and congener biotransformation

“…Relatively high d 15 N in black guillemot was also shown in previous studies (Fisk et al, 2001a;Hop et al, 2002). This indicates that black guillemot feeds higher in the food web, presumably on demersal or larger fish during pursuit diving, whereas kittiwake is a surface feeder on smaller pelagic fish, and occasionally on amphipods and euphausiids (Lønne and Gabrielsen, 1992;Mehlum and Gabrielsen, 1993).…”

“…Increasing PCB levels with trophic position have been shown previously for seabirds and seals in Arctic marine food webs (Fisk et al, 2001a;Hop et al, 2002), and among Arctic seabirds from the Canadian Arctic (Buckman et al, 2004). In the present study, however, PCB levels were high in little auk occupying the lowest trophic position, and generally lower in black guillemot occupying the highest trophic position.…”

“…Alternative prey and migration does not help explain the high PCB levels in little auk, which is a northern species and a strict feeder on herbivorous calanoid copepods with low trophic position and contaminant concentrations (Hop et al, 2002). However, like in kittiwakes, the higher feeding rate in little auk (due to its lower body mass) may contribute to the relatively high PCB concentrations, despite its low trophic position.…”

“…Stable isotope ratios were analysed in seabirds' muscles at the Institute for Energy Technology, Kjeller, Norway as described in details by Hop et al (2002 15 N into trophic levels, the formula for seabirds by Fisk et al (2001a) was used (trophic level Z 3 C (d 15 N ÿ 10.1)/3.8).…”

Characterization of Trophic Transfer for Polychlorinated Dibenzo-p-dioxins, Dibenzofurans, Non- and Mono-ortho Polychlorinated Biphenyls in the Marine Food Web of Bohai Bay, North China

“…Although it is not possible to specially compare the difference between Naito's results and the results of this study, a reasonable cause may be that the food web used in Naito's study excluded organisms such as seabirds or mammals at high trophic level. Several studies have demonstrated that the TMFs estimated based on food webs only including poikilotherms (fish) are usually lower than those estimated based on food webs including homeotherms (seabirds and mammals) (14,19,30). In addition, no obvious increasing trend was found on the TMFs of nonand mono-ortho PCBs with log Kow, considering that the regressions of concentration-trophic level for PCBs 77, 81, 126, 156, and 167 are not significant.…”