Predatory bioaccumulation

Johnston TA, Leggett WC, Bodaly RA, Swanson HK. 2003. Temporal changes in mercury bioaccumulation by predatory fishes of boreal lakes following the invasion of an exotic forage fish. Environ Toxicol Chem 22 2057-2062. 

Many hydrophobic organic contaminants pose a threat to human health because they bioaccumulate to high concentrations in predatory fish that are eaten by people. From a human health standpoint, there is little concern of... 

Considerable attention has been given to the investigation of organochlorine residues in the marine polar ecosystems where the two effects of global distillation and bioaccumulation combine to produce high residues in predatory species such as marine mammals, fish and sea birds. As these compounds preferentially reside in fatty tissues, the high fat content of many of the northern marine species, and the inherited contamination through lactation, indicate that such ecosystems may be some of the most vulnerable. 

The risk assessors conclude that Octa can be considered persistent in the environment but that the available laboratory data indicates a low potential for bioaccumulation. Furthermore, it is concluded that Octa shows no toxicity towards aquatic organisms up to the limit of water solubility, and that effects in other organisms are only observed at relatively high concentrations, based on standard laboratory tests. Nevertheless, the risk assessors note that environmental monitoring of concentrations in biota indicate that Octa, as well as HexaBDE, and HeptaBDE are present at low concentrations in fish, marine mammals and predatory birds eggs. 

The bioaccumulative effects of persistent organochlorine pesticides in raptors and other predatory wildlife (Moore, 1967 Hickey, 1969). 

Metal pollution not only affects humans but also impacts on the entire ecological system. In the Arctic, reindeer and caribou have been documented to be accumulating Cd which has been linked to kidney dysfunction (AMAP 1997), while filter feeders, such as mussels, have also been shown to accumulate toxic metals such as Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn (Mubiana et al. 2005). Mercury has been found to be bio-concentrating at critical levels in the marine environment, with higher concentrations documented in predatory fish and in marine mammals such as ringed seals (AMAP 1997). This has resulted in subsequent bioaccumulation in human populations who consume large amounts of fish, such as the populations of the Faroe Islands in the Northern Atlantic, Maderia off the west coast of North Africa and the Inuit people of northern Canada (Grandjean et al. 1992 Renzoni et al. 1998 Wheatley et al. 1979). 

In addition, bioaccumulation in food chains will lead to increased levels of PFC in animal-derived foods. Bioaccumuladon of fish has been shown to be the main influences of PFC in dietary exposure. In a market basket study in Sweden, Berger et al. found that PFOS and PFOA cmicentrations were below the quantification limits in composite samples of foods of animal origin. However, predatory fish from the largest lake in Sweden had substantially elevated levels of several PFC. 

In the global cycle of mercury the accumulation in the aquatic food chain plays a predominant role [6]. Inorganic mercury species are methylated in the water chemically or by microorganisms. The organomercury compounds formed enter the food chain. Caused by bioaccumulation in any of the several steps of the aquatic food chain, the highest levels of mercury can be found in the tissues of large predatory fishes such as marine tuna, swordfish, shark, turbot, or halibut and... 

Fig. 9.4. The new mixed model for metals in lakes. Load (or dose) parameters are related to the input of metals to the lake (direct load and load from the catchment), the metal amount in the lake water is distributed into dissolved and particulate phases by the partition coefficient (Kd). Sedimentation is net sedimentation per unit of time (the calculation unit is set to 1 year for Hg and 1 month for Cs). The sensitivity parameters influence biouptake of metals from water to phytoplankton (but they may also be used in other contexts, e.g., to influence the Kd-values, as illustrated by the dotted line, or the rate of sedimentation). The biological or ecosystem variables include pelagic and benthic uptake, bioaccumulation and retention time in the five compartments (lake water, active sediments, phytoplankton, prey and predator fish). The ejfect parameter is the concentration of the metal in predatory fish (used for human consumption). One panel gives the calculation of concentrations, another the driving parameters (model variables should, preferably, not be altered for different lakes, while environmental variables must be altered for each lake). The arrows between these two panels illustrate the phytoplankton biomass submodel...

Then, finally, the metal can enter the target compartment, predatory fish (like pike or large perch) via bioaccumulation prey to predator (regulated by bioaccumulation rate prey to predator). This means that this model gives a mean amount or concentration in the predator. More complex models may be used to distribute the metal to various organs of the predator, like liver, kidneys, skin, muscle, etc. 

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