Top predators

Vine, E., Shears, J., and van Aerie, R. et al. (2005). Endocrine (sexual) disruption is not a prominent feature in the pike (Esox lucius), a top predator, living in English waters. Environmental Toxicology and Chemistry 24, 1436-1443. 

Hogan LS, Marschall E, Folt C, Stein RA (2007) How non-native species in Lake Erie influence trophic transfer of mercury and lead to top predators. J Great Lakes Res 33 46-61... 

The food of top predators generally comprises small birds and/or mammals. Bioaccumulation of chemicals from soil to small birds and mammals takes place in at least two steps, namely a BCF from soil to food (plants and/or invertebrates), followed by a BAF to small birds and mammals. 

Spatial and time monitoring programmes of the type discussed above will also give information needed to assess the risk to top predators including man in a particular ecosystem. 

Decomposition rates of some organic substrates are reduced. Substantial changes in the species composition of primary producers occur. The richness of phytoplankton species is reduced, while biomass and productivity of phytoplankton are not reduced by acidification. The biomass of herbivorous and predaceous zooplankton is probably reduced because of reductions in numbers of organisms and/or reduction in their average size. Many benthic invertebrates such as species of snails, clams, crayfish, amphipods, and various aquatic insects are intolerant of low pH and are seldom found in acidic lakes. However, certain large aquatic insects such as water boatmen and gyrinids are very acid tolerant and may become the top predators in some acidified lakes. Acidification of aquatic systems has major effects on fish population. 

Leonards, P.E.G., Van Hattum, B. and Leslie, H. (2008). Assessing the risks of persistent organic pollutants to top predators a revieuw of approaches. Integrated Environmental Assessment and Management, Vol 4, 386-398. 

DDT Insecticides Accumulates in food chain till eventually kills top predators... 

The length of the food chain has the largest effect on the observed accumulation of PCBs in top predators [268]. However, one of the more sensitive aspects of trophic transfer in food webs is the initial uptake of PCBs into the primary trophic level, phytoplankton [263]. The BCF from water to phytoplankton is approximately 105 -106, and subsequent BMFs to higher trophic levels are on the order of two to five. Due to the life cycle of most phytoplankton, their rate of growth is on the same order as their rate of uptake of PCBs, thus making their uptake very time-dependent [227,269-271]. Bioaccumulation into top predators will be greater if phytoplankton have a chance... 

There have been a few large-scale field studies of PCBs in the food webs of the lakes. These include two EPA mass balance studies, the Green Bay Mass Balance Study and the Lake Michigan Mass Balance Study. The field data collected for these studies was used to calibrate the complex contaminant models, which were developed as the primary goal of the studies. The ultimate objective of these mass balance studies was to predict concentrations of PBTs in top predator fish from only knowing the external loadings of the PBTs. Thus the models linked food web models to fate and transport, hydro-logic, and nutrient models. To calibrate the food web models, an extensive collection of all major trophic levels over both space and time was done and analyzed for PCBs and other selected analytes. 

The Lake Baikal food web included pelagic whitefish (Coregonus autumnalis migratorius) as the top predator... 

There have been numerous measurements of PBDEs in fishes from the Great Lakes, and these data are summarized in Table 6. The concentrations range from 1000-3000 ng/g lipid for top predator fishes (such as trout and salmon) sampled recently down to 1-10 ng/g lipid for fish sampled in 1980. Taken as a whole, there is a strong relationship of concentration with time (see Fig. 5, note the logarithmic concentration scale), and this relationship holds... 

Class Asteroidea, sea stars, is one of the most widely recognized groups of marine organisms due to their prevalence upon the shoreline and their characteristic shape. Asteroids are top predators in benthic ecosystems, often preying upon bivalves from the phylum Mollusca. The isoprenoid compound mytiloxanthin, for example, has been isolated from both the sea star Asterias rubens and the bivalve Mytilus edulis,119 The class Concentricycloidea was first identified in 1986 and consists of two species in the genus Xyloplax. Class Ophiuroidea, brittle stars, contains the greatest number... 

If necessary from the perspective of risk, the government directs the manufacturer or importer to conduct a hazard (long-term toxicity to humans or top predators) survey.87... 

For ecological receptors, a similar approach may be employed for secondary receptors that could be influenced by a change in the soil environment. For instance, it is possible to model the potential for soil to influence an adjacent surface water body and therefore to screen the soil criteria for impacts on an aquatic receptor. When applied, this leads to intercompartment harmonization of standards, by which soil or sediment standards pose no problems for water bodies and vice versa. In addition, it may be possible to use screening-level models to assess the potential for a bioaccumulable substance to influence a tertiary ecological receptor, usually a top predator or a protected species. In this approach, the reference dose can be borrowed from other sources (e.g., use of an aquatic criterion to determine a critical water concentration). The model is then used only to assess how the soil may influence transfer to the critical receptor. However, it should be noted that this type of procedure cannot be used for guideline development related to primary terrestrial receptors since there are no reliable models to estimate dose-response relationships for these receptors. Therefore, other techniques described in this chapter are recommended for screening against primary receptors. 

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