Foodweb

Another contaminant of concern for the Delta is Se. Selenium occurs in high concentrations in the soils of the western San Joaquin Valley associated with salts that have accumulated in this region [10]. Selenium is recycled through agricultural retom flows to the river and transported to the Delta and San Francisco Bay. The Se is transformed into a more bioavailable form by microbial communities and aquatic plants. The Se is passed through the foodweb with particular concern for bottomfeeding migratory waterfowl and predatory fishes. The hydrodynamics of water from the San Joaquin River is an important consideration in the intensity and distribution of Se contamination within the Delta. 

Foodwebs of the Delta have been altered in many ways through the multiple changes that have occurred within the Delta in recent decades. For example, the turbidity and organic matter supply to the Delta have been generally decreasing due to land use changes and upstream reservoirs. Phytoplankton populations also have... 

The canopy effect, carbon isotope ratios and foodwebs in Amazonia. Journal of... 

Variations in bone collagen nitrogen isotope ratios in C3 foodwebs are illustrated in Figure 4.2. 

Van der Merwe, NJ. and Medina, E. 1991 The canopy effect, carbon isotope ratios and foodwebs in Amazonia. Journal of Archaeological Science 18 249-259. 

Ambrose, S.H. 1991 Effects of diet, climate and physiology on nitrogen isotope abundances in terrestrial foodwebs. JoMrna/ of Archaeological Science 18 293-317. 

Seven diets were constructed from purified natural ingredients obtained from either C3 (beet sugar, rice starch, cottonseed oil, wood cellulose, Australian Cohuna brand casein, soy protein or wheat gluten for protein) or C4 foodwebs (cane sugar, corn starch, com oil, processed corn bran for fiber, Kenya casein for protein) supplemented with appropriate amounts of vitamins and minerals (Ambrose and Norr 1993 Table 3a). The amino acid compositions of wheat gluten and soy protein differ significantly from that of casein (Ambrose and Norr 1993). 

The second Advanced Seminar (Sillen and Armelagos 1991) wimessed a significant increase in the sophistication and complexity of scientific research. Two papers focused on recent advances in the imderstanding of variations in stable carbon isotopes (Tieszen, van der Merwe) and one focused on variations in nitrogen isotopes (Ambrose) in terrestrial foodwebs. Two papers focused on... 

Fig. 2. Foodweb model for southern African herbivores and carnivores representing enrichment/depletion from the baseline (X) value for vegetation (adapted from Lee-Thorp, 1989).

Booth, G.M. and D. Ferrell. 1977. Degradation of dimilin by aquatic foodwebs. Pages 221-243 in M.A.Q. Khan (ed.). Pesticides in Aquatic Environments. Plenum Press, New York. 

Figure 10.3 Generalized isotopic trophic level diagram for marine and terrestrial foodwebs. (Adapted from O Connell, 1996, with permission.)...

Gobas (1993) published a foodweb bioaccumulation model to predict chemical concentrations in phytoplankton, macrophytes, zooplankton, benthic invertebrates, and fish, based... 

Morrison, H.A., F.A.P.C. Gobas, R. Lazar, and G.D. Haffner. 1997. Derivation of a benthic/pelagic foodweb bioaccumulation model for organic contaminants. Environ. Sci. Technol. Under review. 

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