The role of roots in the uptake of nonessential trace metals by aquatic macrophytes was investigated Elodea canadensis. Plants were grown in 2 lakes in which metal concentrations in the water differed. Specimens in each lake were anchored in either control sediment or in sediment contaminated with Cd and Pb. Plants grown in the same water but in sediment from different sources had significantly different concentrations of the 2 metals. Elodea samples rooted in sediments from the same source but grown in water with different levels of metals also accumulated significantly different amounts of Cd and Pb. Thus the importance of both sediment and the surrounding water as sources of metals for aquatic plants was demonstrated. Samples grown in water and sediment containing low levels of metals had minimal concentrations of 0.32 mg/g Cd and 5.2 mg/g Pb, while plants grown in metal—contaminated water and sediment accumulated up to 32.33 mg Cd/g and 160.9 mg Pb/g.

Bluegill (Lepomis macrochirus) from two industrially contaminated Indiana lakes were analyzed for cadmium, zinc, and lead content. Bluegill collected from several uncontaminated sites were used to establish background metal concentrations. The highest mean concentrations of Cd and Zn were found in Palestine Lake bluegill (3.4 gg Cd/g and 220 gg Zn/g) and the highest mean concentration of Pb was found in Little Center lake bluegill (6.1 gg Pb/g). These mean concentrations were significantly higher than background.There is a growing concern about the longterm impact of chronic exposure of aquatic ecosystems to potentially toxic substances. Many laboratory studies have demonstrated that chronic exposure to sublethal concentrations of substances such as cadmium, zinc, and lead can cause impairment of the growth and reproduction of fish (Benoit et al. 1976; Brungs 1969; Davies et al. 1975; Eaton 1973, 1974; Holcombe et al. 1976; Pickering and Gast 1972; Spehar 1976). While ample evidence has been gathered from laboratory studies, relatively few data have been collected showing the effects of these metals in natural systems. Pb ND ND ND Little Center Lake b Cd 2.0 (0.3-6.0) 1.1 (0.2-8.7) 394 (95-785) Zn 172 (5-2,300) 31 (2-210) 7,530 (1,550--17,550) Pb 20.1 (6.0--95.0) 7.0 (3.0--14.0) 450 (200-900) Data from Shephard 1976. Data from Bishop 1976.

Distribution and forms of the metals cadmium (Cd) and zinc (Zn) in sediment and the possible significance of a die‐off of the aquatic macrophyte Potamogeton crispus in Cd cycling in a metal‐contaminated lake were studied. Metal levels in the upper 5 cm of lake sediment ranged from 2.54 ppm Cd and 115 ppm Zn in an uncontaminated area of the lake to 805 ppm Cd and 6,120 ppm Zn near the entrance of a metal‐bearing ditch to the lake. Evidence of metal contamination existed at a depth of 30 cm in sediments in contaminated areas of the system. Dominant forms present in the sediment were the carbonate for Cd and carbonate and organic for Zn. Analysis indicated Cd levels as high as 89.6 ppm in P. crispus in the lake with a maximum burden of 1.5 kg Cd held by the lake's P. crispus population. Release of the total amount could raise water concentrations by a maximum of 1 µg/liter.

This investigation has shown that not only the extent of fetal resoprtion and malformation but also the types of malformation seen in rats depend upon the strain used and day of gestation. Furthermore, the effects of zinc deficiency and cadmium administration on the fetus can be at least additive, as was seen for malformations. For fetal resorption, zinc deficiency potentiated the action of cadmium.

Phosphorus (P) concentrations in water and sediment of a highly eutrophic lake were monitored before and after application of diquat to control the macrophyte Potamogeton crispus . Only a relatively small and short-term increase in P concentration in water occurred shortly after plant die-off resulting from herbicide application. Phosphorus concentrations in shallow water sediments decreased during the summer, and those in deep water sediments increased. Although a large increase in P concentration in the water occurred in late summer, it was not attributed to diquat . No major secondary effects of herbicide application were found during this study.