Heavy metal accumulation by aquatic fungi and reduction in viability of Gammarus pulex fed Cd2+ contaminated mycelium

The addition of Pb²⁺ (1.0 and 2.5 μg ml^?1) and Cd²⁺ (2.5 and 5.0 μg ml^?1) to growth medium decreased the growth of aquatic fungi, while Zn²⁺ even at a concentration of 10 μg ml^?1 had no inhibitory effect. Low concentrations of Cd²⁺ and Zn²⁺ on the other hand stimulated mycelial growth. The fungi accumulated considerable amounts of metal from the growth medium, generally in the order Zn²⁺ > Pb²⁺ > Cd²⁺ · Cd²⁺ was also accumulated by fungi from successive changes of medium containing low concentrations of the metal. Application of Langmuir and Freundlich isotherms to the results showed that the metals were accumulated largely by adsorption to the surface of the mycelium.Three species of aquatic fungi supported the growth of the freshwater shrimp. Gammarus pulex when provided as sole food source, sustaining from 30 to 60% of shrimps fed for a period of 21 days. A marked reduction in shrimp viability occurred however, when G. pulex was fed Pythium sp. containing Cd²⁺ (150–170 μg g^?1), with none of the shrimps surviving beyond 13 days, compared with a survival rate of 60% after 21 days for shrimps fed uncontaminated mycelium. Bodies of poisoned shrimps sampled on day 13 were found to contain Cd²⁺ (22.03 μg g^?1) showing that the metal can be transferred from aquatic fungi to G. pulex, the first step in a food chain involving freshwater fish and higher organisms.