Impacts of warming on aquatic decomposers along a gradient of cadmium stress

Abstract

We evaluated the effects of cadmium and temperature on plant-litter decomposition by examining diversity and activity of aquatic fungi and leaf consumption by Limnephilus sp., a typical invertebrate shredder of Iberian streams. Freshly fallen leaves were immersed in a stream to allow microbial colonization, and were exposed in microcosms to a gradient of cadmium (≤11 levels, ≤35 mg L-1 ). Microcosms were kept at 15 ºC, a temperature typically found in Iberian streams in autumn, and at 21 ºC to simulate a warming scenario. The increase in temperature stimulated leaf decomposition by microbes, fungal reproduction and leaf consumption by the shredder. Conversely, increased cadmium concentrations inhibited fungal reproduction and diversity, and leaf consumption by the invertebrate. Cadmium concentration inhibiting 50% of fungal reproduction, microbial decomposition and leaf consumption by the shredder was higher at 15 ºC than at 21 ºC, suggesting that higher temperatures can lead to increased metal toxicity to aquatic decomposers.