Alteration of leaf decomposition in copper‐contaminated freshwater mesocosms

Abstract

The influence of copper on leaf litter decomposition was examined in experimental streams. Controls and three levels of contamination (5, 25, and 75 microg/L) were tested in triplicate in 20-m-long mesocosms. Equal quantities of alder, maple, and oak leaves were enclosed in mesh bags and placed in the upper and lower mesocosm sections that exhibited different habitat characteristics (shallow with pebble substrate or deep with fine substrate and macrophytes, respectively). Decomposition rate in the upper section of the 75 micro.g/L mesocosms was significantly reduced to 28% of control values. No significant reductions in the decomposition rate were seen in the lower section. No differences in the leaf-associated mycelial biomass and sporulation rates were observed between treatments, but they were consistently higher in the upper sections. The aquatic hyphomycete community was not affected by the contamination. The abundances of total leaf-associated macroinvertebrates and the dominant shredder (Gammarus pulex) were considerably reduced in the upper sections at 75 microg/L. Therefore, the reduced leaf decomposition probably resulted from a reduction in the abundance of macroinvertebrate detritivores. In addition, local variations in physical and biological characteristics of the habitat along the mesocosms significantly influenced the effects of copper on leaf-associated decomposers.

Conservation from the bottom up: forecasting effects of global change on dynamics of organic matter and management needs for river networks

“…Shifts in riparian vegetation resulting from landuse change affect the quantity and quality of detritus supporting aquatic food webs. DOC = dissolved organic C, POC = particulate organic C. Processing: faster processing because of nutrients, but slower because of metal toxicity and sedimentation that buries detritus and algae Schofield et al 2004, Roussel et al 2008, Griffiths et al 2009, Tank et al 2010 54 J. S. KOMINOSKI AND A. D. ROSEMOND [Volume 31 the quantity, characteristics, and processing (including retention) of detritus ( Fig. 1, Table 2).…”

“…These factors include negative effects of genetically modified crop by-products on detritivore growth rates in agricultural streams ), inhibition of biological processing by acid and heavy metals in mining regions (Dangles et al 2004, Roussel et al 2008, and general increases in sediment loading that reduce algal production and invertebrate processing of organic matter (Schofield et al 2004, Pascoal et al 2005.…”

Modelling copper bioaccumulation in Gammarus pulex and alterations of digestive metabolism

“…Now it is well known that the accumulation and effects of metals on biota depend rather on their bioavailability than on their total concentrations in water. Although Cu is an essential element for all biota, its excessive input in water can exert toxic effects on living organisms, affect biodiversity by acting as a factor of species selection and disturb ecosystem functioning (Atli and Canli 2011;Roussel et al 2008;Vinot and Pihan 2005). Indeed, Cu travels up food webs and distributes in the whole of biotic compartment of freshwaters because of its non-degradability.…”

Reproduction of aquatic hyphomycetes at low concentrations of Ca2+, Zn2+, Cu2+, and Cd2+

“…They parallel fungal responses to the estrogen mimic and endocrine disruptor 4-n-nonylphenol [21]. Even though this is the first study to link metals explicitly to a hormetic response in aquatic hyphomycetes, stimulation of their growth or reproduction has repeatedly been observed and documented in the past [11,16,17,31,39,40]. This suggests that the hormetic response is widespread in these fungi, as it is in most organisms and cells.…”