The effects of humic substances on copper toxicity to Ceriodaphnia silvestrii Daday (Crustacea, Cladocera)

Abstract

A major question in the field of ecotoxicology is how DOM affects copper accumulation and toxicity in planktonic organisms; copper acute toxicity and bioaccumulation in Ceriodaphnia silvestrii were investigated in the presence and absence of humic substances (HS) under controlled laboratory conditions. Copper was determined as free Cu2+ ions in the media and total copper in the animals; metal ion buffers were used for ion selective electrode calibration, extending the lower detection limit to 10(-11) mol l(-1). Groups of 20 adult females of similar sizes were exposed (24 h) to a range of nominal copper concentrations. Based on total added copper, LC50 was 4.4 x 10(-8) mol l(-1) without HS, whereas with 20 mg l(-1) HS, it was 25 times higher (1.1 x 10(-6) mol l(-1)). Based on free Cu2+ ions LC50 was statistically similar either with (2.8 x 10(-8) mol l(-1)) or without HS (3.3 x 10(-8 )mol l(-1)). The present results showed that natural DOM reduced copper toxicity and that free Cu2+ ions correlates to the bioavailable fraction to zooplankton. Nevertheless, copper bioaccumulation by C. silvestrii was similar either in the presence or absence of humic substances, suggesting that C. silvestrii regulates its body copper content up to 3.0 x 10(-8) mol l(-1) free Cu2+ ions in the media. The organisms were not able to deal with higher free Cu2+ ions concentrations in the media.

Influence of dissolved organic carbon on toxicity of copper to a unionid mussel (Villosa iris) and a cladoceran (Ceriodaphnia dubia) in acute and chronic water exposures

“…Wang et al [6] evaluated the acute toxicity of Cu to juvenile mussels (Lampsilis siliquoidea) in various natural and reconstituted waters with a wide range of dissolved organic carbon (DOC; 0.3-11 mg/L as carbon [C]). The acute toxicity of Cu to the mussels was strongly influenced by DOC [6], which is consistent with many studies with freshwater fish and other invertebrates (e.g., [7][8][9][10][11][12][13][14][15][16]). Biotic ligand models (BLMs) have been developed to enable mechanistic modeling of Cu bioavailability and acute toxicity as a function of water quality variables including pH, hardness, and DOC [17,18].…”

Change in life cycle parameters and feeding rate of Ceriodaphnia silvestrii Daday (Crustacea, Cladocera) exposure to dietary copper

“…Although we did not measure copper loss from algal surfaces in this study, free Cu 2+ ions concentration in the animals culture media was determined and kept low (around 10 -10 mol l -1 ) throughout the concentrations tested. These values are 100 times lower than that considered toxic to C. silvestrii according to Santos et al (2008) who demonstrated that 3 9 10 -8 mol l -1 free Cu 2+ ions concentration was toxic to C. silvestrii . Therefore, we assume that the toxic effect obtained through copper loss from algae surface into the animals culture media was insignificant.…”

“…The importance of studies relating dietary copper intake and its toxicity to cladocerans, considering both particulate metal (dietborne) and free ions concentration in the test media (waterborne) rely on the high bioavailability of the metal in its hydrated form to the first and second trophic levels of aquatic food webs, such as phytoplankton (Lombardi et al 2002;Lombardi et al 2007) and zooplankton (Santos et al 2008;Nogueira et al 2005). As algal surfaces are negatively charged (Kaulbach et al 2005), some of the particulate fraction of the metal ions may be released when algal cells are transferred to the zooplankton media.…”

Interactions between accumulated copper, bacterial community structure and histamine levels in crayfish meat during storage

“…The toxic effect of the cupric ion (Cu 2+ ) on microorganisms in water is also influenced by dissolved organic material such as humic substances, aerobic–anaerobic conditions and salinity, all which may vary depending on the geographical region and aquaculture practices. While a positive effect of copper exposure on the crayfish meat was observed in this study, it might be interesting to look further at the effect of certain environmental conditions on the microbial communities as well as histamine accumulation.…”