Meaning of the C in the unit "mg C L-1" Could somebody tell me what the "C" signifies in the unit mg C L-1? I was wondering if it stood for concentration but it seems redundant as litres are mentioned. Thanks.

The paper which uses the unit is "Dissolved Organic Carbon Thresholds Affect Mercury Bioaccumulation in Arctic Lakes" by French et al. 2014.
Given the subject matter of the paper, I'd assume that it stands for carbon, and the whole expression refers to milligrams of carbon (or organic carbon) per litre of lake water.