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Table 1 Definition of “present” and “past” sediment parameters

From: Shifts among Eukaryota, Bacteria, and Archaea define the vertical organization of a lake sediment

We define present parameters as the principal components of all context

data derived from (a) pore water analysis, which indicates that chemical

gradients are caused by the consumption and production of ongoing

biological processes (e.g., sulfate and methane), and from (b) directly

measured parameters of microbial activities (e.g., bacterial protein

production). The present parameters are therefore an expression of

recent microbial processes.

Past parameters are the principal components of conservative

parameters, which once introduced into the sediments will not change

significantly and are therefore an expression of the lake’s history (e.g.,

heavy metals). Here, we also categorize the total amount of elemental

carbon, nitrogen, hydrogen, and sulfur as mainly conservative parameters.

The past parameters are therefore an expression of historical changes.