Growth of Bacterioplankton on Dissolved Organic Carbon in Hamilton Harbour and Western Lake Ontario

Abstract

Abstract Bioassay procedure was used to measure dissolved organic carbon (DOC) and biodegradable dissolved organic carbon (BDOC) in Hamilton Harbour and western Lake Ontario using batch experiments with an incubation time of 12 days in four experiments. Three different levels of natural DOC concentration were assayed; high concentration of DOC, 20.2 mg C/1 (influence of sewage treatment inflow); intermediate concentration of DOC, 16.7 mg C/1 (STELCO plant, industry polluted water); and an unaffected locality with low concentration of DOC, 12 mg C/1 (predominantly autochtonous input from photosynthetic activity in Lake Ontario). Decreasing DOC in all samples was observed during the first five days of experiments followed by a stabilization of DOC at a constant level. The value of the labile fraction of DOC represented 75% of total amount of DOC in the sewage sample water, 57% in the sample affected by industrial waters and 66% of DOC in unaffected sample from Lake Ontario. Bacterial growth started rapidly from the first day of batch experiments and maximal biomass was reached after two to three days. The highest bacterial biomasses were reached in the samples affected by sewage treatment waters (2.37 mg C/1) and the lowest value was observed in Lake Ontario (0.51 mg C/1).