Survival of faecal bacteria in Antarctic coastal waters

Abstract

The effect of solar radiation on the survival of Escherichia coli, Salmonella zanzibar and a faecal Streptococcus strain in seawater was tested in laboratory experiments, and survival of E. coli was tested under natural light conditions at Davis Station, Antarctica. Exposure to artificial light of wavelengths 290–800 nm caused a rapid decline in viability of each strain examined. T₉₀ values (the time taken for 90% of the population to be inactivated) were ~50 min, 40 min and 2 h for E. coli, S. zanzibar and the faecal Streptococcus respectively. Selective removal of UV-B wavelengths of (<320 nm) increased survival of E. coli and S. zanzibar, resulting in T₉₀ values of ~2.5 h. Screening out wavelengths of <370 nm (UV-B and most of UV-A) increased T₉₀ values to 5 h for E. coli and 10 h for S. zanzibar. The visible band of the spectrum (400–800 nm) also had deterimental effects on faecal bacteria, when compared with survival in the absence of light. Rates of decline for E. coli in natural light in Antarctica were similar to those from laboratory experiments. However, resuscitation of sub-lethally damaged cells under optimum conditions resulted in greater recovery rates than were observed after exposure to artificial sunlight. Faecal bacteria were rapidly inactivated when exposed to sunlight in Antarctic waters, and as repair mechanisms are unlikely to operate under in situ conditions, resuscitation of sub-lethally damaged cells is improbable.