Influence of seasonal environmental variables on the distribution of presumptive fecal Coliforms around an Antarctic research station

Abstract

Factors affecting fecal microorganism survival and distribution in the Antarctic marine environment include solar radiation, water salinity, temperature, sea ice conditions, and fecal input by humans and local wildlife populations. This study assessed the influence of these factors on the distribution of presumptive fecal coliforms around Rothera Point, Adelaide Island, Antarctic Peninsula during the austral summer and winter of February 1999 to September 1999. Each factor had a different degree of influence depending on the time of year. In summer (February), although the station population was high, presumptive fecal coliform concentrations were low, probably due to the biologically damaging effects of solar radiation. However, summer algal blooms reduced penetration of solar radiation into the water column. By early winter (April), fecal coliform concentrations were high, due to increased fecal input by migrant wildlife, while solar radiation doses were low. By late winter (September), fecal coliform concentrations were high near the station sewage outfall, as sea ice formation limited solar radiation penetration into the sea and prevented wind-driven water circulation near the outfall. During this study, environmental factors masked the effect of station population numbers on sewage plume size. If sewage production increases throughout the Antarctic, environmental factors may become less significant and effective sewage waste management will become increasingly important. These findings highlight the need for year-round monitoring of fecal coliform distribution in Antarctic waters near research stations to produce realistic evaluations of sewage pollution persistence and dispersal.

FIG. 1.

Map of Rothera Point showing the position of the seawater sample sites (+), East Beach water sample sites (+, EB1 to EB4), sewage outfall (SO), sewage pipe (SP), and site of special scientific interest (SSSI Number 9).

FIG. 2.

Daily UVB, UVA, and PAR doses recorded at Rothera Point between September 1998 and May 2000. Seawater sample dates are indicated (∧). The horizontal bar indicates the period when the sun was permanently below the local horizon.

FIG. 3.

Seawater temperature in Ryder Bay and sea ice conditions in North Cove and off East Beach during 1999. Seawater sample dates are indicated (∧).

FIG. 4.

Mean chlorophyll a concentration in the upper 5 m of the water column (solid line) and percent transmission of PAR at a 5-m depth (dotted line) in seawater around Rothera Point. The February seawater sample date is indicated (∧).

FIG. 5.

Contour map of seawater salinity (per mille) within North Cove from 11 to 12 February 1999.

FIG. 6.

Monthly mean and maximum fur seal and Adélie penguin counts on East Beach, Rothera Point between February 1999 and January 2000. Seawater sample dates are indicated (∧).

FIG. 7.

Human population of Rothera Research Station between October 1998 and October 1999. Seawater sample dates are indicated (∧).

FIG.8.

The extent and number of viable fecal coliforms in North Cove on 11 to 12 February (a), 23 to 24 April (b), and 28 September (c) 1999. Numbers represent the common log exponent of viable fecal coliform numbers per 100 ml of seawater.

FIG. 9.

Percent survival of E. coli 10243 (•) and E. coli UFC1 (○) with exposure to solar radiation (± standard error of the mean). Irradiances were weighted according to the DNA damage action spectrum of Setlow (38).