From all the samples the highest value of TBN was represented by the depth of
15 m on KG2 station, located adjacent to the fjord shore (4.3 × 10
5 cells cm
−3 ). The
lowest value corresponded to 35 m on KG1 station (1.2 × 10
5 cells cm
−3 ). In
Kongsfjorden, the increase in TBN was observed on 10 m (1.5–2.7 × 10
5 cells
cm
−3 ; mean 1.9 × 10
5 cells cm
−3 ) and 15 m (1.8–4.3 × 10
5 cells cm
−3 , mean
2.6 × 10
5 cells cm
−3
). These are the depths corresponding to the change in temperature and salinity profile (water density change region), where suspended
organic matter, being the food source for bacteria, tends to accumulate. Also high
TBN and BBM values were recorded in surface water samples from Hornsund
(Fig. 2). Regarding the number of bacteria in the entire water column, the highest
value was represented by HG2 station (3.6 × 10
5 cells cm
−3 ) and the lowest was
observed on the KG1 station (1.5 × 10
5 cells cm
−3 ).
BBM fluctuations were inconsistent with TBN fluctuations in case of depths at
certain stations. The lowest BBM value were observed at 35 m on KG1 station
(1.4 mg C m
−3 ) and the highest at 25 m on HG2 (16.1 mg C m
−3 ). However, the
tendencies of entire water columns were similar: the highest BBM was recorded on
HG2 (14.2 mg C m
−3 ) and the lowest on KG1 (5.1 mg C m
−3 ) (Fig. 2).
In general, total bacterial number and biomass were greater in Hornsund (mean
for three stations: TBN = 3.3 × 10
5 cells cm
−3 ; BBM = 12.2 mg C m
−3
) compared
to the Kongsfjorden (TBN = 1.8 × 10
5 cells cm
−3
; BBM = 6.3 mg C m
−3 ). Despite
the lower mean water temperature, TBN and BBM was almost two times higher in
Hornsund than in Kongsfjorden (Fig. 3a, b, d).
There was a significant difference in the salinity, temperature, TBN and BBM
between fjords (Student’s t-test; p < 0.05).
4 Discussion
The results presented in this paper generally correspond to the values from other
publications from Arctic region. Noted differences in TBN and BBM counts may be
the result of applying different counting methods and various stains (Table 1).
DAPI, used in this research, is nowadays commonly used technique of direct
counting under fluorescence microscopy. Acridine orange (AO) used widely in the
past research (Jankowska et al. 2005; Naganuma et al. 2006 or Gradinger and
Zhang 1997), caused overstating the results, which was mentioned in several
publications (Posch et al. 2001; Sherr et al. 2001; Suzuki et al. 1993; Porter and
Feig 1980).
Observed in this research water temperature values fall within the range of usual
temperature of Arctic fjord waters, which may be as low as around −2 °C (Cottier
et al. 2005; Lydersen et al. 2002; Jankowska et al. 2005) in the deepest parts of a
fjord and as high as 4–6 °C (Piwosz et al. 2009) in the surface waters in summer.
Water masses on the surface were warmer due to the constant solar radiation during
polar day and several meters underneath the temperature decreased due to the
glacier activity. In the layers localized beneath, the warming activity of Atlantic
Microbiological Survey in Two Arctic Fjords …
121
15 m on KG2 station, located adjacent to the fjord shore (4.3 × 10
5 cells cm
−3 ). The
lowest value corresponded to 35 m on KG1 station (1.2 × 10
5 cells cm
−3 ). In
Kongsfjorden, the increase in TBN was observed on 10 m (1.5–2.7 × 10
5 cells
cm
−3 ; mean 1.9 × 10
5 cells cm
−3 ) and 15 m (1.8–4.3 × 10
5 cells cm
−3 , mean
2.6 × 10
5 cells cm
−3
). These are the depths corresponding to the change in temperature and salinity profile (water density change region), where suspended
organic matter, being the food source for bacteria, tends to accumulate. Also high
TBN and BBM values were recorded in surface water samples from Hornsund
(Fig. 2). Regarding the number of bacteria in the entire water column, the highest
value was represented by HG2 station (3.6 × 10
5 cells cm
−3 ) and the lowest was
observed on the KG1 station (1.5 × 10
5 cells cm
−3 ).
BBM fluctuations were inconsistent with TBN fluctuations in case of depths at
certain stations. The lowest BBM value were observed at 35 m on KG1 station
(1.4 mg C m
−3 ) and the highest at 25 m on HG2 (16.1 mg C m
−3 ). However, the
tendencies of entire water columns were similar: the highest BBM was recorded on
HG2 (14.2 mg C m
−3 ) and the lowest on KG1 (5.1 mg C m
−3 ) (Fig. 2).
In general, total bacterial number and biomass were greater in Hornsund (mean
for three stations: TBN = 3.3 × 10
5 cells cm
−3 ; BBM = 12.2 mg C m
−3
) compared
to the Kongsfjorden (TBN = 1.8 × 10
5 cells cm
−3
; BBM = 6.3 mg C m
−3 ). Despite
the lower mean water temperature, TBN and BBM was almost two times higher in
Hornsund than in Kongsfjorden (Fig. 3a, b, d).
There was a significant difference in the salinity, temperature, TBN and BBM
between fjords (Student’s t-test; p < 0.05).
4 Discussion
The results presented in this paper generally correspond to the values from other
publications from Arctic region. Noted differences in TBN and BBM counts may be
the result of applying different counting methods and various stains (Table 1).
DAPI, used in this research, is nowadays commonly used technique of direct
counting under fluorescence microscopy. Acridine orange (AO) used widely in the
past research (Jankowska et al. 2005; Naganuma et al. 2006 or Gradinger and
Zhang 1997), caused overstating the results, which was mentioned in several
publications (Posch et al. 2001; Sherr et al. 2001; Suzuki et al. 1993; Porter and
Feig 1980).
Observed in this research water temperature values fall within the range of usual
temperature of Arctic fjord waters, which may be as low as around −2 °C (Cottier
et al. 2005; Lydersen et al. 2002; Jankowska et al. 2005) in the deepest parts of a
fjord and as high as 4–6 °C (Piwosz et al. 2009) in the surface waters in summer.
Water masses on the surface were warmer due to the constant solar radiation during
polar day and several meters underneath the temperature decreased due to the
glacier activity. In the layers localized beneath, the warming activity of Atlantic
Microbiological Survey in Two Arctic Fjords …
121