fying bacteria in estuarine sediments in respect of the physico-chemical parameters which
modulate their activities.
MATERIALS AND METHODS
Sampling sites
The main sampling area was in a tidal region of mud flats at Kingoodie Bay in the River
Tay estuary, west of Dundee and 16 Km from the river mouth. Samples from the top
50 mm sediment were taken at low water using a sterile 50 mm diameter X 150 mm long
perspex corer. All samples were processed within 1 hour of collection and aseptically
sectioned as described by Macfarlane and Herbert (1982).
Physical characteristics of Kingoodie Bay sediments
Measurements of E h , temperature and dissolved O
2
tension were made in situ in 10 mm
increments according to the methods described by Macfarlane and Herbert (1982).
Enumeration of nitrate respiring and nitrifying bacteria
Population densities of nitrate respiring bacteria and nitrifying bacteria were determined
according to the methods described by Macfarlane and Herbert (1984a).
Determination of nitrate respiration rates using 15 NO -
3
Nitrate respiration rates were determined according to the method of Macfarlane and
Herbert (1984a).
Determination of nitrification rates
Nitrification rates were determined according to the methods of Billen (1975).
Inorganic nitrogen analysis
Ammonia, NO3 and NO2 concentrations were determined according to the methods
described by Macfarlane and Herbert (1984a).
Chemicals
N-serve (2-chloro-6 (trichloromethyl) pyridine) was a gift from the Dow Chemical
Company and Na
15 NO3 was obtained from BOC Prochem, London, UK. All other
chemicals used were of ‘Analar’ grade and obtained from B.D.H., Poole, UK.
RESULTS
The surface sediments in Kingoodie Bay are composed of fine sands overlain with silt and
are highly reduced within a few mm of the surface. The principal physico-chemical
characteristics of the sediments are summarised in Table 1. The surface sediments are
more oxidised during winter due to a combination of reduced microbial activity and
increased resuspension and oxygenation of the sediments. With the exception of the 0-10
mm horizon total NH4 concentrations are substantially greater than those of NO - 3
and
NO -
2
and increase with depth. In contract N05 concentrations show a reverse pattern
with highest concentrations at the surface.
278
modulate their activities.
MATERIALS AND METHODS
Sampling sites
The main sampling area was in a tidal region of mud flats at Kingoodie Bay in the River
Tay estuary, west of Dundee and 16 Km from the river mouth. Samples from the top
50 mm sediment were taken at low water using a sterile 50 mm diameter X 150 mm long
perspex corer. All samples were processed within 1 hour of collection and aseptically
sectioned as described by Macfarlane and Herbert (1982).
Physical characteristics of Kingoodie Bay sediments
Measurements of E h , temperature and dissolved O
2
tension were made in situ in 10 mm
increments according to the methods described by Macfarlane and Herbert (1982).
Enumeration of nitrate respiring and nitrifying bacteria
Population densities of nitrate respiring bacteria and nitrifying bacteria were determined
according to the methods described by Macfarlane and Herbert (1984a).
Determination of nitrate respiration rates using 15 NO -
3
Nitrate respiration rates were determined according to the method of Macfarlane and
Herbert (1984a).
Determination of nitrification rates
Nitrification rates were determined according to the methods of Billen (1975).
Inorganic nitrogen analysis
Ammonia, NO3 and NO2 concentrations were determined according to the methods
described by Macfarlane and Herbert (1984a).
Chemicals
N-serve (2-chloro-6 (trichloromethyl) pyridine) was a gift from the Dow Chemical
Company and Na
15 NO3 was obtained from BOC Prochem, London, UK. All other
chemicals used were of ‘Analar’ grade and obtained from B.D.H., Poole, UK.
RESULTS
The surface sediments in Kingoodie Bay are composed of fine sands overlain with silt and
are highly reduced within a few mm of the surface. The principal physico-chemical
characteristics of the sediments are summarised in Table 1. The surface sediments are
more oxidised during winter due to a combination of reduced microbial activity and
increased resuspension and oxygenation of the sediments. With the exception of the 0-10
mm horizon total NH4 concentrations are substantially greater than those of NO - 3
and
NO -
2
and increase with depth. In contract N05 concentrations show a reverse pattern
with highest concentrations at the surface.
278