Over the year the relation between TR for leucine and HR for MUF-leucine substrate
analogues (we may call it the pool size ratio) varied between 2.3 and 24.5 at the inner fjord
station. The lowest value was obtained during the warm season (21°C), while the greatest
divergence was observed in late October (9°C) when values for bacteria numbers and
activities as well as chlorophyll levels drastically dropped. Factors of approx. 10 were
obtained during the cold season; from annual average values of TR and HR a relation of
5.6 was calculated. For the outer station (Feuerschiff) the relationship between TR and
HR varied between 0.5 and 13.1. For annual average values it was approx. 1 (Tab. 4).
Parameter
Station Hauptpost (inshore)
average
Station Feuerschiff (offshore)
average
inshore/offshore
1) Saprophytes
70,500
3,100
23
2) AODC
3.6
1.5
2.4
3) V m -leucine uptake
0.08
0.03
2.3
4)
leucine
4.4*
2.6**
1.7
5) V MUF-leucine
m
7.35
4.46
1.6
6) V
m
MUF-a-glucoside
0.26
0.08
3.1
7) V m MUF-glucosaminide
0.23
0.16
1.5
8) V m phosphate
0.03
0.015
1.9
9)
MUF-leucine
0.78*
2.86**
0.3
10)
MUF-a-glucoside
2.87
0.52
5.5
11)
MUF-glucosaminide
0.3
0.03
10
12)
MUF-phosphate
0.23
1.38
0.2
13) Chl. a
9.3
3.5
2.7
Units 1) saprophytes ml
-1 ; 2) total bacteria numbers ml'
1 x 10
6 ; 3) µg Cl -1 h -1 ; 4) % h -1 ; 5) - 7) µg Cl -1 h -1 ; 8) µM Pl -1 h -1 ; 9) -12) % h -1 ;
13)µg m -1 .
* relation T R /H R inshore :~6:1,
** relation T R /H R offshore : — 1:1.
Table 4 : Average values of different parameters obtained from 12 monthly investigations
DISCUSSION
Biochemical properties of aquatic bacterial populations were investigated by means of
selective agar media supplemented with polymeric nutrients such as starch, protein, and
chitin (Sieburth, 1971 ; Kjelleberg and Hakansson, 1977). Through these studies information is provided about the distribution and enrichment of saprophytic bacteria with
distinct biochemical activities in different aquatic biotopes and ecological niches (e.g.
lipid films). Little is known, however, about the quantitative aspect of soluble polymer
degradation in sea water and its importance for the substrate pool equilibrium. Recently a
few attempts have been made to measure soluble polymer degradation at in situ conditions using highly sensitive fluorometric or radiometric methods (Hoppe, 1983 ; Somville
and Billen, 1983 ; Hollibaugh and Azam, 1983).
The method employed here for the determination of extracellular enzymatic activity relies
on the acceptance of methylumbelliferon-linked monomers as substrate analogues for
soluble macromolecules. It has been clearly shown that methylumbelliferyl (MUF)125
analogues (we may call it the pool size ratio) varied between 2.3 and 24.5 at the inner fjord
station. The lowest value was obtained during the warm season (21°C), while the greatest
divergence was observed in late October (9°C) when values for bacteria numbers and
activities as well as chlorophyll levels drastically dropped. Factors of approx. 10 were
obtained during the cold season; from annual average values of TR and HR a relation of
5.6 was calculated. For the outer station (Feuerschiff) the relationship between TR and
HR varied between 0.5 and 13.1. For annual average values it was approx. 1 (Tab. 4).
Parameter
Station Hauptpost (inshore)
average
Station Feuerschiff (offshore)
average
inshore/offshore
1) Saprophytes
70,500
3,100
23
2) AODC
3.6
1.5
2.4
3) V m -leucine uptake
0.08
0.03
2.3
4)
leucine
4.4*
2.6**
1.7
5) V MUF-leucine
m
7.35
4.46
1.6
6) V
m
MUF-a-glucoside
0.26
0.08
3.1
7) V m MUF-glucosaminide
0.23
0.16
1.5
8) V m phosphate
0.03
0.015
1.9
9)
MUF-leucine
0.78*
2.86**
0.3
10)
MUF-a-glucoside
2.87
0.52
5.5
11)
MUF-glucosaminide
0.3
0.03
10
12)
MUF-phosphate
0.23
1.38
0.2
13) Chl. a
9.3
3.5
2.7
Units 1) saprophytes ml
-1 ; 2) total bacteria numbers ml'
1 x 10
6 ; 3) µg Cl -1 h -1 ; 4) % h -1 ; 5) - 7) µg Cl -1 h -1 ; 8) µM Pl -1 h -1 ; 9) -12) % h -1 ;
13)µg m -1 .
* relation T R /H R inshore :~6:1,
** relation T R /H R offshore : — 1:1.
Table 4 : Average values of different parameters obtained from 12 monthly investigations
DISCUSSION
Biochemical properties of aquatic bacterial populations were investigated by means of
selective agar media supplemented with polymeric nutrients such as starch, protein, and
chitin (Sieburth, 1971 ; Kjelleberg and Hakansson, 1977). Through these studies information is provided about the distribution and enrichment of saprophytic bacteria with
distinct biochemical activities in different aquatic biotopes and ecological niches (e.g.
lipid films). Little is known, however, about the quantitative aspect of soluble polymer
degradation in sea water and its importance for the substrate pool equilibrium. Recently a
few attempts have been made to measure soluble polymer degradation at in situ conditions using highly sensitive fluorometric or radiometric methods (Hoppe, 1983 ; Somville
and Billen, 1983 ; Hollibaugh and Azam, 1983).
The method employed here for the determination of extracellular enzymatic activity relies
on the acceptance of methylumbelliferon-linked monomers as substrate analogues for
soluble macromolecules. It has been clearly shown that methylumbelliferyl (MUF)125