Download comparative investigations of organotrophic bacteria and

NATURA MONTENEGRINA, PODGORICA, 3, 2004, 327-332
UDK 579.68:628.473.2(285.2)(497.7)(045)=111
COMPARATIVE INVESTIGATIONS OF ORGANOTROPHIC BACTERIA AND
BIODEGRADABLE DISSOLVED ORGANIC MATER IN THE LAKE OHRID PELAGIC
WATERS
Vera NOVEVSKA 1
Synopsis
Investigations of number of organotrophic bacteria and concentrations of dissolved
biodegradable organic matter (DOM) were performed in the open waters of Lake Ohrid during
one year period.
Material was collected from several depths at a site of 200m depth. Organotrophic
bacteria were cultivated on 20% MPA and incubated at 22 o C during 7 days. Counting of
colonies was done with a binocular. Dissolved biodegradable matter was determined as
KMnO 4 consumption.
Key words: Lake Ohrid, organotrophic bacteria, DOM, mutual relations
Sinopsis
UPOREDNA ISTRAZIVANJA ORGANOTROFNIH BAKTERIJA I
BIORAZGRADLJIVIH ORGANSKIH MATERIJA U VODI PELAGIJALA OHRIDSKOG
JEZERA
U toku jednogodišnjeg perioda, u vodi pelagijala Ohridskog jezera, istraživan je broj
organotrofnih bakterija (fakultativno oligotrofnih) i količina rastvorenih biorazgradljivih
organskih materija (DOM).
Materijal je kolekcioniran sa stacionara na maksimalnoj dubini od 200 m sa nekoliko
dubina. Organotrofne bakterije zasejavane su na 10% MPA-u, i inkubirane na 22 0 C u toku 7
dana. Brojanje izraslih kolonija vršeno je pomoću binokulara. Rastvorene biorazgradljive
organske materije određivane su kao utrošak kalijum permanganata.
Ključne reči: Ohridsko jezero, organotrofne bakterije, DOM, uzajamni odnosi.
1
Hydrobiological Institute, 6000 Ohrid, R. Macedonia; e-mail: [email protected]
328
Natura Montenegrina, 3/2004.
INTRODUCTION
Transformation of organic substrates of utilizable dissolved organic matter stored in the
bacterial biomass is a crucial step in the processing of the organic matter by the
organotrophic bacteria and its direction toward higher trophic levels in the aquatic
ecosystems. Because of that interactions between bacteria and organic matter are of great
interest in the lake functioning. These interactions are also important because of the
structure of the organic matter which, together with other physicochemical factors directly
controls the activity and structure of the microbial communities (W i t z e l , 1990).
Aim of this work is to try and analyze mutual relations of number of heterotrophic
bacteria and the content of dissolved organic matter in the pelagic water column of Lake
Ohrid.
STUDY AREA
Lake Ohrid is a transboundary lake located in the southwestern part of the Republic of
Macedonia with surface area of 358.18 km 2 , from which 118.9 km 2 belongs to the R. of
Albania. Lake Ohrid is the largest and the deepest lake in the Dassaret lake group of Aegean
lake zone with maximal depth of 286 m (Fig.1).
Longterm investigations of Lake Ohrid have shown that this aquatic ecosystem has an
oligotrophic character with unique ecological complex that makes possible the existance of
special endemic and relic living world.
MATERIAL AND METHODS
Samples were collected (within one year period) with Ruttner water sampler at: 5m,
15m, 20m, 25m, 30m, 50m, 100m and 200m from the water column in the pelagic region of
Lake Ohrid.
From microbiological point of view a number of facultative oligotrophic bacteria
developed on 10% MPA (P e t r o v i c 1998) were analyzed. Cultivated material was incubated
at 22 o C during seven days. Content of the dissoved biodegradable organic matter was
determined as KMnO 4 consumption.
RESULTS AND DISCUSSION
Organotrophic bacteria are main consumers of the organic matter in the natural waters and that is
why good knowledge of mutual relation between bacterial metabolism and the trophic state is necessary.
Numerous works indicate that the bacterial growth and the productivity positively corelate with
concentrations of dissolved biodegradable organic matter in lakes. Relatively recent studies present that
bacteria depend much more of the quality of the dissolved organic matter than of their ambiental
concentration (C h r o s t , 1986; C h r o s t & R a i , 1993).
329
NOVEVSKA, V: Comparative Investigations Between Organotrophic Bacteria
Fig. 1. Map of Lake Ohrid
Crn Drim
Sat eska reka
Koselska reka
Velgo{ka reka
Reka ^erava
Annual results for the spatial distribution of the average number of organotrophic
bacteria in the pelagic region of Lake Ohrid are presented in Fig. 2. There can be seen an
uneven distribution with evident changes in the trophogenic layer (5m-50m) in which,
according S t a n k o v i c (1959) I situated main bacterial biomass. Their minimal number
(222 bac·ml -1 water) is evidented at 5m depth, but there are two picks at 15m depth (608
bac·ml -1 water) and at 200 m depth (943 bac·ml -1 water).
330
Natura Montenegrina, 3/2004.
Organotrophic bacteria/ml water
Depth (m)
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
155
160
165
170
175
180
185
190
195
200
205
210
200
400
600
800
1000
Fig.2. Spatial distribution of the average
number of organotrophic bacteria in the
pelagic region of Lake Ohrid .
Depth (m)
In close corelation with the bacterial number is dissolved biodegradable organic
matter which, in the pelagic zone of Lake Ohrid, mainly, is of autohtonous origin. Spatial
distribution of average quantities during this investigated period are presented in Fig. 3. For
this parameter maximal changes are
evident in the trophogenic layer as well.
KM nO4 mg/l water
Minimal average value (3.50 mg·l -1 )
3,20
3,40
3,60
3,80
4,00
4,20
4,40
waterwas evidented at 100m depth, and
5
10
15
maximal (4.30 mg·l -1 water) at 30m depth.
20
25
30
It is reasonable of their decrease in the
35
40
deeper layers. Depth of this aquatic
45
50
55
ecosystem, make available organic matter,
60
65
to be mineralized during sinking. From the
70
75
80
figures it can be seen that, mainly, bigger
85
90
number of the facultative organotrophic
95
100
105
bacteria respond to the lower quantity of the
110
115
120
dissolved biodegradable organic matter.
125
130
135
140
145
150
155
160
165
170
175
180
185
190
195
200
205
210
Fig. 3. Average spatial distribution of
dissolved biodegradable organic matter
values in the pelagic region of Lake Ohrid
331
NOVEVSKA, V: Comparative Investigations Between Organotrophic Bacteria
1000
6,00
800
5,00
4,00
600
3,00
400
2,00
200
1,00
0
KMnO4 mg/lit
number of organotrophic
bacteria/ml water
Opposite situation of these parameters is shown at depth 5m and 30m, which indicate
that bigger quantity of DOM is not always a precondition for more numerous bacterial
population. We suppose that this situation can be the result of some inhibitory impact to the
bacterial enzymatic system that disables utilization of substrate and transformation into
bacterial biomass (V a s i l e s k a 2002). According to H e r n d a l e t a l (1992) solar radiation
(UV-B, 280nm-320nm) can be the a suppressor of the bacterial activity at surface layer (up to
10m).
Also, it should not be neglected that influence of the other plankton constituent
component, the zooplankton community, as a predator, can influence bacterial number
(K o s t o s k i 1998), G u r u n g et al (2000).
Temporal review of the mutual relation of facultative oligotrophic bacteria and
dissolved biodegradable organic matter are presented in Fig.4.
0,00
J/97 F
M
A
M
J
J
A
organotrophic bacteria
S
O
N
D J/98
org.mater.
Fig. 4. Temporal distribution of mean values of facultative oligotrophic bacteria and dissolved
biodegradable organic matter in the pelagic region of Lake Ohrid
It is remarkable that during longer period of these investigations there is a situation of
greater quantity of organic matter and lower bacterial number, what indicates the that bacteria
are not able to transform the organic matter in their own biomass.
According to C h r o s t (1986), this situation could be explained as low bacterial
utilization of the organic matter because of its form, and second, because of the absence of
other auxiliary processes that support their utilization. During the period of May-June there is
a situation where there is an increased bacterial development as its better utilization and
transformation in the bacterial biomass.
One of the components of the metabolic activities in the aquatic ecosystems is the
constructive exchange in which, as the result of biochemical processes, there are utilized
organic matter from the surrounding water and transformed in the bacterial biomass
(D j u k i c , 2000). It is very important energy to be utilized for constructive exchange and the
organic matter to be directed in the metabolic processes to the highest fesible extent
332
Natura Montenegrina, 3/2004.
CONCLUSIONS
According to the analyzes and results obtained during one year period of investigation
of facultative oligotrophic bacteria and quantity of dissolved biodegradable organic matter in
the pelagic water column of Lake Ohrid, it can be concluded that it is necessary to have an
integral approach to analysis of these parameters. It is important to pay more attention to
qualitative composition of the dissolved biodegradable organic matter in terms of their
utilization within constructive exchange. Also, analysis of DOM can not be successful if the
mutual relation of other constitutive elements of planktonic community, phytoplankton and
zooplankton are not taken into account.
REFERENCES
C h r o s t R . J . , (1986): Algal-bacterial Metabolic Coupling in the Carbon and Phosphorus Cycle in
Lakes. In Megusar F, Gantar (eds) Perspactives in Microbial Ecology. Slovene Society for
Microbiology, Ljubljana, pp: 360-366
C h r o s t , R . J . , R a i , H., (1993): Ectoenzyme Activity and Bacterial Secondary Production in
Nutrient Improverished and Enriched Freshwater Mesocosms. Microb. Ecol 25: 131-150
D j u k i c A . D , (2000): Mikrobiologija voda. Prosveta, Beograd
G u r u n g , B . T . , M . M . N a k a n i s h i , J U r a b e , (2000): Seasonal and Vertical Defference
in Negative and Positive Effects of Grazers on Heterotrophic Bacteria in Lake Biwa. Limnology
and Oceanography 45 (8): 1689-1696
H e r n d l , G . J . , M u l l e r - N i k l a s , G . , F r i c k , J. (1992): Major Role of Ultraviolet-B in
Controlling Bacterioplankton Growth in the Layer of the Ocean. Mar. Biol. 113: 341-347
K o s t o s k i , G ., (1998): Dnevno-noćna I sezonska periodičnost vo rasporedot na zooplanktonot od
Ohridskoto Ezero. Doktorska disertacija, Univerzitet “Sv. Kiril i Metodij“ Prirodno-matematički
fakultet, Institut za biologija, Skopje.
S t a n k o v i ć , S . , (1959): Ohridskoto Ezero i negoviot živ svet. Kultura, Skopje
V a s i l e s k a , A . , (2002): Fosfataznata aktivnost vo vodata na Ohridskoto Ezero kako indikator za
negovata ekofiziološka sostojba. Magisterski trud. Univerzitet “Sv.Kiril I Metodij“, Prirodnomatematički fakultet Institut za biologija, Skopje. Pp:205
W i t z e l , K . P ., (1990): Approaches to Bacterial Population Dynamics. In Overbeck J., Chrost R.J.,
(eds) Aquatic Microbial Ecology: Biochemical and Molecular Approaches. Springer-Verlag, New
York p: 96-128