Bacteriological and hydrological studies on acidic

Arch. Hydrobiol.lSuppl. 64 (Monographischc Bcirragc)

4

443-483

Sruttgart, November 1982

Bacteriological and hydrological studies o n acidic lakes in Southern Norway By EINERFJERDINGSTAD, Copenhagen, and JENSPETTERNILSSEN,Oslo With 20 figures and 9 tables in the text

Abstract Lakes in a region in Southern Norway undergoing acidification were investigated. In the headwater lakes, sulphate has replaced bicarbonate as the most important anion, and pH is below 5.0 all year round. Number of bacteria, except for Thiobacillus,was much lower than in oligotrophic lakes in Denmark and Greenland. The reason for this is suggested to be the constant low acidity of the Norwegian lakes, heavy metal accumulation in the sediments, or biocides brought with the acidic rain. Thiobacillus is dominated by the species T.thioparus with a mean pH of 4.7. With increasing acidification, other Thiobacillus may increase in numbers, and since they produce sulphuric acid, add to the acidity of the lakes.

Introduction Acidification of freshwater ecosystems forms probably the most serious threat to nature in Norway the last three decades. The increasing pollution of the atmosphere over Northern Europe is up to now the only factor which can explain the regional acidification (TOLLAN1977, NILSSEN1980a), but a clear-cut relationship between the acidification of the air and the waterbodies is very difficult to demonstrate. The increase in air pollution results from the build-up of industry since the Second World War. The majority of pollutants are produced further south and west in Europe and brought to Norway by low pressure systems (BRAEKKE 1976). The most important elements include: h ~ d r o n i u m , ammonium, sulphates, nitrates, heavy metals like zink, lead, mercury, cadmium, and chlorinated aromatric and aliphatic hydrocarbons. Since precipitation becomes richer in solutes, ionic exchange in soil increases, and results in additional loss of important elements t o freshwater, like aluminium and hydronium, which are believed to affect negatively the biotic communities (BRAEKKE1976, NILSSEN1980a, 1981a). It has been suggested that the process of acidification slows down the breakdown of organic matter, partly by decreasing the amount of protozoans participat-

0341 -2881/82/0064-0443

$ 10.25

@) 1982 E. Schweirrrbar~'schrVcrlagsbuchhrndlung, D-70CO Sruttgarr I

444

EINERFJERDINGSTAD and J. P. NILSSEN

ing in the processes (BICK& DREWS1973), and a shift from bacteria to less efficient fungi (GRANet al. 1974, LUCH& HYNES1973, TRAAEN 1974, LUKE 1976). Except for some few rough observations (GRAN et al. 1974), field studies of bacteriological decomposition and activities are scarce and in addition give no decisive conclusions. The present work aims at studying the bacteria in sediment from lakes of very varying acidity within the same climatic region in Southern Norway. It has been concluded from chemical and sediment analyses of water that this area has undergone an acidification process during the last two-three decades (NILSSEN 1980a, 1980b, 1980c, 1981c).We will consider bacterial decomposition with special emphasis on sulphur-cycling, cellulose, chitin, and lignin decomposition, in addition to hydrology of the various lakes.

The study area The study area is in Southern Norway where the effects of acidification are the most serious in Norway (Fig. 1).

Fig. 1. The surveyed area. A: Situation, T: Treun en meteorological station on which Fig. 4C is based. 8:Lakes 1-14, distribution of pH Eased on 150 localities during autumn circulation period is shown, dotted line: "Great friction breccia", MI and M2: meteorological stations.

1. Climate

Data on precipitation and air temperature are presented in Fig. 2. The climate is semi-oceanic. The prevailing winds are from west and south-west bringing pollutants from the European Continent and the British Isles to Norway. As shown in Fig. 3, the p H in precipitation has a mean value of about 4.5, but considerable acid periods have been recorded. The majority of solutes are deposited during the

Studies on acidic lakes in Southern Norway

445

Fig. 2. The climate. A: Monthly temperature at stations M1 and M2, B: monthly precipitation at the same statlons.

I

Fig. 3. Characterization of preci itation for 1973. Upper fall-out of strong and. (meq/m2) (strong acids: SO,, NO,). Lower an el: p H in rain at the two stations (redrawn from SCHJOLDAGER 1974).

STRONG A C I D S meq/mz

:M2 -. . MI J

F

M

A

pH IN RAIN

M

J

J

A

S

O

N

D

EINER FJERDINCSTAD and J. P. NILSSEN PRECIPITATED SULPHATE 1971 (TONNESIKrnll

D H IN SNOW MARCH 1976

IONS IN R A I N ( ~ r q 1 l )!

pH IN LAKES NOVEMBER 1974

6 55

55

Fig. 4. Chemical status of preci itation and lakes. A: precipitated sulphate (from NILU 1975). B: pH in snow March 1976 (Prom WRIGHT & DOVLAND 1977). C: Chemical composition of rain 1973-76 a t Treungen meteorological station (see Fig. 1) (from SEIP& TOLLAN 1978). D: pH in lakes November 1974 (from BRAEKKE 1976). so-called "episodes" of heavy acidic rain (BRAEKKE1976). Most hydronium ions and a small fraction of ammonium are probably of agricultural and soil origin while sulphates and nitrates are derived from industrial emittants. The acid pollutants show characteristic peaks during winter (as snow), spring and autumn (Fig.3). Dry deposition contains much the same substances as rain, with a possibly smaller share of hydronium and nitrates. The outer part of the study area receives a considerable amount of sea-spray, the most important elements include natrium, magnesium, chlorides and sulphates. Precipi~ationhas been corrected for sea-spray contributions. The study area has among the h o s t polluted precipitation deposited over Norway (Fig. 4). Some of the most acidic clear-water lakes in Norway are recorded in this area (Figs. 1,4), lakes which less than three decades ago carried high biomass of salmonid fishes.


447

2. Geology, vegetation a n d soils T h e area is described in more detail by NILSSEN (1980a). T h e lakes are situated from 4 m t o 287 m a.s.1. Lakes 1-4 are o n marine d e p o s ~ t s(Figs. 6-9) in an area with rich deciduous and spruce and pme forests (Fig. 5). They are p o l y h u m ~ c , natural mesotrophic lakes. Lakes 5- 14 are situated o n poorly-weathered bedrock of Pre-Cambrian origin (Figs. 17-18), with lakes 12-14 on very poor granites (Fig. 19). T h e Quarternary deposits, of similar composition t o the underlying bedrock, are shallow and support n o important agriculture, except for smaller areas due north of lake 10.Vegetation in the area is composed of pine and spruce forests and podzols forms the most important soils.

Fig. 5. Characreristic site near Akvigvann in the Fie area showing with deciduous and spruce and pine forests. Characteristic sites of the middle and inner regions are shown in Flgs. 17- 19.

3. H u m a n impact o n t h e lakes T h e inhabitants are concentrated in the outer area, and less than 500 live inside the "friction breccia" (Fig. 1). N o eutrophication problems have been observed, since less than 2% is farmed, and the inhabitants usually d o not use the main river o r streams for deposition of sewage. T h e main human impact is from forestry. Extensive clear-cuttmg of pine and spruce forests In area C t o o k place in the 1950-60's following construction of many forest roads. T h e forestry activities affected negatively the highly vulnerable freshwater systems.

448

EINERFJERDINCSTAD and J. P. NILSSEN

Fig. 6. Chemical characteristics of the lakes. A: Conductivity, corrected from the contribution of the H+-ion. B: p H . C : Lake colour. D: Bicarbonate content.

4. Chemical and biological changes in the watershed

Chemical changes during the last decades have been demonstrated both in the main river and several lakes. In the river, p H is decreasing while the conductivity and especially the share of calcium and magnesium is increasing. Supporting evidence is found in the lakes, where p H decreases, transparency and the solute contents increase, probably due to relatively unmodified water quality run-off, increased weathering, ion-leaching and ion-exchange processes in the catchment 1980a). area (NILSSEN

Material and media Methods for the hydrological measurements follow standard methods (GOLTERMAN & CLYMO 1969), and are described by NILSSEN (1980a). Sediment samples for bacteriological studies were taken during July (Tables 2, 3, 6, 7, 8) or March 1975 (Tables 4, 5, 9). la) Pretreatment of sludge t o be used for bacteriological investigations: T o one gram of sludge nine milliliters of distilled water was added. The mixture was homogenized by means of a "Wrist-Action Shaker". lb) Media for the cultivation of Thiobacillus PARKER'S medium (1953): (NH,), SO, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . K2HP0, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MgSO,. 7 H 2 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CaCI, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FeCI, . 6 H 2 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MnSO, . 4 H 2 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Na&O,. 5 H 2 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . distilled water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0.1 4.0 0.1 0.1 0.02 0.02 10.0 1000

g g g g g g g ml


SO, mgll

10

-

Fig. 7. Chemical characteristics of the lakes. A: Calcium content. B: Natrium. C : Magnesium. D: Potassium. E: Chloride. F: Sulphate. All in mg/l. 2) WAKSMAN'S medium (1922): a) (NH,), SO, . . . . . . . . . . . . . . . . . . . . . . . . . . . . MgSO,. 7 H z 0 . . . . . . . . . . . . . . . . . . . . . . . . . . KH2P04 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . distilled water . . . . . . . . . . . . . . . . . . . . . . . . . . . . b) Ca,(P0,)2 . . . . . elementary sulphur

...... ......

...... ......

.............................. ..............................

0.2 g 0.5 g 1.0 g 1000 ml 0.5 g 10.0 g

These media were sterilized by steam for one hour each day for three successive days. Both media were adjusted t o a pH-value of 4.2 and a pH-value of 6.2. For estimating the most probable numbers (MPN) of bacteria present in the samples the medium dilution method of five glass tubes for each dilution was applied. The same technique was used for estimating the number of the pollution indicator bacterium Escherichia coli. Incubation was carried out at room temperature (72°C) and lasted three weeks.

3.

Chitin agar as described by Glucose . . . . . . . . . . Peptone . . . . . . . . . .

HOCK(1941):

......................... .........................

1.0 1.0

g g


450 K,HPO, . . . Agar . . . . . redistilled water

...............................

0.005 g 7.5 g 1000 ml

............................... ...............................

The medium, without chitin, was adjusted to a pH-value of 7.8 and sterilized. In contrast to HOCKand other authors, who prepared their own chitin from crustacean shells, we have used purified chitin (B grade No. 220465) supplied by CALBIOCHEM, LOS Angeles, U.S.A. This product is likewise extracted from crustacean shells. The chitin solution was prepared follows: T o 20-30 grams of chitin, 50 ml of 50% sulphuric acid was added. After vigorous agitation, the solution was left untouched until the next day when 780 ml distilled water was quickly added under constant agitation. The solution then stood for two days to ensure maximum precipitation. The precipitation was collected by filtration through a millipore filter ( H A W G O 4700 type HA) with suction provided by a water-jet air pump. Subsequently the filtrate was rinsed with distilled water until the water had reached a p H of 7.8. The filtration and rinsing procedure required one week. After collection on the filter, the filtrate was scraped into a pre-heated blender t o which 50 ml of the agar medium was added, and homogenization in the blender carried out. After this the medium was ready for use. Cultivation at 21 "C took place under aerobic as well as under anaerobic conditions. Counting was not made until after 7 days incubation as growth does not begin until three days have elapsed. 4. Tannic acid agar: KH2P04 . . . . (NH4)2HPO, . . Tannic acid . . . Agar . . . . . . Distilled water .

............................... ...............................

............................... ...............................

...............................

0.25 g 0.17 g 30.00 g 20.00 g 1000 ml

The medium was adjusted to a pH-value of 5.6, and then sterilized. Aerobic as well as anaerobic cultivations at 21 "C. Blind determinations were made. A minimum of 20 gr. agar was necessary for setting the medium. 5.

Gallic acid agar: KH,PO, . . . (NH,)2 HPO, . Gallic acid . . Agar . . . . . Distilled water

.....................

... . . ... .

.

.

................................ ................................

................................ ................................

0.25 g 0.17 g 10.00 g 30.00 g 1000 ml

The medium was adjusted to a pH-value of 5.6. 6.

HENRICI'Smedium for isolation of saprophytic actinomyces: Glycerol . . . . . . . . . . . . . . . . . . . . . . . . . . . Sodium Asparaginate . . . . . . . . . . . . . . . . . . . . . Dipotassium phosphate . . . . . . . . . . . . . . . . . . . . Agar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tap water . . . . . . . . . . . . . . . . . . . . . . . . . . .

........ ........

........ ........ ........

10 1.0 1.0 15.0 1000

ml g g g ml

The medium was adjusted to a pH-value of 6.0 and sterilized. Cultivation at 30°C. Counts were made after 7 days1 incubation. For the other bacteriological investigations, the media mentioned by FJERDINGSTAD & BERG(1973) were used.


Results and discussion 1. Chemical characteristics of t h e investigated lakes

The investigated lakes (Fig. 1, Tab. 1) are situated within the same overall petrographical region of Southern Norway, but differ considerably in their chemical composition (Figs. 6-8). This is due to sea-spray, ion-leaching from marine deposits (e. g. marine clay, mollusc sand), airborne acidic pollutants and varying geochemistry of the catchments. Lakes near the coast have both high p H , buffering capacity, solute and organic contents (Fig. 6). It is well known that humic lakes show increasing colour with increasing p H (GJESSING1976). Lakes near the coast are polyhumic, while the other lakes are oligo- to mesohumic. Most lakes probably had stronger colour some decades ago (NILSSEN1980a, 1981b, 1981c), but increasing input of acidic pollutants has probably resulted in a de-colouration of the waters (cf. HORNSTROM et al. 1973, ALMERet al. 1974). Coastal lakes have a p H always above 7.0, while lakes in the innermost region have p H below 5.0, and are in addition subject to considerable seasonal variations in p H (NILSSEN 1980a). Conductivity (corrected for H + contributions) seems to follow lakes productivity patterns, and lakes in the innermost region have values close to 10 pS/cm (Fig. 6). Such lakes form vulnerable habitats for freshwater fish which have problems in regulating blood serum composition (cf. LEIVESTAD et al. 1976). The bicarbonate buffering capacity is relatively high near the coast (Fig. 6), but

3 8 rneqll

0.6rneqll

0.4 r n e q l l

Fig. 8. Chemical composition o f the different areas. Left: lakes 2-4, middle: lake 8, right: lake 14 (see Fig. I), under: total amount of anions and cathions summarized.

decreases conspicuously inland, and is absent in the innermost lakes. Possibly another buffer system is in operation (cf. LASTet al. 1980), like AI-species system and humic molecules (JOHANNESSEN 1980). The input of ions to the various parts of the area is reflected in the chemical composition of the lakes (Figs. 7-8). Calcium (Fig. 7) follows closely the distribution of bicarbonate, while magnesium, natrium, chlorides and sulphates mostly reflect sea-spray influence. It is noticeable that sulphate and nitrate (Fig. 7, Tab. 1) due to atmospheric inputs are enriched in the innermost lakes. Potassium exhibits an interesting distribution in that the difference 31"

Archiv f. Hydrobiologie. Suppl.-Bd. 64

452

EINER FJERDINCSTAD and J. P. NILSEN

between the outer and inner areas is less than three-fold (Fig. 7). But this element participates in plant metabolic activities much more than the others, and may indicate lakes influenced by agricultural activities (NILSSENin prep.). Since leaching of calcium and magnesium is increased in acidic regions, the relative distribution of these ions may help to monitor lakes situated in areas potentially subject to acid pollutants (cf. HENRIKSEN 1980). The ionic compositions of lakes 2-4, 8 and 13 are shown in Fig. 8. Lake 1 is not included because its proximity to the sea results in considerable content of sea-spray elements. Lakes near the coast receive their solute contents mainly from sea-spray (natrium, magnesium, chlorides, sulphates), leaching from marine deposits (calcium, bicarbonates), and can be considered so-called carbonate waters (HUTCHINSON 1957: 565), influenced by seaspray. O n the other hand, lakes in regions B and C are so-called sulphate lakes (HUTCHINSON1957: 565), where bicarbonate is very low or absent, and with atmospheric derived sulphate as the dominant ion. TEMPERATURE

-

Fig. 9. Temperature curves for the various lakes during early July 1973. Lakes numbers are encircled.

2. Stratification types of the lakes

The varying morphometry, through-flow patterns and wind exposure result in very different stratification patterns in the lakes (Figs. 9-13). The lakes are situated in a climate with both the continental and maritime traits of Norway. The deep lakes follow HUTCHINSON'Srype I stratification type, with bottom temperature close to 4°C during summer stratification. More shallow localities


453

follow HUTCHINSON'S stratification type 11, with bottom temperature well above 4°C during summer. Site 1 is 1 m deep and follows the air temperature most of the year. Lakes in area A are characterized by being rather sheltered from the wind, and especially sites 3-4 have strongly stratified waters. Site 5 is less stratified than the similar lake 3, but is far more exposed to winds. The considerable oxygen deficit observed in this lake at the investigated date does not seem to be a usual & NILSSEN in prep.). The deeper lakes (6-9) are type I lakes phenomenon (LARSEN (Fig. 9), and their observed oxygen deficit during summer is due mainly to breakdown of allochthonous matter (Fig. 10). The innermost acidic lakes display type I1 stratification pattern (Fig. 9), but their oxygen distribution is not very different from the deep lakes (sites 6-9). O X Y G E N I'I.1

--

Fig. 10. Oxygen saturation curves for the same periods as in Fig. 9.

3. Morphometry

Some morphometrical data are presented in Tab. 1 and depth contours of most lakes presented in Figs. 11- 13. Site 11 is cettle-formed with maximum depth 8 m. All lakes are believed formed by ice erosion, following major fracture zones (see Fig. 11). Through-flow is small in lakes 2-4, slightly higher in lakes 1, 6-9, 14, while lakes 5, 10-13 have considerable through-flow, especially in periods of heavy precipitation.

454

EINERFJERDINGSTAD and J. P.NILSSEN

Fig. 11. Depth map of lakes 1-4. Coast line is dotted. Deepest point marked with dot.

4. T h e investigated localities

a) Alekilen Alekilen is only 1 m deep, and its situation close to the sea makes it subject to considerable sea-spray influence. Local inhabitants reported that this site was connected with the sea in periods of strong winds and floods some 50-60 years ago. However, the lake supports a true fresh-water fauna (NILSSEN1980a), which may question a possible influence from the sea. The whole lake bottom is covered by macrophytes. The immediate area is dominated by deciduous forests and rich pine and spruce forests.

The environment of this lake is dominated by bare rocks, deciduous, and pine and spruce forests (Fig. 14). It is very little influenced by humans, but faeces from considerable numbers of gulls, terns and beavers may over a long period of time have added to the trophy of the lake and rendered it more eutrophic (cf. GOULD& FLETCHER 1978). The lakes have been extensively exploited by beaver populations for a long period, with present population amounting to five families. & AALEN1938, HAUCE1943, Fievann has been examined several times (BRAARUD


Fig. 12. Depth map of lakes 5-8.

Fig. 13. Depth map of lakes 10-14. Contour interval 5 m if not otherwise indicated.

455

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FINERFJERDINGSTAD and J. P. NILSSEN

NILSEN 1974). N o great changes have been detected since earlier times, but the macrophytes, especially the helophytes, have Increased its area considerably. Fievann is relatively exposed to wind, but exhibits considerable oxygen-deficit during stratification periods. Water colour is red-brown and Secchi depth 2-3 m all year round. The spring circulation is often non-existent, so the lake may be considered as spring meromictic. Orange and red light penetrate deepest, while blue light is reduced t o 0.l0/0 of its surface value within the first meter. Iron and manganese accumulate in considerable amounts in the deepest waters, and the chemocline is characterized by large sized colourless sulphur bacteria.

Fig. 1.1. Lnkc F i e v ~ n nl o o k ~ nsoutli. ~

Many of the characteristics given for the previous lakes apply for this lake. It is the most eutrophic of the lakes, probably due to human influence In the watershed some 50 years ago and impact from large numbers of sea-birds and beavers. There is no human influence at present. The lake is very shallow, windsheltered, and strongly stratified. Macrovegetation IS luxurious (Fig. 15), and has increased in the last 40 years (BRAARUD& AALEN 1938, NILSSEN 1974). The chemical data are close to those of Fievann (Tab. I).

d) Kvennevann This 1s the most humic and least eutrophic of the lakes in the Fievann-district. Bare rocks dominate its immediate environment (Fig. 16), and the area is not influenced by humans. T h e lake is strongly stratified and probably meromictic.


457

Fig. 15. Lake d i k v i p a n n looking west. The floating vegetation is conspicuous and covers large parts of the lake.

The chemical data are similar to the previous lakes (Tab. I ) , but large amounts of iron accumulate in the deep water, under a conspicuous layer of sulphur bacteria. Vegetat~onis poorer than in the two former lakes.

e ) Hammertjenn Deciduous and pine forests form the majority of the immediate environment, and the lake is slightly influenced by sewage. It is not usually strongly stratified and is subject to considerable short-term variations in water-level due to heavy through-flow. Especially the helophyte vegetation is luxurious.

f) 0 s t r e Skorstdvann The catchment area of this lake is dominated by pine forests intermixed with smaller areas of moorland. The through-flow is relatively low. Vegetation is poor

Fig. 16. Lake Kvennevann looking south-west.

and the lake is a so-called Lobelia-lake (IVERSEN1929). O t h e r data are presented in Figs. 6-8, 9, 10, 12, and Tab. I .

g) Svarttjenn T h e catchment area is small with n o bogs. Pine forests dominate, but are interm~xedwith b ~ r c hforests (Fig. 17). Water vegetation is virtually absent, and the sediment is dy-like (cf. HANSEN1961). In spite of this, the water is very clear, and the transparency is I 1 - 13 m , the greatest observed in the whole area. T h e lake is probably influenced by ground water (NILSSEN& EIE 1975).

h) Bstre Kalvvann The immediate env~ronlnentof the lake is dominated by bare rocks, bog areas, spruce and pine forests (Fig. 18). The lake is very sheltered from wind, and is fairly deep (like site 7) compared t o its surface area. (Dstre Kalvvann is situated close to Svarttjenn, but i r differs In most characterist~csfrom that lake, irrespective of similar catchment areas. B s t r e Kalvvann, however, is humic and exhibits considerable oxygen deficit during stagnation periods. In some years spring circulation is incomplete (NILSSENin prep.).

Studies on acidic lakes in Southern N o r w a y

Lake Svarttjc oking north.

Fig 18. Lake 0 s t r e Kalvvann looking west.

459

4 60


i) Holmvann One of the deepest lakes in the area, Holmvann, is situated close to the "friction breccia" (Fig. 1). The catchment area is mainly composed of pine and spruce forests with considerable bog areas. The residence time is high. Like many lakes in this area, Holmvann was earlier used as a water reservoir for timber floating, which may have negatively influenced its littoral communities. Water vegetation is sparsely developed and composed mainly of Lobelia and yellow water lilies: Nuphar luteum, The lake is considerably influenced by humus, and an oxygen deficit is observed in the deep water all year round (Fig. 10).

j) Gjerstadvann The lake receives sewage from several slurry tanks in its immediate area, but is only slightly influenced by organic pollution due to its considerable throughflow. The catchment area is large and includes both area C and large parts of area B. The lake is important for recreation, and many people inhabit its immediate environment. Bare rocks and shallow areas with considerable helophyte growth dominate the shore region. The lake formerly produced considerable amounts of fish, but the increasing acidification resulting in a present p H of about 5.0 has wiped out most fish populations.

k) Gunnestadtjenn The lake has a considerable catchment area, and strangely enough its p H seems to be fairly constant around 6.0, since it drains vary acidic regions. The vegetation is poor and the lake is a typical Lobelia-lake.

Fig. 19. Lake Lundvann lookmg north.

Stud~eson ac~diclakes i n Southern Norway

46 1

I) L u n d v a n n T h e catchment area comprises poor forests (Fig. 5), where forest clear-cutting actwities have taken place during the last three decades which probably influenced soil run-off (NILSSEN1980a). Rivers entering this lake carry cons~derableamounts of acid pollutants and have p H of 4.4-4.7 during most of the year. As site 9, Lundvann was also utilized for timber floating and its present water level appears low. The lake has typical dy-sediment, and Lobelia cover the whole shore region (Figs. 19-20). T h e Lobelia stems are densely covered with filamentous algae, mainly the genus Mougeotia. Strong seasonal changes in its water chemistry are characteristic (NILSSEN1980a).

Fig. 20. Characteristic site from the littoral reglon of lake Lundvann. The dominant halophyre is Lobelia dortmanna.

m ) Heilandsvann This lake IS similar in its chemistry to Lundvann, but slightly more acidic than the former lake. Macrovegetation is dominated by Juncus bulbosus f.Jlurtans, and sparse stands of Lobelia and N u p h a r luteum are observed (NILSSEN1980a). The lake is subject to considerable alternations in its chemical environment, affecting the whole water mass (NILSSEN1980a). Heilandsvann was also utilized for timber floating some decades ago. n) Stemtjenn T h e most acidic lake Stemtjenn has very poor vegetation in its catchment, where ombrogenic bogs constitute an important part. Bottom deposits are dy-like,

462

EINERFJERDINGSTAD and J. P. NILSEN

and the water is slightly influenced by humic material. However, this is much less than could be expected from the structure of its catchment area. It is frequently observed that lakes undergoing acidification become less conspicuously coloured, as a result of flocculation processes (ALMERet al. 1974). The lake has similar characteristics to sites 12 and 13, but water vegetation is very poor.

5. Bacteriological investigations The bacteriological investigations of sediment comprise, firstly, 4 lakes where the pH-value of the water is around 7: Alekilen, Fievann, A k v i p a n n , and Kvennevann (localities 1-4), secondly 7 lakes with intermediate pH-values varying from 5.0 to 6.0: Hammertjenn, Bstre Skorstdvann, Svarttjenn, Bstre Kalvvann, Holmvann, Gjerstadvann, and Gunnestadtjenn (localities 5-11), and finally 3 very acid lakes where the pH-value ranges from 4.2-5.2: Lundvann, Heilandsvann, and Stemtjenn (localities 12-14) (Fig. 1). With regard to Ca++ and HCO; the chemical composition of the water shows that also in this respect the lakes can be divided into the said three categories (Table 1). The sediment cultivations were made on: meat-peptone gelatine, meat-peptone agar, media for cellulolytic bacteria, Kings agar for Pseudomonas, media for fecal Escherichia coli, for sulphite-reducing bacteria and for sulphate-reducing bacteria (Desulfovibrio desulfwricans), cf. Tables 2-5. Counts of chitinoclastic bacteria Table 6, counts of actinomycetes on tannic acid Table 7, counts of actinomycetes on gallic acid Table 8, and counts of Thiobacillus Table 9 were performed. Generally the number of bacteria in sediments is by far greater in the surface layer; the number decreases with increasing depth, cf. for instance LLOYD(1931), ZOBELL & ANDERSON(1936), ZOBELL & RIITENBERG(1940) and ZOBELL & FELTHAM(1942). We have come to the same result in our investigations, but, as appears in Tables 4-5 there are exceptions to this rule. The conception heterotrophic is used conventionally in this paper, cf. Tables 2-5, but in actual fact there was no need to distinguish heterotrophic and autotrophic organisms as both of them produce carbon, the former utilizes organic material for the purpose of carbon in the cells, the latter produces cellular carbon through the fixation of carbon dioxide. A distinction must be made between various sources of energy; phototrophic (photosynthetic) organisms can utilize electromagnetic radiation, i. e. light, as a source of energy for growth, and in chemotrophic ( c h e m ~ s ~ n t h e t iorganisms c) the supply of energy is dependent on the reduction and oxidation reactions of the substrates that serve as nutrient. The microorganisms which utilize inorganic H-donors ( H z , NH,, H2S, Fe++, CO and others), are often described as lithotrophic organisms whereas all those utilizing organic H-donors are described as organotrophic organisms.

-

,X

4

E

Table 1. Selected morphometrical and chemical data from the lakes. Chemical data are for epilimnaic waters during the spring circulation period, mean for 1977 and 1978. Lake numbers refer t o Fig. 1. - N o data available. altitude (m)

1. 2. 3. 4.

Alekilen Fievann Akvipann Kvennwann

5. Hammertjenn 0strre Skorstdvann Svarttjenn 0 s t r e Kalwann Holmvann Gjerstadvann 11. Gunnestadtjenn

6. 7. 8. 9. 10.

12. Lundvann 13. Heilandsvann 14. Stemtjenn

surface area (ha)

max. depth ( 4

sum ortho A-ions phosphate and (~rg/l) K-ions (meq/l)

total nitrate ammonium nitrogen ~ h o s - nitrogen P orus (pg4 (pg/l) ( ~ g 4

total nitrogen (Wl)

silicate aluminium (mgll) (pg/l)

EINER FJERDINCSTAD and J. P. NILSEN

464

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Table 3. Number of bacteria gramme sediment in some slight alkalic lakes.

"C meat-peptone gelatine meat peptone gelatine melting meat peptone agar cellbiose agar aerobic cellbiose agar aerobic cellbiose agar anaerobic cellbiose agar anaerobic Pseudomoms agar Pseudomom agar Pseudomom agar coli-aerogenes group Escherichia coli I sulphite reducing Desulphovibrio desulfuricans Thiobacillus spp. Chitinoclastic bacteria

Fievann

Alekilen

Ak~5~vann

Kvennevann

Table 4. Number of bacteria gramme sediment in Heilandstjenn (1=6.6 m water dephts: 2=11.8 m). 1 sediment dephts

meat-peptone gelatine meat-peptone gelatine melting meat-peptone agar cellbiose agar aerobic cellbiose agar aerobic cellbiose agar anaerobic cellbiose agar anaerobic P s e u d o m o ~ sagar Pseudomoms agar Pseudomonas agar coli-aerogenes group

Escherichia coli I sulphite reducing

Desulphovibrio desu@ricans

2 sediment dephts

Table 5. Number of bacteria gramme sediment in some Norwegian acidic lakes. Stemtjenn, water depht 7.0 m sedime; dephts 0-2.5 2.5-5 5-7.5 cm cm cm meat-peptone gelatine meat-peptone gelatine melting meat-peptone agar cellbiose agar aerobic cellbiose agar aerobic cellbiose agar anaerobic cellbiose agar anaerobic Pseudomonas agar Pseudomonas agar Pseudomonas agar cob-aerogenes group Escherichia coli I sulphite reducing Desulphovibrio desu[furicans

Lundvann, water depht 10 m sediment dephts 0-2.5 2.5-7.5 cm cm

@stre Kalwann. water depht 24.6 m sediment dephts 0-2.5 2.5-5 5-7.5 cm cm cm

Gunnesradtjenn. water depht 8 m sediment dephts 0-2.5 2.5-5 cm cm

Gjerstadvann. water depht 25.5 m sediment dephts 0-2.5 2.5-5 E cm cm 2 0

468


Table 6. Number per gramme of chitinoclastic bacteria in sediment from Norwegian acid lakes compared with number of chitinoclastic bacteria in some Danish lakes. Danish Lobelia-Isoetes lakes 1,510,000,000 Moss0 (Roldskov) Store 0 k s s 8 2,510,000,000 Madums~ 50,000,000 Hampens0 140,000,000 Moss4 (Ry) 35,000,000

Norwegian lakes Fievann Alekilen Akvigsvann Kvennevann Hamrnertjenn 0 s t r e Skorstdvann Holmvann 0 s t r e Kalwann 0 s t r e Kalwann wet soil from the beach Svarttjenn

typical Danish eutrophic lakes Esroms~ Sjaels~ Sanders0 west S ~ o n d e r east s~ Sanders0 south N ~ r r e west s~ Hejredes~ Rsgbslless north R ~ g b d e s asouth

Table 7. Counts of actinornycetes on tannic acid agar by aerobic cultivation gramme bottom material. lakes Fievann Alekilen Akvlpann Kvennevann Harnrnertjenn 0 s t r e Skorst0lvann Holmvann 0 s t r e Kalwann 0 s t r e Kalwann (soil near the beach) Svartjenn

great white

30,000.000 200,000,000 850,000,000 3,300,000 31,000,000 45,000,000 38,000,000 78,000,000 700,000.000

- number per

pigment colour of colonies small white dark total numbers


469

Table 8. Counts of actinomycetes on gallic acid agar aerobic and anaerobic cultivation in brackets number x 10' per gramme bottom material. pigment color of colonies great white small white

dark

total numbers

Fievann Akvigvann Kvennevann Hammertjenn 0stre Skorstdvann Holmvann 0stre Kalwann @stre Kalwann (soil near the shore) Svartjenn

Pseudornonas The heterotrophic genus Pseudomonas, with more than 150 described species comprises many soil and freshwater forms, the major part of which are plant pathogens, and only a few animal pathogens (e. g. F! aeruginosa); some are able to decompose cellulose, chitin o r lignins. Samples of sediment for incubation at 21°C, drawn from the acid lakes Heilandsvann Station 1 and Station 2 at a depth of 0-1 cm, showed Pseudomonas colonies amounting to 90,000lgram and 20,00O/gram, respectively, which is maximum for this depth of sediment. As regards the two acid lakes Stemtjenn and Lundvann, the lakes of intermediate pH-value @sue Kalwann, Gunnestadtjenn and Gjerstadvann, the number of Pseudomonas colonies was very small at 21°C incubation and, in almost all cases, also at 30°C incubation. In this connection it should be mentioned that in a sample from the 0 s t r e Kalwann lake, drawn from a sediment depth of 0-2.5 cm there were only 200 colonies/gram whereas at a depth of 2.5-5 cm, there were 40,000lgram. Samples from Gjerstadvann showed 5001gram at 0-2.5 cm depth and 40,000lgram at 2.5-5 cm depth. A t 37°C incubation, there was, on the whole, only sparse and sporadic growth of Pseudomonas; the growth was somewhat denser in samples from Lake Heilands-

Table 9. Number of Thiobacillus gramme sediment in some Norwegian acidic lakes. Stemtjenn, water depth 7.0 m

Lundvann, water depth 10 m

@stre Kalwann, water depth 24.6 m

sediment depths 0-2,5 cm 2.5-5 cm 5-7.5 cm

sediment depths 0-2.5 cm 2.5-7.5 cm

sediment depths 0-2.5 cm 2.5-5 cm 5-7.5 cm

Gunnestadtjenn, water depth 8 m sediment depths 0-2.5 cm 2.5-5.0 cm

450 0 thiooxydans 0 0 1,300 550 concretivorns 1,200 48.000 neapolitanns 4.500 159,994,200 159,997,800 159,952,000 thioparus

0 0 35,000 159,965,000

0 0 920,000 159,908,000

0 0 0 2,300 2,300 200 16,000,000 240,000 1,400 143,997,700 159,757,700 159,998,400

0 200 2,600 35,000 810 159,964,800 159,996,590

totalnumber

160,000,000 160,000,000

160,000,000 160,000,000 160,000,000

160,000,000 160,000,000

160,000,000 160,000,000 160,000,000 Gjerstadvann, water depth 25.5 m sediment depths 0-2.5 cm 2.5-5.0 cm

0-1 cm

thiooxy duns concretivorus neapolitanus thioparns

2,800 6,400 1,200 200 730 7,400 159,995,270 159,986,000

780 2,800 1,700 159,994,720

0 1,300 1,500 159,994,400

0 0 24,000 159,976,000

0 4,900 180 159,954,420

0 2,300 1,600,000 158,497,700

total number

160,000,000 160,000,000

160,000,000 160,000,000 160,000,000

160,000,000

160,000.000

160,000.000

0-1 cm

Heilandstjenn, water depth 6.6 m sediment depths 1-2 cm 2-3 cm 3-4 cm 4-5 cm

0 0 160,000 159,840.000

Heilandstjenn, water depth 11.8 m sediment depths 4-5 cm 1-2 cm 2-3 cm 3-4 cm

5-7.5 cm

thioorydans concretivorus neapolitdnus thiopurus

780 1,700 159,957,520

0 0 1,800 159,998,000

0 2,300 5,600 159,992,100

0 0 0 0 11,000 7,500 159,992,500 159,989,000

0 2,300 540,000 159,457,700

totalnumber

160,000.000

160,000,000

160,000,000

160,000,000

160,000,000

0

160,000,000

5-7.5 cm

0

P u o


471

vann Station 1 and Station 2, 0-1 cm depth: 300/gram and 500/gram, respectively. In samples from Gjerstadvann drawn from a depth of sediment of 0-2.5 cm, there was n o growth, but in samples from a depth of sediment of 2.5-5 cm the number of colonies was 5,00O/gram, cf. Tables 2-5. As regards the two Danish Lobelia-Isoetes lakes, Grane L a n g s ~and Kalgaard SB, cf. FJERDINGSTAD et al. (1979, Table 4), counts of Pseudomonas colonies in sediment samples gave the following results: at 21°C incubation 4,00o/gram and 300,000/gram, respectively, and at 30°C incubation 4,00O/gram and 2,OOO,OOO/ gram, respectively. That the number of Pseudomonas colonies cultivated at 21 "C in samples from Norwegian lakes is so very small - in some cases, for instance in Hammertjenn (pH-value varying from 5.0-6.7) and Fievann (pH-value about 7.0), the numbers were nil - is very surprising, particularly in view of the conditions prevailing in the lakes with pH-values of 5.0 t o 6.0, Bstre Kalwann (3,000,000/gram) and Holmvann (20,000,000/gram) and in the two lakes with p H values around 7.0: Kvennevann (100,000,000/gram), and Akvigvann (80,000,000/gram). Parts of North East Greenland including Mestersvig in south (7Z015' Lat.N., 23"54' L0ng.W.) and the northern coast t o the Washington Land (80" Lat.N., 66" L0ng.W.) are areas, which, apart from Mestersvig, Danneborg and a few weather stations, are completely unspoilt, characterized by a very low temperature during winter and relatively seldom precipitation. For further details see FJERDINGSTAD & VANGGAARD (1982). Of the 44 samples of sediment collected in Greenland, 25 had Pseudomonas colonies varying from 50/gram to 380,00O/gram at 21°C incubation, 16 had Pseudomonas that varied from 100/gram to 5OO/gram.

Counts of bacteria o n meat-peptone agar By the use of this culture medium it should be possible to get an impression of the aerobic heterotrophic bacteria that are able to grow at a temperature of 30°C. Analyses of sediment samples drawn from Norwegian lakes show that the total number of bacteria grown on meat-peptone agar at an incubation temperature of 30°C reaches a maximum in samples from the Bstre Skorst~lvannand the Fievann lakes with l,050,000/gram and 1,030,000/gram respectively, cf. Tables 2-5. As far as the Danish Lobelia-Isoetes lakes are concerned the numbers obtained by corresponding culture investigations are much higher: for lakes Grane L a n g s ~ 362,000,000/gram and Kalgaards s8 8,000,000/gram, cf. FJERDINGSTAD et al. (1978, Tables 4, 8).

472

EINERFJERDINGSTAD and J. P. NILSEN

Gelatine-peptone substrate Cultivation on this substrate is a test method usually applied in the examination of drinking water. The number of aerobic heterotrophic bacteria able to grow o n this medium at the temperature 21°C will give an impression of the condition of the drinking water. Growth on gelatine-peptone substrate showed a greatly varying number of bacterial colonies in the samples of sediment of 0-2.5 cm depth. The numbers ranged from 21,00O/gram in the acid lake Lundvann to maximum 800,00O/gram in the acid lake Heilandsvann Station 2. In Bstre Kalwann (a lake with an intermediate pH-value) at a depth of sediment of 0-2.5 cm, there were 55,0OO/gram whereas there were 300,000/gram in a depth of sediment of 2.5-5 cm. Somewhat similar are the samples of sediment from Gjerstadvann, another lake of intermediate pH-value, where the numbers were 25,00O/gram and 130,00O/gram for the respective depths, cf. Tables 2-5. With regard to the Danish Lobelia-Isoetes lakes, the numbers found o n gelatine-peptone substrate were for lake Madum s 0 320,00O/gram and for lake Hampen s 0 20,00O/gram, cf. FJERDINGSTAD et al. (1975, Table 3). In samples from Northern Greenland the number of colonies on gelatine-peptone substrate likewise varied greatly, but it is noticeable that 14 of the 44 samples examined had a number of colonies that exceeded 1,000,000/gram. Maximum for the samples was 2,400,000/ & VANGGAARD (1982). gram and minimum 1,500,000/gram, cf. FJERDINGSTAD Escherichia coli It has not been possible to find fecal Escherichia coli, and coliform-like bacteria were found only in small numbers, up to 300/gram sediment in 4-5 cm depth, in the Heilandsvann Station 2.

Cellulose decomposition Cellulose is the chief constituent of the cell walls of fresh water and marine plants. The microbial degradation of very large quantities of cellulose is of great importance to the carbon cycle as it prevents the accumulation of organic matter and returns carbon dioxide to the atmosphere. Especially in sediments in ~ o n d s and lakes, cellulose may constitute the major part of the organic matter. For further details, see the description of cellulose decomposition by FJERDINGSTAD et al. (1978). In aerobic environments the decomposition of cellulose is affected mainly by Myxobacteriu, Pseudornonas, Vibrio, Cellvibrio, Cytophaga and Sporocytophaga. FLEISCHER& LARSSON(1974) have studied cellulose degradation in various types of limnetic environments. These authors, like many other research workers, e. g. (1975) and HOFSTEIN& EDGERG(1972), KNOPP& WEBER(1960), RHEINHEIMER


473

have examined the decrease in tensile strength of chemically untreated cotton threads that have been exposed at different levels in lake water and lake sediment, and the quotient of the tensile strength before and after exposure was taken as a measure of the potential cellulolytic activity. Incidentally, ROGERS(1961) has stated that the cotton fibre itself consists of a very thin primary wall o r cuticle, containing pectin and waxes with cellulose fibrils interwoven in it, an inner secondary wall, and a lumen. In our investigations we therefore used inoculation in a carboxymethylcellulose agar, which, in our opinion, provides a better means than cotton threads for measuring the cellulolytic activity. Cultivation was made at 21°C and at 30°C in both instances under aerobic as well as under anaerobic conditions. Aerobic cultivation at 21°C gave a greater number of colonies than cultivation at 30°C. The maximum numbers of colonies were found in samples from Bstre Skorstdvann, 340,000,000/gram, and Holmvann 890,000,000/gram. The smallest number in samples from Svarttjenn: 44,000,000/gram. All three lakes mentioned have a p H value of about 5.0-6.0. Anaerobic cultivation at 30°C resulted in a very great number of cellulolytic bacteria in samples from the slightly alcaline lake Kvennevann: 660,000,000/gram, the smallest number in samples from Lake Svarttjenn (pH value 5-6), 43,000,000/ gram. Decomposition of cellulose by cellulolytic bacteria in sediment shows great variations, sometimes small and sometimes extremely great, in the Danish LobeliaIsoetes lakes, Grane Langss, Kalgaard s8, Hampen s 8 and Madum s8. Aerobic cultivation at 21 "C: 324,600,000/gram, 1,700,000/gram, 12,00O/gram, and 710,000/ gram, respectively. Aerobic cultivation at 30°C: 17,000,000/gram, 5,300,000/gram, 31,00O/gram, and 80,00O/gram, respectively. In the case of anaerobic cultivation at 21°C: 270,000,000/gram, 5,300,0001 gram, 19,00O/gram, and 55,00O/gram. Anaerobic cultivation at 30°C: 198,000,000/ gram, 8,000,000/gram, 24,00O/gram, and 31,00O/gram, respectively, cf. FJERDINGSTAD et al. (1975: table 3 and 1979: table 4). Similar variations in the number of cellulolytic bacteria are noticeable if we compare our findings with investigations of a sample from sediment in East-Greenland lakes. Aerobic cultivation at 21°C of samples from Centrum Lake: 5,170,000/ gram (at 30°C: 5,145,000/gram), Hovgaards~:3,50O/gram (at 30°C: 4,50O/gram) and Midsommer s 8 640/gram (at 30°C: 1800/gram). The corresponding figures for anaerobic cultivation: 37,720,000/gram (at 30°C: 35,640,000/gram), 6,50O/gram (at 30°C: 3,20O/gram) and 820/gram (at 30°C: 550/gram).

Chitin decomposition Chitin (Polyacetylglucosamine) is a polymer consisting of at least four acetylglucosamine units, cf. PORTER(1950: 839). It occurs in the exoskeleton of crustacea, in some coelentera and protozoa, cf. ZOBELL(1946), and in the cellular wall of

474

EINER FJERDINCSTAD and J. P. NILSSEN

certain lower fungi, and filamentous yeast, cf. NABEL(1939). It has been estimated that several million tons of chitin are produced annually by the copepoda, a subclass of planktic crustacea, and if this chitin was not decomposed its accumulation would soon cause a serious drain on the water carbon and nitrogen, cf. i.a. ZOBELL & RI~TENBERG (1938) and CAMPBELL & WILLIAMS(1951). Dissimilation of chitin appears to be a fairly widespread property in various genera of bacteria, cf. ROGERS(1961: 285). CLARKE & TRACEY(1956: 188) found that the enzyme chitinase is produced by some bacteria (e. g. Cromobacteria, Klebsielkz, Psendomonas, Clostridium, Vibrio, and Escherichia). Also microorganisms of the actinomycetes and Myxobacteria genera are common chitin scavengers and so are some filamentous fungi, cf. also FJERDINGSTAD et al. (1979: 80). The number of chitinoclastic bacteria is dependent on the occurrence of chitinous organisms with exoskeleton, especially zooplankton, which is produced in the individual lakes. The acidity of the water, however, may have a reducing effect upon the numbers of zooplankton. Chitinoclastic bacteria exist in greatly varying numbers in Norwegian lakes, but the variations are far smaller than in the Danish lakes where, according to FJERDINGSTAD et al. (1978), maximum was found in the lake Store 0kss8: 2,510,000,000/gram an minimum in lake Sanders6 east: 3,300,000/gram. In the Norwegian lakes maximum was found in the lake Fievann: 139,000,000/gram and minimum in Bstre Skorstdvann (pH value: 5-6): 70,000,000/gram. cf. Table 6.

Decomposition of lignin Lignins, which are chemically bound to cellulose and synthesized by plants, are complex aromatic compounds of phenylpropane, especially coniferyl, sinapol cumaral alcohol, cf. RHEINHEIMER (1975: 131). Typically, lignins constitute from 10 to 20% of the organic matter in phytoplankton and from 30 to 48% of the organic residue in lake bottom deposits. The possibility of microbiological degradation of lignin has been much discussed, cf. FJERDINGSTAD et al. (1978). KUZNEZOW(1959) has given the following information concerning the percentage contents of some substances in organic sediments: min.

max.

Wax and bitumen . . . . . . . . . . . 1.91 Hemicellulose . . . . . . . . . . . . . 3.63 Lignin-humic acid complex . . . . . . 33.85 Total carbon . . . . . . . . . . . . . . 32.12 Total nitrogen . . . . . . . . . . . . . 1.90

23.93 14.12 77.99 59.43 5.86

The lignin-humic acid complex thus constitutes the greater part of the organic

Studies o n acidic lakes in Southern N o r w a y

475

sediment, and the number of lignin-decomposing organism cannot be determined simply by cultivation o n agar plates without special nourishment. It has been postulated that certain substances, e.g. tannic acid and gallic acid are closely related to lignin in their chemical structure and, therefore, can be used as alternative substances in lignin studies. GOTTLIEB& PELCZAR(1951: 59), however, have stated that the only structural relationship between the two materials mentioned is the presence of free phenolic groups, which are more abundant in tannic acid than in lignin. It is often maintained that, unlike cellulose, lignin sediments if they reach an anaerobic bottom layer, cannot be docomposed through hydrolytic reactions. We have not been able to verify this, cf. Tables 7-8. The lignin degradation probably proceeds very slowly via oxidative cleavage by most strains of the bacterial genus Micromonospora. The lignins are oxidized to vanillin and hydrogenated to compounds of the c y c l o h e ~ y l p r o p ~type. l Other lignin decomposers are said to be species of the genera Pseudomonas, Flavobacterium and Achromobacter, all obligate aerobic organisms, common in soil and water. jr. (1951: 72) concluded that the tannic acid reaction GOTTLIEB& PELCZAR and similar culture reactions (gallic acid) can be used as a general indication of white rot activity for wood rotting fungi, but it should be recognized that there are notable exceptions, and that the reaction is not infallible. (1968). Several authors, cf. GOLDSTEIN& SWAIN(1965), BENOIT& STARKEY have referred to the fact that tannins inhibit the growth of microorganisms because these substances are capable of binding strongly to proteins and p~l~saccharides. Enzymes are wholly o r partially inactivated by complex formation with tannins, cf. also GRANT(1976) who found a strain of Penicillium adametzi in enrichment cultures with condensed tannins as carbon source. The ability of tannic acid to inhibit growth does not occur, however, unless its concentration is of 10-2O%, cf. PORTER(1950). We have been able to verify this by using tannic acid agar as substrate for our microorganism cultivation. The results were as follows: at 21°C minimum 30,00O/gram in the lakes Fievann ( p H about 7.0) and Svarttjenn (pH: 5-6) and maximum in the lake 0 s t r e Skorstdvann (pH: 5-6) 4,700,000/gram. In a sample of soil from the Kalwann beach: 50,600,000/gram. In the Danish Lobelia-Isoetes lakes, Grane Langs6: 220,00O/gram, in Kalgaard s8: 20,00O/gram, but in Store 0kss6: 5,110,000/gram. Samples drawn in the late autumn gave the result: 120,0OO/gram, 20,00O/gram and 5,110,000/gram, respectively. In the case of aerobic cultivation on gallic acid agar, minimum was 30,0OO/gram in a sample from Fievann and maximum 1,730,000/gram in a sample from Akvigsvann. The number of actinomycetes in samples from Fievann lake was the same no matter which substrate was used: tannic acid agar o r gallic acid agar, but when

476


a sample from the 0 s t r e Skorstdvann lake was cultivated on tannic acid agar, the result was 4,700,000/gram, and on galIic acid agar only 1,600,000/gram. Anaerobic cultivation at 21°C on gallic acid agar of a sample from the Akvigsvann lake resulted in 1,750,000/gram, which must be considered as corresponding to the number obtained from cultivation under aerobic conditions. A sample from 0 s t r e Skorstdvann lake gave 18,700,000/gram, which was maximum. A comparison was made of the results obtained from cultivation on gallic acid agar of samples from Norwegian lakes and samples from the Danish Lobelia-Isoetes lakes: Grane L a n g s ~ Kalgaardss~, , Moss0 in the Rold Forest, Store 0 k s s 0 , Madum s0 and Hampen s0. The numbers found under aerobic conditions and, in paranthesis, anaerobic conditions in samples from the Danish lakes were as follows: 16,00O/gram (40,00O/g), 220,00O/gram (80,00O/g), 240,00O/gram (260,00O/g), 220,00O/gram (1 80,00O/g), O/gram (20,00O/g), 270,00O/gram (310,000/ g), respectively, which clearly indicates that the production of actinomycetes on gallic acid agar is greater for the samples drawn from the Norwegian lakes than from the Danish lakes (cf. FJERDINGSTAD et al. 1976, Table 4).

T h e sulphur cycle Previous investigations by FJERDINGSTAD et al. (1976, Table 8) of Thiobacilli in sediments from Danish lignite pits have revealed that these bacteria occurs in very great numbers and that 7: thio-oxidans and, often, 7: concretivorus predominate. In samples drawn from 15 localities in lignite pits, 9 had Thiobacilli in a number of 1,600,000,000/gram. The number of Thiobacilli occurring in the Norwegian acid lakes is much smaller - about one tenth of the number in the Danish lignite pits - and 7:thio-oxidans has been observed only in small numbers in few Norwegian samples. It has been possible to demonstrate the occurrence of 7: concretivorus and 7:nenpolitanus in all samples, but in greatly varying numbers, from 730,00O/gram to 16,000,000/gram. O n the other hand, 7:thioparus was found in all the Norwegian sediment samples in extremely large numbers and is thus the predominant Thiobacillus species found, cf. Table 9. The Danish Lobelia-Isoetes lakes have the following p H values: lake Medum s0 4.0-5.7, lake Hampen s 0 5.4-8.5, lake Store 0 k s s 0 4.0-5.2, lake Kalgaard s0 5.65-7.1. It appeared that Thiobacillus species were virtually non-existent in sediments from these lakes. Thiobacilli were found only in the lake Madum s0 in numbers of 170/gram. In none of the Danish lakes investigated were there any Thiobacilli in surface samples (cf. also FJERDINGSTAD et al. 1975, 1977). The reason is probably that these lakes are rich in humic acids and not sulphuric acids.


477

Sulphite-reducing bacteria In comparison with other bacteria, sulphite-reducing bacteria are relatively sparsely represented in sediment samples from the Norwegian acid lakes, from 60 to 9,20O/gram. Sulphate-reducing bacteria N o sulphate-reducing bacteria (Desulfovibrio desul+cans) strated in any sample, cf. Table 4.

have been demon-

Considerations With the only exception of the sulphur oxidizing species of the genus Thiobacillus and organisms decomposing lignins (actinomycetes), the bacteria found in the Norwegian lakes occur in far smaller numbers than in samples of sediment from Danish Lobelia-Isoetes lakes and samples from Northern Greenland. I t would be quite natural to investigate the reason for these differences. 1. The climatic conditions offer no explanation. In Norway temperature during winter is, indeed, lower than in Denmark, but temperature in North Greenland is even lower than in Norway. 2. If the existing chemical analyses of the water are viewed in relation to the bacteriological investigations, cf. Tables 1 - 11, it will appear that the quantities of C a + + and sulphur bacteria d o not offer any explanation why there are so enormous variations in the number of bacteria from lake to lake, or why samples drawn from different depths of sediment in the same lake may likewise vary so widely in this respect. The group comprising the 4 lakes with p H value about 7, has the largest content of HC0;-, varying from 11-32 mg/liter. Consequently these 4 lakes have a much greater buffering capacity, but this does not offer a causal explanation for the prevailing conditions. 3. The growing acidity of the Norwegian lakes is accompanied by an increase in the concentrations of heavy metals. This increase occurs either through direct precipitation, through influx of acid melt water during spring, acid rain water mainly during autumn, and through the fact that heavy metals become more easily liberated from the sediment with increasing acidity. It is well known that ions such as Zn, Cu, Pb and C r may have a bactericidal effect. This support the hypothesis that increase in heavy metal concentration might account for the varying and often very low numbers of bacteria in the individual lakes, as well as in the various sediment depths. From ERIKFJERDINGSTM& NILSSEN(1981) which discusses the content of heavy metals (Zn, Cu, Pb, C r and Mo) in the different depths of sediment, it appears, however, that the number of bacteria cannot be related t o the total quantity of these elements.


478

4. It is easy to conclude that certain bacteria might be antagonistic towards other bacteria, but this does not seem to be the case either. A study of the Tables 7 and 8 reveals that the increased acidity effected by the sulphur decomposition by species of the genus Thiobacillus cannot be decisive of the number of other bacteria, as the total number of Thiobacillus is almost constant in all depths of sediment in all lakes. 5. The acidity is more constant in the Norwegian lakes than in the Danish Lobelk-Zsoetes lakes examined, and the p H values of the Greenland lakes is probably even near to neutral point. The more constant of the Norwegian lakes, may be the reason why these have a lower number of bacteria than the lakes with which they have been compared. In this connection reference must be made to PORTER(1950: 261) who states: "The disinfectant action of highly dissociated mineral acids, such as sulphuric acid, depends upon the number of free hydrogen ions present per unit volume and not upon their normal strength, but we also know that the hydrogen-ion concentration necessary to bring a destructive action varies considerably from organism to organism". 6. Another possibility is that the precipitation, in addition to the elements mentioned under point 3 may supply other trace elements, which are bactericidal & NILSSEN198l), as such, might influence the number and (ERIKFJERDINGSTAD & NIFONG (1971, Table 9) are stating that the comof bacteria. WINCHESTER position of particulate emission from fuel oil combustion include the elements As, Ag, Ba, Ca, Co, Cu, Si, S and Zn, cf. FJERDINGSTAD et al. (1975, p. 145). Some of these elements are known to have a toxic effect on bacteria. An important point is now to consider the Norwegian acidic lakes and their bacteria flora in the acidification development. Sulphur oxidizing Thiobacillus excretes sulphuric acid, least amount in 7:thioparus, larger amount in T: neapolitanus and 7: concretivorus, and largest amount in T: thio-oxiduns. As stated by FJERDINGSTAD (1964) and FJERDINGSTAD et a]. (1976: 237) in a sulphur medium the presence of 7: thioparus causes p H to drop to pH: 4.73f 0.36, 7: neapolitanus to pH: 3.79 0.42, 7: concretivorus to pH: 2.73 fi 0.42 and 7: thio-oxidans to p H : 2.73 2 0.32. As appears from Table 9, 7:thioparus is dominating Thiobacillus in all samples. 7: thioparus, T: neapolitanus and 7: concretivorus all contribute to accelerate the hydrolysis, simultaneously, as well as alternatively (FJERDINGSTAD 1956: 235). It is therefore most probable that the lakes will become more acidic, since only the acid emittants are increasing. The dominating Thiobacillus, 7:thioparus will therefore be succeeded by the acid-producing species 7: neapolitanus and T: concretivorus, and finally 7: thio-oxidans will be the most common bacteria resulting in even more acidic lakes. This can be predicted from localities with Thiobacillus in Denmark (FJERDINGSTAD 1976). The development towards 7:thiooxidans will take time since the less acidic lakes near the coast are well buffered, and the more acidic lakes also possess a large number of weaker buffering systems

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(cf. NILSSEN 1980a, 1981b, LAST e t al. 1980, JOHANNESSEN 1980). Nevertheless, t h e acidifying role of t h e s u l p h u r bacteria c a n n o t b e ignored i n t h e acidic N o r w e g i a n lakes.

Summary Lakes in a region undergoing acidification were sampled. Close t o the coast the lakes can be considered as bicarbonate lakes considerably influenced by sea-spray. The innermost lakes are sulphate lakes, and have a p H below 5.0 all year round. Sulphate, nitrate, aluminium are enriched in the inner lakes, while very low concentrations of calcium, magnesium and potassium are recorded; the differences can be accounted for by the difference in the geochemistry in the catchments. Acidic lakes can be divided into clear-water acidic lakes and humic acidic lakes, where the latter probably have been naturally acidic since the introduction of spruce t o Southern Norway about 1000 years ago. The number of bacteria, except for Thiobacillus, is much lower than in the Danish Lobelia-Isoetes lakes and ultra and oligotrophic lakes in Greenland. The reason for this may be the constant low acidity of Norwegian lakes, heavy metal accumulation in the sediments, o r biocides brought with the acidic rain. The degradation of lignin seems increased in Norwegian lakes compared with the other areas. Also the number of Thiobacillus is very high in Norwegian lakes, but dominated by 1 thioparus with mean p H of 4.7. With increasing acidification of Norwegian lakes, other Thiobacillus species may increase in number, and since they produce sulphuric acid, add to the acidity of the lakes. The buffering capacity of the lakes surveyed, suggests that lakes in the innermost area are most vulnerable t o the environmental alternations described.

Zusammenfassung In einer Region mit zunehmender Aziditat sind in Binnenseen Proben entnommen worden. Nahe der Kuste, wo die Seen von Schaumspritzern des Meeres beeinfludt werden, konnen die Seen als Bikarbonatseen bezeichnet werden. Weiter im Binnenland handelt es sich bei p H