AE-407 STUDSVIK, AKTIEBOLAGET Zooplankton E. Central This consent ces
Almquist
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NYKOPING, intended author.
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ATOMENERGI Lake
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Magelungen, a
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1970
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AE-407 UDC
591.52 593.1:
AE-407
ZOOPLANKTON FROM LAKE MAGELUNGEN,
CENTRAL SWEDEN 1960-63
Elisabeth Almquist
ABSTRACT
The investigation of the zooplankton of Lake Magelungen, Central Sweden, was carried out over a period of three years. The aim of the investigation was to illustrate the qualitative and quantita tive composition of the zooplankton before the release of waste water from the Agesta Heat and Power Station began. Vertical sampling series were collected once a month at three different stations in the lake. The highest volumes of zooplankton were obtained in the summer . The ciliates predominated when the conditions were un favourable for other zooplankters , as in winter just below the ice. The rotifers dominated during and immediately after the spring circulation. With one exception the crustaceans reached their peak volume values in August or September. The composition of the zooplankton indicates that Lake Magelungen is highly eutrophic.
Printed and distributed in November 1970. LIST OF CONTENTS Page Introduction 3
Methods 3
List of Species 7
Seasonal and Vertical Distribution of the Zooplankton 1 1
Species Account 1 3
Comparison Between the Three Stations In the Lake 21
The Trophic State of the Lake 22
Conclusions 24
References 25
Tables 1 -5. Volume of zooplankton, Stations MA, MOB, and MH (average values) . 27 - 30
Table 6 . The phytoplankton - zooplankton ratio 1962. 30
Table 7. Species regularly occurring in plankton of the three stations. 31
Table 8. Most common zooplankton species found in earlier investigations in Lake Magelungen. 32
Figure captions 33
Figures 1- 47 34 - 61 INTRODUCTION
Lake Magelungen (map Fig. 1) is situated on the boundary bet ween Stockholm and the municipality of Huddinge , about 1 0 km S of the centre of Stockholm. It has a length of about 6 km, its area is 2 . about 2. 4 km , and the maximum depth about 16.4 m. A more thorough
description of the lake is given by Willen [21 ].
The investigation of the zooplankton of Magelungen was carried out as part of a team job aiming to provide information about the limno logical state of the lake with special respect to future changes due to the outlet of waste water from the Agesta Heat and Power Station. The
research work was planned and started by Professor W. Rodhe of the
Institute of Limnology, Uppsala, and Dr. P-O. Agnedal and his staff at Studsvik [1 ]. The phytoplankton was investigated by Dr. T. Willen of the Institute of Limnology, Uppsala [21 ].
The zooplankton collections began on March 28, I960, and went on until May 28, 1963. To begin with, all sampling was done at the main station MA (map Fig. 2) near the point of the future outlet of waste water. From 1961 on, additional collections were made at two other stations, MH and MOB. During 1 962 and 1 963 a direct comparison of the three stations was made.
METHODS
Sampling and preserving
The zooplankton samples were collected once a month at the main locality, Station MA (Fig. 2), during the period March 28, I960, to
May 28, 1 963. Samples were taken more frequently in spring and au tumn. In order to check the plankton distribution of the lake, samples were also taken, from 1 961 on, at Stations MH and MOB. - 4 -
Both qualitative and quantitative collections were made. A No.
25 Muller gauze plankton net was used for the qualitative samplings hauled up from bottom to surface. These samples were mostly ex amined alive or, when this was not possible, immediately preserved with a portion of formalin to make a 4 per cent solution.
The determination of ciliates and rotifers has mostly been per formed on living material. Some species, such as the Synchaetae, which are best studied when they are quite relaxed, were treated with a 2 per cent cocaine solution.
The quantitative plankton samples were collected simultaneous ly with a Ruttner 1.51 sampler and a Rodhe 5 1 sampler [16] at the following depths: at Station MA 0.2, 1 , 3, 5, 8, and 10. 5 m; at Station
MH 0.2, 1, 3, 5, 8, 10.5, and 12.5m; and at Station MOB at 0.2, 1 ,
3, and 4. 5 m. During the first year of investigation all organisms in every sample were counted. From the middle of 1961 the "Vollplankton" samples collected with the Ruttner sampler were used for counting pro tozoans, rotifers, nauplii, and the smallest crustaceans. The filtered
5 1 Rodhe samples were used for counting all crustaceans but nauplii.
All samples were counted in Utermohl chambers with inverted microscope [1 9 ].
Plankton volumes
The volume of each except the rarer zooplankton species in the
Magelungen material has been calculated stereometrically or by weigh ing (adult copepods and cladocers).
It is for many reasons difficult to determine the true volumes of the zooplankters . Besides the seasonal and developmental size varia tions there is also a variation in size from lake to lake 9 ?. A com - 5 -
parison between my material and the dimensions given, for instance, by Monti, Axelson, and Nauwerck [7, 3, 8] showed the risk of trans ferring the volume numbers of a species from one water to another without checking and sampling a fairly large material. In this paper
I have applied the method introduced by Halme [5 ] to calculate the zooplankton volumes on the basis of the biomass factor ("Biomasse
Faktor", BmF) for each species. This may be a way of facilitating comparisons between the standing crops of different waters.
Graphical presentation
The "cake" diagrams, Figs. 3-6, show the distribution of the zooplankton expressed as per cent of the total volume. These diagrams give no indication of the number of individuals; thus the sample col lected from 3 m depth at station MOB on April 8, 1961 , contained 208 small ciliates and 1 copepodite of Diaptomus per litre, whereas the sample from the same depth and station collected on May 7, 1963, con tained about 52 000 ciliates of different sizes, 200 rotifers, 0.2 cladocers, 3.6 copepods, and 25 nauplii per litre.
The diagrams, Figs. 7-35, are constructed according to Pejler
[l 1 , p. 226]. They show the frequencies of the most common species at different depths and on different occasions over the sampling period.
Empty circles indicate catches from which the species in question was absent, black dots represent samples containing the species. The diam eter of each dot is proportional to the third root of the number of in dividuals per litre. The isotherms for 6 , 1 0, and 20 °C as well as the isopletes for 2 mg per litre are drawn in the diagrams. The dia grams, Figs. 42-45, which show the distribution of the total zooplankton volume, are drawn in the same manner, but for technical reasons the - 6 -
black dots are replaced by circles. In these diagrams, samples con taining no zooplankters are represented by an x.
Figs. 39 and 40, showing some typical forms of Daphnia occur ing in Magelungen, are drawn from the micros cope with the aid of a
Treffenberg drawing apparatus constructed by Wild. LIST OF SPECIES
Rhizopoda
Arcella vulgaris Ehrbg
Difflugia hydrostatica Zacharias
D. limnetica Levander
C iliata
Coleps sp.
Didinium nasutum Mull. 3 3 Epistylis rota ns Svec BmF 1 0 p
E_. sp. , on Diaptomus
Lionotus cf. folium Duj. 4 3 Metopus es Miill. BmF 1 0 p
Paramaecium aurelia Ehrbg
P. sp.
Spirostomum cf. minus Roux
Stentor sp.
Strombilidium gyrans (Stokes) Kahl Tintinnidium fluviatile (Stein) Kent BmF 1 0^
5 3 Tintinnopsis lacustris Entz BmF 1 0 p 3 3 Vorticella sp. , on Microcystis BmF 1 0 p
V. sp. , on Daphnia
V. sp. , on Diaptomus
Zoothamnium sp. , on Diaptomus 5 3 Ciliata spp. , large specimens BmF 1 0 p . 4 3 medium sized BmF 10 p small BmF 10^ p^
Suctoria sp. - 8 -
Rotatoria Anuraeopsis fissa (Gosse) BmF 1 0^ p^
Ascomorpha saltans Bartsch / O Asplanchna priodonta Gosse BmF 10° p
Brachionus angularis Gosse BmF 10 p B. calyciflorus Pallas BmF 1 0^ p^
B. quadridentatus Hermann B. urceolaris Mull. BmF 1 0^ p^
Collotheca pelagica (Rousselet) BmF 10^ p^
Colurella sp. / O Conochiloides natans (Seligo) BmF 1 0° p
Conochilus hippocrepis (Schrank)
C O C. unicornis Rousselet BmF 1 0 p
Euchlanis dilatata (Ehrbg) Filinia longiseta (Ehrbg) BmF 1 0~* p^
C o Kellieottia longispina (Kellieott) BmF 10 p
Keratella cochlearis (Gosse) BmF 10 p K. quadrata (Mull. ) BmF 1 0~” p^
Lecane luna (Mull. )
E. nana (Murray)
Lepadella patella (Mull. ) Polyarthra dolichoptera (Idelson) BmF 1 0^ p^
P. major (Burckhardt)
C O P. remata (Skorikov) BmF 1 0 p P. vulgaris Carlin BmF 1 0^ p^
5 3 Pompholyx sulcata Hudson BmF 1 0 p
Synchaeta oblonga Ehrbg BmF 1 0 p - 9 -
S. pectinata Ehrbg BmF 1 0^
5 3 S. truncata von Hofsten BmF 1 0 |i
Trichocerca birostris (Minkiewi.cz) BmF 1 03 p
T. capucina (Wierzejski and Zacharias) T. cavia (Gosse) BmF 1 0^ |i^
T. porcellus (Gosse) T. pus ilia (Jennings) BmF 1 0^
T. rousseleti (Voigt) BmF 1 0^
. Cladocera
A Iona quadrangular is (Mull. )
A. rectangula Sars
. . 7 3 Bosmina coregoni Baird BmF 1 0 |i
B. longirostris (Mull. )
Ceriodaphnia pulchella Sars
C. quadrangula (Mull. ) 7 3 Chydrous sphaericus (Mull. ) BmF 1 0 p
Daphnia cristata Sars s. str. 7 3 D. cucullata Sars s. str. BmF 10 |i D. longispina Mull, s. str. BmF 10^ - 10®
Diaphanosoma brachyurum Lievin
Graptoleberis testudinaria (Fischer) Leptodora kindti (Focke) BmF 1 0^ - 1 0^
Pleuroxus uncinatus Baird
Sida crystallina (Mull. )
Branchiura
Argulus foliaceus (L.) - 10 -
Copepoda 7 3 Cyclops ins ignis Claus BmF 1 0 p 7 3 C. strenuus Fischer s. 1. BmF 10 p . 7 3 Diaptomus gracilis Sars BmF 1 0 (i. 7 3 Eucyclops serrulatus (Fischer) BmF 10 p 7 3 Mesocyclops leuckarti (Claus) BmF 1 0 |i. M. oithonoides (Sars) BmF 1 0?
Paracyclops fimbriatus Fischer
Insecta
Chaoborus sp. , larvae - 11
SEASONAL AND VERTICAL DISTRIBUTION OF THE ZOOPLANKTON
Like the phytoplankton the zooplankters reached their highest volumes in the summer. The occurrence of high values varied accord ing to the qualitative composition of the zooplankton (Figs. 3-6).
In I960 no marked peak values were observed; it is, however, possible that high values occurred during intervals when no sampling was done. The peak in spring 1 961 (Fig. 42) was due to Bosmina coregoni, the peak in autumn 1 962 (Fig. 43) mainly to Chydorus sphaericus and Daphnia cucullata, though at Station MH (Fig. 45) pre ceded by a heavy bloom of rotifers. In spring 1 963 (Fig. 43), when the investigation was concluded, the rising values were mainly due to crustaceans, especially nauplii and copepodites of Cyclops.
Ciliata
The ciliates predominated at periods when the conditions were unfavourable for other zooplankters, as in winter just below the ice.
In spring at about the time of the break-up of the ice they were more or less evenly distributed throughout the whole water column, in sum- mar they appeared in the deeper more or less oxygen-depleted water layers.
Rotatoria
The rotifers formed the dominant group in all water layers dur ing and immediately after the spring circulation. In July and August
1 962 they were the most abundant group in the topmost water layers.
The earliest of these large populations consisted mostly of
Synchaetae followed by Polyathrae and Keratella cochlearis. Highest - 12
values in the peak of July 1 962 were reached by Kerate 11a cochlearis, in August 1 962 by T richocerca pus ilia and Pompholyx sulcata.
C rustacea
Among the cladocers Bosmina coregoni reached a peak in June
1 961 at Stations MOB and MA and in July 1 961 at Station MOB. These high values were never recorded again during this investigation nor were Bosmina found in such large numbers at Station MH.
The most numerous cladocers were Daphnia cucullata and
Chydorus sphaericus , the peaks of the latter being always coincident with the bloom of the Cyanophytes [21 fig. 7 ]. The occurrence of
Daphnia cucullata extended over a longer period of the year: often, as in 1 961 , Daphnia came earlier than Chydorus and was also found in numbers right on to early winter (December).
The Copepods were represented by Diaptomus gracilis and some species of the collective genus Cyclops. Diaptomus gracilis was present practically all the year round; it was volumetrically dominant in many autumn and winter samples. The Cyclops, of which the most important was C. strenuus , reached their highest values in the late spring when their nauplii and copepodites dominated in a great number of samples.
The seasonal and vertical distribution of the total volumes or
"standing crop" of zooplankton is shown in Figs. 42-45. The annual cycle starts with very low values in early spring in connection with the break-up of the ice. The highest values were always recorded in
August or September (tables 1 -5), with the exception of 1961 when the early spring caused a high peak of Bosmina coregoni in June. This peak was followed by a lower one in August. -13-
SPECIES ACCOUNT
Rhizopoda
Arcella vulgaris Ehrbg. Occasionally. Station MA.
Difflugia hydrostatica Zacharias. Occasionally. Station MA.
D. limnetica Levander . Single specimens in net samples from
Station MOB.
Ciliata
Coleps sp. Stations MA and MOB. They were mostly found just under the ice before the break-up and near the bottom immediately after the break-up.
Didinium nasutum Miill. Mostly single speciemens. The highest numbers were found at Station MH on May 22, 1 962 (1 m: 1 40 inds/l;
8 m: 60 inds/l), and at Station M on May 7, 1963 (0. 5 m: 30 inds/l;
1 m: 20 inds/l).
Epistylis rota ns Svec. Typical summer form found only May-
October, always at temperatures above 10 °C. The species seems to avoid oxygen values lower than 2 mg/l. Most concentrated in the upper water layers. Peak values in 1 961 at Station MOB on June 12 (0.5 m:
440 inds/l) and at Station MA on July 1 7 (0. 5 m: 1 00 inds/l), and in
1 962 on August 6 Station MOB (0. 5 m: 440 inds/l), Station MA (3 m:
320 inds/l), and Station MH (0. 5 m: 250 inds/l).
.E. sp. Quite frequent on Diaptomus gracilis.
Lionotus cf. folium Duj. Mostly found in late winter and early spring in connection with the break-up of the ice. In near-bottom samples also in summer at the oxygen-deficit period.
Metopus es Mull. Found only in the deepest water layers at Sta tions MA and MH at the oxygen-deficit period. Mostly in great numbers
(> 1 2 000 inds/l). -14-
Paramecium aurelia Ehrbg. In net samples from Station MOB.
IP. sp. was found during the winter mostly in 0. 5 m samples
(just below the ice cover). Also in deep-water samples during sum mer. Most frequent at Station MOB.
Spirostomum cf. minus Roux. In net samples from Station MOB.
Stentor sp. In net samples from Stations MA and MOB.
Strombilidium gyrans (Stokes) Kahl.
Tintinnidium fluviatile (Stein) Kent was found in fairly great numbers from April to December at all three stations. Peak values
August 6 , 1962, at Station MOB (1 m: 1 3 000 inds/l) , at Station MA
(0. 5 m: 1 4 000 inds/l), and at Station MH (1 m: 3 000 inds/l). A great outburst occurred simultaneously at all three stations on May 7, 1963, with peak values at Station MOB (3 m: 39 900 inds/l), Station MA (5 m:
3 200 inds/l), and Station MH (3 m: 3 200 inds/l). Only once found below the ice cover (April 1 6 , 1 962, Station MOB 0.5 m: 2 inds/l).
This species is by many authors found to be a cold-water form
[cf. 20, pp. 222, 228; 8, p. 40 ]. Halme [5, p. 39, and Abb. 4, p. 38], however, during his investigations in the Pojo bay, found the species to behave as a distinctly stenotherm "mild-water organism" reaching its peak above 1 8 °C. Also during the years of this investigation the species appeared as a summer plankter, most abundant at a tempera ture of about 1 8 °C or more.
Tintinnopsis lacustris Entz (» Codonella cratera (Leidy)). Fig. 7.
Eurytherm. Found throughout the year at all three stations. The species seems to avoid periods of low oxygen values.
Vorticella spp. Anabaena , Microcystis and other cyanophytes were very often infested with small vorticellae. Other small vorticellae were not infrequently found on Diaptomus and Daphnia . - 15 -
Zoothamnium sp. The most commonly found epizootic ciliate on
Diaptomus gracilis.
Suctoria sp. A small Acineta -like suctorian was sometimes found on Diaptomus spp.
Ciliata spp. As most ciliates were rendered more or less un identifiable by the preservative, they were all counted together except
Codonella cratera, Epistylis rotans , Metopus es, and Tintinnidium fluviatile.
Rotatoria
Anuraeopsis fissa (Gosse). Found only during the summer period
April-October. In quantities only July-September . The highest values were found in the 1 -3 m water layers August 6 , 1 962, Station MOB
(1 m: 6 200 inds/l), Station MA (3 m: 7 900 inds/l), and Station MH
(1 and 3 m: 4 200 inds/l). This is quite in contrast to the findings of
Pejler [11, p. 227], who found practically all the specimens of this species in the deepest water layers of Osbysjon. Only on two occasions did I find the Anuraeopsis population to be more or less concentrated to the deepest water layers: on October 1 1 , I960, at Station MA (1 0. 5 m:
2 700 inds/l) and on October 1 , 1 962, at Station MH (1 2. 5 m: 1 80 inds/l).
These two samples were taken just towards the end of the period of low oxygen content.
Ascomorpha saltans Bartsch. Occasionally found at all three stations .
Asplanchna priodonta Gosse. Fig. 8. Males November 8, I960,
Station MA; eggs November 8, I960, Station MA, and May 1 5, 1 961 ,
Stations MOB and MA. -16 -
Brachionus angularis Gosse. Fig. 9. Common but never in great
quantities . Except during the winter 1 961 this rotifer appeared as a
spring and autumn species. Males February 1 3 and 28, 1961 .
B. calyciflorus Pallas. Fig. 10.
B. quadridentatus Hermann. Single specimens at Station MA
July 5, I960, and September 21 , I960.
B. urceolaris Mull. Single specimens at all three stations.
Collotheca pelagica (Rousselet). In rather small numbers Station
MA July-November. Specimens with 1 -2 eggs found in the autumn
catches.
Colurella sp.
Conochiloides na.ta.ns (Seligo). Fig. 1 1 .
Conochilus hippocrepis (Schrank). Single specimens, mostly from
Station MOB.
G. unicornis Rousselet. Fig. 12. No finds from summer 1 960.
Same distributions at all three stations.
Euchlanis dilatata Ehrbg. In a net catch from Station MH.
Filinia longiseta (Ehrbg. ). Fig. 13. Throughout the year but
scarce during the colder seasons. Same distribution at all three sta tions. Females carrying 1 -2 eggs each were found at all seasons. In
April 1 961 about 1 0 per cent of the females in the upper water layers were found with 3 eggs each and at Station MOB about 3 per cent with
4 eggs.
Kellicottia longispina (Kellieott). Fig. 14. Absent in spring and summer i960, then common but never in great quantities from Septem ber 6 , I960, to February 26, 1962. Absent again during the summer
1 962 until November 20. -17 -
Keratella cochlearis (Gosse). Fig. 15. The most common rotifer of the lake, missing only around the periods of great oxygen deficit.
During the present investigation Keratella cochlearis showed a pro nounced seasonal variation along the tecta series line: f. macracantha in winter, f. typica in spring and autumn, and ff. micracantha and tecta in summer, Fig. 36. Transitional forms between macracantha and t ypica and between typica and micracantha were abundant, between, micracantha and tecta much rarer. According to Pejler [12, p. 6 ff. ] this variational pattern is well consistent with the physical and chemi cal conditions of Magelungen.
K. quadrata (Mull. ) Fig. 16. Found throughout the year, only avoiding the oxygen deficit periods.
Lecane luna (Mull. ) Single specimens Stations MOB and MA.
L, nana (Murray). Single specimens Station MA. On June 1 2,
1 962, 1 200 inds/l were found at 5 m and 200 inds/l at 10.5 m. Here we very likely encountered a littoral outflow; other littoral species as well were found at Station MA on this occasion.
Lepadella patella (Mull.) Station MA June 1 2, 1962. The speci mens found belonged to the quadricarinata type [1 3, p. 347 ff. ].
Polyarthra dolichoptera (Idelson), Fig. 1 7, and P. vulgaris Car lin, Fig. 18. P. dolichoptera was practically absent during i 960. In
1 961 , however, it increased in numbers and in the samples of April 25 was the dominating rotifer in the upper water layers. Figs. 37 and 38 according to Pejler [9, p. 49; 1 0, p. 49; see also Amren 2, p. 239 ].
P, dolichoptera , where they occur together, are mostly driven to the less favourable water layers by P. vulgaris. Perhaps P. dolichoptera got a better start in spring 1 961 than P. vulgaris, which in summer 1 960 was very often found infected with small globular bodies [11; p. 229-30 ]. -18-
P. major (Burckhardt) was found only once, in September I960, at Station MA.
P. remata (Skorikov) was found at all three stations but never in great numbers .
Pompholyx sulcata Hudson. Fig. 19. Pejler [14, p. 467 ] points out that this species has a more or less pronounced preference for waters with low transparency values . In the present investigation the peak values of P. sulcata occur at the period when the transparency is lowest [see also 21 ; Fig. 4].
Synchaeta oblonga Ehrbg. and S. truncata von Hofsten. Fig. 20.
It was not possible to distinguish between these two species in the pre served material. They have therefore been counted together and the diagram is made up of the values so obtained. The net catches, however, showed that S. truncata was by far the most common of the two, causing the peaks in April and May. S. oblonga was mostly found in the autumn to early spring catches.
S. pectinata Ehrbg. Fig. 21 . Common in spring and autumn but never in quantities. Specimens carrying 1 -2 eggs were found in April.
This species was often more numerous at Station MA, Station MH showing the lowest values .
Trichocerca birostris (Minkiewics). Fig. 22.
T. capucina (Wierzejski and Zacharias). Occasional in September,
Stations MOB and MA.
T. cavia (Gosse). This rotifer was found regularly at all three stations during July to September. Except at the shallow Station MOB it was never found in the bottom layer of the water.
T. porcellus (Gosse). Station MA I960, September to November, and 1 961 , July 1 7 and September 4. Highest values found: 40 inds/l. - 19 -
T. pus ilia (Jennings). Fig. 23. .Quantitatively insignificant during
1 960 and 1 961 , it reached a high peak on August 6 , 1 962, and was on that date both volumetrically and numerically the dominant zooplankter
in the 0.5 m layer.
T. rousseleti (Voigt). Occasionally July-September, Stations
MOB and MA.
C la doc era
A Iona quadrangular is (Miill. ). Single specimens found at Station
MA August 2, i960, and in a net sample November 8, I960, the latter with eggs.
A. rectangula Sars. Single specimens Station MA September 4,
1 961 , and in a net sample November 1 3, 1 961 .
Bosmina coregoni Baird. Figs. 24 and 25.
B. longirostris (Mull.). Occasionally at Stations MOB and MA.
Ceriodaphnia pulchella Sars. Station MA on May 15, 1961.
C. quadrangula (Mull.). Single specimens at Stations MOB and
MA August 2 - October 11,1 960, and August 1 4 - October 9, 1 961 . Fe males carrying ephippii were observed on October 1 1 , I960, at Station
MA and October 9, 1961 , at Station MOB. Two specimens of the var. hamata were caught at Station MH on October 9, 1961 .
Chydorus sphaericus (Mull. ). Figs. 26 and 27.
Daphnia cristata Sars. s. str. A few specimens were occasionally found at Stations MA and MH. Fig. 39.
D. cucullata Sars. s. str. Figs. 28 and 29. This species seems to be the most regularly occurring cladocer of the lake. Males in August and October-November. Females with ephippii were observed in July-
August and in November-December. D. cucullata showed a marked seasonal variation. Fig. 40. - 20 -
D. longispina Miill. s. str. was found practically throughout the year but never in quantities. In summer , however, it was found mostly in the deeper water layers.
Diaphanosoma brachyurum Lievin. Single specimens occasionally at Station MA in late summer.
Graptoleberis testudinaria (Fischer). One female with eggs in a net catch, Station MA, September 21 , I960.
Leptodora kindti (Focke). June-October : Stations MA and MH.
Most finds from the upper water layers. 1 -2 inds/l.
Pleuroxus uncinatus Baird. One specimen, Station MA, September
4, 1961 .
Sida crystallina (Miill. ). Single specimens , Station MA, June 12,
1961, and Station MOB, September 4, 1962.
Branchiura
Argulus foliaceus (L.) was found in a few net catches at Station
MH in summer.
C opepoda
Cyclops spp. Figs. 30-32. C. strenuus was the most important of the Cyclops, found all the year round at Station MA. At Stations MOB and MH, however, it was not caught in samples from early spring. It was always the most numerous Cyclops in the samples from the deeper water layers, often succeeded towards the surface by C. ins ignis (Claus),
Mesocyclops leuokarti (Claus) or M. oithonoides (Sars). Fig. 41 . Eucy - clops serrulatus (Fischer) was only found at Station MA, often in samples which contained other more or less littoral species. Paracyclops fimbri- atus Fischer was found in a few net samples. - 21
Diaptomus gracilis Sars. Figs. 33-35. The females carried
mostly about 1 2-1 6 eggs from summer to late winter. As a rule no
females with eggs were caught during March and April. In late spring
and early summer, however, they were carrying about 20-30 eggs each.
The highest numbers of Diaptomus nauplii were found in late summer,
and of copepodites in April.
Inseeta
Chaoborus larvae were found in near -bottom water samples,
mostly at Station MH, a few finds from Station MA.
COMPARISON BETWEEN THE THREE STATIONS IN THE LAKE
A mere glance at the map (Fig. 1) reveals a certain difference between the tree stations, MH, MA, and MOB. The roughly 1 3 m deep station MH is surrounded by steep hillsides which give the station a certain shelter from the winds. This condition, its relative depth and the fact that the station is situated off the main flow in the lake, contri butes to the pronounced summer stratification of the water of this station.
Station MA, which is about 1 1 m deep, is situated within the main flow of the lake. It is more openly situated and consequently more exposed to the winds. Its summer stratification is usually somewhat less accen tuated than that of Station MH. Station MOB is also situated within the main flow; the influences of wind, flow and depth (about 5 m), however, cause a more unstable summer stagnation: the stratification is some times broken down even in the middle of the summer. Station MOB is further distinguished by the fact that it receives polluted waters from e. Affluents to the NW part of Magelungen and from Lake Agesta previous to Station MA. - 22
As mentioned above, the seasonal distribution of the standing
crop of zooplankton is about the same at all three stations (Figs. 42-45
and tables 1 -5).
Fig. 47 shows the situation during 1 962 and 1 963, when a direct
comparison between the three stations was made . In the diagram the
average - value curves for the total volume of zooplankton are drawn for the whole water column from surface to bottom.
The ciliate fauna of Station MOB, the most eutrophic (well
nourished) of the three stations, was more richly developed and varied
than that of the other two stations. The rotifers were the same at all three stations, with the exception of some accidental littoral or rarely
found species. Also the crustaceans are the same at all three stations with the exception of those indicating high oligotrophy. Daphnia cristata was very rarely found at Stations MA and MH, and Leptodora kindti was not found at all at Station MOB. Chaoborus sp. was also missing
in samples from Station MOB.
THE TROPHIC STATE OF THE LAKE
The trophic degree (nutritional standard) of Lake Magelungen is much higher than would be expected in view of its morphometry. Thus,
of its about 36 species regularly occurring in plankton (Table 7), no less than 1 0 species (Station MA), or 28 per cent, are indicators of
eutrophy [l 4, p. 467 ff. ]: Coleps sp. , Anuraeopsis fissa, Brachionus an gular is , Filinia longis eta, Karatella cochlearis f. tecta, Pompholyx
sulcata , Trichocerca birostris, T. pus ilia, Chydorus sphaericus , and
Daphnia cucullata , a fact which indicates a very high degree of eutrophy.
Also when scoring the lake according to some of the common point sys tems used in assessing the trophic degree of a lake, we obtain the same - 23 -
result: thus according to the system of Thunmark [l 8, p. 45 ff. and
Tab. 1 ] Lake Magelungen is to be placed amongst the "sehr stark
eutrophe Seen". The score system of Pejler [14, p. 468 ] gives for
Stations MH and MA 23, for Station MOB 25 points out of possible 2 7,
which marks the highest degree of eutrophy. The comparatively low
score of Stations MH and MA is due to their depth, which gives only
2 points out of possible 5, which further emphasizes the fact that the
lake is more eutrophic than would be expected.
The present high eutrophy of Lake Magelungen is undoubtedly
due to pollution, mostly from Lake Agesta and the Pagers jo district.
That the whole lake suffers from this pollution is illustrated by a com
parison with earlier investigations performed by the Stockholm City
Municipal Services Department [4 ] (Table 8). Among 15 zooplankton
species counted in 1 945 in samples from Hammartorp (Station MH in
the present investigation) only 3 indicators of eutrophy were found. In
the years 1 954-1 955 the indicators of eutrophy at Hammartorp had in
creased to 6 , which gives a percentage nearly as high as that for the
same years at the sampling station Pagers jo at the NW end of the lake
[4 ]. During the present investigation no less than 9 indicators of eutrophy were regularly found at Station MH (1 0 at each of Stations MA and MOB).
It is interesting to notice how in Magelungen, in contrast to
Nauwerck's findings in Lake Erken [8, p. 1 05 ], the zooplankton curve
(Fig. 47) follows that of the phytoplankton (Fig. 46), the zooplankton maxima in general appearing somewhat later than the phytoplankton maxima.
During the present investigation is was found that the average volume of zooplankton is the same as that of phytoplankton (Station MOB) - 24 -
or somewhat more (Stations MA and MH, Table 6). As a comparison it may be mentioned that the average phytoplankton: zooplankton (P:Z) ratio of the mesotrophic Lake Erken is 0.18 [8, p. 104], i.e. about
5. 5 times more zooplankton than phytoplankton volume. Raws on [1 5, p. 20 ] has found values up to 40 times more zooplankton than phyto plankton volume in the oligotrophia Cree Lake in Northern Saskatchewan.
CONCLUSIONS
As already pointed out by Willen [21 , p. .28], further additions of nutritional elements to the lake would augment the phytoplankton pro duction. At present the average volume of zooplankton is about the same as that of phytoplankton. It is not likely that an increased growth of phytoplankton would alter this ratio to the advantage of the zooplankton.
What could be expected is a continued decrease of the zooplankton in proportion to the phytoplankton and fouling of the shores and bottom as a result of water bloom.
The effect of the release of waste water is not easily anticipated.
The waste water may stir up mud and water containing hydrogen sul phide during the winter and summer stagnation [cf. 6 ], which would deteriorate the conditions of animal life in the lake. It is, however, possible that, if the waste water contains a sufficiently high amount of oxygen, the release and the augmented flow might exert a beneficial effect upon the lake during the oxygen-depletion periods and also di minish the risks of an increased unbalance in the production of the lake.
An investigation of these problems might give results of vital interest for other lakes which threaten to become unbalanced. - 25 -
REFERENCES
1. AGNEDAL, P-O., (Personal communication.)
2. AMREN, H. , Ecological and taxonomical studies on zooplankton from Spitzbergen. Zool. Bidr. Uppsala 36 (1964) p. 209.
3. AXELSON, J., Zooplankton and impoundment of two lakes in Northern Sweden (Ransaren and Kultsjon). Rep. Inst. Freshw. Res. Drottningholm 42 (1961) p. 84.
4. CRONHOLM, M. , (Personal communication. )
5. HALME, E., Planktologische Untersuchungen in der Pojo-Bucht und angren- zenden Gewassern. IV. Zooplankton. Ann. Zool. Soc. "Vanamo" 19 (1958):3.
6 . KARLGREN, L. and LINDGREN, O., Luftningsstudier i Trasksjon. Vattenhygien 19 (1963) p. 67.
7. MONTI, R., Numeri, grandezze e volumi degli organism! pelagici viventi nelle aque Italiane, in relatione alVeconomia lacustre. Mem. 1st. Lombardo di Scienze e Lettere 23-24 (19 36) p. 83.
8. NAUWERCK, A., Die Beziehungen zwischen Zooplankton und Phytoplankton im See Erken. Symbolae Botan. Upsalienses 1 7 (1 963):5.
9. PEJLER, B., On variation and evolution in planktonic rotatoria. Zool. Bidr. Uppsala 32 (1 957) p. 1.
10. PEJLER, B., Taxonomical and ecological studies on planktonic rotatoria from Northern Swedish Lapland. Kgl. Sv. Vetenskapsakad. Hand!, ser. 4. 6 (1 957):5.
1 1 . PEJLER, B. , The zooplankton of Osbysjon, Djursholm. I. Seasonal and vertical distribution of the species. Oikos 1 2 (1 961) p. 225. - 26 -
12. PEJLER, B., On the variation of the rotifer keratella cochlearis (Gosse). Zool. Bidr. Uppsala 35 (1 962) p. 1.
1 3. PEJLER, B. , On the taxonomy and ecology of benthic and periphytic rotatoria. Investigations in Northern Swedish Lapland. Ibid. 33 (1962) p. 327.
14. PEJLER, B., Regional-ecological studies of Swedish fresh-water zooplankton. Ibid. 36 (1 965) p. 407.
1 5. RAWSON, D.S. , Limnology and fisheries of Cree and Wollaston Lakes in Northern Saskatchewan. 1959. Fisheries Report 4. Dept, of Natural Resources. Saskatchewan.
16. RODHE, W., Zur Verbesserung der quantitativen Plankton-Methodik. Zool. Bidr. Uppsala 20 (1941) p. 465.
1 7. RYLOV, W.M., Das Zooplankton der Binnengewasser. Binnengewasser 15 (1935).
18. THUNMARK, S., Zur Sociologie des Susswasserplanktons. Folia Limnol. Scand. 3 (1 945).
19. UTERMOHL, H.,_ Zur Vervollkommung der quantitativen Phytoplankton-Methodik. Mitt. Int. Ver. fur Theor. und Angew. Limnologie, 1958:9.
20. V A LI KANG AS, I., Planktologische Untersuchungen im Hafengebiet von Helsingfors. I: Uber das Plankton, insbesondere das Netz-Zooplankton des Sommerhalbjahres. Acta Zool. Fennica 1 (1926) p. 1.
21. WILLEN, T., Phytoplankton from Lake Magelungen, Central Sweden, 1 960-1 963. (AE-21 9) 1 966. - 27 - Table 1 Volume of zooplankton, Station MA I960 - 1 96 3 (average values 0.2 - 5.0 m; in 10^ ^/l).
1 960 28/3 20/4 10/5 5/7 2/8 6/9 21/9 1 1/10
Ciliata 74 0 46 11 27 Rotatoria 8 5 35 345 260 101 75 75 Cladocera 27 28 92 380 1490 128 128 220 Copepoda 29 75 748 1240 490 433 315 305 Nauplii 1 6 13 47 74 97 63 31 44
Total volume 80 121 922 2113 2337 771 560 671
1 961 8/1 1 6/12 29/12 1/2 2/2 13/2 28/2 14/3
Ciliata 46 6 23 51 1 1 74 96 106 Rotatoria 62 25 9 6 6 8 9 1 4 Cladocera 123 33 3 0 7 0 10 1 1 Copepoda 203 21 9 0 3 3 5 5 Nauplii 1 7 1 3 1 1 8 5 6 10 14
Total volume 451 98 55 65 32 91 1 30 150
10/4 25/4 15/5 12/6 17/7 1 4/8 4/9 9/10
C iliata 258 38 119 9 10 1 2 8 Rotatoria 65 1 780 1215 74 1 35 244 207 64 Cladocera 0 1 37 820 1 3875 760 3350 1850 898 Copepoda 1 40 66 399 243 595 1035 1 31 455 Nauplii 27 116 249 182 156 205 107 223
Total volume 490 2137 2802 1 4383 1 656 4835 2297 1648
1 961 1 962 13/11 18/12 21/1 26/2 26/3 16/4 25/4 22/5
Ciliata 5 1 2 1 4 30 1 75 27 Rotatoria 21 3 1 3 2 0 1 513 C ladocera 283 1 7 78 29 1 0 26 C opepoda 388 1 33 77 8 1 48 4 25 140 Nauplii 14 1 3 4 1 2 2 0 2 107
Total volume 711 141 91 102 185 35 203 813
12/6 9/7 6/8 4/9 1/10 29/10 20/11 1 1/12
Ciliata 2 119 192 1 43 53 23 28 61 Rotatoria 215 832 1 908 463 343 17 15 10 Cladocera 1 41 383 1 425 7925 1278 296 161 56 Copepoda 238 159 309 143 227 300 1 88 120 Nauplii 433 42 140 1 45 58 20 21 31
Total volume 1029 1 535 3973 8819 1959 656 413 278
1963 8/1 12/2 11/3 8/4 7/5 28/5
Ciliata 80 62 22 1 395 67 Rotatoria 5 9 2 1 40 183 Cladocera 1 1 5 15 20 0 804 Copepoda 25 47 48 436 1 10 2045 Nauplii 4 14 8 3 31 995
Total volume 125 1 37 95 461 576 4094 28 - Table 2 -5,0 m; inlO^p Volume of zooplankton , Station MH 1 961 - 1 963 (a\ erage values 0. 2 Vo-
1961 1962 1/2 28/2 14/3 21/1 26/2 16/4 22/5 12/6
Ciliata 1 0 29 1 24 23 4 16 48 0 Rotato ria 8 6 18 2 5 0 608 1 04 Cladoc e ra 3 5 20 12 57 0 1 243 Copepoda 5 5 5 16 1 1 3 0 64 625 Nauplii 30 20 30 1 2 0 240 208
Total volume 56 65 197 54 1 81 16 961 1 1 80
1 963 6/8 4/9 1/10 20/11 1 1/12 11/3 7/5 28/5
C iliata 51 1 67 145 21 65 17 303 9 Rotatoria 18728 160 39 10 10 3 46 1 16 Cladocera 1 950 2825 228 66 68 T5 1 398 C opepoda 77 95 59 87 25 76 285 1 705 Nauplii 90 1 1 1 30 10 18 36 8 805
Total volume 21356 3258 501 194 1 86 1 47 643 3233
Table 3
Volume of zooplankton, Station MOB 1961 - 1 963 (average values 0.2-5 0 m; in 106 h3A).
1961 2/2 28/2 14/3 . 25/4 15/5 12/6 14/8 4/9
C ill at a 64 360 1 37 1 30 633 19 3 20 Rotatoria 9 2 31 1280 5050 1 38 1 12 1 3 i C ladocera 5 0 0 15 106 1000 475 995 Copepoda 0 0 40 1 1 1 78 200 0 0 Nauplii 2 1 9 153 370 410 320 1 78
Total volume 80 363 217 1589 6337 1787 91 0 1224
1 962 9/10 13/1 1 18/12 21/1 26/2 26/3 16/4 25/4
C iliata 37 1 4 29 1 4 22 1 09 680 840 Rotatoria 1 75 20 7 2 1 0 2 0 Cladocera 1 1 70 16 13 21 23 0 25 Copepoda 2180 4 146 514 364 0 3 1 08 Nauplii 365 1 3 8 2 18 0 1 1 1 5
Total volume 3927 67 203 553 428 109 721" 964
22/5 12/6 9/7 6/8 4/9 1/10 29/10 1 1/12
C iliata 50 0 121 69 25 35 22 5 7 Rotatoria 990 190 510 1890 1260 1030 58 1 5 Cladocera 52 264 84 2225 8125 983 1 36 15 Copepoda 240 553 244 69 241 360 47 34 Nauplii 428 232 15 75 218 74 50 29
Total volume 1760 1239 974 4328 9869 2482 313 1 50
1 963 8/1 12/2 11/3 8/4 7/5 28/5
C i liata 57 3 0 0 390 10 Rotatoria 8 0 0 1 49 325 C ladocera 9 3 1 0 54 580 Copepoda 165 5 0 39 38 1948 Nauplii 15 0 0 0 39 1115
Total volume 254 1 1 1 40 570 3978 - 29 - Table 4 Volume of zooplankton, Station MA 1960 - 1 963 (average values 0.2- 10.5 m; in 10^ /1).
1 960 28/3 20/4 10/5 5/7 2/8 6/9 21/9 1 1/10
Ciliata 56 10 50 8 1 1 7 Rotatoria 5 7 24 236 1 74 72 69 60 C ladocera 94 25 64 41 3 1025 1 12 82 179 Copepoda 341 1 78 549 836 340 376 252 315 Nauplii 11 12 32 50 65 63 33 39
Total volume 451 222 669 1591 1614 673 444 710
1961 8/1 1 6/12 29/12 1/2 2/2 13/2 28/2 14/3
Ciliata 42 6 19 39 70 54 79 90 Rotatoria 59 22 8 5 6 6 7 1 1 C ladocera 109 50 18 1 5 34 2 15 36 Copepoda 255 99 101 63 98 12 30 1 82 Nauplii 19 14 1 1 7 7 4 6 16
Total volume 484 191 157 129 215 78 137 335
1 0/4 25/4 15/5 12/6 17/7 14/8 4/9 9/10
Ciliata 255 61 91 12 8 16 30 8 Rotatoria 598 1232 825 61 92 164 1414 51 Cladocera 10 92 558 10717 680 2525 1773 773 Copepoda 157 60 326 191 401 810 104 388 Nauplii 29 89 201 158 112 ] 66 81 162
Total volume 1049 1 584 2001 11139 1 293 3681 3402 1382
1961 1962 13/1 1 18/12 21/1 26/2 26/3 16/4 25/4 22/5
Ciliata 6 1 2 3 3 21 125 26 Rotatoria 21 5 2 3 1 0 0 386 Cladocera 262 57 64 54 19 0 0 1 7 Copepoda 360 175 90 12 104 6 33 104 Nauplii 18 1 1 4 8 2 0 1 76
Total volume 667 249 162 80 129 27 159 609
12/6 9/7 6/8 4/9 1/10 29/10 20/1 1 1 1/12
Ciliata 4 88 187 1 16 126 22 31 67 Rotatoria 150 556 1280 324 237 1 4 1 3 1 3 C ladocera 94 257 969 6207 1652 602 221 92 Copepoda 217 1 11 222 1 34 202 310 186 177 Nauplii 437 28 97 107 39 19 19 38
Total volume 902 1040 2755 6888 2256 965 470 387
1963 8/1 12/2 11/3 8/4 7/5 28/5
C iliata 71 43 15 1 279 46 Rotatoria 7 7 1 1 27 122 Cladocera 54 7 10 13 0 5 37 Copepoda 62 37 39 291 80 1415 Nauplii 6 1 1 5 2 21 698
Total volume 200 105 70 i V o CO 407 2818 - 30 - Table 5 Volume of zooplankton, Station MH 1961 - 1963 (average values 0.2 - 12.5 m; in 10^ ^ /1].
1 961 1 962 1/2 28/2 14/3 21/1 26/2 16/4 22/5 12/6
C iliata 10 79 127 1 3 3 9 56 1 Rotatoria 8 8 1 3 5 6 0 386 68 Cladocera 33 19 23 157 67 0 0 139 Copepoda 85 1 37 46 164 1 89 1 86 395 Nauplii 26 51 26 1 1 0 179 236
Total volume 1 62 294 235 340 266 10 707 839
1 963 6/8 4/9 1/10 20/1 1 11/12 11/3 7/5 28/5
C iliata 292 94 233 26 65 10 192 6 Rotatoria 1071 1 91 25 9 1 1 2 27 67 C ladoc era 1115 2199 304 100 70 9 1 227 Copepoda 45 75 76 -- 102 40 45 165 977 Nauplii 51 68 32 1 3 26 21 4 466
Total volume 12214 2527 670 250 212 87 389 1 743
Table 6
The Phytoplankton - Zooplankton ratio 1962.
Date Phytoplankton volumes Zooplankton volumes Phytoplankton : Zooplankton in 106 u 3A in 1 0 u /£
MOB MA MH MOB MA MH MOB MA MH
21/1 224 256 160 553 91 54 0. 41 2.81 2.96 26/2 45 68 43 428 102 181 0.11 0.67 0.24 26/3 102 58 - ' 1 09 1 85 - 0. 94 0. 31 - 16/4 329 164 106 721 35 16 0.46 4.69 6.63 25/4 1631 341 - 964 203 - 1.69 1 . 68 - 21/5 3250 3470 6771 1760 81 3 961 1.85 4. 27 7.05 12/6 11187 5350 1 1230 1239 1 029 1 180 9.03 5.20 9. 52 9/7 9370 4244 - 947 1553 - 9.89 2. 73 - 6/8 5066 2376 4910 4328 3973 21356 1.17 0. 60 0.23 4/9 1 152 728 828 9869 881 9 3258 0. 12 0.08 0.25 1/10 3586 1 758 468 2482 1959 501 1.44 0. 90 0.93 20/1 1 - 161 1 74 - 41 3 1 94 - 0. 39 0. 90 1 1/12 540 43 66 150 278 1 86 3.60 0. 15 0. 35
M 3040 1 463 2476 1963 1496 2789 1.04 0.98 0.89
(data on phytoplankton from Willen 1 966) Table 7. Species regularly occurring in plankton of the three stations.
MH MA MOB Indicator of eutrophy E
CILIATA Coleps sp. + + E Epistylis rotans + + + Tintinnidium fluviatile + + + Tintinnopsis lacustris + + +
ROTATORIA Anuraeopsis fissa + + + E Asplanchna priodonta + + + Brachionus angularis + + + E B. calyciflorus + + + Conochiloides natans + + + Conochilus unicornis + + + Filinia longiseta + + + E Kellicottia longispina + + + Keratella cochlearis + + + E K. cochlearis, f. tecta + + + E K. quadrata + + + Polyarthra dolichoptcra + + + P. remata + + + P. vulgaris + + + Pompholyx sulcata + + + E Synchaeta oblonga + + + S. pectinata + + + S. truncata + + + Trichocerca birostris + + + E T. cavia + + + T. pusilla + + + E
CLADOCERA Bosmina coregoni + + + Chydorus sphaericus + + + E Daphnia cucullata + + + E D. longispina + + + Leptodora kindti + +
COPEPODA Cyclops insignis + + + C . strenuus + + + Diaptomus gracilis + + + Mesocyclops leuckarti + + + M. oithonoides + + +
INSECTA Chaoborus sp. , larvae + + Number of species 35 36 34 Number of indicators of eutrophy 9 10 10 % of indicators of eutrophy 26 28 29 32 -
Table 8
Most common zooplankton species found in earlier investigations of lake Magelungen.
Hamma rtorp Hammartorp Fagersjo 1945 1954 - 1955 1954 - 1955
RHIZOPODA Difflugia limnetica + +
CILIATA Coleps sp. E + Epistylis rotans + + Tintinnidium fluviatile + + Tintinnopsis lacustris + + +
ROTATORIA Anuraeopsis fissa E + + Asplanchna priodonta + Brachionus angularis E + + B. calyciflorus + + Filinia longiseta E + + + Kellieottia longispina + + Kerate 11a cochlearis + + + K. quadrata + + + Polyarthra remata + + + Pompholyx sulcata E + + Synchaeta pectinata + Trichocerca birostris E +
CLADOCERA Bosmina coregoni + + B. longirostris + Chydorus sphaericus E + + Daphnia cristata + D. cucullata E + Diaphanosoma brachyuum + Leptodora kindti +
Number of species 15 16 1 3 Number of indicators of eutrophy (E) 3 6 5 % of indicators of eutrophy 20 37.5 38.4 33 -
FIGURE CAPTIONS
Fig. 1 Map of Lake Magelungen.
Fig. 2 Map showing the sampling stations .
Figs. 3-6 Diagrams showing the distribution of the zooplankton expressed as per cent of the total volume: Fig. 3 Station MA 1 960-1 961 Fig. 4 Station MA 1 962-1 963 Fig. 5 Station MOB 1 962-1 963 Fig. 6 Station MH 19 62-19 63
Figs. 7-35 Diagrams showing the frequencies of the most common zooplankton species over the sampling period.
Fig. 36 Seasonal variation of Kerate 11a cochlearis in the upper water layers (0-5 m) of Stations MA and MOB.
Figs. 37-38 Seasonal distribution of the Polyarthra spp. in the surface water layers (0-5 m) of Stations MA and MOB.
Fig. 39 Some Daphnia cristata from Station MA.
Fig. 40 Some seasonal forms of Daphnia cucullata from Lake Magelungen.
Fig. 41 Seasonal distribution of the Cyclops spp. (average distri bution for the period 1 960-1 963).
Figs. 42-43 The distribution of the total zooplankton volumes , Station MA.
Fig. 44 The distribution of the total zooplankton volumes, Station MOB.
Fig. 45 The distribution of the total zooplankton volumes, " Station MH.
Fig. 46 Total volume of phytoplankton, average values 0. 2-0. 5 m (from Willen 1 966).
Fig. 47 Total volume of zooplankton.
35 -
Fagersjo LAKE MAGELUNGEN
From Lake Agesta
To Lake Drevviken
Hammartorp
Fig. 2 MAGELUNGEN Station MA 1960-1961
i v> On )
Fig. 3 MA GELUNGEN Station MA 1962-1963
1 962 21.1 26.2 26.3 16.4 25.4 22.5 12.6 9.7 6.8 4.9 1.10 29.10 20.11 11.12
Per Cent of Total Volume Zooplankton. i U1 *~i i Ciliata - Ci
Rotatoria = Ro
Cladocera = Cl
Copepoda = Co
Nauplii = N
F i MAGELUNGEN Station MOB 1961-1963
Fij. > 39 -
MAGELUNGEN Station MH 1962-1963
1963
1 m Per Cent of Total Volume Zooplankton.
3 m Ciliata
Rotatoria 5 m Cladocera
Copepoda
Nauplii
Fig. 6 — 40 —
TINTINNOPSIS LACUSTRIS STATION MA 19GO-1963 1961 10*
JANJFEB. ImAR. Ia PR. I HAY I JUN.I JUL. I AUG I&EP. ! OCT I NOV I DEC I JAN IFEB I MAR lAPP I MA zIjUNIJU lI AUG.I3EP. I OCT.I NOV.I DEC.
Fig. 7
A5PLANCHNA PRIODONTA STATION MA
2 mg / £ f 10*15'
2ms/< 2ma/€ 2ma/< lmg/t...... JAN.lFCe.lMAR. lAPP. f MAV | JVN. I JUL . I AU6.I5EP.I OCT.I NOV.I DEC.I JAN. |FCB Ima R.Ia PR.I MAY I JUN.I JUL. I AU&I&EP. I OCT.I NOVl DEC.
Fig. 8 41
STATION MA BRACHIONUS ANGULARIS 1960 - 1963 DEPTH m I960
2mg / i
NOV. I DEC.! JAN.I fC8.IMAR. lAPR . I MAV I JUN. I JUL. I AUG ISEP. I OCT.! NOV I DEC
Fig. 9
BRACHIONUS CALYCIFLORUS STATION MA depth I960 — 1963
jan .Ifeb. I mar . Upp . I may I jun . I jul . I aug I&ep. Ioct I nov Tdec I jan tree. I map . Iapi T l may I jun . I jul . I aug .Isep, I oct I
Fig. 10 — 42 —
C0N0CH1L0IDES NATANS STATION MA 1960 -1363
JAN. |FEB . I MAR. Ia PR. I MAvIjUN.I JUL. AUST5EP I oct .I nov . I dec .IjjTn Ifeb Imar .Iapb I MAYlJUN | JUL. I aus Tsep. I ocr7l NOV.
Fig. 11
STATION MA CONOCHILUS UNICORNIS 1960-1963
JAN.I fEB.Ih AB. Ia PB. I MAY I JUH. I JUL. I AUS.ljEP.ToCT. I NOV. I DEC. I JAN-I FEB. I MAH . 1APB. I MAyljUN I JUL. I AIM. ISEP . I OCT. I NOV.I DIC.
Fig. 12 43
STATION MA FILINIA LONGISETA 1960 -1963 DCPTU
I J !,
2mg/t ______r. I nov X dec .Tjan . Ifeb.Tmah . Iapp .Thav Ijun TIjul . I aus .Isep. Ioct J nov .I dec .
Fig. 13
STATION MA KELLICOTTIA LONGISPINA DEPTH 1960-1963
JAN.lFEB. ImAR.I a PH. I MAy| JUN.IjUL. I AU« ISEpTI OCtTn OV. I DEC.I J AN. IFEB. I MAP. UPS. I MAY I JUH. | JUL. / AUS.lMP. I OCT. I WOK I OEC
Fig. 1 4 — 44 —
STATION MA KERATELLA COCHLEARIS DEPTH 1360-1963
Fig. 1 6
STATION MA KERATELLA QUADRATA 1960-1963
6 * 10*15'
Fig. 16 45
STATION MA POLVARTHRA DOLICHOPTERA 1960-1963 °mTH I960
6* 10*15'
inw ’/l JAN.lRE8.lMAR. I APR . I MAY IJUH. IJUL . I AU6.lsEp7. I OCT.I NOV.I OEC.I J AN.IFE8.1 MAR.! ACS. HAy IjUN. IjUL. I AUS.I3EP. I OCT. I MOV. I DEC.
Fig. 17
POLXARTHRA VULGARIS STATION MA DEPTH 19G0-1963
0% 2m3ft
2m9/< ims/l ...... JAkIFEB.ImaR. lAPR. I MAVIJUN.IJUL. I AU& |3EP .lOCT.I NOV. I DEC.I JA N.lFES. ImAR . I APR. I MAY IjUN.IjUL. I AUS.ISEP. I OCT.I NOV. I DEC.
Fig. 1 8 — 46 —
STATION MA POMPHOLVX SULCATA OCPTW 13GO-1963 1960
JAN IPEB. ImAR.I a PC7( MAY IjUN.I JUL. I AUG |5EP. I OCT I NO v Td EC JAN IfEB ImAR.I a PR.I MAyljUN.IjUL.i AUG.I SEP.FoCT I NOV. I DEC
Fig. 19
SXNCHAETA spp. BmF 10® STATION MA DEPTH 1960-1963
?mg / i 196*2
jan Jfeb. Imab Iapr . I may Ijun . Ijul .I aus . Isep.Toct . I NOV. I oec Ijan . Ifeb. Imar . Iapr . I mav Ijun . Ijul . I AU4 I SEP. I OCT I NOV.I OEC.
Fig. 20 47
STATION MA S/NCHAETA PECTINATA 1960-1963 DEPTH 1360
2 mg /C
19 63
JAN IFEB. IMARTT a PR . I MAY I JUN I JUL I AUG.I5EP DEC I JAN IpEB.Ima R Ia PR I JUN. I JUL. I AUG ISEP. I OCT. I NOV. I DEC.
Fig. 21
STATION MA TRICHOCERCA BIR0STR1S 1960-1963
Fig 22 - 48 -
TRICHOCERCA PUSILLA STATION MA DEPTH 1960-1963
jan .Ipeb.Imar .Iapp . I H*yl jun TT jui.l aus TIsepTI oct I nov I dec Ijan . Ipeb.Imar Iapr .I mat Ijun .Ijul . I auc Jsep. I oct . I nov I ote.
Fig. 23
STATION MA BOSMINA COREGONI 1960-1963
Fig. 24 49
STATION MOB BOSMINA COREGONI DEPTH 1361 -1962
STATION MH 1961 -1962
nIfEB.ImarTUpR I MAVljUN. I JUL. I AUS.IsEP. I OCT I NOV I DEC I JAN. IFEB ImAR. UpR. MAT IjUN I JUL I AU&ISEP. I OCT I NOK I DEC.
Fig. 25
CHYDORUS SPHAERICUS STATION MA 1960 - 1963
JAN IPEB. IMAP IaPR. I MAYI jUN.I JUL. I AUG.IsEP. I OCT I NOV I DEC I J AN. IFEB . ImaR.IaPR. ' MAvl JUN.I JUL. FAUcISEP. OCTl NOV.I DEC.
Fig 26 - 50 -
STATION MOB CHyDORUS SPMAERICUS 1961 -1962
Fig. 27
DA PUN IA CUCULLATA STATION MA 1960 - 1963 °i i°
——o-\—
jan V es MAR I ap ». I may I jun .I jul . I aus Isep. I oct .I nov I dec I jan Ifeb Imab Iapb .I M»yl jun .Ijul . I AUOlSEP. I OCtI NOV.I DEC.
Fig. 28 51
STATION MOB DAPHNIA CUCULLATA Zmg/t 1961 - 1962
JAN Ifeb TmA rTTa PR. I MAY I JUN. IjUL.I AUS ISEP I OCT ! NOV I DEC. I JAN IfeB. I MAR . Ia PR ' M*vl JUN. I JUL. I AUG ISEP I OCT ! NOV 1 DEC
Fig. 29
CYCLOPS spp. ADULTS AND COPEPOD1TES STATION MA 1960 - 1963
Fig. 30 52
eye lops spp. STATION MOB ADULTS AND COPEPODITES 1961-1962
DEPTH 2r m 1961 0. ^77717^777777"
STATION MH 1961-1962
JAN. I PEB. I MAR . IaPR . I MAY IjUN. I JUL. I AUS ISEP. I OCT. I NOvTdEcT JAN. IpEB. ImArTIaPR I MAY IjUN .1JUL I AUS |8EP. I OCT. I NOV I DEC.
Fig. 31
CYCLOPS spp. NAUPLII STATION MA DEPTH 1960 - 1963 • i •/
JANIES. ImAR.IaPR.I MAvIjUN I JUL. I AUsIsEP. I OCTl NOV I DEC I JAN IFEB.' MAP. I APR . I MAvl JUN. I JUL. I AUGlSEP.I OCT. I NOV. I DEC.
Fig. 32 53
DIAPT0MU5 GRACILIS NAURU I STATION MA 1960 - 1963 DEPTH 10* V • 11* • •
Fig. 33
DIAPTOMUS GRACILIS STATION MA ADULTS AND COPEPODITES 1960 - 1363
i i* '!
2mg/( ...... JAN IfEB. Ima R.Ia PR. | MAV|JU n 7|jul I AUG ISEP f OCT | NOV I DEcTjAnIfeLB . i MAr IaPR I MAy | JUN. I JUL. I AUG.ISEP .
Fig. 34 54
DIAPTOMUS GRACILIS STATION MOB ADULTS AND COPCPODITCS 1961-1962
F H7
STATION MN 1961-1962
' JAN IPEB. I MAR. I APR. I MAY IjUN. I JUL . I AU& i SEP I OCT. I NOV ! DEC I JAN IFEB. IMAR. iAPR I MAY !jUN. IjUL. 1 AUG i5EP. i OCT. I NOV I DEC
Fig 35 55
SEASONAL VARIATION OF KERATELLA COCHLEARIS IN THE UPPER WATER LAYERS (0-Sml OF STATIONS MA AND MOB.
STATION MA
STATION MOB 1962 1963
THE DIAMETER OF THE CYLINDER CORRESPONDS TO THE CUBE ROOT OF THE MEAN VALUE OF INOS/l.
I JAN. I FEB I MAR. I APR I MAY I JUN I JUL TAUG I sEP To CtT NOvTb£c"t JAN I FeITT MART a PR I MA V I JUN 1 JUL I AUG I SEP I OCT.I NOV.I OEC.I
Fig. 36 56
SEASONAL DISTRIBUTION OF THE POLYARTHRA spp IN THE SURFACE
WATER LAYERS (0-1 m) OF STATION MA
STATION MA 1960 1961
P OOUCHOPTERA * —^-
P VULGARIS
P REMATA
1962 1963
P OOLICUOPTERA
P VULGARIS
P REMATA
THE DIAMETER OF THE CYLINDER CORRESPONDS TO THE CUBE ROOT OF THE MEAN VALLE OF INOS/L
OCT I NOV I DEC i JAN ! FEB I MAR I APR 1 MAY I JUN ! JUL I AUGT sCP 1 OCT FNOV FDEC 1 I JAN I FEB I MAR I APR I MAY ijUN I JUL I AUG I SEP
Fig. 37
SEASONAL DISTRIBUTION OF THE POLYARTHRA spp. IN THE SURFACE
WATER LAYERS ( 0 - 1 m) OF STATION MOB.
STATION MOB 1960
P VULGARIS
P REMATA
1962 1963
P OOUCHOPTERA
P VULGARIS
P REMATA
THE DIAMETER OF THE CYLINDER corresponds TO THE CUBE ROOT OF ' THE MEAN VALUE OF INDS/L
| JAN I FEB I MAR I APR I MAY T JUN [ JUL I AUG i SEP t OCT l NOV i OEC ] JA n TFEB MAR ' APR MAY l JUN JUL ’ AUG I SEP 1 OCT Fnov ' OtcF
Fig. 38 - 57 -
Some seasonal forms of Daphnia cucullata from Lake Magelungen
March-May. I960 May. 1962 May. 1962 Juv. June. 1961 July August and August. 1961 Mole. August and September. 1961 September, 1961 September-November November • December October November
May. 1961
Fig. 39
Some Oaphma cristate from Station MA
Fig 40 SEASONAL DISTRIBUTION STATION MH STATION MOB STATION MA N.I B,
FE
b DISTRIBUTION T
MAR FOR
I
APRl THE
MAY
PERIOD mi
OF I
JUN
THE
I
JUL
1960
CYCLOPS I
AUG
-
1963)
I
SEP Fig.
spp
I
OCT
I
NOV (AVERAGE 41
I
58 DEC
I
( (5 4 3 3 4 5 2 4 2 5 3 1 2 1 1
.
EUCVCLOPS MESOCYCLOPS MESOCYCLOPS CYCLOPS MESOCYCLOPS CYCLOPS EUCVCLOPS MESOCYCLOPS MESOCYCLOPS CYCLOPS CYCLOPS EUCVCLOPS MESOCYCLOPS CYCLOPS CYCLOPS
1NS1 STRENUUS STRENUUS INSICNIS W//X INSIGNlS
STRENUUS
SERRULATUS)
SERRULATUS GNIS LEUCKAPTI
SERRULATUS OITHONOIDES LEUCKAPTI LEUCKARTI
OITHONOIDES OITHONOIDES EGGBEARING
)
FEMALES - 59 -
Station MA 5 3 Total zooplankton volumes 10 p /[
0,2 mg/1 0,2 mg/1 0,2mg/l
~ ' F ' M ' A ' M l~J l—J ' A ' S ' 0 ' N ' □ I, J ' F ' M ' A ' M ' J I 1 ' A ' S ' 0 ' N ' 0 I960 '1961 '
Fig. 42
Station MA Total zooplankton volumes 105 jj/I
J' f'm’a'm'j'j'a's'o’n'dIj'f'm'a'm'j 1962 1963
Fig. 43 60 —
Station MOB 5 3 Total zooplankton volume 10 p /I m 1961 02 2mg/l 0z2mg/l 2o»c
S ' 6 ' N D ~1 J 1 F ' M ~1 A 1 M A ' S ' 0 1 N ' 0
Fig. 44
Station MH 5 3 Total zooplankton volumes 10 p /I
~1 1 F ' M ' A ' HT T~ ' A ' S ‘ 0 ' N 1 D ' J r F 1 M ' A ' M ' J ' J 1962 1963
Fig..45 61
Fig. 46
Total volume (average values) Vsto^l 0-10 5m MA ----- 0-12 5m MH ...... 0- 4.5 m MOB ———
Jan I FebTMar.TApr. TMay I Jun l Jut. I Aug I Sep 1 Oct I Nov l Dec I Jan I Feb I Mar 1 Apr ] May
Fig. 47
LIST OF PUBLISHED AE-REPORTS 380. An expansion method to unfold proton recoil spectra. By J. Kockum. 1970. 20 p. Sw. cr. 10:—. 381. The 93.54 keV lever "Sr, and evidence for 3-neutron states above N=50. 1—340 (See back cover earlier reports.) By S. G. Malmskog and J. McDonald, 1970. 24 p. Sw. cr. 10:-. 341. Nonlinear dynamic model of power plants with single-phase coolant reac 382. The low energy level structure of 2,11r. By S. G. Malmskog, V. Berg, tors. By H. Vollmer. 1968. 26 p. Sw. cr. 10:-. A. Backlin and G. Hedin. 1970. 24 p. Sw. cr. 10:-. 342. Report on the personnel dosimetry at AB Atomenergi during 1967. By J. 383. The drinking rate of fish in the Skagerack and the Baltic. By J. E. Larsson. Carlsson and T. Wahlberg. 1968. 10 p. Sw. cr. 10:-. 1970. 16 p. Sw. cr. 10:—. 343. Friction factors in rough rod bundles estimated from experiments in parti 384. Lattice dynamics of Nad, KCI, RbCI and RbF. By G. Raunio and S. Ro- ally rough annuli — effects of dissimilarities in the shear stress and tur landson. 1970. 26 p. Sw. cr. 10:-. bulence distributions. By B. Kjellstrom. 1968. 22 p. Sw. cr. 10:-. 385. A neutron elastic scattering study of chromium, iron and nickel in the 344. A study of the resonance interaction effect between 238U and u *Pu in the energy region 1.77 to 2.76 MeV. By B. Holmqvist, S. G. Johansson, G. lower energy region. By H. Haggblom. 1968. 48 p. Sw. cr. 10:—. Lodin, M Salama and T. Wiedling. 1970. 26 p. Sw. cr. 10:-. 345. Application of the microwave discharge modification of the Wilzbach tech 386. The decay of bound isobaric analogue states in ”Si and 13, Si24 5 using6 7 (d. ny) nique for the tritium labelling of some organics of biological interest. By reactions. By L. Nilsson, A. Nilsson and I. Bergqvist. 1970. 34 p. Sw. cr. 10-. T. Gosztonyi. 1968. 12 p. Sw. cr. 10:-. 387. Transition probabilities in 1”Os. By S. G. Malmskog, V. Berg and A. Back 346. A comparison between effective cross section calculations using the inter lin. 1970. 40 p. Sw. cr. 10:-. mediate resonance approximation and more exact methods. By H. Hagg blom. 1969. 64 p. Sw. cr. 10:—. 388. Cross sections for high-energy gamma transition from MeV neutron cap ture in 206 Pb. By I. Bergqvist, B. Lundberg and L. Nilsson. 1970. 16 p. 347. A parameter study of large fast reactor nuclear explosion accidents. By J. R. Sw. cr. 10:-. Wiesel. 1969. 34 p. Sw. cr. 10:-. 389. High-speed, automatic radiochemical separations for activation analysis in 348. Computer program for inelastic neutron scattering by an enharmonic crystal. the biological and medical research laboratory. By K. Samsahl. 1970. 18 p. By L. Bohlin, I. Ebbsjo and T. Hogberg. 1969. 52 p. Sw. cr. 10:—. Sw. cr. 10:-. 349. On low energy levels in 185W. By S. G. Malmskog, M. Hojeberg and V. 390. Use of fission product Ru-106 gamma activity as a method for estimating Berg. 1969. 18 p. Sw. cr. 10:-. the relative number of fission events in U-235 and Pu-239 in low-enriched fuel elements. By R. S. Forsyth and W. H. Blackadder. 1970. 26 p. Sw. cr. 350. Formation of negative metal ions in a field-free plasma. By E. Larsson, 10:—. 1969. 32 p. Sw. cr. 10:-. 391. Half-life measurements in 13 EOS-tryckerierna, Stockholm 1970