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FISHERIES RESEARCH BOARD OF CANADA
Translation Series No.
2642
.Different.forms.of eutrophication in eastern alPine
lakes '
• by I. Findenegg
Unterschiedliche formen der eutrophierung Von
Original title:
.
ostalpenseen
.
,
From:
••
Schweizerische Seitschrift fûr Hydrologiè
85-95,'197•1 ,
• for Hydrology), 33(1) .
Tr'anslated by the Translation Bureau( AK) '
, Foreign Languages Division
,Department of the Secretary of State of Canada
: Departirtent of the EnvironmentH •Y
• Fisheries Research Board of Canada
Great Lakes Bioliffinology , Laboratory
'Burlington, Ont.
'
1973
15 pages typescript
(Swiss -Review
Cr V
l) f)
/
af,
tee
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IÏIOR - AUTEUR
I. Findeneu
..__
iLiTilLE IN ENGLISH - TITRE ANGLAIS
Different Forms of Eutrophication in Eastern Ï.1pine Lalœs
!l
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Different Forr:^^s of Eutrophication in Ecstern j^lpi.ne Lakes
by I. Findene^g
I.B.P. I,abor&.tory "Production of Austrian Alpine Lakes"
of the E?ustrian hcac7emy of Sciences
In the course of the oast 15 years, the tourist traffic alon_; the
beaches of the Austrian lakes has increased considerably, and during the
roa,st five years, due to the arrangement of numerous c^^.mnin;; sites alon;.;
the lakeshores, it has ^rown to the extent that commercial and domestic
sewage systems in the drainaE.;e area..s of the la'.es can no longer cope with
the increased. discharge. k?ence, many lGkes are now in a. process of slow
eutrophication;
in some lakes, a massive increase in the algal production
has already set in. For many years, the author recorded chemism and p].ankton of about two dozen Eastern Alpine lakes, since 1967 in the framework
of the Austrian I.B.P. Project "Production of Austrican Alpine Lakes", in
cooperation with Dr. H. SAA-iP:L and 'Mr. G. IZ(JPRECHT of Klagenfurt, and
Dr. MZCiC;R and Dr. G. SCiï(T:U!'Z of Schurfl.ing on the Mondsee.
As is known from inve^tin;ations carried out in other lakes, which
became eutrophic earlier, the most striking indicvtor of trie eutrophication
process is the sudden massive 2.ppelrance of ci.lge..l species which, previously,
UPlEU31't:n Tf;AN^LAï1(^td
Ccr isa4arrniiinn °nly
&-]00._10-31
.
'S3J•11•07.D•y332
7RAbt3C^ {^3s^ NOW
p•)...,,te ^eulct^^^`^
2.
were not found in the lake, such as the invasions of Tabellaria fenestrata
and Oseillatoria rubescens in the Lake of Zurich around the turn of the
century. However, from the investigations carried out in Austria, it results that in many cases srecies that had always been present, and occurred
in most lakes, such as Ceratium hirundinelk, suddenly increase to the extent that they constitute up to 95% of a phytoplankton biomass increased
by several times.
In other cases, certain trophieity indicators appear;
these species remain for years in low numbero, until suddenly one of them
supplants the others, and causes for itself a massive phytoplankton growth.
However, it may also occur that one srecies that is characteristic for
higher trophic levels, for decades determines the plankton picture of a
lake, yet is suddenly joined by a second species with similar environmental
reauirements, which thus causes a further increase in the algal biomass.
Hereinafter, examples of such eutrophication phenomena will be
shown. There is first of all the completely divergent development of the
plankton algal biomass in two minor Northern Alpine lakes of very similar
constitution, the Waller and Obertrumer lakes;
opment led to huge biomasses and water bloom.
in both lakes, this develThen, there is the sequential
appearance of phyLoplankton populations in a somewhat larger, neighboring (86)
lake, the Mond lake, which combines the developmental tendences of the
other two Northern Alpine lakes. From the Southern Alpine basin of Carinthia,
two lakes will be dealt with which, though more different from each other
than the comparative lake pair, the Waller and Obertrumer lakes, started
developing from a quite comparable initial condition; yet, since about
eight years, they have developed in a completely different planner to eutrophic lakes. These are the Millstiitter and Ossiacher lakes. Their conditions vill be compared with that of the WUrther lake which has reacted
3
1
relatively weakly to the increasing sewage load originating from the tourist
industry. Before dealing in detail with the separate cases, a. survey of
the morphometric and hydrochemical conditions of the six lakes will be given.
Morohometry
:\lorphouv.•trit.
Deepth- -
t,ttinnter,
f,
)
\Ft). m"
it If 2
h,-1
Obcrtrurner Sts().
)1101tIsee
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tor
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Würtherwe
•
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•
Chemism at the beinning of the acute eutrophication (19b5/66)
chemist-Hu,
r al;u1A)n
1):1)11 ■ 1 ■ )'
rung )1 , itri
(iii)
-
Tot.
1:1 N
Nt 1..
N
:Jr:
\\sillor)itu
. ()1),•rti ■ Inwr
Mill-;'...t.11))1 .
hur S,)•
\\*,-, 111149-s).‘•
1
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231
.):»
12 ', i
11, 2z
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1..1.›. t?, t:
R2 11, 5
ti3t-0,(i
(1,15 11,•1›,
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1..21 11,1«
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231
1» 2,1
:-t
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7
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2,>1
6-23;
0.72
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•
;: It tt 5
l,
From this list, it may be seen that the Waller and Obertrumer lakes
. show considerable similarities. They are only 7 km apart, in the Salzburg
.lower Alpine region; they are moraine-barrier lakes formed by the Salzach
glacier durin the glacial epoch, and their drainarr,e areas show similar geological and veetational structures.
Also the wind exposure and kind of
sewage load are not essentially different. Nevertheless, thjs lake pair
is an example of a completely divergent phytoplankton development as a result
of the eutrophication process. Fie,. 1 is a general view of the amounts and
composition of the phytoplankton under one square meter of surface, for the
late-summer conditions of the various observation years.
The phytoplankton
amounts arc indicated as fresh-weight; this latter was dete'rmined by cell •
count or measurement of the filament lengths in 100 ml of sample water from
4.
the separate lake de-pths, and multiplication of the cell number by the
average cell volumes of the snecies.
The pro-portions of the more frequent
oenera of the total wei!;ht are indicated by symbols explained in Fig. 2.
Uidfït _S
r•' `A
f.1iJE4
MILLS7AT'rEP
4. Fz
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and composition of T^}.ytop lanl:ton from five
Fig. 1.
.^u.strian .,lpirle lakes, in 1.ate sumrier of each year, after the
starL of the acute eutrophication. Indications in grams below
one square me::er of lake surftace.
1...
i^l
ï^ t:n:lrrr 1'l;t,:•llgrtt
ill ri••r^• .\i;;,..
Fi,7,. 2. Ex-plana.tion of the symbols used in the fi ^^;ures for the
a.l>ral ^;e_iert_ .
If in Fig. 1, the Waller lake (bottom, right). is compared with the
Obertrumer lake, the l.ate-stunmer seasons of 19,55 and .1966 result in a c7uite
similar plankton spectrum which is rather normal for oli8otrophic or
•
mesotrophic lower-Alpine lakes, with feu Peridineoe, plenty of DynobrIon
and Oogystis, and some Cryltomones. For the year 1967, unfortunately, no
data are available. However, in 1968, the phytoulankton fresh-weight of
the Waller lake increased by eight times, in 1969, by twelve times, with
respect to the initial stage;
this hu,-;e increase was due almost exclusively
to Ceratium hirundinellm which, previously, had been rather scarce. There
is no need to emphasize that this species occurs in most lakes, so that by
no means it can be considered as a trophicity indicator. Also in the
(88)
Obertrumer lake, there was a substantial increase in the al; ,:al freshueight since 1965. However, in this case, if 196, a eutrophication forerunner apueared in small numbers, the "Bur7undy-blood" al .7,a, which subsec.luently increased the plankton weirtt by more than four times. It is
true that in the course of last year, this development slowed down again
somewhat. Since the columns in Fig. 1 show only the late-summer aspects,
the following illustrations will show the stratification pictures of the
planktonic algae at various seasons of the year.
Fig. 3, lower part, de-
scribes the previous history of the acute eutrophication of the Waller lake.
The dot-dash-line curve corresponds to the temperature stratification existing on the observation day, the dashed-line curve to the decrease in the
radiation intensity at the time of the investigation, indicated in millicalories per square centimeter per minute.
It may be seen that in 1961 and 1962, Dinobryon, Cyclotella, and
Cryutomonas built up a.modest algal stand;
then, the Peridineae started
increasing, and substantial numbers of Tabellaria fenestrata, Cryptomonas,
and Oocystis joined. them.
Fig.
4,
finally, shows the dislodging of most
of the previously dominating species by Ceratium.
6.
, ,' i>
o
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l / '
. Stratification of the algie, in the Obertrumer and
Fis;.
Waller lakes before the start of the massive eutro-aliication.
Dot-dash-line curve = temperature, dashed-line curve = radiation
in mca,l/cm2 per minute. 11,lga.1 fresh-weight in nrams per m3
of water.
In the Obertrumer lake-v*here, unfortunately, the investigation
started only in 1905, there is at first a certain predominance of Chlorococcales and other green algae; in the autumn of 1966, Oscillatoria rubescens
appears for the first time in rather large numbers, in most of the strata,
at temneratures of 8 to 1C°C (Fig. 3). During 1967, where no investigation
data are available, the "Bur;;undy-blood" alt^.a, apparently, had vigorously
asserted itself against the existing algal stand, for in the spring of 1968
(FiE. 5), the phytoplankton consisted practically only of Oscillatoria.
rubescens.
After a short development of tlnabaena. flos aquae in late summer,
Oscillatoria again dominated the a.utumn aspect. It is noteworthy that in
the Obertrumer lake, this alGa does not show, or only slightly so, the
rigorous stratification which is ^enerally observed in other lakes. In
1969, Oscillatoria remains clearly predominant only in spring, and autumn;
(90)
7
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2
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Fig. 4. Plankton stratification. Temperatures and radiation
in the Waller lake, 1968 and 1969.
[.).- n
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Fig. 5. Plankton stratification. Temperatures and radiation
in the Obertrumer lake, 1968 and 1969.
1. •
simultaneously) the Pei'idineae play a part;
yet, the Chlorophyceae,.
(90 )
which had been very important before the Oscillatoria invasion, did not
return.
The divergence in the development of the algal stand observed in
association with the eutrophication, that is, in the Waller lake to an
plankton
almost pure Ceratium plankton, in the Obertrumer lake to
dominated
by Oscillatoria rubescens, is now found in a strange com-
bination in the Mond lake.
As Fig.
6
shows, also 3n the Mond lake, before
the start of the acute eutrophication, the phytoplankton was very similar
to that of the above mentioned lakes in previous years. however, in the
summer of 1968, a phytoplankton developed which reminds very much of that
of the Waller lake of the same year, with the difference only that in the
Mond ].ake two thirds of the Ceratium stand consisted of Ceratium cornutum.
514-A VÇ. P;f1 /'
01111,/
1111
111 2:1.7 es [ill
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So
6. Plankton stratification, temperatures, and radiation
in the Mond lake before (19 5 and 19..;;) and after the start
of the massive eutrophication (1968).
• -
Yet, in autumn, an invasion of the Mond lake bv rscilla.tor:i.a rubescens
started, fully anU.l.ogous to the invasion that took place V. year earlier
in the Obertrumer lake. However, i t never led to such a vi,,;ornus decrease
of the species previously contained in the lake, not even in 19L'39,.a.s this
was temporarily the case in the Obertrumer lake; rather, the Perid.ineae
and Oscillatori.e. contributed at about eclual ratios to the iresh--ereigh.t..
Ref;arding the total fresh-v-eight, it increased by about fifteen tixn.es
since 1966 (Fi;;.. 1);
one should add, hc,rever, that already in 1961, the
Mond. lake had substantially higher biomasses, and that its slow eutro-
(.91)
phication of 1961 and 191")2 was delayed and reversed temporarily by the
influx of large amounts of claylike material during the construction of
a highway.
in
If one considers the conditions / the three 1Vorthern Alpine lakes
thus far dealt with, various auestions co?ne to mi nd: . Ylrstly, the question
as to how it was possible that in the Waller and Obertrumer 1:ake.s such
different successions of algal populations could appear; secondly., -why
during the peak eutrophication in the 'Haller 1a1-,e, no eui:rophl cation :indica.tors, such as Stenh4.nodiscus hantnscnii or Dabellaria fenestrata,
Alicroc.Ystis or Anabaena appeared in noteworthy .numbers, and even Oscillatoria
rem.ained absent.
The objection that the blood nJ.;a cannot live in the.
shallow Waller lake, since as a shade-loving foxm, or due to -excess.ive
Nummer termera.tures, it can exist only in deeper layers, seems invalid
in view of the fact that in the nei ;nborinL; Obertsamer lake, this a1^
not only survives the s.uriner in surface-close layers, but that it even
disl.odôed most of the other species. And why iTas Cera:t_iuni unable, in the
ObertriLmer lake, to survive in note;vorthy numbers in 1.9ôS, beside Osçâ.ll^.tar.:i.n.,
11
10 .
as was the case in the Mond lake, at the time of the Oscillatoria invasion. All these apparent contradictions may be explained only if one
keeps in mind that in the development and change of the biocoenoses of a
lake, not only physiological, experimentally reproducible processes play
a part, but that the starting point of any such development is a quite
determined, instantaneous condition, which may be due to previous weather
conditions exerting their effect on the thermal end chemical stratification
of the lake, the-momentary radiation conditions, and not least to the occupation, at the time, of the ecological niches by vital populations of
competing species which are in the process of full de7elopment or degradation. It sometimes is the historical moment, the, maybe, unique combination of different environmental factors,which decides as to which species
will be populating the pelagic zone of a lake for the near future or even
for a prolonged period of time.
The lakes of the Carinthian region, the second group, differ far
more from one another than the above descr rbed lakes of the Northern Alps.
• While the Millsttter and Ossiacher lakes have similar areas, their
depths are very different. Moreover, the MillstUtter lake is strongly
alkaline, due to waste-water discharge from a factory, and its pH values
are at 9.5.
The Wrther lake has the largest surface; however, due to
lake-bottom shelves, it is divided into three basins.
This is associated
with its marked meromictic behavior, and a strong accumulation of plant
nutrients in the monimolimnion, which are more or less excluded from the
substance cycle. Thus, the P and IN values of the above shown comparative
table disregard the monimolimnetic nutrient contents. It is noteworthy that
around 1966, the three Carinthian lakes had lower'P and N contents than the
two small Northern Alpine lakes, yet somewhat higher ones than the fond lake.
il.
The Millst,.itter lake will be dealt with first. Although with its
pli value of 9.5, a comparison of its phytopJ_ankton with that of other
1akes would appear to be highly doubtful, it may be seen that this is not
the case. Fig. 1 already shows that before the acute eutrophication
(92)
(about before J.9û,S), the lake had a quite normal plankton stand, where
the usual forms, such as Ceratiiim, Fr ;iJ_aria, CJ.oteJ.la, and Qocyst:i.s,
were predomina.nt.
Even Oscil:La.toria, which appeared in the lake around
1960, was present already in modest nunbers. Pilso the plankton freshweiglits were quite in accordance with, or even higher than, those of other
Alpine lakes of equal troplïicity (T'i_;. 1) .
If for the years before 19^G,
^
an average biomass of 7 m.c^ra`- is assumed for late sununer, there has been
scarcely a threefold. increase since.
In tlïis respect, there exist parallels
to the td.^rther lake ^riï.ere the increasin;; sewage load of the last de.ca.ci.e
also resulted in a merely moderate increase in the tïhytoplankton biomass.
Therefore, one cannot really speak of an acute eutrophication phase with
re,r,),,ard to the algal amounts.
spectrum.
Fowever, what did cl.an^e, is the plankton
In 19^3, for the first time, rather large numbers of unicellular
green alrvae anpearecl;
in 1905, An€a.baena appeared in rà.ther large numbers.
-Since 19:i6, the stuiuner plankton has been dominated by Oocystis and Ankistroc'esmus.
Toward autumn, also Anabaena may play a part in the formation
.
of water bloom; however, it is no longer as numerous as a.round. 1965 (Fij;.7).
OscilJ.atoria, r.ube^cens has increased in n•ambers;
however, during the warmer
season, it shows the t,ypical embeddint-, in the metalimnion. Genera,lly, also
a stronZ Steph^nodiscus hantaschi_i population may be noticed in late winter
or in sprin;;, and in autumn Chroococci:s limneticus and Gomnhos-phaeria
le.ciistris populations .
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Fi. 7. Plankton stratification, temperatures, and radiation
in late summer. Above: Millstfttter lake between 1963 and 1968 .
lake between 19:-35 and 1958.
Osiacher
However, a very regular increase in the late-summer algal bio mass
in the Ossiacher lake (Fig. 1).
Since 1964, it has tripl ed. maybesn
in this lake, Anabaena, mo s uyMorev,itmayedlbsntha
A. flos eouae, plays a very important part. Occasionally, also the genus
Cryptomonas is not without siylificance.
In 1968, also Oscillatoria
rubesçens appeared, and in 1969, it was already an essential constit uent
of the phytoplankton.
( 93)
During the past few years, the planktonic annual
cycle cenerally proceeded in such a manner that after a Cryrtomonas wave
an ample Din9bryon aspect, succeeded by Cyclotellae (gzs,lomensis,
therfolwd
C.glomeratai C.comta), and Stenhanodiscus astraea.
From July on, Anabaena
may predominate, and it sometimes causes considerable water bloom in autumn.
The Chlorococceles remain without sk-nificance (Fig. 7).
In contrast t o
the Millstftttcr lake, where the most striking eutrophication characteristic
is the massive developme.nt of Stephanodiscus hantzschil in early sprinv
and of an Oocysti, -llnlcistrociesnu.is population in midsuinmer, the Ossiacher
lake would have to be designated as a Cvclotella-Ana.baena lake.
^YnRrH_^R sct-
1964
I
J}'i^ç; V?drther lake: Fresh-weight of al;.?-a1 -Qlan:^ton
below 1 m2, in grams, in various seasons of the years
l9,:S)4, 1967, and 19'.)9.
In conclusion, also the change in the phytoplankton community of
the lddrther lake, which proceeds parallel to its eutrophication, will be
briefly described.
As mentioned at the beginning, this lake has reacted.
relatively little to the sewage load caused. by the steadily increasing,
tourist industry.
Fig. 8 shows the tilankton ;-tei„lts det-ermined below one
square meter of surface, and the percenta_;e; of the main ûenera. There
are four, seasonally about corresponding series each, from the years 19^^lE,
1907, and 1939, which allow a comparison of the production of these years.
Two thin:;s will be noticed immediately: Firstly, the relatively
low increase i n the planktonic fresh-ceei;;lit which scarcely more than doubled
during, the past five years, and secondly, the dominatine, position of
0scil.lator.ia rubescens.
However, this latter is not of recent date; it
has been pi•esent at least since 1930. Data from previous regular investigations
[11
[
r1
•
14.
do not exist; however, it is known that in 1910, this alga caused for
the first time water bloom in winter. Ever since, the WUrther lake has
been a marked rubencens lake, and most probably, the apparently low plankton production in the real trophogenic strata is associated therewith.
At
(94)
an annually recurring rhythm, toward the end of winter, a massive increase
in Oseillatoria occurs (Fig. 8
,
which at this time populates the epi-
limnion, thus so completely depleting the nutrients available here after
the winter circulation that, after its mi g ration to the metalimnion, it
leaves behind only very modest nutrient reserves.
The abrupt thermocline
that develops in May, largely obstructs the *supply of new nutrients from
deeper layers, so that in summer the epilimnetic plankton production of
this lake is extremely weak, compared to the previously mentioned Carinthian
lakes. During the warm season, water bloom hardly ever forms. Since 1966,
a new arrival, Tabellaria fenestrata„ appears in the lake.
As a relatively
heavy form, it can maintain itself floating in the pelap;ic zone only at
considerable turbulence;
yet, such a turbulence in the Wirther lake occurs
only at the time of the winter circulation currents; its appearance in
the plankton therefore remains restricted to the cool season.
(1
SUW, LM ■ Y
(1 into : ■ ›tato nf advanced vutrophicittion
.\ tu.arian lakos ha \ t: 11
Sinco about 1 , )f'i
had a
ail 1
the pr1111.1,,,,
becati3O
tItt. planhtic c ■ annuinitiis
tuplantoon !•pt•eits. \Vith
of \...r\- sistolar
C11 11 ollwr iii
laku, slutilar
hi( 111 \lays, 1 '.1) 1 1.
1 ,110;`.
d.•\•.•11itil 11 c,.1:11.1..1tly
most Iiinnologwal
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ts .1,111.mst1alud 1! 1 i• \
1.1
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it \vm Inv adod by Ost ill a tort a rube
. 11.111
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hatg,r
In tho NIond-r.. , t
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inva,ion oi
In 11 Millstattor
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till 01
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1\
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1
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1 litany (tocad.-; 11 has In , U
tht• inurt.a ,d• 1,1 ililh,1 U
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1111 11111 11 sr
the sup riji1il hIri
livt's
41.11n -union hult.re rot iring into 1 11.•hi1tiiilhuihlh1ihl \- th.• utiarl1 hurminlinv 111,t.k , ilii inipot t 4 if
biomas-: runi .tin› . 1..)or (twin:), .-tinttnor.
nut iITIIS front t1‘...1; ■ •1- ' 1 r:tut,
111 Intal a!Ral
(95)
i> .
Bibliw.r. a.pYly
,'r; l',:!,r.t:,:rnut'rvrIll, :ru,'urriurr, IL„,t:.,rr
'l' I"t»Irr:xxar,,f.,!.tutu„/,,,ttirlu•rnurrisr/trrrt7,i (
IN
•hr'
^r. 7. !•t;rLc•i,i u,! IIt1f cr,.. !I ..I..
u.•
ti,•e•
.111
1?.hitJrr
u!l;ultsftvh'ra :i lhr•u.,,. dc. „r
L l:i l!l I lr)!r_'il ,it.
r lirrr.,: ?:i•rrr: rl:., l'hv!nrlrru;;l, r< hi den
t^ Pt^üt•.^t:r u, 1., I)rr• li,drrrhntg d-,x ;I rt..lrttr.:rln': lfir ,
V Oafu!/!ru. rn, Sc!r.crtt. Z. II)rln,L 29, 123 1•1'1 1, 106-.
ir: Crr(.Ir:r:u,, r•r,^^l. Wa".•r. II \I,v• Fin-,r11.
3, Ft\ ni:<ttr,r,, L. 1, , lirIII- ,,,',rrrrntC d,•: .Il
I39^1•I•I 1'In^rt.
\n,chrift c!t. \rrfas,rs.
l'rrrl. I tr. I;r„r, I.'iuJrui^;(i . fZust•nta!or ti trastic 63 .\...c;u
ut t, r t:;!, rr rrh.
(1) 1^indene^, ^„ I., Limnolo;;i.cal and FisY:ery-BioloJical Investigations in
an Alpine Lake Alkalized by Waste Triater, the 14illst,",tter Lake in
Carinthia (l:tJs tria) .
(2) Findeneg;;, I., Si;nif.icance of Exchange for the Development of
Phytoplankton in the Eastern Alpine Lakes.
(3) Findenel, ;, I., Eutrophication of the I^iondsee in the Salzkammergut
(^^ustria) .
1?utYior's address:
Prof. Dr. In ;o Findeneû,;, Ro sentaler Stras se v'2, A-9020 Klagenfurt, Aus t ria .