EPA-600/3-78 004
January 1978 EcolORical Research Series
A PALEOLIMNOLOGICAL COMPARISON OF
BURNTSIDE AND SHAGAWA LAKES,
NORTHEASTERN MINNESOTA
Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Corvallis, Oregon 97330
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U.S Environmental
Protection Agency have been groupec into nine series These nine broad cate-
gories were e: tablished to facilitate further development and application of en-
vironmenta technology Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields
The nine series are
1 Environments! Health Effects Research
2 Environmental Protection Technology
3 Eco ogical Research
4 Environmental Monitoring
5 SoC'oeconcmic Environmental Studies
6 Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8 ' Special Reports
9 Miscellaneous Reports
This report has been assigned to the ECOLOGICAL RESEARCH series This series
describes research or the effects of po lution on humans, plant and animal spe-
cies, and materials Problems are assessed for their long- and short-term influ-
ences Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terres'nal. and atmospheric environments
This document is available to the public through the National Technical Informa-
tion Service Springfield, Virginia 22161
-------
EPA-600/3-78-004
January 1978
A PALEOLIMNOLOGICAL COMPARISON OF
BURNTSIDE AND SHAGAWA LAKES,
NORTHEASTERN MINNESOTA
by
J. Platt Bradbury
U.S. Geological Survey
Box 25046, Denver Federal Center
Denver, Colorado 80225
With pollen analyses by
Jean C. B. Waddington
Department of Geography
University of Minnesota
P.O. No. 04J1PO-0605
Project Officer
Donald W. Schults
Marine & Freshwater Ecology Branch
Corvallis Environmental Research Laboratory
Corvallis, Oregon 97330
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
-------
DISCLAIMER
This report has been reviewed by the Corvallis Environmental Research
Laboratory, U.S. EnviranmentaI Protection Agency, and approved for publi-
cation. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
11
-------
FOREWORD
Effective regulatory enforcement actions by the Environmental Protection
Agency would be virtually impossible without sound scientific data on pollu-
tants and their impact on environmental stability and human health. Respon-
sibility for building this data base has been assigned to EPA's OfTice of
Research and Development and its 15 major field installations, one of which
is the Corvallis Environmental Research Laboratory (CERE).
The primary mission of the Corvallis Laboratory is research on the effect of
environmental pollutants on terrestrial, freshwater-, and marine ecosystems;
the behavior, effects and control of pollutants in lake systems; and the
development of predictive models on the movement of pollutants in the
biosphere.
This report describes the results of a paleolimnological comparison of
Burntside and Shagawa lakes in northeast Minnesota to determine the historic
natural and cultural trophic changes in these lakes.
A. F. Bartsch
Director, CERL
-------
ABSTRACT
The paleolimnological records of Burntside and Shagawa Lakes in
northeastern Minnesota reveal that these two adjacent lakes have been
limnologically distinct for many years prior to the late 19th century
activities of white nen thai: polluted Shagawa Lake. Although both lakes
occur within the same vegetation type and share much of their water, the
diatom stratigraphy of their bottom sediments indicates that Burntside
Lake was less productive in its natural state than Shagawa Lake. The
causes for this natural difference are not clearly known, but differences
in relative size of drainage area and in bedrock geology may be responsible.
Intensive white settlement around Shagawa Lake beginning in 1866
supplieo1 nutrients that increased its productivity and finally supported
the massive blooms of blue-green algae that characterize culturally eutrophic
lakes. Burntside Lake was spared such intensive eutrophication, but its
diatom record shows 1 hat nutrients derived from shoreside recteational cabins
and related construction activity are increasing the lake's productivity.
The results o~ this study show that paleolimnological studies may pro-
vide better comparative information for lake rehabilitation programs than do
biological and chemical analyses of contemporary unpolluted water bodies.
This report is contribution #155 of the Limnological Research Center,
University of Minnesota and was submitted in fulfillment of P.O. 04J1PO-0605
under the sponsorship of the U.S. Environmental Protection Agency.
-------
TABLE OF CONTENTS
Foreword ............... . ....... .... iii
Abstract ....... .... ................ Iv
List o£ Figure Captions. ...... ............. vi
List of Table Captions ........ ........ . , . viii
List of Plates ... ......... ...... ...... Jx
Acknowledgments ......... . ........... , , . x
Summary. .... ..................... . . 1
Introduction ..... , ............ ....... 3
Geology and Limnology ..... . ......... . ..... 6
Vegetation ............... , ........ , . J 8
Settlement History .................... . . 19
Stratigrapnic Studies
Methods ..... . ........ . . ..... ..... ?3
Vegetation History . ..... ....... ....... 2j
Core Correlation ..................... 28
Paleo] iitmology .................. , , . . 32
References ......... ........... ...... 47
-------
FTCURE CAPTIONS
Page
Fig. 1 Map of Burntside and Shagawa Lakes and their drainage
basins. Large dots show sampling stations and triangles
show coring sites. Adapted from Schults et al. (1976). 4
Map showing values of specific conductance in |jmhos/cm
for lakes and rivers in relation to bedrock geology in
the area of Burntside and Shagawa Lakes. Metasediments
and rietavolcanics (the Ely Greenstone) are enclosed
within the dashed line. Mean conductivity (^mhos/cm)
of water bodies on the Ely Greenstone = 70.4 (n = 7);
on the gran Lt ic rocks of the Vermilion Massif arid the
Giants Range granite conductivity = 47.2 (n - 21). ... 7
Seasonal distribution of diatoms in the surface water
of Shagawa Lake for April 1973 and the 1974 open-water
season 10
Fig. 4 Mean specific conductance (umhos/cm) of major Shagawa
Lake influents and effluents 1970-1976. Data from
U.S. Geological Survey, adapted from Malueg _e_t aJL.
(1975) ~ ~. ... 15
Fig. 5 Seasonal distribution of diatoms in the surface water
of Burntside Lake for the 1974 open-water season .... 16
Tit;. 6 Distribution of settler's cabins near Burntside Lake
1880-1894. Dates indicate when each township was sur-
veyed. Data extracted from land-survey reccrds by
Jean C. B. Waddingcon. . 20
!'u;. 7 Population of Ely since 1890, and ore shipments from
mines near Shagawa Lake 21
Fig, 8 Selected poLJen curves for a short core fro Gurntside
Lake. The Line at 19 cm marks the rise in jxillen of
Ambrosia (ragweed) and thus the time cf regional vege-
tation disturbances (about 1890) 26
Fig. 9 Selected poLlen curves for a short core frcm Shagawa
Lake. The Line at 39 cm marks the rise in pollen of
Ambrosia (ngweed) and thus the time of regional vege-
tation disturbance (about 1890) 27
VI
-------
Page
Fig. 10 Selected stratigraphic profiles of diatoms, pollen,
and geochemistry from Shagawa Lake (Bradbury and
Waddington, 1973) 30
Fig. 11 Selected diatom and other stratigraphic profiles
from Burntside Lake. The Ambrosia rise marks the
time of cultural disturbance 31
Fig. 12 Selected diatom and sediment stratigraphic profile's
for Shagawa Lake (Bradbury and Waddington, 1973) .... 33
Fig. 13 Influx of microfossil types for Shagawa Lake (Bradbury
arid Waddington, 1973) 36
Vll
-------
LIST OF TABLE CAPTIONS
Table 1 Concentrations of major dissolved ions (mg/1) in
Shagawa Lake compared with mean concentrations in
northeastern Minnesota and Ontario lakes
Table 2
Table 3
Table 4
Table 5
Table 6
Size, morphology, and drainage area of Shagawa and
Burntside Lakes (Schults et al., 1976).
Mean concentration (averages of mean values in hypo-
limnion and epilimnion) as selected parameters in
the water of Shagawa and Burntside Lakes suring 1971
and 1972 (Schults et al. , 1976) ,
Comparison of major cations in Burntside Lake,
Burntside River, and Shagawa Lake. Data from
Schults et cd. (1976) and Larsen (1974)
Analytical nethods for sediment cores from Shagawa
and Burntside Lakes;
Comparison of importance percentage of witness trees
at the time of land survey at Shagawa and Burntside
Lakes witi pre-settlement and recent pollen percentages
11
13
14
24
29
Vlll
-------
LIST 01- PLATES
I'age
Plate 1 Light micrographs of Cy_cl_oL_ei_la sLelJ_i^er_a C] . & t.iijn,.
and ^plo_t_£ll_a_ £l.omcrat_a Bachmann. Burnt side Lake,
0-0,3 cm". . . ". .""", 7 i9
Plate 2 SEM micrographs of Cyclo_t_ella st_e i 1 igerji Ci. & Gru!
arid Cyclotella gl_qniera_ta Bachmann. BurnLside Lake
40.5 cm. Scale = 1 Urn . ,
-------
ACKNOWLEDGMENTS
This report results from a research contract between the Environmental
Protection Agency anc H. E. Wright, University of Minnesota. The interest
of Donald W. Schults of the EPA CorvallLs Environmental Research Laboratory
is appreciated.
-------
SUMMARY
The liranologic and paleoJ .imnologic investigation of Shagawa Lake and
Burntside Lake places the two lakes in a time perspective that permits a
more accurate evaluation of their modern limnology. This was done to help
answer the following questions:
1. Does the sediment stratigraphy of Shagawa Lake record the impact of
mining and urban settlement that began in the late 1800s, and, if so, can
these changes in sediment chemistry and paleontology be distinguished from
those produced by natural 1imnologic causes?
2. Were Shagawa Lake and Burntside Lake limnologically similar before
cultural activities at Ely extensively polluted Shagawa Lake?
3. Is Burntside Lake, which is relatively unproductive by present standards,
affected in any significant way by settlement activities along its shores?
The first question is affirmatively answered by the paleolimnological
study of Shagawa Lake. The diatoms, Cladocera, pollen, and sediment
chemistry record various types of perturbations within Shagawa Lake that can
be reasonably ascribed to settlement activities. Similar conditions have not
existed under the natural environment for the last 2,000 year.1.. It is
doubtful that natural changes could replicate those caused by man,
considering the year-round human nutrient input to Shagawa Lake and the
variety of distinctive pollutants that man places in its water. Neverthe-
less, confirmation of this likelihood must await detailed knowledge of the
life cycles, nutrient requirements, and habitat and environmental preferences
of the organisms preserved in lake sediments. Superficially, the diatom
community of Shagawa Lake after pollution resembles those of more eutrophic
lakes in southern Minnesota (Bright, 1968), but it must be remembered that
these lakes have probably also undergone some pollution, and that a detailed
comparison would reveal significant differences, particularly with respect
to the diversity of the diatom assemblage (Bradbury, 1975).
The second question relates to the advisability of using Burntside Lake
as a standard by which pollution-abatement efforts in Shagawa Lake can be
measured. The paleolimnological evidence from Shagawa and Burntside Lakes
suggests that the two lakes have been dissimilar for a long time. Shagaua
Lake has always been more productive (at least for the last ?,000 years)
than Burntside Lake. The reasons for this lie partly in the fact that
Shagawa Lake occupied a terrane of easily weathered metasedimentary and
metavolcanic rocks and that some of its tributaries cross thi-; terrane,
bringing dissolved ions and nutrients to the lake. Some ground-water
-------
: ; - in;*! is i; oiff "once:, !'nrn' .iilo l:i't'' ...i
lo,^ , N'1,:! ;,,!>'. I''K< , \\ ' : h-. i r 0:' ; ' n..;','" .:;'." i;
1 , ! i' f' ii >- m::i e n re,;:- <1< i i i cr -, i n.; 1 ;.
1 ! ' i.', '. si >_ O- '11 i )'.,T OH "iQ
"\ ,1 i \ ' ;' r i i ;!(.'< "ioro vv.lter
. r' -o N -\ ;i' . r- ! " : he ^ajnr
..ji.iii.-o -- o-; ;uf "'.out > t c^
.t! hv ' i)L !_ , L jr^ > -. .. ; ii^io O;'
io -^ . tri i!.i rr ', sc.- !> -i h t h' .en
i') I ,\;j i . fcO'U'i, j ' ' '. .io' - 't » i"i t \ of i ;i', i >.-;
['re1 ',(. i t' -L';! >' i i r;i M ! o 4%.' .'f iv; riiT ^ ' do i ,ik- na.i ii,1 ,
--"fa'i'.'.M ''_, tin -' i -ML i ; raph i ,- i udy- - |>roh'ib i v ii
brv<":i- ^iit'ti.!1' .:).' i c; oci, i'i.)st like ;' .t'^ a r.:.ii,i
i t c> -.:,!--. It t n . > i n r i ( 'Mient cont ; an.1-", t 'K 1
r"-' o '.'it ' r. r'."-o;";i 1 o i I;,it of {i r . -->o t t i i- of .sh,-;
r i ii,i iS.irr r >; i v.K i M' i: i^r i i 1 1 o -^ ^ !' \ o^lo^ t ; \: t !i .
-------
\^ I'Uf'M ! .! t . '' TJ 11Hi i in';:-. ; : , i ! ])'("-,UI (" : i 1 ^ i. me ! ' 'ij
rt'SUutVf' °- , S. ! -ii I i f : ,' ,. '!(.' ]", li ' ' . i. 0,1 "v : ,' '>"(' ,r i .MU^Cl' '
Kilter : ! J t v ,'u' < ^'' "',.''', <:;!(! n'l ' .:( ' '! i.' t i on : -, i'CMil;,
t ec t ; r,kv>- ami i ; ' . .'., ;:v i n i M . i i »,.,). ; i ; -, {c ,<>;
C>;t S.1 i -> ; V'C i \ Jv'i!!:,: ' ;> .'i ','',' ,' i" ,'; i -,1 ''',,: tTO^-l X' .
ic- i C ,i ' . ( :] i I (>(
1{U> ' " t , ' ' i , j 'l 1 l M t;'i, i
I iitiC"^'! ' i.''J. >" ! .')-!' !'
', i iiits,> ' i i i ! . * ' , * v . 1 vvi O7\i'- , > !
ii inur'i . i ,' i.i. i I.i. !!(,". i't , , 'jrctiivic
-. t ', t Ii - , ' . i (.:\" , ,; .,! ii: M i '. : \ ' ;\ : , t
-------
3 Miles
MINNESOTA
^
5 Kilometers
Figure 1 Map of Buri.tside and Shagawa Lakes arid their drainage basins.
Large dots show sampling stations and triangles show coring sites
Adapted from Schults et al. (1976).
-------
limnologically distinct from Burntside Lake for at least 2,000 years. It is
misleading to compare the present trophic state of Shagawa Lake with that of
Burntside Lake, and unwise to expect that sewage treatment facilities now in
operation at Shagawa Lake can convert this water body into a limnological
counterpart of Burntside Lake.
Three related problems have prompted this paleolimnological study. The
first was to attempt to discriminate between natural and cultural limnologi-
cal changes in the stratigraphic record of Shagawa Lake, and to document
those changes caused by the settlement of Ely, Minnesota. The second
problem was to see if Burntside Lake, well known as a very clean, oligo-
trophic lake, has been affected by the relatively minor amount of settlement
activity along its shores. The third problem was to test the assumptions
that (Ij the present limnological and trophic status of Burntside Lake once
existed in Shagawa Lake, and that (2) the modern limnology of Burntside Lake
could be used to evaluate pollution abatement efforts in Shagawa Lake by com-
paring the pro-settlement palcolimnological record of the two lakes. These
assumptions appear logical because the lakes are adjacent and share the same
climate, vegetation, and some of the same water. Their natural morphological
differences appear to be slight compared to the massive cultural impact
that caused the rapid eutrophication of Shagawa Lake.
-------
CFULOdY \ND LIMNOLOGY
Both lakes are ocated in St. Louis County, northeastern Minnesota, in
a rejrane of metamorphosed lower Precambrian sedimentary and igneous rocks
(Figure 2]. Burntside laj\e and its watershed lie entire]}' within the
Vermilion granite, i predominantly granitic intrusive 'massif that also
contains biotite sr'ii.-t, Jinohibolitc, and trondhjemite (Sims, 19"75). Just
south of Burnt side ,ake an otensivi and complex series jf faults has
placed the Vermilion massif in contact with the I'.ly Greenstone and related
fornatiors. These coisist of a variety of low-rank metamorphosed volcanic
rocks (chiefly basalts, but also including intermediate and felsic lavas and
tuffs) anc their derived sedimentar} rocks, mostly gr.iywacke ard locally
impure siliceous ma.rble along with banded ferruginous charts (the Soudan
Iron-formation Member of the Liyl. Shagawa Lake lies within these meta-
niorphic rock types. lyd^ot hcnnal alternation and replacement cf tne Soudan
Iron-formation Meiiiber has produced a rich lens of hematitic iron ore along
the southern shore of Shagawa Lake (Machamer, 1968).
Glacial sediments, including sand, gravel, and lacustrine silts and
clays, overlie the Lrecambrian rocks in a patchy distribution. The lacus-
trine silty clays are slightl^ calcareous and appear to continue beneath
the organic deposits of S'nagawa Lake. They may represent the deposits of
a precursor of glacial Lake A.gassiz. Similar clays ire 'Jound near the east
end of Burntside Lake,
The limnology of Shagawa Lake is fairly u<. " 1 kuoKv, (Mcgard, i9(i9;
1 Ma! nog, 1970, Sch\:!ts ct_ al_. , 197^}.
::- i "I'-ap depth nf f-,. ; n;. In 5, . i. '9.2 km ' . ,
d.epth it typifjes- niany lakes of ihis region. The
drains in that direction. Sh jgawa Lake has i-nrfacc inflow at the west end
by the Burnt side River, which annually provides about 80°,, of the water to
the lake. hxcludirif Birntsid;- and Sliagawa Lakes ^hemst ! ves, ths total
drainage area is abt'iu 251 km- (Schults rjt al . , 1976'). In general the lakes
in northeastern Minnesota .are biologically unproductive and characterized by
nutrient-poor water1; of low conductivity. The specific conductance of
Shagawa Lake (t>5 Miuics cm~l) reseml'les that of" neighbcrmg lakes and major
tributaries that lie 01 the Xewton Lake formatioi or Ll> Greenstone (mean of
1 sites = 7Q i,mho-; cr>r!j. Most of the lakes on th.<^ granitic recks of the
Verrrdlion massif have a lower specific conductance, as dv, Lakes located on
the ''Tants Rarge Granl:e soutiicast of lily (mean cf 21 site-. "r -1»". I umhos
cm" J ) (Figure 2). Coiicentrat i ons of major and minor element - in Shagawa
Lake genc"all> rel'kJt the mean valu-;:-. of lakes in thi-. region [Table 1),
nithough phosphorus is >'-> tii,,cs higher in Shagawa Lake (rre'in of 5 localities
-------
0) I
^
0)
>
H
H
13
d
CO
co
0)
V1,
cti
rH
J_,
O
U-l
B
CJ
^-^
CO
o
_{"*
^
^1_
d
H
01
a
d
cO
4J
O
d
13
d
o
J
CJ
H
(4-1
-r-t
O
0)
a.
cr:
M-H
C
CO
CD
3
i '.
cO
£>
W)
d
M
^j
O
rd
X
Q-
cO
J^
.
to
0)
^
CO
1 '
CO
^2
cO
ti£
cO
,-Cj
en
'd
cO
OJ
TM
H
CO
4-1
d
^
^
pc
(-M
o
rt
cu
^
CO
Qj
t_tr!
4 '
d
H
P-"~
OL
O
i I
C
o
oL
.V
y
o
S^J
ij
a;
j~->
Q
4_J
C^
0
H
J_;
T3
r-J
OJ
V.
d
.,-j
jj
d
H
.d
H
|j
13
0)
CO
o
r-H
CJ
0)
c;
^-i
CO
^ ^
0)
p
o
4_)
co
d
0)
0)
V4
o
>^
^H
fi 1
CU
X
J-J
^ ^
CO
o
H
d
CO
CJ
i-H
O
£>
cO
4-1
OJ
B
n^j
d
cO
Cf]
4-J
d
QJ
£'
H
^
OJ
cc
rl
jj
cu
?
a)
0)
^
O
I 1
td
01
r~!
4-J
P
O
co
01
H
13
Q
,0
J_4
O)
4-J
cO
£
U-)
0
, s
g
CJ
CO
o
^
g
'
^
4-J
H
>
H
4_J
CJ
^3
ra
d
o
u
d
cO
_0)
X
cu
d
-H
, I
-a
0)
*d
co
cO
13
13
d
cO
H
co
CO
CO
r*I<
C
O
H
H
£
^-i
0)
f--^_
OJ
.-£
4-J
M-(
0
CO
T vj
U
O
j-i
CJ
H
4-J
H
j_4
rt
^_(
oC
a;
1-C-'
4-J
C
O
. r>
s~^
\-~^
\\
a
s_^
,
4-)
"H
>
H
J-J
U
^J
T3
d
o
o
01
4J
H
d
CO
V*j
o
o
M)
d
crj
^
co
i.)
d
cO
H
O
o -
O3 O
to
-------
TABLE 1. CONCENTRATIONS OF MAJOR DISSOLVED IONS (MG/1)
I'\T SHAGAWA LAKE COMPARED WITH KEAN CONCENTRATIONS
TM NORTHEASTERN MINNESOTA AND ONTARIO LAKES
Mean for 19
Saagawa northeastern '-'ean for 40
Lake Minnesota Ontario lakes
lakes*
Calcium
Magnesium
Sodium
Potassium
Bicarbonate
Chloride
Sulfate
Salinity (mcq/1)
*Bright, 1968.
a
Armstrong and
9.90 10.2
3.36 3.0
2.00 1.5
0.60 0.8
26.80 39.0
0.10 0.1
13.80 5.7
1.62 1.7
Schindler, 1971.
1.6
0.9
0.9
0.4
3.8
1.4
3.0
0.4
-------
in 1968 = 45 ug/1) than in surrounding lakes. Until early I1-) ,->, about 7."-.';
of the phosphorus and 22';-, of the nitrogen entering Shagawa lake came from
the municipal sewage treatment plant at Ely (Malueg ejt aj . , 197S). 'Jhis
large nutrient influx, particularly phosphorus has produced i xtcnsive
blooms of blue-green algae.
Because Shagawa Lake is relatively shallow, it overturn1, easily in
the spring. By midsummer, when surface-water temperatures exceed 18~'C, it
stratifies with a thermocline at approximately 3 m. The cpilimnion may
have very high chlorophyll a. concentrations and a pi I greater than 10.
Below 4 m, oxygen may disappear and the pH is neutral.
In summer the dominant phytoplanktcrs are blue-green algae
(Aphanizomenon flos-aquae and Anajba_eri_a spp.), but in the early spring and
fall diatoms are comparatively abundant. The seasonal succession of diatom
species in 1974 (Figure 3) shows that small species of Stj?jjjianojdi/Lc_us (S_.
minutus, S. hantzschii, and S_. siib_tij_is) characterize the eailv spring
blooms. In some years, blooms of these diatoms occur under v icar ice in
the winter months (e.g. February and March 1968) (Megard, 19t'9, 1973).
Following the initial bloom of small Stepjianodi scus species, \sterioji_ej_l_a_
formosa, Fragilaria crotencnsi s , Me 1 o sir a _gr ami 1 a t a , Stejrhjinodi scus dubiiis,
Stephanodiscus niagarae, and finally ^lejk^sijra ambigua dominate the planktonic
diatom flora. The relative dominance of A_stcrionel_la formosa at the end of
1974 is of little quantitative significance because all diatom1-- become very
scarce once the lake freezes over. It is not known if this success!ona1
pattern characterized Shagawa Lake before pollution control M-asu;es took
effect. Evidence from Megard (1969) indicates that early spimg blooms of
small Stephanodiscus species occurred in 1968, five years bemrc the
Environmental Protection Agency (EPA) advanced treatment plart went into
operation (Megard, 1973), but the reduced phosphorus level.1- M, ti'e waste
water now entering the lake as a result of the plant's opera i ,v>n could very
likely be responsible for changes in both the quantity and qua]UN of
phytoplankton as well as in other llmnological parameters. \nalyses of
algae during the summer of 1967 (Megard, 1969) show that Meiosira ambi_g_uji
was the only diatom present in a phytoplankton community dominated by the
blue-green alga Aphanizomenon flos-aquae on the dates 79 VII I9t>7 and 14
VIII 1967. For this time period in 1974, the diatom flora i considerably
more diverse (Figure 3).
Burntside Lake is about three times the size of Shagaw.. Lake (about
29.2 km )(Table 2), and its long, intricate shoreline and j t-. many islands
(Figure 1) suggest a complex limnology. Isolated basins in rhe east arm of
the lake attain depths of 25 to 40 m, and its mean depth (IT. 'mj is
significantly greater than that of Shagawa Lake. Xeverthcl e ->->, Burntside
Lake's large size (maximum northeast-southwest dimension about 13 km) allows
sufficient fetch for the wind to mix its water, which reinaiir- aerobic to
the bottom throughout the year (Schults c_t a_l_. , 1976). Samlv, relatively
inorganic sediments at iiitermcdi ate depths in mid Lake also -aggeM thai
oxygenated water and currents frequently reach the bottom.
The concentration of most chemical parameters in Burnt -ide Jake is
less than in Shagawa Lake, although the differences are not consistently
9
-------
A e e *. 15
-.1. ...
30
S'ep^oned/scus
fenuis +
Stephonod/scu'S
Subf;/'S
\stenonella
formosa
Synedra rumpens
Melosira ifallca
Fragilaria crotonensis
Me'osira granulata
Step^.onodiscus ducius
Sfephonod-scus n/agoroe
25
25
25
40
IX X
xr
1974 -
Ji=i
P Tr"""""P~->--
i i j I rrz:
i:^:::
- 1 f - J.. . J3
25 r
Melosira crr.bigua
Week -15
_ 1... L
20
-L __L 1 u
30
12: ^L m: ;2n. 3zm iz x TTT
Year 1973 ------------------------- 1974 ----------------------------
Figure 3 Seasonal distribution of diatoms in the surface water 3f Shagawa Lake
for Anril, 197"^, and the 1974 open-water season.
10
-------
Watershed area fkrn")
-)
Lake surface area (knf )
Mean dcptli (mj
Maximum depth i'mj
Volume (kiif )
Shagawa Lake
100.
Bujntsidc lake
131.
48.
-------
proportional [Table 3), Both lakes have nearly the same concentrations of
potassium, chloride, and sulfatc ions, but sodium, calcium, magnesium, and
silica arc enriched in Shagawa Lake by factors of nearly 2 to 3. Iron and
manganese are highly concentrated in Shagawa Lake, particularly in the
lower waters during tines of thermal stratification. These differences in
concentration result from a number of factors, one being the high concen-
trat ion of the waste water entering Shagawa Lake from the town of Ely. The
high iron and manganese concentrations in Shagawa Lake, however, probably
reflect the greater frequency and intensity of anoxic bottom-water conditions
in Shagawa Lake than in Burntside Lake, for during such times these elements
will be reduced and nove from the bottom sediments into the overlying water.
However, not all chemical differences can be easily related to Ely's
waste water or to limno]ogical characteristics of the two lakes. Table 4
shows a progressive coi centration in specific conductance and major cations
as water from BurntsLde Lake flows along the Burntside River and into
Shagawa Lake. This Increase in concentration of total dlssolvec solids is
from 75 to 851> of the ;verage Shagawa Lake value, and it ii accomplished
in only about 5 km of river travel. In addition, the specific conductances
of the minor tributaries to Shagawa LaLc ire all significantly higher than
Burntside Lake (Figure 4). These tributaries amount to about 19°o of
Shagawa Lake's inflow (Malueg e_t al_., 1975).
Despite the fact that Malueg et al. (1975) did not locate a significant
ground-water inflow 70 Shagawa Lake, there are indications that ground-
water plays an impor"ai t role in controlling water chemistry in the lake.
All tributaries to Shagawa Lake either cross or flow along major faults that
place slices of mafic metavolcanic and metasedimeTtary rocks in contact;
Armstrong Creek, for example, crosses five such faults in a distance of 3 km.
The '-our.se of the Burntside River is largely determined by the Burntside
fault., in which :;enes cf mylonite indicate extreme slipping and crushing
along the fault wails (Sims, 1973). The common minerals of the Ely Green-
stone, plagioclast. chlorite, hornblende, epidote, and calcite (Mac'iamer,
1968), are relatively labile and rich in sodium, calcium, and magnesium.
The higher concent rations of these elements in the Burntside River is
probably related to the abundance of these elements in the bedrock and to the
proximity of fracture zones 1 hat might serve as conduits for ground-water
flow. The fact that the hematite mines of Ely must be Jewatered by
punp;ng further attest^ to the presence and movement of ground-water in the
area. Although Burntside I ale is similarly surrounded anil underlain by
faults, the dominant lithologies of this area are the granites and biotite
schists of the Vermi"ion massif, which in general contain less labile
minerals than the mafic rocks nearby. Perhaps this partly accounts for the
low conductivity of Burntside Lake.
The biology of Burntside Lake reflects its more dilute water. Diatoms
characteristic of oligotrophic lakes such as Tabe1laria flocculosa (Bright,
1968- Bradbury, 197.S" become important in the Burntside Lake phytoplankton
community during the summer months (Figure 5), and the planktonic diatom
assemblage in general lesembles those of undisturbed Lakes in northeastern
Minnesota (Bradbury et n1_., 1975) and the Experimental Lakes Area lakes of
northwestern Ontario ("Stocknt r, 1971). Summer algal productivity
12
-------
TABLE 3. MEAN CONCENTRATION (AVERAGES OF MEAN VALUES IN
HYPOLIifNION AND EPILIMN10N OF SELECTED PARAMETERS
IN THE WATER OF SHAGAWA AND BURNTSIDE LAKKS DURING
1971 AND 1972 (FROM SCHULTS et al., 1976)
Parameter
Specific conductance (ymho/cm)
Calcium (mg/1)
Magnesium (mg/1)
Sodium (mg/1)
Potassium (mg/1)
Iron (yg/1)
Manganese (yg/1)
Silica (mg/1)
Sulfate (mg/1)
Chloride (mg/1)
Total phosphorus (mg/1)
Orthophosphate phosphorus (mg/1)
Total -N (mg/1)
Ammonia -N (mg/1)
Nitrate -N (mg/1)
PH*
Total alkalinity (mg/1)
Dry weight (seston) (mg/1)
Chlorophyll a (yg/1)
Phaeophytins (yg/1)
Shagawa
Lake
65.0
9.0
2.3
1.60
0.7
914
275
4.9
10
2.7
0.11
0.06
1.1
0.17
0.063
7.3
23.6
2.0
10.9
2 . 2
Burnt side
Lake
32.0
3. 3
1.0
0.95
0.6
50
9.0
2.0
10
2.4
0.01
0.0025
0.7
0.02
0.024
6.9
7.4
0.7
2.3
0.7
Ratio
Shagawa Lake/
Burntside Lake
2.0
7 -7
-> ^
1 .7
] ^
18.3
30.5
2.4
I .0
].]
11.0
24.0
J .6
8.5
2.62
1 . 0
3.2
2.8
4. 7
3. 1
''median
13
-------
TABLE 4. COMPARISON OF MAJOR CATIONS IN BLRNTSTDE LAKE,
BJRNTSIDE RIVER, AND SHAGAWA LAKF. DATA F'lOM
SCilULTS et al. (1976) AND LARSEN CORAL COMMUNI-
CATION, 19/4) [MEAN MONTHLY SAMPLES (SHAGAVA LAKE)
AND BIMONTHLY SAMPLES (BURNT SIDE LAKE) OF EPILLMNION
AND HYPOLIMNION FOR 1971 and 1972J
Ratio Ratio
Burntside Burnt side Shagawa Burntside Shagawa/
Lake River-^ Lake River/Lake Burntside
Lakes
Specific Conductance
(ynhos/cm)
Sodium (mg/1)
Potassium (mg/1)
Calcium fmg/1)
Magnesium (mg/1)
32
1
0
3
1
,0
.6
. 3
.0
57
1.2
0.6
7.6
1. 5
62
1
0
9
2
.6
.7
. 0
.1
1.8
1.2
1.0
2 . 3
1.3
1.
T
i .
1.
"5
2.
9
6
2
7
1
Mean of samp Lei taken between 1970 and 1974.
14
-------
in
m
o
03
en
a)
3
03 di
S >
03 P
bl 3
03 CO
O -H
r-i &C
03 O
6 -H
O
0 00
o
" --- K^
Ul
o e
^ o
e ^
73 u-i
oj
a) -u
o 03
d P
03
4-J
O
LJ~|
r--
a)!
IT)
If)
N-
C- O^i iI
O .H ^
CJ I
O
CJ f-
M C^ i1
m ii 03
H
a
a)
a c
M 0) bO
3 OJ
03 M-4 rH
a) M-I cd
^
-------
Asterionella formosa
Synedra filiformis
Tabellaria flocculosa
Synedra acus -+- 5. rum pens
Cyclotella glomerata
Cyclotella kutzingiana
Cyclotella com fa
Melosira italica
25,-
0
25
0
"
T r-
Week 20 30
Month 1L 3ZI "VTT IVTU IX
40
XL
Figure 5 Seasonal distribution of diatoms in the surface water of
Burntside Lake for the 1974 oper-water season.
16
-------
(organisms per ml) in Burntside Lake is one-third to one-tenth that of
Shagawa Lake before the phosphorus reduction program began. The composition
and abundance of the benthic fauna in Burntside Lake are further indicators
of its oligotrophic status (Schults et al., 1976).
17
-------
VEGETATION
The natural vegetation of the area surrounding Burntside and Shagawa
Lakes consists of a conifer-hardwood forest whose species show affinities
with the boreal regions to the north and the Great Lakes- St. Lawrence
forest region to the east (Heinselman, 1973). The principal boreal conifer
species are Pinus b_aiik_s_iana, Picea glauca, £i_c_ea_ mariana, Abies balsamifera,
Larix laricina, and ^^li'i?: occidental! s. Pinus resinosa and Pinus strobus are
elements of the Great lakes-St. Lawrence forest region to the east. These
and many deciduous trees (principally Popu]us, Betula, Quercus, Ulmus,
Fraxinus, Juglans, O^Vrys_, and Acer) exist in a complex mosaic of communities
that relate to variations in soils, drainage, and fire history (Bradbury
and Waddington, 1973: Heinselman, 1973). Since the late 1800's some changes
in the local forest character have been brought about by Euro-American
settlement activities.
Periodic forest fires have characterized this part of Minnesota for
centuries (Heinselman, 1973). All of Burntside Lake's shoreline was burned
at one time or another in the last 200 years. There were fires on the
islands in the southwest end of the lake in 1742-1755, and again about 1850.
The north arm of Burntside Lake had fires in 1822, 1803-64, and 1894 (M.L.
Heinselman, written commun., 1976). Most of the fired of this region
before 1880 were probably natural.
18
-------
SETTLEMENT HISTORY
The northern part of St. Louis County was originally surveyed in 1880.
At that time the only signs of man's activity were trails that ran short
distances through the woods. By 1894 a number of cabins had been erected in
the vicinity (Figure 6), and the towns of Tower (1883), Soudan (1887), and
Ely (1887) were founded (Figure 2), after the discovery of )>ch deposits of
iron ore (hematite) nearby. By 1900 five mines were in opejution near
Shagawa Lake, and the tonnage of ore shipped from these mints reached a
maximum at this time (Figure "') . SubsequentLy, mining fluctuated according
to national economic conditions. At Fly, the deposits grade.) 1 iy became
exhausted after World War II, and the last mine was shut den,/, in 1967.
Lumbering began at the same time as mining, principal!;, in response to
the demand for mine timbers and construction materials. The drainage basin
of Burntside Lake was logged between 1895 and 1915. Nearly ail the big white
pine (Pinus strobus) and red pine (Pjinus^ res_inps_a) were cut as \\ell as some
cedar (Thirjji occi dental i sj and spruce (Picea). Fires frequently followed
logging due to uncontrolled slash fires (Ileinse Iman, 1973, and written
commun., 1976). Most of the timber around Shagawa Lake was *. ut by 1895,
and it may be assumed that soil erosion associated with aJl -"ettlement
activities including local clearing for agricultural land 1- > pt pace with the
abrupt population increase fro)!,- 1890 to 1900 and to a lessc extent there-
after.
The shores of Burntside Lake are shown as subdivided plots in the plat
book of 1916 (Hixon and Co., 1916), and cabin building around the lake
increased about 1920. Since- this time some road work has boon done in the
vicinity of Burntside Lake, and roads are currently being (".tended
(Heinselman, written commun., 1976). Cabin construction ag.iin increased
after 1945 and still continue1-.
The permanent population of lily reached a maximum (6,000 persons) in
1930 and gradually declined thereafter (Figure 7). Early population
increases are clearly related to increasing, mine shipments, but after 1900
there is less correlation. Much of lly's economy today is related to summer
tourist use of the north wood-' lakes. This transient population is not
measured by census statistics, but it undoubtedly lias a gre'st impact on the
lacustrine environment of Shagawa Lake and to a lesser degree of Burntside
Lake. Between 1953 and 1965 annual visitor use of the wilderness in this
part of northeastern Minnesota increased from 50,000 to 25'',000. A large
majority of the canoeists, fishermen, and campers spend some time in Ely, a
major outfitting center for wilderness travel ;Lucas, 19o4i.
-------
R ^ 2 W
R4H W.
Trails
Cobins
A School
0
6 Miles
^-h
10 Kilometers
Figure 6 Distribution of settler's cabins near Burntside Lake
1880-1894. Pates indicate when each township was
surveyed. Data extracted from land-survey records by
Jean C.B. Waddington.
-------
o
CO
ro
O
O
c
CL)
e
c
cc
CC
ii
0)
u
ci
H
CO
J-J
rt
ii
O
p..
r-~
a)
M>
I
-------
Ely has had a municipal sewage system since 1901, and since that time
municipal wastes have been entering Shagawa Lake. In 1912 two Imhoff tanks
(in which particulate sewage settles and is anaerobically decomposed) were
installed in the system, and by 1954 treatment facilities included a primary
settling tank, a high-rate trickling filter, and a secondary settling tank
(Brice and Powers, 1969J. Nevertheless, nutrient-rich water was still
entering Shagawa Lake causing severe blooms of blue-green algae (Larsen and
Malueg, 1976). In 1963 the treatment plant operated within its design
capacity and treated up to one million gallons of sewage/day by reducing the
biological oxygen demand (BOD) from 100 mg/1 to 20 mg/1. Algal blooms
continued, however, and in 1973 the Environmental Protection Agency
established a tertiary treatment plant for Ely's municipal wastes in which
phosphorus and nitrogea were chemically removed from the water before it
entered Shagawa Lake.
2.2
-------
STRATIGRAPH1C STUDIES
Methods
Lake-sediment cores for stratigraphic paleolimnological analysis of
Shagawa and Burntside Lakes were taken with a 5-cm diameter piston sampler
(Gushing and Wright, 1965). The 1.64-m Shagawa Lake core (taken in the fall
of 1971) came from the east basin of the lake under 12 m of water. The
Burntside Lake core (taken in the fall of 1974) came from a protected bay
on the east arm of the lake, 0.6 km south of the entrance of Dead River
(Figure 1), in a water depth of 15 m. The cores were subsampled at 0.3-to
2.5-cm intervals in the field by controlled upward extrusion from the coring
tube. Analytical methods are summarized in Table 5.
Vegetation History
The pollen record from Burntside "Lake (Figure 8) is basically similar
to that of Shagawa Lake (Figure 9 and Bradbury and Waddington, 1973). The
major stratigraphic change in each core is identified by an increase in the
percentages of Ambrosia (ragweed) pollen and a simultaneous decrease in the
Pinus strobus (white pine). This change occurs at 18-cm depth in Burntside
Lake and at 39-cm depth in Shagawa Lake. Chenopod-Amaranth pollen increases
with Ambrosia, and other disturbance weeds such as nettles (Urticaceae),
dock (Rumex), and Russian thistle (Salsola kali) make their appearance
or become more common at this time. Salsola kali, introduced to this country
from Asia by the 1880's (Weaver and Clements, 1929) positively identifies
this upper zone as the post-settlement horizon. In all probability these
pollen changes are synchronous in both lakes.
The decline of Pinus strohus pollen is best discussed as the ratio of
this species to total pine pollen. Pinus strobus contributes approximately
one-quarter of the total pine pollen rain prior to settlement. After that
time, probably because of selective logging of this species. P. strobus is
reduced to one-sixth of the total pine pollen (Bradbury and Waddington,
1973). This ratio seems to hold true for all the sites in northeastern
Minnesota that have been studied to date.
The pollen records from Burntside and Shagawa Lakes are as similar as
might be expected from different basins within one lake. The differences
probably reflect variation in the local vegetation because of fire history
and edaphic factors and differences in lake morphometry and microclimate
which influence the amounts of different pollen types that become incorpo-
rated into lake sediment. The large variation in importance percentages of
23
-------
TABLE 5. ANALYTICAL METHODS FOR SEDIMENT CORES
FROM SIIAGAWA AND BURNT SIDE LAKES
Analysis
Pollen,
fungi,
charcoal .
Fli a 1~ nmrlimant- rl i a p* c: -f- A rl Uj i 1~ J~t
Sample
Size
0.5
ml
n :>
Shagawa Lake
Same method.
Poi Len count
500-800
( Bradbury &
ivaddington,
1975) .
S^-rn^ Tni^^hnH
Sample
Size
0.5
ml
n t;
Phytoliths.
and hema-
tite silt.
Cladocera
Organic
matter
Biogenic
opal
Clastics:
sand,silt,
and clay
cone. FNO + 30°. H20?. Residue
washed free of oxidants and
mounted in "Hyrax". Frequency
established by 500-valve count
excluding phytoliths and hema-
tite silt.
Not done
I
Percent of dry weight estab-
lished by loss on ignition
at 550°C (Dean, 1974).
Percent of dry weight esta-
blished by digesting ashed
sediment in 0.5 N NaOH for
2 hrs at 100°C. Residue
washed, centrifuged, and
weighed.
Percent of dry weight deter-
mined by difference: dry
sediment weight - % organic
matter - *-o biogenic opal.
0.5
1 £
iValvc count
1000 per level
(Bradbury §
Waddington,
1973).
Fresh sediment
disaggregated
with 1(1% HC1,
followed by
boiling in 10%
KOH. Cladocerans
concentrated by
'sieving through
67 ym mesh.
Sane method
Ashed sediment
digested in 4N
D
ml
5.0
ml
to
0.5
boiling NaOH for
10 inin. Residue g
washed, filtered,
and weig/.ed (Bradbury
'i, Waddington, 1973).
Same method
1 g
-------
Analysis
TABLE 5. ANALYTICAL METHODS FOR SEDIMENT CORES
FROM SHAGAWA AND BURNTSTDE LAKES
(CONT.)
Burntside Lake
Sample
Size Shagawa Lake
Sample
Si ze
Water
content
Iron
Calcium
Tannin and
lignin
Phosphorus
Fresh sediment weighed,
dried at 110°C and reweighed
Not done.
Atomic absorption analysis
after digestion of sediment
ash with cone. HC1.
Dry sediment digested at
0.12 N KOH 1 hr at 100°C.
Determination by spectro-
photometry (900 ynun) after
addition of Tyrosine
reagent.
Ashed sediment (550°C)
digested with 4N HC1. P
reduced with ascorbic acid
and determined spectrophoto-
metrically after addition of
3 g Same method.
50
ing
5 to
20 ing
6 to
10 mg
3 g
Dried sediment 0.4
(110°C) digested g
with cone. HC1.
Fe reduced wi th
SnCl? and t itrated
with~K,-Cr_,0
Not done.
Not done.
Same, but fresh 0.1
sediment digested g
with K9S?0 in
pressure-cooker.
25
-------
T
i
O in O tn o u~> o ui ^ ,'
(£ (D T^ r^ CO CO CTl (T> ^ u
'°-> r
-Jp p H.30I«|(,3S- |S
03 O
O CD
c e
H -H
^ (->
0) CD
j=; ^
H -P
C
03
CD
CD
03 03
f-H
O
f-i o3 oo
O
o
3
O
.£>
O O W
_ f~^ CD
C O
C
03
10
CD T3
> CD
?H c/^ C
3 -H O
O ^t -H
p
C CD o3
CD X -P
r-H P CD
Ul CD
13 03
CD e
CD cr. CD
CD '< ?H
oo
CD
p
26
-------
a I
_j
_l I I L
'*,.
'e?,
>_L
, I (D
X
CD «->
-Sv_[
*&_[
'°^A
0)
^
rt
03 0)
M CD
03 S
CO 03 O
f-i CJi
6 *' 00
O
?-( o3
<-H -H
t/1
O
O
4-> CD
5-1 <-H O
O O C
J-l O
O Pn
(/) 'H (H
txO
-T3 03 O
M r-. "%. :
^J O'l
** ^ * xapui iDODJoyo
C
o 6 o
U O -U
CO M-l C
S C« T3
O ^! T3
^ 2 »3
» i 1 O
a) ^J S-£
iJ 0)
tfl 0)
to o
W) 0) r-l
tO rH CO
r; a) C
c/2 c/) <
k
r
>
xu
1
F&*
i
>
L^
fi
y»
11
^
u>
..'
^J
!
w.
9
£\
^'
/^~
8 1
/"
_x^
3
Lb
v'
J
~a
-~x^
c
2
^~y
1
7
-L-_
\^
^
o
CD
J__
v
'~~~^sr
O 1
ff» 1
-A-
^~-
o
o
1
*
~\^
f
-O_
-^^^-
! 1
S^2?
_L__
^- '
_^^
8
[MXi
U44d-
j -
x.
? 1
WJ
-
^-^~~
! i
fe
*m;
-
^
? i
1
3
4
^
I I -M tlO
"° f o g o
~£ | CD O f-l
2 CD CTi 4-1
S CO M O
Til I' m
, i W)
IK I" >H
[ ° tL.
Efl
|T
-------
witness trees noted by surveyors around the lakes in 1880 (Table 6) illus-
trates the patchiness of plant distribution within the forest. The pollen
percentages from approximately corresponding pre-settlement levels (20 cm
in Burntside Lake and 40 cm in Shagawa Lake) are very similar, however. This
relationship supports the concept of a regional pollen rain in northeastern
Minnesota, and that local forest inhomogeneities only affect the pollen
record of very small Lakes in this area. Because of this regional influence,
the pollen record of Shagawa and Burntside Lakes cannot be expected to
provide much information on the local vegetation history relevant to the
development and limnoLogical character of the lakes.
The pollen records from Burntside Lake and Shagawa Lake are generally
similar to records in the Boundary Water Canoe Area to the north. For
example, the pollen profiles from Dogfish Lake and Meander Lake about 40 km
NW of Ely (Bradbury e_t al. , 1975) and from Lake of the Clouds 60 km NE of
Ely (Swain, 1973) demonstrate that all these lakes have existed in the mosaic
of mixed deciduous-coniferous forest that has resulted from natural forest
fires in northeastern Minnesota over the past 10,000 years (Heinselman, 1971,
1973; Swain, 1973). The stability of the vegetation pattern in spite of
frequent pre- and post-settlement fires is partly due to the innumerable
lakes and marshes in this region that act as fire breaks and prevent the
eradication of local seed sources. Thus man's activities so far have caused
only minor vegetation changes on a regional scale.
Core Correlation
The cores from Burntside and Shagawa Lakes can be correlated by the
percentage increase in Ambrosia pollen (the Ambrosia rise) and the sharp
decrease in Pinus strobus pollen. However, it is not known exactly what
date these stratigraphic changes represent. A date of 1898 has been
established for the Anbrosia rise in Lake of the Clouds ((34 km NE of Shagawa
Lake) based on pollen counts from varved sediments at two-year intervals
(Swain, 1973). Because the drainage basin of Lake of the Clouds has never
experienced logging or agriculture, it is assumed that the 1898 date for the
Ambrosia rise is a regional effect which could be applied to Burntside and
Shagawa Lakes. Confirmation of the 1898 date comes from the abrupt increase
in silt sized particles of hematite in the sedinents of both Shagawa and
Burntside Lakes, recording the beginning of mining at Ely (Figures 10, 11).
The mines had to be dewatered, and it was customary to pump the mine water,
charged with hematite dust from the mining operation, into Shagawa Lake,
where it settled tc produce a distinctive marker layer on the lake bottom.
The hematite that entered Burntside Lake was probably airborne. Once the ore
was brought to the surface, wind could have transported hematite dust from
the ore piles and railroad cars to nearby lakes. The marked increase in
hematite silt in the sediment cores from Shagawa and Burntside Lakes should
correspond to a date of 1888 (Figure 7). This correlation seems fairly
certain, even though organisms burrowing in the lake sediment blur this
stratigraphic marker somewhat, and some hematite silt may have entered
the lakes naturally by erosion of nearby glacial deposits.
28
-------
TABLE 6. COMPARISON OF IMPORTANCE PERCENTAGE OF WITNESS
TREES AT THE TIME OF LAND SURVEY AT SHAGAWA AND
BURNTSIDE LAKES WITH PRE-SETTLEMENT AND RECENT
POLLEN PERCENTAGES
Burntside Lake
Pre-
Imp. settlement
Witness tree
White pine
percent
35.29
Jack/Red pine 19.97
Aspen
Birch
Spruce
Tamarack
Cedar
Fir
Black ash
Maple
[ Importance
12.28
10.77
8.66
4.75
3.20
2.95
1.34
0.82
Percentage =
pollen %
15.0
46.0
2.1
7.4
7.9
0.9
2.1
1.8
0
0
Recent
pollen %
8.3
44.5
0.8
8.5
10.3
1.3
0.8
1.3
0.5
0.3
relative dominance
where relative dominance = Sum of
and relative density
Sum of
= Sum of
Shagawa Lake
Imp.
percent
13.83
20.04
9.51
15.33
20.50
6.88
5.07
4.11
1.43
0.65
+ relative
2
P re-
sett] ement
pollen %
25.0
35.0
] .5
9.0
5.3
0.8
6.8
0.7
0.5
0.4
densitv
Recent
pollen %
7.0
39.5
1.6
11.0
7.0
0.4
2,2
0.6
0.2
0.6
basal areas for taxon i
basal areas for all
all trees
of taxon i
taxa
. i
Sum of all trees
29
-------
Oj
e
o
X
e
CD
^
O
O
CD
to
13
cxJ
C
0)
£ Cn
O ^H
4->
cd >
H C
-d o
4-J
U-^ b/)
O C
H
(/) T3
CD 13
i^ C\j
H |S
O 13
PH Oj
O X
r-l ?M
X 3
ct)
f-4 OJ
CD ci
O ej
CD bo
CO 00
O
,i
CD
I'M 8 I
-_ .
f 1 1 1 1 1 1
o o O o i p I O O
ix « fi as i K i « j>
' : * ! ! S>
ta 1 s .H
O CT> ^" t^-t
"*o
I 1 1 1 1 1 "^
0 0 t ° ° ° 1 ° °
o ^ ; CM fi
-------
Tannin - Ugnin
as Tannic
Organic , .. Biogenic _. . Acid _
matter Clastics 0^Q| Phosphorus Ca
Hettite Phytoliths
grams/g biogenic
elastic sed opal
# ^ ^ -\0" -\° x° ^
11 i\ V"J v
?
0 <0 0
Percent of total diatoms
Figure 11 Selected diatom and other stratigraphic profiles from Burntside Lake,
The Ambrosia rise marks the time of cultural disturbance.
31
-------
Paleolimnology
The paleolimnology of Shagawa and Burntside Lakes has been determined
largely from the stratigraphic analysis of fossil diatoms and sediment
chemistry. Fossil Cladocera stratigraphy has provided additional informa-
tion in Shagawa Lake. The limnological history of Shagawa Lake has been
discussed in some detail previously (Bradbury ard Megard, 1972; Bradbury and
Waddington, 1973; Bradbury, 1975) and need be orly summarized here. The
pre-cultural diatoir and Cladocera stratigraphy of Shagaua Lake indicates a
natural trophic level greater than many lakes in northeastern Minnesota and
southern Canada. Thii is particularly suggested by the persistent dominance
of Fragilaria capucina and species of Melosira (Figure 12). Although these
diatoms are widely distributed in Minnesota lakes (Bright, 1968; Bradbury,
1975) and are therefore apparently able to take advantage of a wide range of
limnological conditions, F_._ capucina is known to reach its greatest relative
abundance in eutrophic lakes (Stoermer f, Yang, 1970). Frequently _F^ capucina
lives among aquatic vegetation of eutrophic lakes (Jorgensen, 1948).
Similarly the stratigraphic distribution of Me 1 cs ira urnb_i_gua, M. granulata,
and M. italica in other Minnesota lakes shows that these diatoms generally
increase in abundance when erosion resulting frcm land clearance increases
nutrient loads (Bradbury, 1975) . The fact that C_ycJ^o_t£lJ_a. ste lligera and
Tabellaria flocculosa--diatoms characteristic of oligotrophic Lakes in this
region (Stockner, 1971)--are only of minor importance in the pre-cultural
record of Shagawa Lake further suggests that this lake had relatively high
nutrient levels before settlement.
The Cladocera s;ratigraphy also indicates that Shagawa Lake was
eutrophic or certainly mesotrophic in its natural state (Figure 10). The
two dominant cladocerans in the lake during pre-settlement times were
Bosmina longirostris and Chydoris sphaericus. In the oligotrophic lakes of
western Ontario, BosmLna longirostris generally dominates, and Chydoris
sphaericus is rare or absent (Patalas, 1971). In enriched lakes, £_._
sphaericus often dominates, sometimes entering the plariktonic habitat by
attaching itself t~> floating blue-green algae (Bradbury and Megard, 1972).
The background frequency of C. sphacricus (50-60") in Shagawa Lake in pre-
cultural times suggests that relatively enrichec conditions and perhaps
blooms of blue-green algae existed for nearly 2,000 yeais.
Even though Shagawa Lake was moderately eutrophic before modern
settlement began, man's impact in this area considerably increased the load
of nutrients entering the lake. Changes in the hematite and phosphorus
profiles can be approximately correlated with krown cultural events, such as
the beginning (1888), maximum (1902), decline (1951), and termination (1967)
of mining activities, and the introduction of phosphate detergent C1948)
(Figure 10). These tLme-stratigraphic horizons, together with a C-14 date
(15 A.D. + 125 years) at the bottom of the core, permit the determination of
influx values of organisms (in numbers/cnr-/yr) incorporated into the lake
sediment (Figure 13). The increase in pollen influx and particularly in
the influx of fungal 'ivphae and spores at 30 cm depth very likely relates to
the erosion and subsequent deposition of nutriert-rich top soil in Shagawa
Lake, because pollen and fungal material occur abundantly in the uppermost
horizons of forest soils. The increase in nutrients to the lake from this
32
-------
OH
OJ
f-H
0)
S
O
OJ
6
o
4 >
aj
%,
^V>,^ L
^Wi
Xj^7
i/l
+J
C
CD
B
H
T3
CD
in
-a
03
6
o
4-J
o3
H
CJ
0)
CD CT,
C/D r-l
bC
33
-------
process caused a greater product i vj ty and influx of diatoms end i'Jvdocera
that dramatically illustrate the course 01 eutroph ic:! Sanr;er (197f'-.j have shown
that the post-settlenent sediments (~>f Siiaeawa bake contain appreciable
amounts of this pigin-jnt . Soii:e myxoxanthin is :.iso present in pre- se tlement
levels (E. Gorhim. oral ecm.ii. , }97"!li.
Sewage ^reatrne.it facilities at Flv v\-e."r- inipri,-\,od in 19S4 O-irJce and
Pouerr> , 1969), and if may be possible' to see tt~e effect of this nstailarion
in the sediment? of Shngaiva l.nke, !n the upper S -i;. ..f tho 'r'hag'Ka bake-
core, phosphoru- levels f Figure 10, --which, in |;ciicial n i i ror : he increase '. n
St ejphanodi scus h_a_nt.:.Mii i '-nd related ^pcc i cs- -a ro reJ:;cc^ r:^a_^,;laria
crot,on_ensi s and -'^t_£/'-I_OjH'l_l_a_ f.cl£lr!jl->a began t" lepl'icc <=;t(''j>h_:i_n''>i^i_5cj_is_ ir tnese
sane levels, and Ch^lor_Ls sphae_ri cus, while ;-1 i i i \;< <\ jifviadar l, ^e
decline. These trends niay represent the in^f iliatii", ;t soccndnt}
facilities in 1954. Ilr -. ti-patment jm'on'<;d a r;\(v. ;'."tc i ri ckn ^ u.'
and ri secondary sett ing taci- . It is not cleat ju'-t hov 'v J?f i c i .vit
modifications workod anJ tlie system w;;s equipped v. ith l\vr>ass..-s rh.'-t '-.'ere in
operation some of the time rn.W. :->chults, written t oiimLin - . 19"" i. \everthe-
less, additional fLLt:f. ring and sett ling ia>. ils'ic - wr-.U p.^bibly reduce the
load of particulatj >cwct.-;p to Shti;,awa bake. !..i_ii th.o;iyt .'hosi'horus in
particuJate sewage i . nor inmediateiy a\'aJlable for .'i^as growth. it -.ould
become so once it .a., deposi-ted and reduc'.'d in aro>ic, rypol i JUK t i^. region.-
of the lake and rciirculated to the epi1imninn during priiods of turnover.
The removal of some- of the phosphorus - ri ch pa rt i cul;; ce -'cicage load to
Shagawa l.ake would therefore cause a reduction in the v?t,.J nutrient load
for the lake. Following this reasoning- nutrient l">:d.'£ to Sliagawa Lake
-------
would have been greatest between J948 (__int7'oductioii of phosphate
detergents) and 1954 (establi shmcnt oi" secondary treatment facilities). This
time period (6 years) would be represented in the core by the sediment
between 14 and 5 cm and would have accumulated at the rate of i.5 cm/year.
After that time, the sedimentation rate dropped to about 0.3 cm/year, a rate
characteristic of the average sediment deposition rate between 1902 (30 cm)
and 1948 (14 cm).
The effect of the current (beginning in 1973) tertiary treatment plant
for lily's wastes can be seen in the modern algal samples (1974; from Shagawa
Lake (Figure 3), Diatoms that bloom in summer and early fall are abundant,
particularly F_. crotonensis. Melosijra spp. , and As^erioneljji formosa. The
diatom flora is becoming more diverse, and algal blooms in general are
decreasing in intensity (Larson et aJ., 1975).
Shagawa Lake has still not returned to its pre-cultural !imnological
and trophic status as judged by the sediment record, and phosphorus, entering
the lake from profundal sediments, produces large algal blooms in some years.
Nevertheless, the trend is towards less eutrophy and further changes can be
expected as the nutrient influx decreases.
In Burntside Lake the increase in hematite silt is more gradual than
at Shagawa Lake. If the Ambrosia rise is taken as 1898, the average sedimen-
tation rate from that time to the present is 0.2 em per year. This is less
than half the average sedimentation rate for Shagawa Lake during the same
time interval (Figure 15, and Bradbury and Waddington, 1973). Ihe lower
sedimentation rate partly reflects the lower productivity of Burntside Lake,
and partly the fact tnat the core came fiom a basin slope rather than its
center. Unfortunately the age of the bottom of the Burntside Lake core is
not known, and it is not possible to calculate pre-settlenient sedimentation
rates. Hven though the same diatom species are found throughout the core
(Figure 11) and suggest a general similarity between pre- and post - settlement
limnology, it is doubtful that the average sedimentation rate-.-, of the post-
settlement period can be applied to the pre-sett]ement levels,
The diatom stratigraphy of Burntside Lake suggests that it has been
limnologicaUy different from Siagawa Lake for a long time. The dominant
species are Cyciotclla g^lomerata and Tabellaria flocculosa, Suhdominants
are Fragilaria cmist_riien_s v. venter, f~_yc l_ot_e ]:] a kutzii\j^iari_a. Acluiant_he_s_ spp..
and Mclosira spp. In general the diatom flora of Burntside lake- is very
similar to that of Meander and Dogfish Lakrs, largely undisturbed wilderness
lakes about 30 km to the northwest (Bradbury et al., 1973).
The pre-sett1ement diatom stratigraphy in Burntside Lake is character-
ized by two zones (103-80 cm am! 42-2? -, m) where C_yc_lotel_ 1 a _gj_fiiiiera_ta is
less frequent and is replaced bv higher percentages of MeJosrra i_t_a]_i_c_a_ spp.
subarctica, Cyclotella kut?ingianu v. radiosa, and Frajalaria construens v.
venter (Figure 11).
Much remains to be learned about the habitat and ecological preferences
of all these species, j^beJ_J_ari.a flocculosa characterizes oligotrophic lakes
in several parts of the world rSfockner, 1971), and it occurs in both
35
-------
-V
^
_<°
.o-
DEPTH
(cm)
,- 0 -i
- HO -
- 20 -
30
- 40
- 50
- 60 -
- 70 -
- 80 -
- 90 -
- ^30-
0 I 4
15
0 5 10 ^5 20 25 30 35 40
units x-IO'Ycm /yr
Figure 13 Influx of microfossil types for Shagawa Lake (Bradbury and Waddington,
1973).
36
-------
planktonic and benthic habitats. Its wide distribution, however, suggests
that it is a eurytopic species (Stoermer and Yang, 1970; Bradbury, 1975).
The distribution of C_^ glomerata is not well known, although it is
generally considered a planktonic diatom of mesotrophic to eutrophic lakes
(Sreenivasa and Duthie, 1973; Huber-Pestalozzi, 1942). Alive, C. glomerata
is recognized by its chain-like filaments, but after death and sedimentation
or after acid cleaning, the chains break apart and the individual cells
appear very much like those of (]_._ stelligera, particularly C^ stelligera v.
tenuis. The density of marginal striae separates the two species for the
most part (Plates 1 and 2), and if this distinction were consistently made
the distribution of C_._ glomerata might be much larger and would extend to
the very oligotrophic lakes of northern Minnesota. For example, in an
earlier report (Bradbury _et_ a 1. , 1975), C_._ stel ligera was stated to dominate
the sediments of Meander Lake, St. Louis County, Minnesota. On reexamin-
ation, the dominant Cyclotella species more closely resembles (.]_. glomerata,
although C_._ stelligera is present as well.
In Meander Lake, C. glomerata makes up about 40% of the surface-
sediment diatom assemblage. The sediment contains approximately 40 x 10
frustules of this species per gram dry weight, yet it did not dorinate the
limnetic plankton during the open-water season of 1972 (B. Speziale, written
commun., 1975). Its distribution in Meander Lake seems to be related to
turbulence, when other diatoms of littoral and benthic environments enter the
plankton. Bright (1968) also reported C. glomerata from benthic habitats of
a variety of Minnesota lakes, some of which are rather productive (water
conductivity 200-400 ymhos/cm).
Cyclotella stelligera is considered both a planktonic diatom (Stockner,
1971; Merilainen, 1971) and a meroplanktonic (opportunistically planktonic)
that spends some time in the littoral zone (Huber-Pestalozzi, 1942). Even
though it can dominate the profundal sediments of oligotrophic lakes
(Stockner, 1971) it is not always found in abundance in corresponding
plankton samples (Schindler and Holmgren, 1971). It was common in the
littoral periphyton (especially at a depth of 1 m on glass slides) in Lake
240 in northwestern Ontario in early May, 1969 (Stockner and Armstrong,
1971). Merilainen (1971) suggested that this species inhabits the deeper
zones of the mixolimnion of meromictic Lake Vclkiajarvi, Finland. It is
reported in the plankton of meromictic Green Lake, Fayettevil]e, New York
(Culver and Brunskill, 1969), where it also dominates the laminated profundal
marls. Paerl et al. (1974) reported a massive bloom of C. stelligera in the
spring of 1973 in Lake Tahoe, California-Nevada. Huber-Pestalozzi (1942)
listed C. stelligera as a littoral diatom that sometimes becomes planktonic,
and current information supports this generalization.
However, the likelihood of taxonomic confusion between (_._ glomerata
and C. stelligera (particularly the smaller varieties) casts some doubt on
validity of habitat and nutrient requirements for these species as reported
in the literature. The colonial growth form of C__. glomerata seems appro-
priate for a planktonic existence, or at least a meroplanktonic existence.
Planktonic diatoms require limnetic nutrients, and it is not surprising
that C_._ glomerata is recorded from the plankton of eutrophic and mesotrophic
37
-------
PLATE 1. LIGHT MICROGRAPHS OF CTO^TELLA STELL1GERA CL.
& GRIJN. AND CYCLOTIT'l.MSRATA "BACHMANN.
EURNTSIDE LAKE, 0-~0 . 3 CM.
1. Cyclotella stelligera
2. Cyclotella stelligera
3. Cyclotella stelligera
4, CyclotelLa stelligera
5 . Cyclotel L_a stelligera
Cell diameter = 10 ym, 9 striae/10 jjm
of circumference.
Cell diameter = 10 ym, 9 striae/10 ym
of circumference. Same specimen as 1.
Cell diameter = 13 ym, ]1 striae/10 ym
of circumference.
Cell diameter = 9 ym, 10 striae/10 ym
of circumference.
Cell diameter - 7 ym, 12 striae/10 ym
of circumference.
6. Cyclotella glomerata
7. Cyclotella glomerata
Cyclot_el_la glomerata
Cell diameter ~ 6 ym, 13 striae/10 ym
of circumference.
Cell diameter = 6 ym, 14 striae/10 ym
of circumference.
Cell diameter = 5.5 ym, 17 striae/
10 ym of circumference.
38
-------
\' /
V
5
8
Plate 1
-------
PLATE 2. SEM MICROGRAPHS OF CYCLOTELLA STELLIGERA CL. eT GRUN.
AND CYCLOTELLA GLOMERATA BACffilANN. BURNTSIDE LAKE,
40.5 CM. Scale = 1 prn
1. Cyclotella stelligera. Cell diameter = 8 ym, 11 striae/10 ym of
circumference. The internal view of this and the following
specimens illustrates the striae characteristics. Note that
this individual does not have a central stellate pattern of
striao (Lowe, 1975).
2- Cyclotella stelligera. Cell diameter = 7 ym, II striae/10 ym of
ci r;ui iference. Note presence of central stellate arrangement
of striae.
3. Cyclotella stelligera. Cell diameter = 8 ym, 11 striae/10 ym of
circumference.
4. Cyclotella glomerata. Cell diameter = 4.5 ym, 20 striae/10 ym of
circumference. Note the short, interposed striae on this
specimen. These can also be seen on the specimens in Plate
1, and may be a potential character for separating C.
glome'rata from small varieties of C. stelligera.
40
-------
'late I1
41
-------
lakes (Out hie and ^i-'en i vasa, 19/lJ. Perlup--- .p ; i ;_'u' i .> >p.i-.- li'..>-~ '
_gj_(5mejratci remains jlose ic the nut~i<.nt rich bo Tr:r, ,p.] ; -, oil!;. c i >t ->-\ l;urcv
to the Limnetic re?,LOT and 1 tic prnfiind.il sedime
Icnce. This nay he the case in Me-' r,dc r '-il-o, v,
became a significant representative of fir.- |)lru
he fore therm! s;~r!t fjc-ttion i? c t ;iol Lshed
' '1 are b'isic.'lly siinJiai, -, I though . o-u
Cyclotel] a kut :;ngiu_'Ki i > fr>.-queai '; ido.if.fiod n-
oligotrophie Jakes, .ird occasionally IT i -; found 'r : \ ;
Experimental Lakes Vo:; of northwestern Oirtari-- ^TOL'-.'
dominate only in one ;{ trie If Ld-.es ho -'tud.'!. !!1,!L'"-!
large, exposed Lak:- ,>f very lou prodiu^rii !> ^r.'. ge:i.
sediments (Schindier 19"rL; Sc.hip.dler and ;.->; r ;re!, , i'1"!
kli t_z i.ngi ^r a is cons i ae red a bcnt}n. 01 I'ttor, ;; ! ,.
1912; >kv.der and lynui. 196^), but ui !;.r;:, . -:k,- u
as in Lake Michigan Stt^^riner 'ind Vni;', I'1 '''.. i; . - ',
tant of streams and other flo,;i-:o ,.,;:tf-rs ho.-:i ;;, r
°^ £JL kj'rtzingiana m^ - n i ;o Deported, in r!.c ^e-''>. p"
particularly Lake Store Vik ' ingcr. a:1.,! \ ^^ ''!<: 1 :j. i>;
39'; respectively } {":':-r; I ai i.en, 19"! !, and '
abundant in the sedi '.i---;it s o; i'-r.-en !,arO, i -y, ;
Lake in Ontario also cont,-J-i.^ 1'i t >',o iui:i'lv;-.% (
Duthie, ]9"?!, as do.-- L .we i.-'Sal... fake M; ;
not unk])ov;n fron> the S'-H! i r;rn ts oi' li.L'l.tiv .
Tlie aval la''i 1 it; of -i'rtr <\-^ 'J--~> h.-nthonii- >
ch'"j racteri rat ion o f ru.-rorjankton.jc diai.'ps d
neasurements ,ir*? :r,nde for limr.etie ';:, a>
only occa.s i on'il i\ relev.'Tir :o niei'O "! a .',' :-r.'.
Inwiolegieal niO cui .'are -tnd-es o ; 'n ;. J
rv. .".,ui rejnc'nt s ii.iif 10 " !/cen made +u ; > - n ..
as £^ £ii:iILi.;i .
depth of approxiniat--iy ]*, -n. Hou- >T :i .'"-
and witli varieties of J-j ae'J ! "-r_i.a ^^ MI ^ tr^icj;-.
are of mumr i rrTorta.i ,:e, Af tins -.anic le -.
reported high levels of sediMentary clnor'.;
tary carotene, id- uliicli tlicy inte^p '(^te; .'-
ciated witi; eli'ia^'r jn-,.- ir-ra^ion ;-"r.v^-t 1".
witi; the aiumda.'.: of i'. cr^r rnens i s ; i d i '<
lakes (.Ttoormer art s''r'^. !'""('; at thrit 1- A
In '->r,nfj-'h iak?, ''irvtrii! s, Cyc I ot i 1 I'1
8c cm of the las e- sc J : ment pivfilt- '-Uk'kd
and Sten.'ianodi seus j.r.'t -.!!' '"'veinieli' '"
-------
\t the- hot turn of K-hre's f!9f._-'' kunebm «, profile f requeue! es ,
kiit/'ingiana mav be ;.-- high i- >';'!" but at the top j* faJli to !;'' as Mc-_lq_si_ra
g_ranu]atn bc.cc ;pe< i ii( ..iomi..;;:)! J;a?om. I'ehro fl-)(> ", iiiterpretta these
changes a-- a r rvie i r i ^n from sligj-.* o] * got ropm fC. k_utz_inj;unja dominance; to
marked out repiiv i' ^nd
F->agUjri_a crotciifr is f^tark, 10" | ) . Ibis n^.-cmblage GXJ sted during the
Quercv.s-Graniiiivac- \rt cm: s i a ami vjuervus-Ost rya pollen zones (ca. 8,000-2,000
years ago), wht-n the 'liniasc' ua- thought to bo warmer and driej than today.
i'resiiiiiab 1\ j ir, i .',ik ec' ''irlni 1 ci ex ir'.;ii uiaus assc-ciated with sa vnitiah-J J ke
vegetation durinj: rh! t i rm ao' ". 111 od 4or this assemblage (Brru-uiy, 197S).
Jhese oxiiiupJcs indieart, riiat ^y_eJotella kut^i7i_g_iaiia is not restricted
to o] i got tophi e Jake-.. It r.ppe.-t:- to be a eur\'topic diatom thai can increase
v\ i 1 h 1 i x?\ i on -, \ (. i'.aen i .
I'he ecology i.f Melo^if .1^ ii-.a Shi:. s_ubarc_t_.i_ca is somewhat better
kno.^n tiuougii trie studies oJ" I u'd ;!i)54j who (Considered it a pianktonic
diatom requiring tarhulcTil eonditiorss tc- remain suspended. 11 -,ecms to pre-
fer aeithei stronglj. ol i got ropn i > nor st'ongi) cut r opine uatei', and it is
able to peisi'-t i;, J'enlhie environments for considerable periods of time
ant i l :t is "e sn^j tMided !>}' turi^i^nec to the limnetic env'iromne'it .
fragiiaria i oio'. rucnc- \' x'c-ntej1 ; s a vcr> v\idcspread did'"]" that com
monly resides in or ,aear the littoral ; one of small lakes 01 in ., light 1>
dee])ei' walci- *.> f l-'i»r ia'kes i i:r'adbur>", 1 '* ~".>, Jo i'gensen , J 9-Kv', . Its distri-
butiu;. in lakes in ."'iiinesota il I'j^t/l, ]'.!i,^i and Finland (Moldei and 1'ynni,
i9/')j niUieates ih.'l t is fol'. ran! ot' wide -ar'ety of \\atir *\'pes and
flUl J . i !' t (. lard J t 1 O'l.'
'Jhese genej'a I ecological i omrnents allow a tt-ntative interpretation of
the pro-set t 1 ement pa i eol i mnoJc.s i, ai eients in Burnt side Lake, The fact that
l'rj\S:::J-'1J.^'J construcns v. vcnt_cj , f'yt ;ute!l_a kilt zi n^iana and v. radiosa. and
Mje_losi._ra italjc_a ssj). subaictic\. twice partly jepiace a dominance of
Cvclo^tellj _g_lomerata ;rif,rir" 11; suggests 0!i° or' 'iiore basic controlling fac-
tors, perhaps related to LJimati i 01 hydrologr. changes outsidt the lake.
r-a^n; thar; to randct:, f i net u;; t i oa> betva "ii separate diatom pop(, i at i ons .
The-jo pulses mosj likely tc-iate i ' an exf'ansion oi the littora1 and subiit-
toral diatom common: t j es oi Purnt-ide kak-'-. or at ieast a gi'catc; input from
them. i'he in:re-'S" i?: diat ::: clt..-,eiy associated i.'ith the litt'ia! environ-
-------
merit occurs at the expense of planktonic diatom inputs, chiefly identified by
the distribution cf Cyclotella glomerata, which shows a large pre-settlement
increase between 85 and 15 cm. It is noteworthy that other planktonic diatoms
frequently associated with moderate limnetic enrichment, such as Fragilaria
crotonensis ,Asteriono_lla formosa, and species of Synedra, increase in concert
with C. glomerata. Tie stratigraphic changes for these species are not so marked
as that of C. gloirera_ta_, but they are clearly significant (Figure 11). It is
also important to note that these species and C. glomerata regain their domi-
nance during nost-settlement times (after the Ambrosia rise, 'igure 11), when
lumbering and cultural activities would be expected to maintain jn increased
nutrient loading of Burntside Lake.
The littoral pjlses (identified principally b\ the distribution of
Fragilaria construens v. venter and Cyc lot el la kiitjnjigi ana v. raciosa) suggest
either lower water l3vels, with an increased sedimertation of littoral species,
or increased oligotrophy, with a diminished importance of planktonic and rnero-
planktonic diatoms. Higher water levels and slight enrichment could account
for the observed diatom distribution between 85 and JS cm.
Profiles of sediment mineralogy and chemistry only approximately reflect
the changes in pre-s3ttlement diatom stratigraphy. Hicgenic opal (Figure 11)
is somewhat higher ii the zone where C. glomerata is most abundant (85-45 cm),
supporting the intenretation of greater diatom productivity during this time.
Hematite silt, and to a lesser extent opal phytoliths, are also more abundant
at this time (Figure 11) and might relate to general!}' higher water levels from
increased precipitation, which could have resulted in increased transport of
nutrients to Burntside Lake via tributaries such as the Dead River (Figure 1).
The profiles for calcium and for elastics suggest 'rcreased input of littoral
sediments for the lower pulse of littoral diatoms (105-85 cm) but not for the
upper one (42-22 cm). Other sediment profiles (phosphorus, tannin-1 ignin, and
organic matter) show gradual stratigraphic charges, but it is not clear how
(or if) they relate to the diatom stratigraphy. Furthermore, the lack of an
absolute time scale makes limnological interpretation of such changes very
speculative.
However, the tine over which the stratigraphic changes in diatoms took
place can be suggested in a general way by analogy to Shagawa Lake, where a
C-14 date at the bottom of the core provides information about sedimentation
rates. The pre-settlement sedimentation rate in Shagawa Lake is about 0.7
mm/year, so about 15 years would be required for 1 cm of sediment to accumulate.
The Shagawa Lake pre-settlement sedimentation rate is probably higher than that
for Burntside Lake, because the latter has beer, less productive and the Burnt-
side Lake coring locality ("igure I) was not in the deepest part of a basin.
Nevertheless, by assuming sedimentation rates of about the same magnitude for
Burntside Lake, the changes in diatom stratigraphy become several hundred years
in length. Possibly they correlate in some way with climatic changes such as
the "Little Ice Age" (ca. 1550-1850 A.D.), whose climatic effects are suggested
by the charcoal stratigraphy of nearby Lake of the Clouds (Swain, 1975). How-
ever, speculation about the limnologic and climatic mechanisms for pre-settle-
ment diatom stratigraphy are premature without an absolute time scale for the
Burntside Lake sediments.
44
-------
Tentative correlation between the Burntside Lake pre-settlenient diatom
profiles and the Shagawa Lake pre-settlement profiles remains a topic for
future study. The two peaks of Fragilaria capucina (110-90 cm and 50-35 cm)
in the Shagawa Lake diatom stratigraphy might indicate an increase in lit-
toral diatom populations similar to those suggested for the Burntside Lake
core, and the flow-through characteristics of the two lakes could easily link
the diatom stratigraphies to the same cause. However, their correlation also
requires an independent time scale for the two cores.
Increases in opaline phytoliths, hematite silt, and Ambrosia pollen
signify that the top 18 cm of the Burntside Lake core were deposited in the
late 1800's, probably about 1890. The opaline phytoliths probably reflect
increased erosion (and possibly increased herbaceous vegetation) in the
Burntside Lake area and thus represent events related to the Ambjrp_s_i_a rise.
Dramatic limnological changes do not coincide with the beginning of
settlement, however. The increase in relative frequency of Cyclotella
glomerata began before the Ambrosia rise, possibly as a result of climatic
factors, as mentioned earlier. Immediately after the Ambrosia rise, diatom
populations remained comparatively stable, and no significant changes are
recorded until the upper 5 cm, where Asterionella formosa increases to
unprecedented levels.
Asterionella formosa is a widespread planktonic diatom that occurs
in a wide variety of trophic conditions. It occurs in the more productive
lakes of the English Lake District (Lund, 1949), and stratigraphic studies
in Lake Windermere show that Asterionella formosa becomes dominant probably
as a consequence of human settlement in the drainage area (Pennington, 1943).
This is in accord with the hypothesis of Kilham (1971), who postulated that
A. formosa is more successful than other species in eutrophic but low-silica
environments.
The distribution of A. formosa in Burntside Lake very likely relates
to a slight enrichment of the water caused by settlement activities along
the lake shore. Nutrients such as phosphates and nitrates supplied by
lakeside cabins would seem the most obvious cause, because cabin building
in this area, which has been increasing since the 1920's and particularly
since 1945, is a comparatively late phenomenon. If the hematite- rise (15 cm)
in Burntside Lake is taken as 1888, and sedimentation since that time is
assumed to be about constant, the increase in Asterionell^a formos_a at 5 cm
would date to 1949, approximately coinciding with both an increase in cabin-
building activities (post-1945) (M.L. Heinselman, written commun., 1976)
and with the introduction of phosphate detergents (1948) (Bradbury and
Waddington, 1973).
The most noteworthy aspect of the Burntside Lake post-settlement
diatom stratigraphy is that even though this lake is generally regarded as
oligotrophic and unaffected by human settlement, the present-day plankton
diatom community with large spring and fall maxima of Asterionella formosa
(Fig. 5) is clearly a recent, and in this case probably man-caused phenom-
enon. It emphasizes the sensitivity of diatom populations to environmental
changes, and how easily the delicate limnologic balance of a natural lake
can be changed.
45
-------
REFERENCES CITED
Armstrong, F.A.J., and Schindler, D.W., 1971, Preliminary chemical charac-
terization of waters in the Experimental Lakes Area, northwestern
Ontario. Jour. Fisheries Research Board of Canada, Vol. 28, no. 2,
p. 171-187.
Behre, K-E, 1962, Pollen- und diatomeenanalytische Untersuchungen an
letztinterglazialen Kieselgurlagern der Liineburger Heide. Flora,
Bd. 152, p. 325-370.
Bradbury, J.P., 1975, Diatom stratigraphy and human settlement in Minnesota.
Geol. Soc. America Spec. Paper 171, 74 p.
Bradbury, J.P., Tarapchak, S.J., Waddington, J.C.B., and Wright, R.F., 1975,
The impact of a forest fire on a wilderness lake in northeastern
Minnesota. Verh. Internat. Verein. Limnol. Proc., vol. 19, p. 875-883.
Bradbury, J.P., and Megard, R.O., 1972, Stratigraphic record of pollution in
Shagawa Lake, northeastern Minnesota. Geol. Soc. America Bui 1 ., vol.
83, p. 2639-2648.
Bradbury, J.P., and Waddington, J.C.B., 1973, The impact of European
settlement on Shagawa Lake, northeastern Minnesota, p. 289-307 in
Birks, H.J.B., and West, R.G. (e^s.), Quaternary plant ecology.
Blackwells, Oxford, 326 p.
Brice, R.M., and Powers, C.F., 1969, The Shagawa Lake, Minnesota, eutrophi-
cation research project. Proc. Eutrophication-Biostimulation Assessment
Workshop, Berkeley, California, 1969, p. 258.
Bright, R.C., 1968, Surface-water chemistry of some Minnesota Jakes, with
preliminary notes on diatoms. Univ. Minnesota Limnological Research
Center Interim Report No. 3, 59 p. (multilith).
Culver, D.A., and Brunskill, G.J., 1969, Fayetteville Green Lake, New York.
V. Studies of primary production and zooplankton in a meromictic marl
lake. Limnol. Oceanogr., vol. 14, p. 862-873.
Gushing, E.J., 1964, Redeposited pollen in late-Wisconsin pollen spectra
from east-central Minnesota. Am. Jour. Sci., vol. 262, p. 1075-1088.
Crshing, E.F., and Wright, H.E., 1965, Hand-operated piston corcrs for lake
sediments. Ecology, vol. 46, p. 380-384.
47
-------
Dean, W.E., 1974, Determination of carbonate and organic matter in calcareous
sediments and sedimentary rocks by loss on Ignition. Jour. Sed.
Petrology, vol. 44, no. 1, p. 242-248.
Duthie, H.C., and Sreenivasa, M.R., 1971, Evidence for the eutrophication of
Lake Ontario from the sedimentary diatom succession. Proc. 14th Conf.
Great Lakes Research, Internat. Assn. Great Lakes Res., p. 1-13.
Florin, M.-B., 1970, Late-glacial diatoms of Kirchner Marsh, southeastern
Minnesota. Nova Hedwigia, Beihefte, Heft 3L, p. 667-746.
Gorham, E., and Sanger, J., 1967, Fossilized pigments as stratigraphic
indicators of cultural eutrophication in Shagawa Lake, northeastern
Minnesota. Geol. Soc. America Bull., vol. 87, p. 1638-1642.
Heinselman, M.L., 1971, Restoring fire to the ecosystems of the Boundary
Waters Cance \rea, Minnesota, and to similar wilderness areas. Proc.
Tenth Tall Timbers Fire Ecology Conference (Frederictoi, New Brunswick,
1970), p. 9-23.
Heinselman, M.L., 1973, Fire in the virgin forests of the Boandary Waters
Canoe Area, Minnesota. Quaternary Research, v. 3, p. 329-382.
Hixon, W.W., and Co., 1916, Plat book of the state of Minnesota, Rockford,
Illinois.
Huber-Pestalozzi, G. , 1942, Das Phytoplankton des Susswassers. I_n
Theinemann, A., Die Binnengewasser, Band XVI, TeiL 2, 2. Halfte:
Stuttgart, 549 p.
Hustedt, F., 1930, Bacillariophyta (Diatomeae). Jji Pasher, A., (ed.), Die
Susswasser-flora Mittel-Europas. Jena, Gustav Fischer, vol. 10, 466 p.
Jorgensen, E.G., 1948, Diatom communities in some Danish lakes and ponds.
Kongelige Danske Videnskabernes Selskab, Biologiske Skrifter, Bind V,
Nr. 2, 140 p.
Kilham, P., 1971, A hypothesis concerning silica and the fresh-water plank-
tonic diatoms. Limnol. Oceanogr., vol. 16, p. 10-18.
Larsen, D.P., Malueg, K.W., Schults, D.W., and Brice, R.M., 1975, Response
of eutrophic Shagawa Lake, Minnesota, U.S.A., to point-source
phosphorus reduction. Verh. Internat. Verein. Limnol. Proc., vol. 19,
p. 884-892.
Larsen, D.P. and Malueg, K.W., 1976, Limnology of Shagawa Lake, Minnesota,
prior to reduction of phosphorus loading. Hydrobiologia, vol. 50,
p. 177-189.
Lowe, R.L., 1975, Comparative ultrastructure of the valves of some Cyclotella
species (Bacillariophyceae). Jour, of Phycology, vol. 11, no. 4,
p. 415-424.
48
-------
Lucas, R.C., 1964, Recreational use of the Quetico-Superior Area. Lake
States Experiment Station Publication, U.S. Forest Service Research
Paper LS-8, 50 p.
Lund, J.W.G., 1949, Studies on Asterionel la I. The origin and nature of
the cells producing seasonal maxima. Jour, of Ecology, vol. 47,
p. 389-419.
Lund, J.W.G., 1954, The seasonal cycle of the plankton diatom
italica ssp. subarctica. Jour. Ecology, vol. 42, p. 151-179.
Machamer, J.F., 1968, Geology and origin of the iron ore deposits of the
Zenith Mine Vermilion District, Minnesota, Minnesota Geol . Survey,
Spec. Publ. SP-2, 56 p.
Malueg, K.W., Larsen, D.P., Schults, D.W., and Mercier, H.T., 197S, A six-
year water, phosphorus, and nitrogen budget for Shagawa lake,
Minnesota. Jour. Environmental Quality, vol. 4, p. 236-212.
Megard, R.O., 1969, Algae and photosynthesis in Shagawa Lake, Minnesota.
Univ. Minnesota, Limnological Research Genter Interim Report no. 5,
20 p.
Megard, R.O., 1973, Rates of photosynthesis and phytoplankton growth in
Shagawa Lake, Minnesota. U.S. Env. Prot . Agency, Ecol. Res. Series
EPA-R3- 73-039, 70 p.
Merilainen, J., 197], The recent sedimentation of diatom frustules in four
meromictic lakes. Ann. Bot . Fennica, vol. 8, p. 160-176.
Molder, K. , and Tynni , R. , 1968, Uber Finnlands rezente und subfossile
diatomeen II. Bull. Geol. Soc. Finland, vol. 40, p. 151 -l^O.
Paerl, H. , Thomson, R. , and Goldman, G.R., 1974, Microbial interactions and
detrius formation during a dominant diatom bloom at Lake Tahoe,
California-Nevada. 19th Congress International Assn. Limnol (SIL),
Winnipeg, Canada, vol. 19, p. 826-834.
Patalas, K. , 1971, Crustacean plankton communities in forty- five lakes in
the Experimental Lakes Area, northwestern Ontario. Jour Fish. Res.
Bel. Canada, vol. 28, p. 231-244.
Pennington, W., 1943, Lake sediments: the bottom deposits of the north
basin of Windermere, with special reference to the diatom succession.
New Phytologist, vol. 42, p. 1-21.
Sanger, J.L., and Gorham, EviJle, 1972, Stratigraphy of fossil pigments as a
guide to the postglacial history of Kirchner Marsh, Minnesota.
Limnology and Oceanography, vol. 17, no. 6, p. 840-864.
49
-------
Schindler, D.W., 1971, a hypothesis to explain differences and similarities
among lakes in the Experimental Lakes Area, northwestern Ontario.
Jour. Fish. Res. Bd. Canada, vol. 28, p. 295-301.
Schindler, D.W., and Holmgren, S.K., 1971, Primary production and phyto-
plankton in tne Experimental Lakes Area, northwestern Ontario, and
other low-carbonate waters, and a liquid scintillation method for
determining ^C activity in photosynthesis. Jour. Fish. Res. Bd.
Canada, vol. 28, p. 189-201.
Schults, D.W., Malueg, K.W., and Smith, P.O., 1976, Limnolog Leal comparison
of culturally eutrophic Shagawa Lake an
-------
TECHNICAL REPORT DATA
,1'icaic read Intuition!! on the tci'crsc belon coinplc ting)
T NO
EPA-600/3-78-004
AND SUBTITLE:
A Paleolimnological Comparison of Burntside and
Shagawa Lakes, Northeastern Minnesota
13 RECIPIENT'S ACCESSION-NO
5 REPORT DATE
January J97B
6 PERFORMING ORGANIZATION CODE
-;.i. i~Hb"ms)
J. Platt Bradbury
PI HPORMING ORGANIZATION NAME AND ADDRESS
Iimnological Research Center
University of Minnesota
Minneapolis, Minnesota
8 PERFORMING ORGANIZATION REPORT NO
Limnological Research Center
Contribution ^155
To ~FROG"R AJvTtTF ~MEN"T "NO
_T_BA031_
|i"i CONTRACT/G'RANT NO
P.O. f/04J!PO~0605
I? SI ONSORINC AGENCY NAME AND ADDRESS
US. Environmental Protection Agency
(orvallis Environmental Research Laboratory
200 S.W. 35th Street
Corvallis, Oregon 97330
b SUPPLE ME NTARY NOTES
r,
13 TYPE Of REPORT AND PERIOD COVERED
1 O/ 74 J 2/75]
14. SPONSORING AGFNCY CODE
FPA/600/02
1f> ABSTRACT
The paleolimnological records of Burntside and Shagawa Lakes in Northeastern Minnesot
reveal that these two adjacent lakes have been 1imnologically distinct for many years
prior to the late 19th century activities of white men that polluted Shagawa Lake.
Although both lakes occur within the same vegetation type and share much of their
water, the diatom stratigraphy of their bottom sediments indicates that Burntside
Lake was less productive in its natural state than Shagawa Lake. The causes for
this natural difference are not clearly known, but differences in relative size of
drainage area and in bedrock geology may be responsible.
Intensive white settlement around Shagawa Lake beginning in 1886 supplied nutrients
that increased its productivity and finally supported the massive blooms of blue-
green algae that characterize culturally eutrophic lakes. Burntside Lake was spared
such intensive eutrophication, but its diatom record shows that nutrients derived
from shoreside recreational cabins and related construction activity are increasing
the lake's productivity.
The results of this study show that paleolimnological studies may provide better
comparative information for lake rehabilitation programs than do biological and
chemical analyses of contemporary unpolluted water bodies.
DESCRIPTORS
Kt Y WORDS AND DOCUMENT ANALYSIS
h IDENTIFIERS/OPEN ENDED TERM?
Lakes
Limnology
Al gae
Diatoms
N STATEMENT
Release unlimited.
paleolimnology
eutrophication
'j SECURITY CLASS , This Report i
| Unclassified
120 SECURITY~CuASs7'-/'l« pagel"
\ Unclassified
COSATI 1 ichi''Group
06F
08H
21 NO OF PAGES
60
: PA Form 2220-1 (9-73)
51
------- |