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

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                                      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

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                                  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

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                                   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

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                                  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.

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                       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

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                               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

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                                                                    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

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                           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

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                                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	 .  ,

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                               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.

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                                   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

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                                                                  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).

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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.

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                            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

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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



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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 T—r"""""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

-------
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-------
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.

-------
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-------
      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

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              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

-------
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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

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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

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                                    Tannin - Ugnin
                                      as  Tannic
Organic     „,  ..     Biogenic _.    .      Acid       _
matter     Clastics     0^Q|   Phosphorus            Ca
                                                                      He™ttite  Phytoliths
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                                                                      elastic  sed  opal
            #   ^ ^ -\0" -\° x° ^
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      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

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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

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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

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    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

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  \' /
V
                                                       5
                                                      8
                         Plate 1

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  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

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'late  I1





  41

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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'  '"

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 \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-

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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

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      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

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                              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.
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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
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Bradbury, J.P., and Megard, R.O., 1972, Stratigraphic record of pollution in
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Bradbury, J.P., and Waddington, J.C.B., 1973, The impact of European
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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
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      Center Interim Report No. 3,  59 p. (multilith).

Culver,  D.A.,  and Brunskill, G.J.,  1969, Fayetteville Green Lake, New York.
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      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

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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

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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

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