A STUDY OF SEVERAL ASPECTS
OF TEMPERATURE AND SEC CHI VISIBILITY
IN INDIANA WATERS OF LAKE MICHIGAN
AN HONORS THESIS
SUBMITI'ED TO DR. THOMAS :tv:cCOMISH
•
by
STEVEN J. FERMI
BALL STATE UNIVERSITY
MUNCIE, INDIANA
MAY, 1973
~pCdl
The~. :':_~
TABLE OF CONTENTS
PAGE
TABLE OF CONTENTS
LIST OF FIGURES
i
ii
INTRODTJCC]'ION
1
DESCRIPTION OF TRE STUDY AREA •
1
YiliTHODS AND MATERIALS •
4
RESULTS AND DISCUSSION
5
Temperature • • • • • • • • • • • •
Surface tempera ture • • • • • • •
Tenperatures below the surface
Secchi visibility
• • • •
Station differences
Yearly changes • • • •
•
5
5
22
25
25
35
SUMMPRY AND CONCLUSIONS
38
LITERATUllli CITED
40
APPENDIX
41
LIST OF FIGUPES
Page
J'igure
1.
2.
3·
4.
r::
/.
6.
Inciana -waters of Lake Hichigan shmvir:.g
established 5, 10, 15, and 18 m stations on
Michigan City (M), B'~rn:= Ditch (B), and Gary
(G), Indiana transects . . . . . . . .
2
taytime surface tem}Jeratures at the 5m stations
en Michigan City, Burns Ditch, and Gary
transects for 197C', 1971, a::ld 1972.
6
Daytime surface temperatures at the 10m
rotations on :r>':ichigan City, Burns Ditch, and
Cary transects for 1970 and 1971. .
7
Daytirrie surfa(:e temperatures at the 15m stations
un Michigan City, Burns Ditch, and Gary transects
for 1970, 1971, 1972. . . . . .
. . . . .
8
Daytime surface temperac=,ures at the 18m stations
on Michigan City, Burns Ditch, and Gary transects
for 197C and 1971. . . . . . . . . . . . . .
9
~:emperatures
at the surface and 1 and 5 rn belm-l
the, surface at tr.e 5rn station at Michigan Ci ty
in 197C, day and night.. . . . . . . . . . . . .
7.
~:emperatures
8.
~~emperatures
9.
10.
11.
12.
13
at the surface and 1 and 5 III belowthe surface at the 15m station at Michigan City
~.n 1972, day and night.
. . . .
at depths of 10 and 15 m at the 15m
station .s.t Michigan City in 1972, day and night.
15
Daytime surface temperatuy·:='s of the 5, 10, 15, '111.0. 18 m
~3tatio:1.s at Michigan City, Burns DHch, and GHry
:Ln 1970 . . . . . . . . . . . . . . . . . . . . .
16
Daytime surrace temperatures of the 5m stations
at ~lichi2:an City, Burns Ditch. and Gary fo::, 1970
Hnd 1971. . . . . . . . . . . .
. ....
18
D&ytimf: surface temlieratures of the 10m sta'tlons
at Michigan City, Burns Ditch, and Gary for 1970
and 1971. . . . . . . . . . . .
. ....
19
Daytime surface tempe-ra'tures of the 15m stations
at Michigan City, Burns Ditch, and GClry for 1970
and 1971. . . . . . . . . . . . . . . . . . . . .
20
ii
Page
Figure
.
13.
14.
15·
10.
17.
18.
19·
..
20.
Daytime surrace temperatures of the 18m stations
C1t MichigAn City, Eurns Ditch, and G&ry for 1970
and 1971 . . . . . . . . . . . . . . .
21
Daytime temperatures at Michigan City in 1972
at depths of 0, 1, and 5m for the 5m station
and depths of 0, 1, 5, lu, and 15 for the 15m
station. . . . . . .
23
Secchi visibility of the 5, 10, 1), and 18 TIl
stations at Mjchigan City, Burns Ditch, and
Gary for 1970. . . .
........ .
2b
Spcchi visibility of the 5, 10, 15, and 18 ill
statlons at Michigan City, Burns Ditch, and
Gary for 1~'(1. . . ,
........ .
27
Secchi visiDil.Lty of th'2 5, 10, 15, 1'1l1d 18
stations at Michigan City Tor 1972 . . . .
28
ill
Secchi visibility of Michigan Clty. Burns Ditch,
and Gary at the 5, 10, and IS m stati·,ms.
31
Secchi visibility for 1970 of Mic~higan City, Burns
Ditch, and Gary at the 18m station 2nd for 1971
of Michigan City, :Surns Ditch, ana Gary at the 5
and 10 m stations . . . . . . . . .
32
E;ecchi visibility for 1971 of Michigan City, Burns
Ditch, and Gary at the 15 and 18 m stations.
33
21.
E;ecchi visibi:i ty of 197C, 1971, and 1972 at Michigan
City for the 5, 10, and 15 ill stations . . . .
22.
~)ecchi visibility of 1970 and 1971 at Michigan City
for the 18m station. . . . . . . . . . . . . .
iii
37
INTRODUCTION
Temperature profiles were taken at stations of depth 5, 10, 15, and
18 meters on transects near Michigan City, Burns Ditch, and Gary in Indiana waters of Lake Michigan.
The study was conducted in the months of
May through October in 1970 and 1971 by greduate students investigating
zooplankton population dynamics under the direction of Dr. Thomas
McComish.
In 1972 only the Michigan City transect was studied.
The
profiles eonsisted of the tempereture measured in one foot intervals from
the surfaee to the bottom of each station.
sured at the stations under study.
Secchi visibilty was also mea-
The data were organized in several
ways, not only to get a clearer look at the actual temperature and secchi
conditions for the three years, but also to see whether any obvious
changes occurred in temperature or secchi visibility over the years of
the study or among stations or transects.
Temperatures vrere also exsmin-
ed to see whether any changes occurred from day to night.
STUDY AREA
The area in which this study was conducted is exactly the same as
that described by Johnson (1972) as follows:
Three transects were established in Indiana waters of Lake Michigan,
each with stations at depths of 5, 10, 15, and 18
ill
(Fig. 1).
The approx-
imate distances from shore were determined for each station (Table 1).
The Michigan City transect (M) base is located 1770m (5805.6 ft)
east of
,-
t:~e
point where the East Government Pier intersects with the shore.
It extends from the base location into Lake Michigan on a heading of 325
--I
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,. - 18m
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.-t
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..--- -
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'--. _____ 0-
,.-'--
....-
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"r-
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5m
II
.---') /../;-
./.--15m
/'
, . . .:::::-'::--/-'lO:rn
l-_./
-/
-~
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__-.-
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10000
_.-i
C
lOCOO
.1 -,
.
C'~(V\()'
r('('
),,)l)
)1).1_
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:{.
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t. • • • • •
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o
,
8'"7, 3C'
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- - - _'.....' .,,-..-1ifichicrm
'
Ha!llillon<1, East
-----------F---~--·\ jm _-------.j~~Little C8~lf'~~. ,:::--=----'.-~_
Chic8g0, Gary
';i:frnsWatenray
~
-"""--0:
20000
~Tc::'trJPoli tan Area
\
~ --~
Mcter:3
~ _ _ _~
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( - ,
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(,:
.......--',_
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lSe
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---
--._----_.
0:
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1
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---------
5000C
)
4cooo
11:;"(-'C
jv\)'
.------ -
1000;
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-
30000
-----_ ---_.
Statute Miles
5
7 . .. _SJ_ .-, 11
_
.
~.. - . . . . __..______
'J
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4
G
8
10
Cib050
13
.-J
12
1
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3
Table 1.
Approximate distance of stations from the base (shore)
of transects in the Indiana waters of Lake Michigan,
1970. (From Johnson, 1972)
Distance from base
Station/depth
Transect
Michigan ::::i ty
Burns Ditch
Gary
(m)
(m)
(miles)
5
420
0.26
10
SOO
0.50
15
2,050
1.27
lS
3,700
2.30
5
4So
0.30
10
840
0.52
15
4,300
2.68
18
8,700
5.40
5
320
0.20
10
590
0.37
15
1,020
0.64
18
14,160
8.So
4
degrees.
The base of the transect is on private land and the area on
both sidef3 of the transect has several scattered private homes.
The
nearest industry to the transect is an electric power producer, Northern Indiana Public Service Company, more than 2000 m (6560 ft) to the
west near the mouth of Trail Creek.
The Burns Ditch transect (B) base is located 90 m (295.0 ft) east
of the mouth of Burns Ditch in Burns Ditch Waterway.
Lake Michigan on a heeding of 350 degrees.
It extends into
The transect base is di-
rectly west of a large National Steel mill.
There are various indus-
trial and municipal inflows into the Calumet River and Burns Waterway
which eventually are released into the lake through Burns Ditch.
The Gary transect (G) base is located 180 m (591.4 ft) east of
the U. S. Steel Corporation canal mouth in Gary Harbor.
on a heading of 10 degrees.
It extenas
There has been extensive dredging in the
harbor and the first three stations are near the shore (Fig. 1).
is heavy
~~raffic
There
in the harbor area.
METHODS AND MATERIALS
Temperature profile data was collected with a Yellow Springs Instrument Company Telethermometer (model
(model 12(0) bathythermograph.
44
T D) and a Dittmore-Friemuth
Stations were located using a sounding
line or a fathometer (Triton Echo-Sounder, model F-850 type A; Raytheon,
model D E - 725 B) and by moving away from shore on a particular transect until the desired depth was reached.
sured with a standard model Secchi disc.
Secchi visibility was mea-
5
RESULTS AND DISCUSSION
Temperature
Surface
~remperature
Yearly changes in surface temperature were examined at each
station on the Michigan City, Burns Ditch, and Gary transects (Fig.
2 to
5).
In some cases interpretation of the graphs is difficult
because sampling was not done as frequently in one year as in another.
The main feature which stands out, however, is that the temperature
through the year is generally higher in 1970 than in 1971 at Burns
Ditch and Gary.
This can be seen at Burns Ditch by the fact that from
early July until mid-September the temperature was as much as 7 degrees
higher in 1970 than in 1971, except for the cold upwelling of 1970
(Johnson, 1972) which appeared on August 10.
In addition, the maximum
at Burns Ditch for 1970 of 25.5 degrees at the 15 m station is over 5
degrees higher than the maximum for 1971, which was 20 degrees and
occurred on June 16.
At the Gary transect the temperatures for 1970 were also above
those of 1971 for most of the summer, only falling below 1971 in October.
At Gary, however, the 1970 temperatures were not as far above the
temperatures in 1971 as at Burns Ditch.
The maximum in 1970 for Gary
of 23.5 degrees on July 31 was only 3 degrees above the July 18 maximum
of 1970.
At Michigan City the temperatures for 1970 and 1971 fluctuated
within a few degrees of each other most of the time, although figures
6
30
Michigan City,
surface, day
5m
/
/
?
~
J>- --- - - ..
,/
/
0'
j
10
OL---41----~---_r--~----T_--l
Burns Ditch, 5m
surface. day
---t.J
'-
\
/
J
'-01
~q"/~v--
20
4l
F-c
.BC11
I
J..
aJ
!
~ 10
C)
1
E-~
I
--~-------~-------t--
o
Gary,
2,)
~
surface. day
I
J.O
-------+------! --------1
5m
~/
I
r
1970 - - 1971-I 1972 -.- - - -
!
,o 'L~ _ _ _ _,,. . _.___«_____L. __________
_/. --~(::~.h
'. . ..L.'_~lr~
_
",
•
t
,
-."
r' r ~ ;
~)
.L '
p.
.. __ L _ _ __
()r~
~ \--'_
'(
30
an City, 10m
Miohig
~
day
surfaoe,
-
.---4/
/
~~
~~~~
-0--
.
f'-I
-o-~f
'"
~o
/
6
o
----
1
Burns Ditch, 10m
surface, day
I
Gary, 10m
surface, day
II
I
~'---.~~-~
-j
~.-o-~~ I
I
--0-
_
,
/
1
\
l
'-----A!rc~
-'--~:3E--P
____.l..l_ - : - : : - ..
Oc!'
8
30
Michigan Cit y, 15m
surface, day
20
10
o
daY~
Burns Ditch, 15m
surface,
,--...
c:.;
'--'
.. / ' \
20
...
0--
....
"
~
E
!T'
-
-
- -
--
__ _
--
'b
-I>-. "-..
0.:::::::::.:._________---0"'1)
'--
I
I
!
Q)
~ 10
~
Q)
~
+------1--
•
9
30
20
Burns Ditc h , 18m
surface, day
/
,,---.
u
.. ~ . ~
-!
-~~-- -~~J
20
~
+=5
<1l
k
CJ
It
10
I
(J)
EO'"'
--~--+-----
o
Gary, 18m
surf ace, day
:20
I
-1-1_ _ _,
j
---+--1 !
-
--------~".~~ I
I
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li
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1
OCT
•
10
4 and 5 show 1970 to be a little above 1971.
Temperature data for 1972
at Michigan City (Fig. 2 and 4) show that temperatures were generally
higher than both 1970 and 1971, at least after early July.
of
2~)
The maximum
degrees on July 24, 1972, is higher than any maximum for 1970 or
1971 by about 3 degrees.
In 1970 and 1971 temperatures did not rise to
their highest level until late August, as compared to late July in 1972.
In ad6ition to yearly changes in temperature, monthly changes in
temperature can be examined from figures 2 to 5 also.
For Michigan City
in 1970, temperatures gradually rose through June to a peak in mid-July
of 21.5 degrees, then showed a mid-summer decline on August 12 to 16.5
degrees, presumably due to the cold upwelling mentioned previously.
The maximum temperature for Michigan City in 1970 of 23 degrees was
recorded on August 25, after which temperatures declined through September and October.
At Burns Ditch, 1970 temperatures showed the same general pattern
as Michigan City with the rise in temperature through June and July, the
decline on August 10 in this case to 16 degrees, a maximum of 25.5 degrees on August 27, and a slow decline through September
and October.
At Gary the amplitudes of the cold upwelling and other maxima
and minbua were not as great as at Michigan City and Burns Ditch, due
possibly to the breakwater protection of the shallower sites and to
mixing c3used by ship traffic in the area or other factors (Johnson,
1972).
In addition, Gary's maximum of 24 degrees on July 31 occurred
before the cold upwelling and not after, as at the other two transects.
After the cold upwelling, which at Gary only lowered the temperature to
11
20.5 degrees, temperatures declined gradually as at Michigan City and
Burns Ditch through the months of September and October.
In 1971 at Michigan City temperatures rose through early June
to 20 degrees and remained fairly stable through July, but on August
4 an upwelling apparently occurred, lowering temperatures.
Sampling
done on August 3 at the 10m station of Michigan City showed no upwelling, but the remaining three stations, which were sampled on
gust
Au~
4, had surface temperatures which were as much as 5 degrees lower
than the 20 degrees recorded the day before.
The temperatures stabil-
ized again at around 20 degrees in late August and remained about the
same through early September, then declined through the remainder of
September and October.
At Burns Ditch in 1971 the temperature fluctuated only slightly
through the summer from a maximum of 20 degrees on June 16 to the minimum of
15.5 in late October.
The main change was the decline in Oc-
tober, which is normal for that time of year.
No upwelling appeared
as at Michigan City, but no temperatures were recorded on August
this transect.
4 on
The apparent stability of temperature may be due to
the low number samples taken at Burns Ditch, but in any case its pattern is still roughly the same as the Michigan City pattern.
Gary showed an increase through June to a maximum of 20.5 degrees
on July 18, followed by a slow decrease through August, September, and
October.
Again no upwelling appeared as no sampling was done on August
4, and like Burns Ditch the pattern of Gary's temperature was similar
to that which occurred at Michigan City.
For 1972, Michigan City temperatures showed a greater range of
12
variation than any other year at any transect (Fig. 2 and
4).
The
minimum temperature of 13 degrees recorded on May 23 was 12 degrees
less than the maximum temperature of 25 degrees, which was measured
on July 21+.
The difference between maximum and minimum temperatures
at the other two transects never rose above 10 degrees.
At Michigan
City in 1972, temperatures rose from late May to the late July maximum,
then dropped in mid-August, only to have risen again by the end of August.
In September the temperatures dropped, in accordance with the
seasonal change.
As opposed to yearly and monthly changes in temperature, figures
6 to 8 allow daily changes in surface temperature to be examined.
In
most cases, especially in May and June, it can be seen that the surface
temperature drops 1 or 2 degrees at night from its value during the day.
This would seem to indicate a cooling of the surface water in the absence of sunlight and the heat of the day.
There are cases, however,
where the temperature increased at night, but this was probably due to
warmer water moving into the aree rather than any increase in the temperature of the water itself.
Finally, surface temperatures were examined in two ways to see
what differences existed at the different stations which were studied.
Figure 9 shows one way in vThich this was done, for stations on the
same transect.
It is immediately evident that the surface tempera-
tures in 1970 at the 5, 10, 15, and 18 m stations of each transect are
very simj_lar.
In most cases the difference among the four stations is
no more than 1 or 2 degrees.
The only major difference was produced
13
Michigan City,
depth-O
Sm, 1972
.20
10
o
Michigan City, 5m, 1972
depth-1m
r--
U
'--
:20
I1.l
~
~=s
a:l
f-,.
(l)
Po
E
10
(l)
~
o
Michigan City, 5m, 1972
depth-5m
:20
II
I
I
~
I
10
~
I
o
!
i
night .'---_ _ _ '-1--._---1..---__-1.._... _ _ _L _ _ _ ---l
__
J
•
I
I
~y
.:'~
:
...'
'J,.....
Ai r~r
OCT
30 I~~~~~~r----r--Michigan City 15m, 1972
depth-O
'
20 -
10
o
MiChdigan City,
epth-1m
1C5~;;--+---+----+---~
)m,1972
."'" 0 -
o
p----
1--- --t-\---
MiCdhigan City, 15m
epth-5m
' 1972
2{) !
10
..
rI
+---
15
)0 . - - - -
MiChigan~C;i~t~y~~~--r--. -r-----r--depth-10m' 15m, 1972
+- --t------1
1
J
MiChiga~-+-depth-15~'
20
I
15m, 1972
r
I
10
o
~,
1
r
Ii
I
I
day
night
-:-;;::__...J _ _ - - _
'..
•
/,"
j
. _-L..-._ A1F;
T".,. ...
~:
! i
11)
1-
30
i higan city, 1970
M c surface, day
1
1-'
Burns Ditch, 1970
sur f ace, day
,,--..
u
'-'
.-
t!
.is1\'1
J.<
Cll
§- 10
Q)
E'-<
o
t-
1-·-
----t
Gary, 1970
surface, day
:Z{)
10
5m
!, i~
1
----
18m ." -,Y'"''
01
__1 - ,
- -:'~t_"l"
--,J I .• .....-L __ ~
'I. '
... ~
-L-_-;. . :_.,~.;_
J'.
,
-_J.._-SSP
OCT
-,
I
17
by the apparent cold upwelling on August 12.
At Michigan City, it
caused the surface temperature at the 5m station to be over 3 degrees
cooler than the remaining 3 stations--16.5 degrees as opposed to 19.5
degrees.
At Burns Ditch the upwelling produced a discrepancy of 4.5 degrees, "\vith the 5, 10, and 15m stations being 16 degrees at the surface
while the 18m surface temperature was 20.5 degrees.
At both Michigan
City and Burns Ditch, then, the upwelling had more pronounced effects
at the sl:Bllower stations than at the deeper stations.
At Gary even the upwelling had no major effects on surface temperature at its stations.
This is perhaps due to the previously noted
fact that the stations on this transect are subject to mixing due to
much lake traffic, and alSO to the fact that no 18m surface temperature was taken on August 12.
StEtions on Lake Michigan are compared in another way by figures
10 to 13.
Here the surface temperatures are compared for stations of
the same depth but on different transects.
For 1970 the most noticeable
feature Et all stations is that the Michigan City temperatures are lower
than temperatures at Burns Ditch and Gary at almost all points.
Gary
and BurnE, Ditch fluctuated closely together for much of the summer, but
temperatcres at Burns Ditch rose a little higher than Gary in late August before the fall decline in temperatures.
The only other major
differences among the three transects arise because of the previously
discussed upwelling which was measured on August 12.
Gary dropped fewer
degrees in temperature--only 2.5 degrees--due to the upwelling probably
19
30
r------··r-I----~r------Ir------~Jr-----~----~
Surface, 10m
1970
20
I-
10
f-
I
-
I•
0
j
I
1
T
I
I
r-,
c
,-.
l!O
t:
Ea!
~
ell
10
~
a>
I
.-
f-
E-<
01"----4
Surface, 10m
1971
..
\-----1-----+---+----1
?C
30
Surface, 15m
1970
l\
.--:b ~'~
~-~~'----'&
\..
'-
~
?O
Y
.
~~,
~
'0
""",
:~o
o
c..:
~----~-----+.------~----~~----~----~
£!O
~
$
III
$...
C)
§- 10
~
o ----+----+.---.. .------t-----t.----i
Surface, 15m
1971
10
l
A:..::--=:-::~~ -tr~~:
I
I
~
I
!
Michigan City - - ; Burns Ditch
I
Gary
___ _
() I. ______ ~.. ___ .. ___. L __ .._..J.--_ __
._-'------ OCT
-
.,
21
30
;w
10
o
I
I
-1
~
----·---¥-I- - - I
Surface, 18m
1971
•
----
22
because of reasons discussed previously and because of the breakwater protection of its shallower stations.
Burns Ditch showed the
greatest drop--B degrees--probably only because its temperature was
highest before the upwelling.
Michigan City's temperature dropped
about 5 degrees from its previous value to a low of 16.5 degrees at
the
~5m
station.
In 1971 the major feature was the similarity of surface tempera-
tures at the three transects for stations of the SClme depth.
The max-
imum temrerature for the summer of 21 degrees was measured on July 30
at the ISm station on the Michigan City Transect.
Temperatures on the
Michigan City Transect remained very close to 20 degrees throughout the
summer, i\-hile Burns Ditch and Gary temperatures were only a degree or
two lower for most of the sampling period.
A few sharp drops in tem-
perature occurred at Michigan City, but the sampling was not complete
enough at the other transects to allow comparison.
Temperatures below the Surface
Using data collected at the 5 and 15m stations in 1972, the temperatures at and below the surface were compared for Michigan City.
Figure lL allows a look at the monthly change in temperature below the
surface through the sampling period.
At the 5m station temperatures
from May through August did not vary more than 3 to
face to -bottom.
4
degrees from sur-
This indicates the absence of a thermocline, probably
because of the stations proximity to shore and the mixing of water
whic1:l occurs in the area.
However, the temperatures belO\{ the surface
are in all cases lower or equal to those above.
This condition would
23
Michigan City, 5m
1972, day
/A,
?O
....
, '",-~
/
'),/
IO
o
,--.
t.)
' j ,!O
f
Enl
J.<
(IJ
~ 10
(I)
E-<
o
Michigan City, 15m
1972, day
ao
o ----,-
J.O
1m
5m
10m
o
¥
..
J·rL
ATT~1
.,
... '- ...
I
15m
____,-1 _____ -1 _ _ _ -'-_ _ _--J,I_
c.rr:'.j
11
....
1_____.--J
SF;P
OCT
24
be normal as the higher density of the cooler water would cause it to
remain below the warmer water above.
On September 15 the temperature
at all depths was 20 degrees at the 5m station, indicating that the fall
overturn had occurred and homothermy was present.
At the 15m station the bottom temperatures were also 4 to 5
degrees below the surface temperatures until early July.
On July 13,
however, the temperature was 6.5 degrees lower at a depth of 15 m than
it was at 10 m down, thus indicating the establishment of a thermocline
or temperature stratification, by definition.
On July 24, the thermo-
cline extended from 5 m below the surface all the way to the bottom.
By the erB of August, however, the thermocline no longer existed and
homothermy was found at the 15m station on September 15, indicating
that the fall overturn had occurred.
In contrast to the 5IT. station,
then, it seems trat the 15m station was deep enough to allow temperature stratificetion to take place.
Sub-surface temperatures can also be examined for daily variation:; by returning to figures 6 to 8.
It is obvious that the varia-
tion from day to night is very slight, especially at the deeper depths.
The maximum drop in temperatu.re at night occurred at 1m under the surface at the 5m station, and that was a drop of only 2 degrees.
most casE's, then, there was very little change, if any.
In
At a depth of
5 m on t:te 5m station the maximum change was 1 degree on May 23.
The
rest of the year showed a change of 0.5 degrees or no change at all.
At the 15m station, again, very little change occurred in subsurface temperatures and when there was a drop it was usually only of
25
0.5 to 1 degree.
This indicates that temperatures do change slightly
from day to night, but the greatest change occurs on or near the surface.
At 5 or 10 m down, it seems, very little change occurs.
SEC CHI VISIBILITY
Station Differences
The secchi visibility of stations on the same transect is examined
on figures 15 to 17.
For 1970 at Michigan City the maximum secchi read-
ing of 16 feet occurred at the 18m station on June 23.
The graphs at
all three transects generally show that the secchi readings increased
with increased depth of station and distance from shore.
On July 22 the
secchi visibility took a sharp drop to 2 feet at all stations on the
Michigan City Transect.
This would most likely b2 due to bad weather
or some internal change in the lake such as a seiche.
At mid-August
the secchi visibility was found to be at normal levels again.
For the
remainder of the year the secchi was rather erratic, but basically it
tended to decline as fall approached.
At Burns Ditch in 1970 the maximum secchi reading was also taken
at the 18m station, on JlUle 22.
Here the 18m ::;,tation at times had a
secchi visibility almost 9 feet more than even the 15m station, and at
no time was its value below any of the other stations.
The 5, 10, and
15m E:tatLms had very similar secchi readings until mid-August, after
which the 5m station I s visibility decreased to 1. 5 feet and all the
other stations increased.
Burns
Dit~h
in 1970.
The 1. 5 foot reading
"TaS
the minimum for
26
10
I
o
Burns Ditch, 1970
-:p
e,..;
20
..-!
..c
()
()
~
(f)
10
Or-------+--------r-------+--------r-------+-------~
Gary, 1970
20
10
5m
10m
o
15m - ~ --18m ~ '" , "-'
JfTL
AUG
SEP
OCT
27
30
U
tr-----c.,
-eo-.
10
-
+-- t-----·- +-------+----·-+--l-----l
o
Burns Ditch, 1971
o.
,
.
.. ,
..., 20
'.
~
&
,
'l
l.
...
( ) ......
':.-,
/
.,.;
,C
t.>
t.>
~
U)
o'
10
u::::-
o
Gary, 1971
20
/'
/
~~
c.
10
....
"
-
"C-_
-'c.._
_-----c/
--
~
-0-
-<>
=
-~
-~----
--
-'G
,---------.....
~-
5m ' - 10m - 15m
18m·· "•. .
---~
0
I
VIAY
J'l'!
J'Tl
'j,
AUG
SEP
OCT
25
30
--------r---'--:--- -----r-- -----j--------__t-----.
-
10 -
o
~------+--------+-------1--------+--------~1------~
Michigan City, 1972
1\
I
-
\
!
..
/
/
V
0
1
/--.,
"""
I
o
/
I
/-:-A..
"
'''///\\\,
,~~'~
~'\,----
-
c
\.
~
j
I
I
\
r
I
I
I
r
I
20 -
-
10 -
-
o
5m--15m
I
MAY
JUN
AUG
SEP
OCT
29
At
stations.
~ary
there was very little change in secchi among the four
Although the 18m secchi reading was usually higher than
the other stations, the difference was only 2 to 3 feet at most.
The
maximum for Gary in 1970 was 11 feet at the 15m station on July 1.
The minimum of 4 feet came on September 2 at the 5m station.
For 1971 the range of sec chi variation was much greater than in
1970.
At Michigan City the maximum secchi reading was 26 feet and
occurred on July 30 at the 18m station.
This was 13 feet more than
the Becchi visibility at the 5m station on the same day.
The minimum
secchi reading of 6 feet occurred on September 18 at the 5m station.
One ver;y interesting feature is the lowering of secchi readings at all
stations to 10 feet which occurred on August
4.
This corresponds ex-
actl;y with the apparent upwelling which lowered temperatures on August
4 at Michigan City.
It looks as if the upwelling caused an increase in
turbidity as well as a decrease in temperature.
At Burns Ditch there is also a wide separation of secchi values
in 1971.
The maximum reading for the summer of 27 feet which occurred
on July 15 at the 18m station is over 24 feet more than the minimum
value, which came on October 25 at the 5m station.
At Burns Ditch the
increase in secchi visibility which occurs with greater depth of station
and distance from shore is very noticeable (Fig. 16).
Secchi readings at Gary in 1971 show little variation, especially
between the 5 and 10m stations.
imit~r
This may be due to the very close prox-
of these stations to one another (Table
1).
The 15m station
shows sOIT..ewhat higher visibility: and the maximum of 25 feet was
30
recorded here on August 17.
At Michigan City in 1972 (Fig. 17) the 5 and 15m stations are
examined.
station.
The maximwn secchi value occurred, as usual, at the deeper
This was a reading of 22 feet on August 28.
5 feet vas recorded on September 15 at the 5m station.
The minimum of
From July
through August secchi visibility was very si:.nilar at the two stations,
but at the beginning and end of the sUTIuner the two were separated by
as much
8S
10 feet.
Figures 18 to 20 compare the secchi visibility at stations of the
same depth but on different transects.
consideTE.ble similarity.
For 1970, the 5m stations show
Secchi values at Burns Ditch were the lowest,
ranging from 1.5 to 5 feet.
Gary followed the same pattern of peaks
and depressions (Fig. 18), but at a range of from 4 to 7 feet.
Michigan
City, hOvTever, did not follow the same pattern and also fluctuated more
than Burns Ditch and Gary over the sampling period, with a difference of
8 feet from its maximum to its minimum readings.
At the 5m stations for
1970 the maximum visibility attained at any transect was 10 feet, and
it occurred at Michigan City.
The minimwn was 1.5 feet at Burns Ditch.
For the 10m stations in 1970 there was considerably more variation
over the sampling period; that is, there were more changes from high to
low visibility over the year.
Michigan City had the greatest range in
values, as it did at the 5m stations.
on June
~23
This time its maximum of 11 feet
was the highest for all three transects and its low of 2
feet was the minimum for all
tra~sects.
This gave Michigan City a
range in values of 9 feet, vrhile the range of Burns Ditch
W8S
only 6.5
..
30 r--1
5m ,
31
197ri
It
2D~
10
/0----
.~
---f-----t-----+-
o
~
~
Crt
r-;Orn,
--
----
~~ ........ ~~i0
~
C
't,__
.,..- "-.....
- - - - •.. -
L
-'-I----v-~··_t_.
1970
20
..-l
..c
tl
0
Q)
{/)
10
10
I
t
I
I
1',
!
....; "--~--
I
-)
32
30
r--·----- -r-----------:-----,------ .--r-'--,--------,
118m, 1970
,
;rolII
!
!
10
I
I-
I
o
--~'-------+_------t-----+----+-----I
5m, 1971
~------~I------+-
33
-" _. - _. - . i ---. --.- .---. ····i- ....- .. -.............,- .... - ..•. -._. T-··---------···
---r-' ------.. -.--.
15m. 1971
1 ;-'j
Ii
~
-'-' I
i
(J
g
20
fJj
.-----1-.-. '-" - . .-- +--.---+ . ----
-+
~
!
~t.
(1C
!' - - - - - - + -
I
1 ()
.J
r"
I
i
j
I
I
!
I
1
() -------+--------+--------+1-,
,
I
18m, 1971
-+--
--- ----- -.
-----
~~-~
t
I
!
oi
L...
i
Michigan City
Burns Di toh
Gary ....l- _ _ _
AUG
SEP
.~~
OCT
feet, and Gary's 5 feet.
The 15 and 18m stations for 1970 were very similar to the 10m
station.
At both stations there was more fluctuation at Michigan City
than at Eurns Ditch and Gary, and at at both stations Michigan City
had the maximum and minimum secchi values for the three transects.
It
is difficult to pinpoint the stations of one transect as having a lower
or higher secchi visibility than the .stations on another transect since
the readings fluctuate so much.
However, the 18m station at Michigan
City in 1970 (Fig. 19) seems to be lower in visibility than the 18m
stations at Burns Ditch and Gary for most of the summer.
For 1971 the secchi visibility of the 5m stations on the three
transects are fairly stable.
Gary has the :highest values for most of
the summer and is very consistent with secchi visibilities between 13.5
and 10.5 feet.
15 feet,
b~t
Michigan City had the maximum value for a 5m station at
in general it stayed in the 5 to 10 foot range.
Burns
Ditch had the lowest secchi readings, mostly between 5 and 2.5 feet,
but its r2ading at mid-June was 8 feet.
At 10m the most noticeable features are the usual stability of
readings at Gary, and the drop on August 4 at Michigan City discussed
previously in connection "lith the upwelling.
At Burns Ditch August 16
saw t:':le r:laximum secchi value for 10m stations of 19 feet, while the minimum of 7 feet came at Michigan City on September 18.
The 15 and 18m stations show again the drop in secchi at Michigan
City on August 4, and also that the Michigan City visibility is generally lower than that at Burns Ditch and Gary.
Aside from these things
..
30 ------,----;--- --------r--- -·--T-----·----r--------.
Michigan City, 5m
10
o
Michigan City, 10m
.,-,
-p
20
fo-I
.....
~
orl
..c::
tl
tol
~I
If.l
10
o ~------~------~------~-------_r------_;------~
Michigan City, 15m
10
o
MAY
JUN
JTTL
AUG
SEP
QCT
37
30
r.--.--.--- --1
,
20
I
~
,
I
lc
o
1
r
I-~~:~:,- ~~t~-- -." ----+-.-----~~
."-.,,
....' 2C~'
~.~..
t - ---
City
I
./'
/'
~I
I
/'
/
/'
I
-I
1
\
......
.
(~
u
(~
r
i
c
10
I
o
L------t------·-~ --.-.---+------+.-- ~--t----!
I
I
i
,,
?(; r-
,
i
i
I
I
1
I
~
10
,,,"
I
1970
1971'- --".
___ ._ _ . _ _l . . -__ ~. __ __ ._1 __ .________
r"·..,
I'
L
-L._" _~_.__ ___L_. _ _ _____L_ _ _ _ _ _
'I
•
SUMMARY AND CONCLUSIONS
Temperature profiles were taken and sec chi visibility measured
from May through October in 1970, 1971, and 1972 at depths of
5, 10,
15, and 18m on transects into the Indiana waters of Lake Michigan
from points near Michigan City, Burns Ditch, and Gary.
The following
conclusions have been drawn from graphs of several aspects of the data.
1.
Surface
temperat'~res
Di teh ane. Gary than in 1971.
were generally ::igher in 1970 at Burns
For Michigan City 1970 and 1971 were
fairly similar, but 1972 temperatures were higher than both 19 [0 and
C
1971.
2.
Monthly changes in surface temperature for Michigan City
Burn:3 Ditch and Gary indicate the presence of upwellings on August
10, 1970 and August 4, 1971.
Generally, temperatures rose through
mid-summer and declined as fall approached.
In 1972 Michiga:J. City
temperatCJres follovled this pattern also.
3.
Daily changes in surface temperature indicate that tempera-
tures normally declined from 1 to 2 degrees at night at Michigan City.
!+,
Surface temperatures were very similar st
t~le
four stations
on one transect in the year examined (1970).
5.
For stations of the same depth but on different transects,
Michigan City wss lower in surface temperature than Burns Ditch and
Gary in 1970.
In 1971 the three trsnsects were similar in surface
temperature, but with Michigan City again being a little lower
especially at the deeper stations.
6.
'remperatures belmv the surface at the 5m stati::Jn of Michigan
39
City in 1972 showed a gradual cooling to the bottom for the entire
summer.
At the 15m station, hovlever, the water "\Vas deep enough to
allOlv a thermocline to develop.
7.
Sub- surface temperatures did not
lower morc thaJ2 0.5 to 1
degree at night from the:Lr daytime values, except for depths near the
surface
8.
Secchi visibility was highest in all years for the stations
fartLest from shore and deepest at all three transects.
9.
than Burns
For 1970 Gary appeared to 'lave a higher secchl visibility
Di.tcl~
generalization.
and Mi chiga::1 City fluctuated too much to allow a
In 1971 Michigan City showed the lowest sf':cchi
visibili ty at most stations, \.Ji th Gary above Burns Ditch in most cases.
10.
At Michigan City secchi visibility in 1970
1971 and 1972.
W3S
lower than
For 1971 and 1972 the seechi visi bili ty ,vas very similar.
40
.LITERATURE CITED
Johnson, D. L. 1972. Zooplankton Population Dynandcs In Indiana WateY'E;
of Lake Michigan in 1970. MA.ster's Thesis. Ball State Ur.iv.
1- ~)6.
41
Appendix 1.
Daytime temperatures (C) in Lake Michigan on the Michigan City Transect at 5, 10,
15 and 18 m stations by depth in 1970.
Depth ~m) --_ _---------------4
10
5
7
OX
1
2
3
Jun 8
18.0
16.5
16.5
16.0
16.0
16.0
Jun 23
17.5
17.0
16.0
16.0
15.0
14.0
Jul 22
21.0
21.0
21.0
21.0
21.0
20.5
Aug 12
16.5
16.0
16.0
16.0
15.0
15.0
Aug 25
22.0
22.0
22.0
21. 5
21. 5
21. 5
Sep 12
20.0
20.0
19.5
19·5
19.5
19·0
Oct 17
13.0
13.0
13.0
13.0
13.0
13.0
18.5
17.0
17.0
16.0
16.0
16.0
16.0
14.5
Jun 23
17.5
16.0
15.5
15.0
15.0
15.0
15.0
12.5
Jul 22
21.0
21.0
21.0
20.5
20·5
20.5
20.0
19.0
Aug 12
19.5
18.0
17.0
17.0
16.5
16.5
16.5
16.0
Aug 25
22.0
22.0
22.0
21. 5
21. 5
21. 5
21. 5
Sep 12
19.5
19.5
19.5
19.5
19.5
19.0
18.5
Oct 10
13.0
13.0
13.0
13.0
13.0
13.0
13.0
Station / Date
..•
5m
10m
Jun 8
*Temperature at the surface, not air temperature
13.0
12
15
18
42
Appendix 1.
cant.
Depth (ill)
Station !... Date
15m
Jun 8
n
~
l
~
2
~
J
'I
c;
-'
'7
I
10
12
15
18
19·0
17.5
17.0
16.5
16.5
16.0
15.5
13.0
13.0
13.0
Jun 23
18.0
16.5
16.0
15.5
15.0
15.0
14.5
13·5
12.0
11.0
Ju1 22
21. 5
21. 5
21. 5
21. 5
21.0
21.0
20.5
20.0
20.0
19.0
Aug 12
20.0
19·0
17.5
17.0
17.0
17.0
16.0
16.0
16.0
15.5
Aug 25
23.0
22·5
22.0
22.0
22.0
22.0
22.0
21. 5
Oct 10
13.0
13.0
13.0
13.0
13.0
13.0
13.0
13.0
13·0
13.0
21.0
18.0
17.0
17.0
16.5
16.5
15.0
14.0
13.0
13·0
13.0
Jun 23
18.0
17.5
16.0
16.0
15·5
15.0
14.5
11. 5
11. 0
10.5
8.5
Jul 22
21.0
21.0
21.0
21.0
20.5
20.5
20.0
19.5
19·5
19.0
Aug 12
20.0
19.0
18.5
17.5
16.5
16.5
16.5
13.0
11. 5
10.5
Aug 25
23.0
22.0
22.0
22.0
22.0
22.0
21. 5
21. 5
21.0
10.5
Sep 12
20.0
19.5
19.5
19.5
19.5
19.5
19.0
15.5
14.5
14.5
Oct 17
13.5
13.5
13.5
13.5
13.5
13.5
13.5
13·5
13.5
13.5
18m
Jun 8
13.5
43
Daytime temperatures (C) in Lake Michigan on the Burns Ditch Transect at
and 18 m stations by depth in 1970.
Date
Depth (m)
4
5
0
1
2
3
16.5
16.5
16.0
16.0
16.0
16.0
24.0
23.0
23.0
22.0
19.0
18.0
16.0
16.0
16.0
16.0
16.0
16.0
25.0
23.0
23·0
21. 5
21. 5
19.5
19.0
17.5
17.0
15.0
15.0
15.0
14.5
14.5
14.5
14.5
14.5
17.0
17.0
16.0
16.0
16.0
23.5
23.0
23.0
23.0
16.0
16.0
15.5
25.0
25.0
18.0
15.0
7
10
16.0
16.0
16.0
22.0
22.0
17.5
17.0
15.5
15.5
15.5
15.5
15·5
24.0
24.0
24.0
24.0
18.0
18.0
17.5
17.5
15.5
14.0
13.0
15.0
15.0
14.5
14.5
14.5
14.5
12
."11lIIDI
1=
s:o;C;oo;;; ; -
_~
0
<>.; "
:>
10, 15
It)
4)
Appendix 3.
Daytime temperatures (C) in Lake Michigan on the Gary Transect at 5, 10, 15 and 18m
stations by depth in 1970.
Station / Date
Depth (m)
4
5
7
10
19·0
18.0
17.0
21. 5
21. 5
21.0
20.0
20.0
20.0
19·5
21.0
21.0
21.0
21.0
15·5
14.5
14.0
14.0
14.0
14.0
0
1
2
3
Jul 1
19·0
19.0
19.0
18.5
1,{·5
Jul 31
23.0
23.0
23·0
21.0
20.5
Aug 11
20.5
20.0
19.5
19.5
19.5
Sep 2
21.0
21.0
21.0
21.0
20.5
20.5
Oct 20
15.0
15.0
15.0
15.0
15.0
15.0
Jul 1
20.0
20.0
19·5
19.5
19·0
Jul 31
23.0
23.0
23.0
22.0
Aug 11
21. 5
21.0
20.0
Sep 2
21.0
21.0
Oct 20
15·0
14.5
5m
17·5
10m
16.0
12
15
18
46
Appendix 3.
!
cont.
Depth ~m)
4"
5
0
1
2
3
7
10
12
15
Ju1 1
20.0
20.0
20.0
19.5
19·0
19.0
17.0
14.5
13.0
11. 5
Ju1 31
23·5
23.0
23.0
23.0
23.0
23.0
18.0
16.5
16.5
Aug 11
21. 5
21. 5
21.0
20.5
20.0
20.0
20.0
15.0
14.5
Sep 2
22.5
22.0
22.0
22.0
22.0
22.0
15.5
13.0
13.0
Oct 20
14.5
14.5
14.5
14.5
14.5
14.5
14.5
14.0
14.0
18m
Jul 31
24.0
23.0
23.0
22.5
22.5
22.5
22.0
19.0
18.0
16.0
Sep 2
23.0
23.0
23.0
23.0
22.5
22.5
22.5
11.0
10.0
10.0
Oct 20
14.5
14.5
14.5
14.5
14.5
14.5
14.0
14.0
14.0
14.0
Station
Date
15m
14.5
18
· 47
Appendix 4.
Daytime temperatures (C) in Lake Michigan on the Michigan City Transect at 5, 10,
15 and 18 m stations by depth in 1971.
Depth (m)
4
5
0
1
2
3
Jun 2
10.5
10·5
10.5
10.5
10.5
10.5
Jun 22
20.0
19·0
19·0
18.5
17.5
17·5
Jul 14
19·5
19.0
19.0
18.5
18.5
18.5
Jul 30
20.5
20.5
20.5
20.5
20.5
20·5
Aug 4
15.5
15.0
14.0
14.0
14.0
14.0
Aug 13
20.0
19·0
19.0
19·0
18.5
18.5
Aug 30
20.0
20.0
20.0
20.0
20.0
20.0
Sep 18
20.0
20.0
20.0
20.0
20.0
20.0
Sep 26
17.0
17.0
17.0
17.0
17.0
17.0
Oct 23
15.0
15.0
14.5
14.0
12·5
12.5
Oct 30
15.5
15.5
15.5
15.5
15.5
15.5
Station / Date
5m
7
10
12
15
18
.48
4.
Appendix
!
cant.
Depth ~m)
Ij:
5
i5
1
2
3
10.5
10.5
10.5
10.5
10·5
Jun 23
19·0
18.5
18.5
18.0
Jul 14
19.5
19·5
19.5
Jul 30
20.5
20.5
Aug 3
20.0
Aug 18
7
10
10.5
10.0
10.0
18.0
17.5
17.0
17.0
19·0
19·0
19.0
18.5
18.5
20.5
20.5
20.5
20.5
20.5
20.5
19·5
19.0
18.5
18.0
17.0
15.0
14.5
19.0
19·0
19.0
18.5
18.0
18.0
18.0
18.0
Aug 31
20.0
20.0
19·5
19.5
19· 5
19.5
19·0
19.0
Sep 1
20.0
20.0
19.5
19.5
19.5
19.5
19.0
18.0
Sep 18
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
Sep 26
17.0
17.0
17.0
17.0
17.0
17.0
17.0
17.0
Oct 2
21.0
20.0
19.0
19.0
19·0
19.0
18.5
16.5
Oct 30
15·5
15.5
15.5
15·5
15.5
15.5
15.5
15·5
Station
10m
Jun. 2
Date
12
15
18
)
)
')
49
Appendix 4.
I
cont.
Depth {m)
0
1
2
3
4
5
7
10
12
15
Jun 2
12.0
12.0
11. 5
11. 5
11.0
11.0
10.0
10.0
10.0
10.0
Jun 22
19.0
18.0
18.0
18.0
17.5
17.5
17.0
14.0
14.0
14.0
Jul 14
20.0
19.5
19.5
19·0
19.0
19·0
19·0
18.0
17.5
17.0
Ju1 30
21.0
19.5
19.5
19.5
19.5
19.5
19.0
19.0
17.0
11.0
Aug 4
15.0
14.5
14.0
13.0
11. 5
10.5
10.5
10.5
10.5
10.5
Aug 18
20.0
19·5
19·0
19.0
19.0
18.0
17.0
13.0
10.0
9.0
Aug 25
20.0
20.0
20.0
19.5
19.5
19.5
19·5
19.0
18.0
13.0
Sep 26
17.0
17.0
17.0
17.0
17.0
17.0
17.0
17.0
17.0
17.0
Oct 24
15.5
15.0
15.0
15.0
15.0
15.0
15.0
13.5
13.0
12.0
Station
Date
15m
18
,51
Appendix 5.
Station
I
Daytime temperatures (C) in Lake Michigan on the Burns Ditch Transect at 5, 10, 15
and 18 m stations by depth in 1971.
Date
0
1
2
3
Depth {m;
4
5
7
10
12
15
5m
Jun 16
19.0
Jul 15
19·5
Aug 16
18.5
18.5
18.5
18.5
18.5
18.5
Oct 3
19·0
19.0
19.0
18.5
16.5
16.0
Oct 25
16.5
16.0
16.0
16.0
16.0
16.0
Jun 16
19.0
Aug 16
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
Oct 3
19.5
19·5
19.5
19·0
19.0
16.0
14.0
13.0
Oct 25
16.0
16.0
16.0
16.0
16.0
16.0
16.0
16.0
Jun 16
20.0
Aug 16
18.5
18.5
18.5
18.5
18.5
18.5
18.0
18.0
18.0
18.0
Oct 3
19.0
19·0
19.0
18.5
18.5
18.0
14.0
12.5
12.0
10.5
Oct 25
15·5
15.5
15.5
15.5
15.5
15.5
15·5
15.5
15.5
15·5
10m
15m
18
•
52
Appendix 5.
Station
!
cont.
Date
0
1
2
3
Depth (m)
4
5
7
10
12
15
18
18m
Jun 16
18.0
Aug 16
18.5
18.0
18.0
18.0
18.0
18.0
18.0
17.0
10.0
10.0
9.5
Oct 3
19·0
19·0
19.0
19.0
19·0
19·0
19·0
15·5
9.0
7.5
7.5
Oct 25
16.5
16.0
16.0
16.0
16.0
16.0
16.0
16.0
16.0
12.5
12.5
)
)
)
. 53
Appendix 6.
Station
I
Daytime temperatures (C) in Lake Michigan on the Gary Transect at 5, 10, 15 and 18m
stations by depth in 1971.
Date
Depth ~m~
4
5
0
1
2
3
Jun 18
16.5
16.0
16.0
16.0
16.0
16.0
Jul 18
20.5
20.5
20.0
20.0
20.0
20.0
Aug 17
19·0
19.0
18.5
18.5
18.5
18.5
18.0
18.0
18.0
18.0
18.0
18.0
Oct 25
16.0
16.0
16.0
16.0
16.0
16.0
10m
Jun 18
16.5
16.5
16.5
16.5
16.5
Jul 18
20.5
20.0
20.0
19·5
Aug 17
19·0
19·0
18.0
18.0
18.0
16.0
16.0
7
10
16.0
15·5
15.0
19.5
19.0
18.5
18.5
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
18.0
16.5
11. 5
16.0
16.0
16.0
16.0
16.0
16.0
5m
Oct
Oct
4
4
Oct 25
12
15
18
55
Appendix 7.
Daytime temperatures (C) in Lake Michigan on the Michigan City Transect at 5, 10,
15 and 18 m stations by depth in 1972.
Depth {m)
4
5
0
1
2
3
May 23
13.0
13.0
12.0
10.0
9·0
9.0
Jun 7
17.0
16.5
15.0
14.5
14.5
14.5
Jun 27
16.5
15.5
15.0
15.0
14.5
14.5
Jul 6
18.0
18.0
17.5
17.0
17.0
Jul 13
21.0
20.5
20.5
20.0
20.0
20.0
Jul 24
25.0
25.0
25.0
25.0
25.0
23.0
Aug 14
20.0
Aug 28
23.0
23.0
23.0
23.0
22.0
22.0
Sep 15
20.0
20.0
20.0
20.0
20.0
20.0
10m
Aug 28
23.0
22.5
22.5
22.5
22·5
22.0
Station / Date
7
10
22.0
21.0
5m
18.0
12
15
.-rs
·56
Appendix 7.
cont.
Depth ~m)
4
5
7
10
12
15
11.0
10.0
9·0
8.5
8.5
15.0
14.5
14.0
13.0
13.0
12·5
15·0
14.5
14.5
14.0
13·5
13·5
13.5
16.5
16.5
16.0
16.0
16.0
16.0
16.0
15.5
20.5
20.0
20.0
20.0
20.0
20.0
19·5
19·0
13.0
25.0
25.0
24.5
24.5
24.5
24.5
15.5
11. 5
9.5
0
1
2
3
13.0
12·5
12.0
11.0
11.0
Jun 7
15.5
15.0
15.0
15·0
Jun 27
17.5
16.5
16.0
Ju1 6
18.5
1r(.5
Ju1 13
23.0
Ju1 24
25.0
Aug 14
20.5
Aug 28
22.0
22.0
21. 5
21. 5
21. 5
21. 5
21.0
21.0
21.0
18.0
Sep 15
19.5
19.5
19.5
19.5
19.5
19.5
19.5
19.5
19.5
19.5
18m
Aug 28
22.0
22.0
21. 5
21. 5
21. 5
21. 5
21. 5
21. 5
21.0
16.0
Station / Date
15m
May 23
18
16.0
11.0
· 57
Appendix 8.
Nighttime temperatures (C) in Lake Michigan on the Michigan City Transect at 5 and
10 m stations by depth in 1971.
Station / Date
Depth (m}
4
5
0
1
2
3
Ju1 27
22.0
22.0
21. 5
21. 5
21. 5
21. 5
Aug 13
19.0
19.0
19.0
19·0
19.0
19·0
Aug 31
20.5
20·5
20.0
20.0
20.0
20.0
Sep 26
17.0
17.0
17.0
17.0
17.0
17.0
Oct 23
16.5
16.5
16.5
16.5
16.5
16.5
13.0
12.0
12.0
12.0
12.0
Jun 23
20.0
19.5
19.0
19.0
Ju1 17
20.0
20.0
20.0
Aug 3
20.0
20.0
Aug 17
19·0
Sep 1
7
10
11. 5
11.0
11.0
18.5
18.5
18.0
17.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
19·5
19.0
19.0
18.5
18.5
18.0
18.0
17·5
17.5
17.5
17·5
19.5
19.5
19.5
19.0
19.0
18.5
18.0
18.0
Oct 2
19.5
19·0
19·0
18.5
18.5
18.5
18.5
14.0
Oct 30
15.5
15·5
15.5
15.5
15.5
15.5
15.5
15.0
5m
10m
Jun 3
12
15
18
58
Appendix 9.
Nighttime temperatures (C) in Lake Michigan on the Michigan City Transect at 5, 10,
15 and 18 m stations by depth in 1972.
Depth
(m)
0
1
2
3
1+
5
May 23
11.0
11.0
10.5
10.0
10.0
10.0
Jun 8
15·0
15.0
15.0
14.5
14.5
14.5
Jun 26
16.0
15.0
15.0
15.0
14.5
14.5
Jul 5
17.5
16.5
16.5
16.5
16.5
16.5
Jul 13
22.0
21. 5
20.5
20.5
20.5
20·5
Jul 24
25·0
25.0
25.0
25·0
25.0
23.5
Aug 13
20.0
19.5
19.0
19.0
18.5
18.0
Aug 29
22.0
22.0
22.0
22.0
22.0
22.0
Sep 16
19·5
19·5
19·5
19· 5
19·5
19.5
Jul 5
17.0
17.0
16.5
16.0
16.0
16.0
Station / Date
7
10
16.0
16.0
5m
10m
12
15
18
59
Appendix 9.
~---
.. - . - -
cant.
---
Depth em)
4
5
-~
15
7
10
12
9.0
8.0
8.0
8.0
8.0
15.0
15.0
14.5
14.0
14.0
13.5
15.0
15.0
15.0
14.5
14.0
14.0
14.0
16.5
16.0
16.0
16.0
16.0
16.0
16.0
15.5
21.0
21.0
21.0
20.5
20.0
20.0
19.5
19·5
13.0
25.0
25.0
25.0
25.0
25·0
25·0
25.0
14.0
11.0
9.5
Aug 13
21.0
20.5
19.0
18.0
17.5
17·5
17.5
17.0
17.0
17.0
Aug 29
22.0
22.0
22.0
22.0
22.0
22.0
21.0
21.0
21.0
20.0
Sep 16
19·5
19.5
19.5
19.5
19·5
19.5
19.5
19.5
19.5
19.5
16.5
16.5
16.0
16.0
16.0
16.0
16.0
16.0
16.0
15.0
0
1
2
3
11.0
11.0
10.0
10.0
9.0
Jun 8
15.5
15.5
15.0
15.0
Jun 27
16.0
15.5
15.0
Jul 5
16.5
16.5
Jul 13
21. 5
Jul 24
Station / Date
15m
May 23
18m
Jul 5
18
15.0
· 60
Appendix 10.
Year
I
Secchi disc visibility (ft) by station in Lake Michigan at the Michigan City Transect at 5, 10, 15 and 18 m stations in 1970, 1971 and 1972.
Station
Date
5m
10m
15m
18m
Jun 8
4.0
5.0
6.0
7.5
Jun 23
8.0
11.0
14.5
16.0
Jul 22
2.0
2.0
2.0
2.0
Aug 12
10.0
10.0
10.0
12.5
Aug 25
6.0
11.0
11.0
12.0
Sep 12
4.5
5.0
Oct 17
3.0
3·5
1.:)'(0
5.0
3.5
6.0
·61
Appendix 10.
!
cant.
Station
5m
10m
15m
18m
1971
Apr 22
2.0
3.0
4.0
6.5
Jun 2
9·5
11. 5
15.0
16.0
Jun 22
9·0
11.0
15·0
Jul 14
8.5
8.5
10.5
25.0
Jul 30
13.0
19.0
20.0
26.0
Aug 4
10.0
10.0
10.5
10.5
Aug 18
15.0
16.0
14.0
15.0
Aug 31
10.0
14.5
15.5
15.0
10.0
10.0
12.0
12.0
YeRr
DRte
Sep 1
14.0
Sep 18
6.0
7.0
Sep 26
9·0
9·0
Oct 2
Oct 24
15.5
6.5
11. 5
· 62
Appendix 10.
Year
I
cant.
station
Date
1972
May 23
5m
10m
15m
11.0
11.0
Jun 7
5·5
17.0
Jun 27
7·5
9.5
11.0
13.5
Jul 13
12.5
13.0
Jul 24
10.5
8.5
Aug 14
10.0
11.0
Aug 28
14.5
Sep 15
5.0
Jul
6
15.0
22.0
9.0
18m
25.5
63
Appendix 11.
Secchi disc visibility (ft) by station in Lake Michigan at the Burns Ditch Tran_
sect at 5, 10, 15 and 18 m stations in 1970 and 1971.
'§tat1on
5m
10m
15m
18m
1970
Jun 22
5·0
5.5
5·5
14.0
Jul 28
3.0
3.5
5.0
9·0
Aug 10
4.5
5.0
5.0
10.0
Aug 26
1.5
10.0
11.0
12.0
Sep 12
1.5
3.5
5.0
Oct 19
5.0
6.0
6.5
1971
Jun 16
8.0
8.0
13.0
Jul 15
3.5
10.5
27.0
Aug 16
5·5
l~.C
20.0
Oct 3
2.5
7.5
12.0
Oct 25
2.5
12.5
16.0
Year / Date
13.0
24.0
19.0
, 64
Appendix 12.
Year
!..
Secchi disc visibility (ft) by station in Lake Michigan at the Gary Transect at 5,
10, 15 and 18 m stations in 1970 and 1971.
station
Date
18m
5m
10m
15m
7.0
7.5
11.0
Jul 31
6.0
10.0
8.5
Aug 11
7.0
8.0
10.0
Sep 2
4.0
5·0
6.0
6.5
Oct 20
7.0
7.0
8.0
9.0
1971
Jun 18
12.0
15.0
14.0
30.0
Jul 18
12.0
12.0
15.0
Aug 17
12.0
13.0
20.0
Oct 4
13.5
12.0
15.5
Oct 25
10.5
9.0
13.5
1970
Jul 1
10.5