Notes on the Vertical Distribution of Organisms in the
Profundal Sediments of Douglas Lake, Michigan"
Gerald A. Cole
Department of Biology, University of Louisville, Louisville, Kentucky
Benthic populations of inland lakes are commonly discussed in terms of
organisms per square meter of bottom surface, often with reference to changes
occurring during some period of time. However, the vertical distribution of
animals within the sediments has been neglected to a great extent in North
America. Lenz (1931) and Berg (1938) have contributed to our knowledge
of this aspect of faunal distribution in European lakes. Moore (1939) and
Cole (1949) have reported on the vertical distribution of the microbenthos
in bottom deposits of certain lakes of this continent, but little information
has been published concerning the stratification of macrobenthic forms, particularly the profundal organisms.
APPARATUS AND METHODS
Thirty benthic collections, each composed of three vertical core samples,
were taken from profundal depths in Douglas Lake, Cheboygan County,
Michigan, from August 4 to August 26, 1950. Eight collections were made
in the upper profundal zone at a water depth of 16 meters, and twenty-two
collections were taken from a depth of 19.5 meters. Both stations were in
the South Fish Tail Bay depression along a transect extending lakeward from
a permanent marker on the west shore. In addition to the 90 profundal core
samples, 8 cores were taken at sublittoral and littoral depths for comparative
purposes.
All benthic collections were made with a small vertical core sampler,
described in another paper (Cole, 1949). An inserted transparent plastic
tube served to collect the core of sediment and its biota. This tube was
removed from the sampler, transported to the laboratory in a wooden rack,
and the included mud was removed in sections for examination. The sectioning was accomplished, after the water overlying the core had been siphoned
off, by pushing a rubber piston up the tube from the bottom. A rod, calibrated in centimeters, was used to push the piston, and hence the mud core,
up through and above the upper edge of the tube. A tight-fitting, waterproof
bowl encircled the tube, and served to catch watery sediment which spilled
over the top. An ordinary glass slide was used to scrape the mud from the
top of the tube, and a rubber syringe was employed in washing the outside of
the tube and in removing the sediment from the bowl. The three cores, comprising one collection, were sectioned in succession and their corresponding
strata consolidated in finger bowls. The upper 10 cm. of each core was sectioned at one cm. intervals and screened with a metal sieve of 80 meshes to
the inch. The second 10 cm. was sectioned at 2 cm. intervals and screened
1 This investigation was made possible by a grant from the Research Fund, University of Louisville.
2 Contribution from the Biological Station, University of Michigan.
252
1953
COLE: DISTRIBUTION OF ORGANISMS IN DOUGLAS LAKE
253
with a 65 mesh Tyler sieve. Strata below 20 cm. were divided at 4 cm. intervals and screened with the 65 mesh sieve. After screening, each stratum was
placed in the proper finger bowl and examined with the aid of a binocular
microscope (magnification 10.5x).
Although a few cores included as many as 30 cm. of sediment, the data
apply only to a depth of 24 cm., each core with a surface area of 3.8 square
centimeters.
Obviously the method of collecting and sectioning cores did not yield
information other than a record of how benthic organisms were distributed at
the time the cores were sectioned. Vertical displacement of the more motile
species could not be determined. However, limiting the collections to three
cores each, and proceeding with the sectioning immediately after collecting
allowed little time for wandering. This source of error might have been
almost completely eliminated by utilizing a "stratification bottom sampler"
similar to those used by Lenz (1931) and Berg (1938).
SAMPLING STATIONS
Physico-chemical factors.—Table 1 shows results of physico-chemical determinations made August 12, 1950 in the South Fish Tail Bay depression.
Throughout the course of this study these factors varied little. Both stations
were in the profundal zone according to the limits defined for Douglas Lake
by Eggleton (1931). The 16 m. station was near the lower limit of the
thermocline, while the 19.5 m. was well within the hypolimnion.
TABLE
Water
Depth
16 m.
20 m.
C°
8.4
6.8
1.—Physico-chemical factors of profundal waters
02
CO2
pH
Total
Alkalinity
Conductivity
0.01 p.p.m.
15.4 p.p.m.
16.5 p.p.m.
7.0
6.9
125 p.p.m.
135 p.p.m.
225 mho
240 mho
none
Sediments.—There appeared to be no difference in the sediments at 16 m.
and at 19.5 m. The upper 15 cm. was blackened and composed of fine
material. Below this there was a trend to brown color which became well
marked at about 20 cm. Here the bottom deposits were more compacted and
decidedly gelatinous. The upper strata were watery, spilling over the top of
the plastic tube when raised a centimeter above it during the sectioning procedure. When the 7-8 cm. stratum was reached the material was usually solid
enough to hold its shape when pushed above the end of the tube. Moore
(1939) has described these sediments in greater detail.
MICROBENTHOS
Many of the microscopic bottom forms were retained in the fine-meshed
screens, and were recorded when observed. Microbenthic populations at the
two stations differed more than did the macroscopic portions of the benthos.
At 16 in. Canthocamptus staphylinoides Pearse was common, but only one
individual was seen in the 19.5 m. collections. Active and encysted individuals occurred from the surface to at least 14 cm. in the ooze. Cysts were
present in the upper two centimeters as well as the underlying strata, and
254
THE AMERICAN MIDLAND NATURALIST
49 (1)
activeindividualswerefoundasfardownasthe14-16cm.level.Atboth
depthsencystedandafewactive Cyclopsbicuspidatusthomasi Forbesinthe
4thcopepodidstagewereabundant,butthegreatestnumberswerefoundin
thedeeperwaters.Theircystswerefoundasfardownasthe16-18cm.level.
Nematodeworms,largeenoughtoberetainedbythescreens,werefoundonly
at16meters,wheretheyoccurredinsmallnumbersdowntothe8-9cm.
stratum.Oftheostracods, Candonasimpsoni Sharpeoccurredinfiveofthe
16tn.collectionsbutwasnotfoundatthedeepstation; Physocypriapustulosa
(Sharpe)was obs
ervedinonesamplefrom16m.,and Cypria turneriHoff
wasnotedfrombothdepthsseveraltimes.
Unusual records included Ilyocryptus sordidus (Lieven)8cm.downin
theoozeat16m.,andtwooccurrences(probablyaccidental)of Mesocyclops
edax (Forbes)at19.5meters.
Thus,fourmicrobenthicforms,onlytwoofwhichwerecommonoccurred
,
were
at the deeper station, while seven species, of which five were abundant
recorded from the shallow station.
MACROBENTHOS
Themacrobenthicanimalssampledintheprofundalcollectionswere
dominatedbytubificidoligochaetesofthegenus Limnodrilus.Eggleton
(1931) recorded L.hoffmeisteri ClaparedeandL. claparedianusRatzelfrom
profundalsedimentsofDouglasLake.Noattemptwasmadetoidentify
themspecificallyduringthecourseofthepresentinvestigation.
Tendipes plumosus (L.) was the next most abundant animal, although
only 10 were collected in the cores. Twelve other dipterous larvae, including
8larval Chaoboruspunctipennis (Say),werealsotaken.Theonlyother
macrobenthicformswereoneindividualofthemolluscangenus, Sphaerium,
andanunidentifiedoligochaete.Altogether,106macrobenthicindividuals
werecollectedinthe90profundalcores(Table2).
Oligochaeta.—Limnodrilus wasmoreabundantinthe16m.collections
thaninthosefrom19.5m.Ofthetotalnumber,morethanninety-one
percentoccurredintheupper14cm.ofsediment.Onlysevenindividuals
werefoundbelowthisstratum.
Aninterestingfeatureofthetubificidstratificationwasthecomparative
scarcityofanimals(7.4%ofthetotal)atthesurfaceandintheuppercentimeterofsedimentwhencomparedtonumbersbelowthislevel.At19.5m.
therewasaconspicuousgroupingofwormsinthe2-3cm.stratum.Thiswas
notsomarkedat16in.,althoughitwasclearthatrelativelyfewwereinthe
uppermoststratum.
The paucity of worms in the uppermost layer differs from what was found
concerninglittoralandsublittoraloligochaetepopulationsinCrystalLake,
Minnesota(cf.Cole,1949).Usingthesamesamplinggearandsectioning
technique,itwasfoundthat60%ofalloligochaeteworms(mostlynaidids)
wereatthesurfaceorintheuppercentimeterofsoftdeposits.Oligochaetes
didnotoccurintheprofundalzoneofCrystalLake,sonoexactcomparison
canbemade.However,aDouglasLakesublittoralcollection(11.5 m.)
comprised of three cores made during August, 1950, contained six worms of
the genus Limnodrilus, including two in the uppermost stratum. Of the
thirtyprofundalcollections,onlyonehadasmanyastwotubificidsinthe
1953
255
COLE: DISTRIBUTION OF ORGANISMS IN DOUGLAS LAKE
TOP centimeter. A core from the littoral zone (4 m.) of Douglas Lake contained three naidids, of which two were in the top layer. These data are too
few to warrant more than speculation as to whether there is a significant difference between vertical penetration of Limnodrilus at different benthic regions,
or between the stratification of the naidids and tubificids.
TABLE 2.—VERTICAL
Depth
in
Cm.
0-1
1-2
2-3
3-4
4-5
5-6
6-7
7-8
8-9
9-10
10-12
12-14
14-16
16-18
18-20
20-24
Totals
distribution of MACROBENTHOS in PROFUNDAL sediments of
Douglas Lake during August 1950
16 Meters (24 cores)
L
T TA CHA S
2
6
7
4
–
–
2
1
1
1
–
1
–
–
–
–
1
3
1
–
–
–
–
–
–
–
–
–
–
–
1
3
1
–
–
–
–
–
–
–
–
–
3
1
1
28
3
–
–
1
–
L
19.5 Meters (66 cores)
Total
T TA CHA 0
4
16
3
3
6
3
5
5
1
1
2
1
1
1
–
–
–
–
–
–
–
1
1
1
–
–
5
1
54
3
1
–
1
–
–
–
1
–
–
–
–
1
–
–
–
–
–
–
–
–
–
–
–
7
1
7
1
12
26
12
12
8
4
8
8
1
2
3
3
5
1
0
1
—
106
Key: L—Limnodrilus spp., T—Tendipes plumosus, Ta—Tanypodinae, Cha– JChaoborus punctipennis, S—Sphaerium sp., 0—Unidentified OLIGOCHAETE.
Dipterous larvae.—No significant difference could be detected between
Tendipes plumosus populations at the two stations. Only one larva was found
in the uppermost centimeter, most of the individuals being present between
two and six centimeters below the ooze surface.
Four larvae of the subfamily Tanypodiwe were found, but only one of
these was collected at 19.5 m. Of the eight Chaoborus punctipennis larvae
found, seven were at the 19.5 m station where almost three times as many
cores were taken. Four larvae were in the upper stratum, the rest scattered
down to the 9-10 cm. layer. With so few animals represented it was not possible to find evidence of migration by comparing morning and afternoon
samples.
As with the annelid worms, there are differences between the Douglas
Lake data and those from Crystal Lake, Minnesota (Cole, 1949). Thirtytwo cores taken throughout the seasons of the year on soft bottom in Crystal
Lake contained dipterous larvae. All of these were tendipedids except for a
ceratopogonid found in the 15-20 cm. layer, and three individuals of Chaoborus, one each in the 0-1, 5-6, and 8-10 cm. strata. Out of a total of 46
animals, 69.57% were on the surface and in the first centimeter of deposits,
and all but 10.87% of the total counted were in the upper four centimeters.
256
THE AMERICAN MIDLAND NATURALIST
49 (1)
On firm sand bottoms the larvae were not found below the second centimeter.
Most of the Crystal Lake data apply to littoral and sublittoral bottoms. Tendipesplumosus didnotoccurinthisbodyofwater,andprofundaltendipedids
werecollectedonlyduringthefalloverturn,beingabsentorextremelyscarce
atotherseasons.
Mollusca.—On oneoccasionayoung Sphaerium wasfoundinthe3-4cm.
stratum at 16 meters.
CONCLUSIONS AND DISCUSSION
The over-all picture of the vertical distribution of profundal macrobenthos
in Douglas Lake during late summer indicates 93.4% of the total population
to be between the surface and 14 cm. in the sediment. Berg (1938) stated
that upwards of 90% of the macroscopic bottom fauna were between 0-15 cm.
in the several Danish lakes he investigated. In Esrom Lake he found a considerable number of animals to occur down to a depth of about 30 cm. and
possibly a few still deeper. Perhaps the deepest occurrence in Douglas Lake
(one Limnodrilus inthe20-24cm.stratum)isnotindicativeofthepenetrationtobeexpectedatotherseasons,orwithagreaternumberofsamples,for
thatmatter.Berg(1938)foundthespringpopulationmaximumtobe
between5and10 an.,whilethesummerandautumnmaximawerefrom
zeroto5cm.Thesefactsindicateseasonalverticalshiftsinpopulations
mightalsobeexpectedinDouglasLake.
SUMMARY
Ninety vertical core samples were taken from the profundal sediments of
Douglas Lake, Michigan, during August, 1950. Cores were sectioned at
intervals and the animals present in each stratum were recorded.
Eight microbenthic forms were identified, more species occurring in upper
profundal depths than in deeper regions. Encysted Cyclopsbicuspidatusthomasi penetrateddeeperinthesedimentsthanothermicroscopicspecies,being
presentmorethan16cm.belowtheoozesurface.
One hundred and six macrobenthic organisms, representing at least five
species, were present in the samples. Ninety-three percent of these were found
in the upper 14 cm. of the bottom deposits, with the 1-2 cm. level containing
more individuals than any other single stratum. The deepest penetration
(Limnodrilussp.) wasthe20-24cm.stratum.
REFERENCES
BERG, K. I938—Studies on the bottom animals of Esrom Lake. Ejnar Munksgaard,
Copenhaven.
COLE, G. A. 1949—An ecological study of the microbenthic fauna of two Minnesota
lakes. Unpublished Ph.D. Thesis, University of Minnesota.
EGGLETON , F. E. 1931—A limnological study of the profundal bottom fauna of certain
fresh-water lakes. Ecol. Monog. 1:231-332.
LENT, F. 1931—Untersuchungen iiber die Vertikalverteilung der Bodenfauna im Tiefensediment von Seen. Em neuer Bodengreifer mit Zerteilingsvorrichtung. Verh. d.
Int. Vet. f. Theor. u. Angew. Limn. 5:232-260.
MOORE, G. M. 1939—A limnological investigation of the microscopic benthic fauna of
Douglas Lake, Michigan. Ecol. Monog. 9:537-582.