Analysis of Littoral and Profundal Benthos
From otsego Lake
Summer 1993
Benjamin Hayes *
ABSTRACT
During the sunmer of 1993 a series of bottem samples were taken frem
several transects in otsego Lake, Cooperstown, New York, as part of an ongoing
study at the Biological Field station. The samples gathered were frem 48 meters
in depth, 40 meters to 10 meters at ten meter intervals, and from 10 meters to
2 meters at two meter intervals. Samples (10 em diameter; 14 em in depth) were
preserved in seventy percent al cohol and rose bengal, an organic dye, that served
to color any organic material present. The samples were agitated, allowed to
settle, and the alcohol was decanted. A denser liquid, sugar water, was poured
over small amounts of the sample at a time, resulting in the organisms floating
to the suLface. The samples were dcminated by the segmented worms (Annelida:
Oligochaeta), fingernail clams (Bivalvia: Sphaeriidae), and chironanid fly larvae
(Insecta: Diptera). SpeCilnen5 were removed and placed in alcohol-filled vials
according to sample site. For each sample, the organisms were taken out and
ot-ganized taxonanically, allowed to dry for fifteen minutes, weighed, and
replaced into their vials for future identification. These collections will be
compared wi th organisms hem previous years to ascertain any change in the biotic
character of the lake ecosystem.
INTRODUCTION
Founded in 1968, the Biological Field Station monitors otsego Lake, the
streams that run into the lake, and the upper Susqueharma. Studying the benthos
of the lake is only one of the many aspects of lake monitoring undertaken. The
benthos are considered to be all the organisms, plant and animal, found in and
around the bottom of a body of water. We separated the fauna into 3 categories:
the eulittoral benthos, which deals with the organisms at the point where air,
water, and land meet; the littoral benthos, organisms occurring below the shore
line, but shallower than the compensation point of the majority of aquatic
plffi1ts; and the deepwater or profundal benthos.
This study dealt with the latter two assemblages. The information gathered
will be ccmpared with past findings to help identify the "health" of the lake.
It may be found that same organisms have declined at some depths and increased
in others, affecting species riclll1ess and biodiversity providing indications of
crumges in ecological integd ty and sustainabi Ii ty.
--~--------------------------------------------------------
*NYAS High School Research Trainee, Sumner 1993.
Cooperstown, N. Y. 13326
127
Current Address: RD#1, Box 258,
MATERIALS AND ME:rHODS
GatheLi ng of samp I es began an June 7, at a depth of 48 meters, and
concluded on August 9, with the collection of samples at the depths of 4 and 2
meters. During this time period, a total of 109 saJT()les were taken hom 37 sites
at 8 different depths in otsego Lake.
To obt.ain these samples, the research vessel "Anodontoides" was set out
with sonar equipment and anchored over the correct depth. An oversized Ekman
dredge was then lowered and sunk into the substrate (bottom) using a hand­
operated winch. The jaws were shut, and the dl~edge was pull ed back aboard the
vessel. On board, the dredge was emptied, without disturbance of the substrate,
into an appropriate container. A "core", 10 em in surface area and 14 em in
depth, was removed han the sample and placed into a two liter container.
Recycled ethyl alcohol (@ 70%) was ~xed with rose bengal (an organic dye) and
poured over the sample into the containers and agitated. The alcohol served to
kill and fix any organisms in the mud. The rose bengal colored them a light pink
to a deep t-ed. rrhis procedure was normally repeated three times at each station.
The full jars were then taken back to the Biological Field station (BFS) to be
analyzed.
At the BFS, the sal"f{lles were allowed to settle, and the alcohol was
decanted back into the drums hom which it came so that it could be fortified and
used again. Sugar water was prepared using approxinBtely 200 mJ of sugar for
every 2 1 of water.
The sugar water was poured over snaIl portions of the
alcohol-saturated mud, and because of the difference in density between the two,
any ot"ganisms in the mud floated to the surface. The sample was then inspected
and the organisms removed. They wet"e put in alcohol-filled vials witll a label
stating the date of collection, location, depth, and any ancillary information.
The organisms in each sample were then separated taxonorracally by Class, left to
dry fifteen minutes, weighed and recorded, and then replaced into their vials for
future identification.
RESULTS
of the three najor Phyla that were found in the collections, each was
dcrninated by a single class (Tables 1 & 2). In the Phylum Annelida, Oligochaeta
(segmented worms) were the most numerous. of the Mollusca, Bivalvia (fingernail
clams) dcrninated, and in the Arthropoda, the Insecta Order Diptera (chironcrnid
fly larvae) occuned. in the largest numbers.
As shown in Figure 1, the
Oligochaeta were primarily found in the deeper water, while the Mollusks were
found in greatest numbers in I ittoral samples.
The Chironcrnidae were most
abundant in the upper hypolimnion.
1 28
TABLE 1:
Depth
~
~
Mollusc
Arthrop
Cnidaria
of
otsego
Turbell
Lake
Total
0.15
9.42
0.52
-----­
0.08
10.02
4 m
0.08
8.74
0.50
0.04
0.15
9.51
6 m
0.27
13.76
0.32
0.08
-----­
14.43
10 m
0.97
13.00
0.59
-----­
-----­
14.56
20
IT'.
0.25
0.30
3.24
-----­
-----­
3.79
30 m
0.61
0.39
3.45
-----­
-----­
4.45
40
IT'.
2.28
0.21
2.03
-----­
-----­
4.52
48 m
4.26
0.38
-----­
-----­
-----­
4.64
Depth
2
II
Annelid
area)
2 m
TABLE 2:
i'
Average biomass (g/m 2 surface
macrobenthos, Summer 1993.
Average
percent
biom.?-ss
of
dominant
colI ected from 100 cm~ surface area in
Surnrner 1993.
Annelida
Mollusca
Arthropoda
Cnidaria
!':".
1. 2%
93.3%
5.1%
4 m
0.8%
91.9%
5.3%
0.4%
1. 9%
95.4%
2.2%
0.5%
6.6%
89.3%
4.1%
20 m
6.6%
7.9%
85.5%
30 m
13.7%
8.8%
77.5%
40 m
50.4%
4.6%
44.9%
48 m
91.8%
8.2%
10
IT'.
!~
;,
macrobenthos
ot s ego Lake,
Turbellaria
0.5%
--r----------t---~---__1I
129
I
I ~~~~~j
Figure 1.
Percent biomass of Annelida (Oligocha.eta), MollL~ca (Sphaeriidae),
and Arthropoda (Chironcxnidae) in otsego Lake, Surrmer 1993, occurring
fram 2 meters to 48 meters in depth.
Percent Biomass by Depth in Otsego Lake
100
90
80
VJ
VJ
70
~
E 60
.2
-
OJ
c:
CI.l
(J
"CI.l
c..
50
40
30
20
10
o­
0
4
2
'10
6
20
30
40
48
Meters
•
Annelida
o Mollusca
rn Arthropoda
~ Other
ACKNCMLEOOEMENTS
I d like to thank the New York Academy of Sciences Research Training
Program for the opportunity to have this experience, Dr. Haman for his
cooperation with the New York Academy of SCiences High School Research Training
Program, Linda Taylor for starting the study and giving rre a lot of help, and
everyone at the BFS who helped get sant>les and process them.
I
BIBLIOGRAPHY
Thorp, James H. and Alan P. Covich. 1991. Ecology and Classification of North
Arrerican Freshwater Invertebrates. Academic Press, san Diego.
130