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Lake Erie, Central Basin Research Update





The following is a summary of research being down on
a hard benthic area of Lake Erie's Central Basin and
a study of the zooplankton.

               THE SHALE REEF AT AVON POINT
            A brief overview of the change taking
            place in 1998. 

          ...like a dog walking on his hinder legs.
             It is not done well; but you are 
             surprised to find it done at all.
                           Samuel Johnson
                             1763

      For the vast majority of people who are not 
acquainted with my biological work in Lake Erie let
me introduce myself by saying I am an amateur naturalist
who works with the most primitive of equipment. I think
of myself as being more closely fitting into the
atmosphere of the late 18th century than with the
current researchers, with whom I have almost no contact.
Though there are are two important exceptions to the feeling
of belonging to 18th century, one is this work is being done 
on a personal computer, the other is to have
the works of G. Evelyn Hutchinson "A Treatise on Limnology"
to use as my primary reference.
     Throughout the ten or so years I have been working
on this project I have been faced with an ecosytem that
has been subject to vast changes. Every time I think I
have achieved a rudimentary understanding of what is 
going on on the reef the whole ecosystem seems to go
through a vast convulsion leaving me with new dynamics
to understand and leaving my earlier works useful only
as comparisons to the changes taking place.
     I study a small shale reef in Lake Erie, found off 
an area known as Avon Point, which lies about half way 
between the cities of Lorain and Cleveland, Ohio. This
area of the Lake rest on a small shelf on the rim of 
the Central Basin of Lake Erie. The water's depth quickly
drops to 10 to 15 feet and remains at that depth for about a
mile out. The reef was formed by the collapse of
the shale cliff walls that form the shoreline and are
the bedrock of the area. Overlaying this shale is an enormous
amount of glacial till. Under the shale and stretching 
out beyond it is a bottom of blue clay. There is very little
sand or mud because this area is unprotected from the large
waves generated by one of the longest fetches on Lake Erie
and the area, because of the peninsula created by Avon Point,
is subject of a littoral drift the runs against the 
prevailing Lake current. Whereas Lake Erie's water generally
flows from West to East, at Avon Point the near shore water
flows from East to West. These combined currents tend to
remove all loose sediment from the bottom area. There is a
stream that empties into the reef area. Though the stream's
mouth is slightly to the West of the reef because of the
ancient stream bed that lies underwater the streams runoff
is turned eastward and runs over the reef.
     There is a basic reoccuring cycle on the reef. The 
cycle is not constant but the following gives an idea of
the dynamics of life even though the population density
and timing of when animals appear fluctuates from year
to year. 
     In the Spring the rocks are dominated by the colonial
peritechs; Zoothamniums and Carchesiums. To give an indication
of the number of colonies found on a typical rock let me give
two examples. May 18th 1997: a rock 13 cm. by 12 cm. and 1 cm. 
thick on its top and sides had 80 Carchesium colonies and 
6 Zoothamnium colonies. On the rock's bottom there were
23 Carchesium colonies and 149 Zoothamnium colonies. There was
no laison and only one Zebra mussel on the rock. The number
of peritechs is highly varible on the rocks from none to 891
on a triangular clay block having 2 sides 12 cm long and a
base 13 cm. long and 3 cm. thick. In years past the peritechs
would disappear by the middle of June but this year, 1998,
they have stuck in reduced numbers right up until the
present (Sept. 1998).
    A final note on these colonies. Zoothamniums are normally
known to be epibonts, this is the first time that the have
been known to live in vast number on inanimate objects.
   Begining in late May and early June the Hydras take 
over as one of the dominant life forms on the bottom
(see chart below).
   By mid June the laison is growing strong and continues
to hold on the upper surfaces of the rocks right into 
October.
   By Late June the Hydras have either disappeared or are
waning in numbers and the insects Ablabsymia and Hydropschye
as well as sponges and up until 1996 Planarians are all 
increasing in numbers
     For the first eight years of this study the Bryozoans 
were extremely rare on the reef. Beginning in 1997 the species 
F. sultana has become one of the most common animals found. 
They are found on about half of all the rocks sampled 
in late Summer. This increase in colonies is continuing 
this year. 
     In the Fall the Colonial Hydra Cordylophora
lacrustis (or Cordylophora caspia) make their appearance.
     The sponges start forming gemmule bodies and the laison
disappears. The ostracods and amphipods begin increasing
in numbers.
    Regretfully, since I lack a dry suit I haven't been
able to explore the reef in winter.
     With the above extremely incomplete introduction, 
I would like to present a look at what is happenning on the 
reef and the waters above it in summary form up to and 
including September 1998. This is by no means a complete 
report it will take me several months (or longer) to put 
all the data in some kind of format and the project is 
an on going one so it is constantly being revised.

                         ZOOPLANKTON
    IN THE FOLLOWING DATA IT MUST BE UNDERSTOOD THAT I AM
NOT SAYING THAT THE POPULATION DENSITY FOR THE LAKE AS A
WHOLE OR EVEN THE CENTRAL BASIN IS REFLECTED IN THE NUMBERS
PRESENTED HERE. THE CRUSTACEANS (AND PROBABLY THE ROTIFERS)
ARE MEMBERS OF THE PLANKTON OR THE NEKTON DEPENDING ON 
WAVE LENGTH AND/OR SEICHE (AND POSSIBLY OTHER FACTORS SUCH
AS MATING AND FEEDING). THEREFORE DETERMINING WHETHER THE
POPULATION DENSITIES OF THE CRUSTACEANS ARE DECREASING OR
INCREASING CANNOT IN ANY ABSOLUTE SENSE BE DETERMINED FROM
ANY OF THE FOLLOWING FIGURES. THE NUMBERS ONLY SHOW A 
RELATIVE CHANGE OF THE NUMBER OF ANIMALS FOUND IN THIS 
PARTICULAR AREA OF THE LAKE UNDER NUMEROUS CONDITIONS.
I FIRMLY BELEIVE FROM THE DATA GATHERED THAT THE DYNAMICS OF
THE ZOOPLANKTON IS FAR MORE COMPLEX THAN IS GENERALLY 
BELEIVED (AND I AM NOT TALKING ABOUT THE CATCHALL "PATCHINESS"
SOME PEOPLE ATTEMPT TO EXPLAIN VARIATIONS IN THE ZOOPLANKTON).

     Before listing the data on the copepods found in the 
waters above the reef I would like to give an example to
those unfamiliar with the great number of animals found in
the waters of the Lake a glimpse of rich in life the 
Lake can hold. The following example is old and, as will
be seen by studying the tables below, the number of 
crustaceans has decreased significantly since this data
was collected. It still give a picture of the enormous
amount of life in the waters. After working with these
numbers I actually starting feeling guilty every time I
took a shower or flushed the toilet realizing the numbers
of animals that died providing my creature comfort.

The data is taken from 1995 using the 12.5 liter plankton
samples and the 5 liter benthic samples and projecting them
into a 1 cubic meter area.
June          Plankton          Benthic
Cyclopoids   13104              1012.4
Calanoids     4079.5             555
Nauplius      9319.68            907.4
Bosmina       7447.68            698.4
Daphnia        304
Diaphansoma   1327.68      
Leptodora       23.76
Ostracoda        0
Polyphemus       0
Harpactacoida    0
Rotifers      4000

      
July           Plankton         Benthic
Cyclopoids    1470.96           445.6
Calanoids      175.68            45.6
Nauplius      2119.68           391.4
Bosmina        820.8             77.4
Daphnia        240
Diaphansoma   1087.9
Leptodora        7.92
Ostracoda       55.44
Polyphemus      95.74
Harpactacoida    7.9
Rotifers       5728

                         COPEPODS
                 Monthly Averages for Copepods
   The following data is based on 12.5 liter samples taken twice
a week. All the samples where taken in the morning from the
same location.
	        Calanoid Copepods 1993 to 1997
       1993      1994     1995        1996    1997    1998
Mar.                        2.2        2.6      .9    1.56
Apr.             7.7        3.7        3.5     4.5    24.1
May            104.3       84.8       37      40.5    11.6 
June   12.75    71.4       56.7       60.7  *144      27.8
July    4.85    22.4        2.4       28.4     8.5     4.6
Aug     4       16.7        5         28.1     7.1     2.6
Sept   26.57    32.1       13.6        6.8    11      12
Oct    15.55    11           9.3      34.6     6.3
Nov     9.11     9.9        5.3        2.9     4.9
Dec     5.57     6.3        7.2        5.6      .8

Average of the  31.3       20.9      23.04    25.3
Calanoids Apr. thru Dec.
1994 to 1997
   *  Except for the extraordinary number of animals found on one
sampling date the number of calanoid copepods would have shown 
a marked decline in 1997. That date was June 15. The sample 
had the extraordinary number of 880 calanoids in the 12.5 liter
sample. The total number of calanoids found for the entire year 
in about 50 samples minus the June 15 date was 1130, thus the one 
sample had more animals than all the samples for the entire 
year. I have belabored the point of the nonrandomness of the
zooplankton in the 1996 report and so will not cover that ground
again. What I want to point out here is that if the June 15 sample
is dropped from the reporting than the copepods had a steep 
drop in their numbers in 1997 and the average for the month of  
June would be 52 per sample rather than 144 per sample. The 
average for the year would drop from 25.3 per sample to 11.4
per sample. Whether this dropping of the sample from the total
counts is valid I leave up to the reader but if the June 15
sample is ignored than the calanoids have had a major decline 
in 1997.

                    Cyclopoid Copepods
     The cyclopoid copepods had a sharp drop in the numbers
found in the samples. The table does not include the
cyclopoid T. Mexicanus pranis. This small copepod was found
very sporadically in the samples until this year. Though when
it was found it could be found in large numbers.
     Comparison of Cyclopoids Copepods from 1993 to 1997
      1993       1994        1995    1996      1997      1998

April             8.6        9.77     3		.3	   2.1  
May              38.33      56.75    50.33     8.9	  34.7		
June   51.5      38.77     182      109.36    35.4        59.1
July   25        26.6       19.55    17.13    30.2         6.3
Aug.   38.5      13.7       19.11     5	       7.7	   3.7
Sept.  17.28     12.5        7.12    17.33     2.9         1.2
Oct.    8.55     13.1        3.77     8.88     2.3
Nov.   12.88      7.7        5.66     1.5      4.3			
Dec.   10.71      5.13       4.4      7.66     1.1

Average for the  18.277     34.23    24.46    10.3  
years 1994 to 1997
Apr. to Dec.
                   Copepod Nauplii
    No attempted was made to distinquish between cyclopoid and 
calanoid copepods. 
                        Nauplii
Monthly averages
         1993      1994       1995       1996   1997    1998
Jan.                                     3.25    3.8     0.3
Feb.                                      .75    1.9     1.4
Mar.                                     9.5     1.4      .9
Apr.               36.16      28         8.25   61.3    33.4
May               133.97     161.25     63.55   13.8    53.4
June     13        61.3      129.44    121.22   64.8    38.5
July     2.71      27.66      29.4      51      48.6     5.2
Aug.     4.5       49.55      70.44     30      15       9.8
Sept.    6.57      26         40.12     49.66   10      38.4
Oct.     4.77      10.22      13.11     44       8.8
Nov.     6.44       2.88       4.44      1.625   2.8
Dec.     4.57       5.62       2.4       1.66     .2

Yearly average     39.26       53.17     41.21   25.03
from Apr to Dec.
                      Cladocerans
     I am leaving out the data on Cladocerans because monthly
averages is misleading in their case and listing 
every date would make this brief report far longer than is
intended here. Why I think monthly averages for these animals
is misleading can be seen from dates given below.

August 27, 1995. The time, between 9 and 9:30 in the morning.
Being underwater I can only estimate that the sample was taken
somewhere between 100 yards and 1/4 mile from shore. There were
no waves. The animals, like in the July 13, 1994 sample, could 
be seen as a white cloud in the water. Sample was taken in 10 to
12 feet of water. The swarm was no more then 10 feet wide, but
I have no idea how long the column was.
Aug. 27 1995
5 liter sample
   Crustaceans
Daphnia retrocurva               340
Leptodiaptomus siciloides        20
L. kindtii                       14
Tropocyclops mexicanus           123
Diacyclops thomasi               75
nauplii                          153

   Rotifers
Polyarthra                        2
Plankton sample
   Regretfully I wasn't able to take a plankton sample on the
27th but did take one on the 26th, so the comparison is not
as strong as the sample taken in July of 1994.  I think
the plankton sample still strongly points to swarming 
behavior of all of the crustacean zooplankton except for 
T. mexicanus.
Aug. 26, 1995
12.5 liter sample
   Crustaceans
T. mexicanus                     308 
D. thomasi                       3
nauplii                          30

Rotifers        
  Polyarthra                     1

Below for the purpose of comparison is the count of the sample
taken on July 13, 1994. While there are differences in both the
number of animals found and the species making up the sample what is 
striking is the simularities between the 2 samples. What is 
especially noteworthy is the presence of so many L. kindtii in
the sample. These large zooplanktoners are never present in this
large of a number in any of the regular 12.5 liter plankton 
samples. (these notes where written in 1994, this year,1998
I've found in on sample taken on Sept. 13 - L. kindtii- 33.
Strange that this Sept. 13 sample also had an extraordinarily
high number of T. Mexicanus pranis - 93.
July 13, 1994
5 liter sample
   Crustaceans
Daphnia retrocurva   674                       1 to 3 mm in length
L. kindtii            5                        4 mm.
D. thomasi           63                       .75 to 1.5 mm.
L.siciloides         3                        1.25 to 1.5 mm.
Nauplii              16                       .10 to .25 mm.
Diaphanosoma          3                         1 to 1.5 mm.
Bosmina               5                         .5mm
    Rotifers
	Polyarthra   40
        Keratella     3
July 13, 1994 Plankton sample 12.5 liters.
	A regular 12.5 liter plankton sample taken within 1/2 hour of 
the 5 liter sample shown above had a count of:
	Daphnia               22
	Cyclopoid copepods    15
	Nauplii               17
            Rotifers
                 Keratella     1
                 Polyarthra   26
      
     Throughout this study I have found that frequently the 
Cladocerans seem to move in clouds.

                        ROTIFERS
   Writing these brief notes I realize how terrible far behind
I am in bringing the data together. The numbers haven't been 
worked out for this important group of animals for 1997 and
1998. 
                      ROUNDED GOBIES
   They have maintained their population density of about 10 
per square meter, a level they reached in 1997.

                         MAYFLIES
    The genus Stenonema has had probably the biggest change in
it population density in 1998 than any other creature on the reef.
Taking as an example of 5 rocks sampled on three different dates 
in August (the mayfly population surge began in August), the 
rocks had a density of 0.1 per square cm. as opposed to 0.01 
per sq cm. in 1997 in sample taken during the same time period 
in 1997.
                       Snail
     The five species (except for the genus Ferrissa) that use to 
inhabit the reef in great numbers continue to be totally absent 
from the area. Two snails of the genus Ferrissa were the only 
snails seen this entire summer.
                   
                         PLANARIANS
    The Triclads of a genus of Dugesia for the first 8 years of 
this study were very abundant.
           # per cm.2                  # per sq. meter                                   
         1994      1995   1996           1994   1995  1996
May     0.002     0.021    0               22   214     0
June    0.022     0.028    0.003          221   287    30
July    0.031     0.035    0.026          318   352   260
Aug     0.053     0.063    0.039          539   635   390
Sept    0.068     0.041    0.042          681   413   420
Oct     0.066     0.038    0.02           664   387   200
    I believe the number of planarians per square meter is 
probably closer to 1/2 the number found in following table. 
I say this because probably only a very few areas on the 
reef provide suitable habitat over an entire square meter.
    In 1997 these animals all but totally disappeared, only 
several were seen the entire year. In 1998 this disappearence
has continued, only 2 have been seen the entire summer.
                          CNIDARIA
Hydras
     Average monthly population density for hydras.
The numbers are the average number of hydras per square cm. 
The rock surface area is only the area of the rocks underside.       

         1993        1994       1995         1996
April               0              
May     0.078       0.0007     0.0016
June    0.203       0.2318     0.4069      0.1344
July    0.281       0.1123     0.1393      0.093
Aug    *            0          0.0091      0.007
Sept   *            0.0016     0.0476      0.014
Oct     0.383       0.0034     0.0254      0.012

    I haven't worked out the numbers but in both 1997 and
1998 the number of hydras seems to have been decreasing.
Again I'm way way behind.

Cordylophora lacrustis (or Cordylophora caspia)
   The opposite of the decreasing numbers for Hydras has
occurred for C. lacrustris. Their numbers this Fall have
increased. There colonies have been found on between a 
quarter and half of all the rocks sampled. It has always
been an interesting point that these colonial hydras only
make their appearance in beginning in late July, they are
never found in Spring or early Summer. Also Hutchinson wrote
that in these colonies the hydranth are always found 
horiziontally or obliquely to the bottom, this is untrue. 
On this reef the animals are almost found with the hydranth 
facing vertically down

                  ZEBRA MUSSELS

     Since the collapse of the Zebra mussel population in
the winter of 1991-1992 the mussels have maintained a 
rather steady state. Each August and September there is
a large spawnING of the mussels and each winter almost all 
of the young and many of the older mussels are torn from
the rocks and washed up onto the beach. This area takes
a tremendous pounding in Winter from the Northeast winds
that seems to rip these mussels right off the rocks or the
rocks themselves smash into each other killing the mussels
living on them. Most upper surfaces of rocks have no mussels
on them at all. Generally it is only the large round boulders
that are mussel encrusted. A ballpark figure would be that
80% of the rocks have no mussels at all on the upper surfaces.
     I can see no evidence that the rounded gobies are
eating the mussels, even with the great number of gobies
present in the area there has been no decrease in the 
number of mussels. For the life of me I can't figure out
what the gobies are eating.

==================================================

    This is only briefest of overviews of what is occurring 
on the reef. I have left out the data on: Sponges, Ablabesmyia, 
Hydropshche, Harpactacoids, Amphipods and many of the lesser 
players in the ecosystem. Anyone wanting data on these animals 
are encouraged to write.

    Much of the older data for the years 1994 and 1995 is 
available in the Science section of the Lorain County Freenet
which can be reached at:
         lcfn.org
       192.232.30.40
login:  guest
password: guest

====================================================

I've seen them set to dance
by waves dragging up the sands,
tossed with directed fury
by meaningless winds of chance.

Rushed to hopeless flight.
Swirling towards death in light.
Claws ripping through water
The Naiads blind to their plight.

                Oct 28. 1997