Robert Zottoli

Professor Emeritus

Fitchburg University

rzottoli@roadrunner.com

Merrymeeting Bay is an extensive tidal freshwater ecosystem formed by the merger of five rivers. The Androscoggin and Kennebec rivers are the largest. Tidal seawater moves along the bottom into the bay with the incoming tide and mixes with seaward flowing freshwater. The salinity of bay water seldom exceeds 5 parts per thousand. Seawater has a salinity of about 35 parts per thousand. Because of the low salinity Merrymeeting Bay is classified as a tidal freshwater ecosystem.

At the end of April and the first part of May, Merrymeeting Bay undergoes an amazing transformation. Varieties of plants emerge from the seemingly lifeless mud surface and form extensive marshes. In September, the marsh disappears. The aboveground parts of marsh plants die back and are partially digested by bacteria reducing them to small pieces (detritus) that can be trapped on the mud surface or flushed out to sea providing food to organisms on the sea floor. In the late fall all that remains are plant stems protruding just above the sediment surface.

The emergent seasonal vegetation provides food for large populations of small herbivorous fishes such as the common mummichog, Fundulus heteroclitus and migrating waterfowl as well as habitat for a variety of invertebrates and small fish. Fundulus on the other hand is consumed by fish eating waterfowl and larger fish such as the striped bass. Nutrients in the bay support large populations of phytoplankton and zooplankton that are eaten by certain plankton feeding juvenile and adult fish (Alewives, Blueback Herring and Shad). Sturgeon feed for the most part on invertebrates living on or in the sediment. The ciliated protozoans are one of the more important invertebrate groups in the sediment. They serves as a major source of food to other invertebrates as well as the fact that they transfer energy trapped in bacterial and plant biomass to the next highest trophic level. Scientists and laymen alike tend to minimize the importance of microscopic organisms other than bacteria and viruses perhaps because of their small-size and difficulty identifying them. Although I am not a Protozoologist, I have an extensive background in Invertebrate Taxonomy and with most identifications, I have included a movie (s) showing the animal moving and feeding in its normal habitat. This will also allow other individuals the chance to observe each genus and check the accuracy of my identification(s).

References used to identify Protozoans

Jahn, T.L., E.C. Bovee and F.F. Jahn . 1978. How to Know the Protozoa. 2nd Edition. Wm.C . Brown Co,, Dubuque Iowa, 279 pp.

Patterson, D.J., 1996. Free-Living Freshwater Protozoa, a color guide. John Wiley and Sons, New York. 223 pp.

Pennak, R.W, 1991. Fresh-Water Invertebrates of the United States. Protozoa to Mollusca.Third Edition. Wiley Interscience, New York, 628 pp.

Thorp, J.H. and A.P., Covich, Eds. Ecology and Classification of North American Freshwater Invertebrates 2010. Third Edition. Chapter 3 ,Protozoa (W. Taylor and R.W. Sanders), Pages 49-90. Elsevier (Academic Press), New York.

Materials and Methods

Samples of surface sediment were collected using a turkey baster in an area approximately 9X9 cm. at two mid-intertidal and two upper-intertidal locations at each site. Site locations and sampling dates are shown below.Sediment samples along with plants within the sample were immediately placed in plastic bags for transport to my home. The contents of each bag were transferred to separate black plastic trays (Approximately 14x24x4 cm) filled with about 200 cc of water. Initially the contents of each tray were examined under a dissecting microscope for macroscopic organisms. Then the sediment was stirred vigorously , allowed to settle, after which samples for microscopic examinationwere collected with an eyedropper at six randomly selected locations in the tray. Two drops of each sample were placed on separate glass slides and examined at 40X under a compound microscope (Nikon Eclipse E200) for large organisms. Then a coverglass was placed over the exposed sample and examined under 100X, 400X , 600X and occasionally at 1000X (oil immersion) . The samples were re-examined each week for three weeks after the collection date. The procedure discussed above was not an attempt to quantify individual species or determine their distribution in the samples but to ensure, as much as possible , that most of the common genera would be found.

General location of collecting sites and the dates that samples were collected in 2014

Baybridge Landing, Brunswick Maine (Androscoggin River) (6/3, 6/20, 8/2, 8/19):
43o 56’ 8.04”N
69o 53’ 21.58”W

Browns Point Road, Bowdoinham Maine (Cathance River) (7/21):
44o 0’ 37.21”N
69o 51” 0.35”W

Green Point, Dresden Maine (Kennebec River) (7/4, 8/16, 8/28, 9/22)
44o 3’ 19.18”N
69o 46’ 52.00”W

Movies were filmed through a trinocular compound (Nikon Eclipse E200 ) microscope with a C-Mount Digital ToupTek Camera (USB3 CMOS 10000K PA) equipped with a 10 Mega pixel chip. The movies were posted on VIMEO and their codes are embedded in the manuscript so that they can be accessed directly. Organisms were identified to Genus whenever possible.

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