Field and laboratory methods
Integrated (surface to 0.5 m above the lake bottom) water samples were collected weekly (May-Oct) from 1 to 5 sites using a tygon tube (1.9 cm inner diameter). Additional samples were collected sporadically (Nov-Apr) each year as the weather allowed. Subsamples of integrated lake water were preserved in Lugol's solution (1975 to 1995) or glutaraldhyde (1996 onwards). From 1975 to 1995, the phytoplankton samples were settled in Utermöhl settling tubes at 10 ml aliquots for bloom phase samples and 25 ml aliquots for clear water phase samples. The samples were left to settle over a 24 hr period, after which the settling slide was placed in a Wild inverted microscope for identification and enumeration. Identification was made at two different magnifications (400x and 100x) to the species level when possible; otherwise, phytoplankton cells were identified to the genus. Phytoplankton were identified to species or higher taxonomic level and abundances were reported in #/mL. Counts were done by Edward Mills (1975-1981, 1983-84, 1986-1988), Nasseer Idrisi (1982, 1985, 1988-1993, 1995), and Christine Morris (1990-1994) and Debbie Chiavelli (1991). Identifications were based on Prescott (1978), Smith (1950) and Patrick and Reimer (1966). Data from 1986 to 1995 were published in Idrisi et al. (2001).
From 1996 onwards phytoplankton samples from different stations were combined prior to analyses and 8 to 14 weekly samples were counted by Phycotech Inc (Dr. Ann St. Amand). No samples were processed from 1998 and 1999. Phycotech counted and measured 400 natural units including all algal cells that were alive at the time of sampling (cells with content) using magnifications of 250x, 500x and 1250x. The 500x magnification was the primary one used. The algae were mounted on slides and the amount of water mounted varied with the density of algal cells (0.1 to 100 mL/slide). Algal taxa were identified to species when possible and measured to provide sample specific biovolumes for the sample, by cell and by natural units (colonies, paired or other multiples of cells).
The combined data set is used in the chapters by idrisi et al. and Schulz et al. in the book Oneida Lake: Long-term dynamics of a managed ecosystem and its fisheries, edited by LG Rudstam, EL Mills, JR Jackson and D Stewart.
Idrisi, N., E.L. Mills, L.G. Rudstam, and D.J Stewart. 2001. Impact of Zebra Mussels, Dreissena polymorpha, on the Pelagic Lower Trophic Levels of Oneida Lake, New York. Can. J. Fish. Aquat. Sci. 58:1430-1441.
Patrick, R. and C.W. Reimer. 1966. The Diatoms of the United States, Exclusive of Alaska and Hawaii. Academy of Natural Sciences Phildelphia. Phildelphia, PA.
Prescott,G.W. 1978. How to Know Freshwater Algae. W.C. Brown. Dubuque, Iowa.
Smith, G.W. 1950. The Fresh-water Algae of the United States. McGraw-Hill. New York, NY.
