Goulden C., D. Kreeger, S. Kilham
Abstract:
Seston samples were collected monthly for two years, 1994-95, from the epilimnion and metalimnion of three north-temperate lakes. Phytoplankton and zooplankton are most abundant in the spring and again in the fall in all three lakes. Lake Giles is an oligotrophic lake with a low pH and has prevalence of chrysophytes, Daphnia catawba and Diaptomus minutus. Lake Lacawac is mesotrophic and has chrysophytes, cryptomonads, Daphnia catawba, Holopedium gibburum and Diaptomus minutus as dominants. Lake Waynewood is culturally eutrophic and has heavy blooms of cyanobacteria, primarily Aphanizomenon and Anabaena; and with Daphnia pulicaria and Diaptomus oregonensis as the dominant zooplankton taxa. Seston samples were analyzed for protein, carbohydrate, and lipid fractions. For characterization of seasonal trends, all sample data were pooled for the three lakes (1995 data) and analyzed by linear regression with an emphasis on regression slope. Polar lipids that compose biological membranes were assumed to be the most conservative component of the seston and therefore the other components were compared with their concentration. Productivity of algal populations in these lakes is generally limited by both nitrogen and phosphorus, despite their different trophic status.
Polar lipid concentration in the seston increases with lake productivity but on a percent composition, decreases during the latter part of the year. Seston protein also increases with lake productivity, and the proportion decreases during the latter part of the year. The proportion of protein composing the seston also decreases during the year and relative to polar lipids in the seston. Bioavailable carbohydrate changes with polar lipids and is not seasonally related.
The part of the seston represented by triglycerides has the most dramatic changes. It is positively associated with date (marginal), polar lipids and carbohydrates but is not associated with protein.
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