PARENT SESSION
Oral Session #56: Aquatic Ecology: Plankton. Presiding: N. Hairston.
Wednesday, August 8, 2001. 1:00 PM to 5:00 PM. Hall of Ideas I.

Vertical structure of seston food quality and quantity in an oligo-mesotrophic subalpine lake.

Park, SangKyu¹, Chandra, Sudeep¹, Goldman, Charles¹, ¹

ABSTRACT- To explore the possibility that seston food quality influences zooplankton diel vertical migration, we measured several seston food quality and quantity variables such as particulate carbon, chlorophyll a, fatty acid content, and phosphorus content as well as macrozooplankton distribution over entire water column (6-10 depths) during the summer season in 2000. Particulate carbon concentration peak moved from 20 m during daytime to 10-15 m at night in June and September while particulate carbon decreased during at night in the epilimnetic water in July and August. 3-polyunsaturated fatty acid content in seston was higher during daytime than at night, especially in the hypolimnion, and the discrepancy between day and night decreased as summer progressed. Molar carbon to phosphorus ratios were higher during daytime than at night, especially in the epilimnion, mainly due to changes of particulate carbon concentration between day and night. Overall, discrepancy in seston food quality between deep and shallow water was smaller at night than during daytime indicating that the diel changes in seston food quality might influence the diel distribution of macro-zooplankton species in Castle Lake including Daphnia.

KEY WORDS: seston, food quality, zooplankton, diel migration