Factors Controlling Phytoplankton Production in Lake Vanda (77°S)

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Vincent, Warwick F., Vincent, Connie L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1982
• Subjects: Ice cap
• Online Access: http://dx.doi.org/10.1139/f82-216; http://www.nrcresearchpress.com/doi/pdf/10.1139/f82-216

At least three floristically distinct communities of algae were distributed down the permanently ice-capped water column of Lake Vanda. Phytoplankton at each depth were highly specialized towards specific conditions of light and temperature. Maximum photosynthesis and algal biomass was at the bottom of the euphotic zone (55–57.5 m) immediately above a region of nutrient-rich anoxic water. This Phormidium-dominated community was adapted towards warm temperatures (18–20 °C) but a dim light regime. Dissolved inorganic N to P ratios in this region were extreme (> 5000:1) and the plankton demonstrated strong cellular P deficiency. A much smaller photosynthetic maximum was recorded in the middle of a large thermohaline convection cell at 25–30 m where P deficiency was less severe, but detectable. A microflagellate community immediately under the ice demonstrated the least response to phosphorus enrichment, but photosynthetic characteristics appeared to be more attuned to the low irradiances which prevail early in the growing season rather than to the relatively bright light regime during midsummer sampling. Algal biomass levels at most depths declined over 4 wk of sampling, further indicating that population maxima are timed early in the season. The low input of phosphorus relative to nitrogen exerts an overall control on phytoplankton biomass in Lake Vanda, but low production rates per unit biomass characterize the shade-adapted populations at all depths.Key words: phytoplankton, photosynthesis, algal biomass, N to P ratios, ice cap