Phytoplankton nutrient deficiency in lakes of the McMurdo dry valleys, Antarctica

• Published in: Freshwater Biology
• Main Author: PRISCU, JOHN C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1995
• Subjects: Antarc*; Antarctica; McMurdo Dry Valleys; McMurdo Sound
• Online Access: http://dx.doi.org/10.1111/j.1365-2427.1995.tb00882.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-2427.1995.tb00882.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2427.1995.tb00882.x

SUMMARY 1. The influence of inorganic nitrogen and phosphorus enrichment on phytoplankton photosynthesis was investigated in Lakes Bonney (east and west lobes), Hoare, Fryxell and Vanda, which lie in the ablation valleys adjacent to McMurdo Sound, Antarctica. Bioassay experiments were conducted during the austral summer on phytoplankton populations just beneath the permanent ice cover in all lakes and on populations forming deep‐chlorophyll maxima in the east and west lobes of Lake Bonney. 2. Phytoplankton photosynthesis in surface and mid‐depth (13 m) samples from both lobes of Lake Bonney were stimulated significantly ( P < 0.01) by phosphorus enrichment (2 μM) with further stimulation by simultaneous phosphorus plus NH 4 + (20 μM) enrichment. Similar trends were observed in deeper waters (18 m) from the east lobe of Lake Bonney, although they were not statistically significant at P < 0.05. Photosynthesis in this lake was never enhanced by the addition of 20 μM NH 4 + alone. Simultaneous addition of phosphorus plus nitrogen stimulated photosynthesis significantly ( P < 0.01) in both Lake Hoare and Lake Fryxell. No nutrient response occurred in Lake Vanda, where activity in nutrient‐enriched samples was below unamended controls; results from Lake Vanda are suspect owing to excessively long sample storage in the field resulting from logistic constraints. 3. Ambient dissolved inorganic nitrogen (DIN) (NH4 + + NO 2 − + NO 3 − ): soluble reactive phosphorus (SRP) ratios partially support results from bioassay experiments indicating strong phosphorus deficiency in Lake Bonney and nitrogen deficiency in Lakes Hoare and Fryxell. DIN : SRP ratios also imply phosphorus deficiency in Lake Vanda, although not as strong as in Lake Bonney. Particulate carbon (PC): particulate nitrogen (PN) ratios all exceed published ratios for balanced phytoplankton growth, indicative of nitrogen deficiency. 4. Vertical nutrient profiles in concert with low advective flux, indicate that new ( sensu Dugdale & Goering, 1967) ...