Nutrient status of phytoplankton across a trophic gradient in Lake Erie: evidence from new fluorescence methods

• Published in: Canadian journal of fisheries and aquatic sciences 2012-01, Vol.69 (1), p.94-111
• Main Authors: RATTAN, Kim J, TAYLOR, William D, SMITH, Ralph E. H
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; Bacteria; Biological and medical sciences; Chlorophyll; Community structure; Correlation analysis; Environmental aspects; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Fluorescence; Fluorometry; Fresh water ecosystems; Freshwater; Fundamental and applied biological sciences. Psychology; Lakes; Nutrient deficiency; Nutrient status; Physiological aspects; Phytoplankton; Plankton; Synecology
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/f2011-135

Variable fluorescence of chlorophyll a was measured by pulse amplitude modulated fluorometry to determine its relationship with measures of nutrient status and phytoplankton community structure in Lake Erie. In 2005, nitrogen (N) deficiency was most common in May, phosphorus (P) deficiency was most common in June, and neither were common in September. The maximum quantum yield (F v /F m ) measured by pulse amplitude modulated fluorometry was lower in May and June than in September. The observed range of F v /F m included many values lower than previously reported in the lower Laurentian Great Lakes, while F v /F m values showed strong inverse correlations with indicators of N and (or) P deficiency. Community structure was also associated with nutrient status. Cyanobacteria were common at sites displaying N deficiency, while flagellates dominated P-deficient sites in all basins. N deficiency is surprising in a lake with generally high nitrate levels, but was supported by N debt, particulate C:N ratios and depressed F v /F m . Further work to characterize and compare results obtained with different variable fluorescence methodologies is desirable, but the present results support the belief that F v /F m can characterize nutrient deficiency of phytoplankton community in this large lake.