title: USE OF PULSE-AMPLITUDE-MODULATED FLUORESCENCE TO ASSESS THE PHYSIOLOGICAL STATUS OF CLADOPHORA SP. ALONG A WATER QUALITY GRADIENT(1).
abstract: This study investigated the application of pulse-amplitude-modulated (PAM) fluorometry as a rapid assessment of benthic macroalgal physiological status. Maximum quantum efficiency (Fv /Fm ), dark-light induction curves, and rapid fluorescence light-response curves (RLC) were measured on the filamentous macroalgal Cladophora sp. from Lake Ontario on 5 d at 16 sites spanning a gradient of light and nutrient supply. For Cladophora sp. growing in situ, light limitation was assessed by comparing average daily irradiance with the light utilization efficiency parameter (α) derived from RLCs. In this study, there was a nonlinear relationship between Fv /Fm and the degree of P limitation in macroalgae. However, only light-saturated Cladophora sp. showed a significant positive linear relationship between Fv /Fm and P nutrient status. The absence of this relationship among light-limited algae indicates that their photosynthetic rate would be stimulated by increased water clarity, and not by increased P supply. PAM fluorescence measures were successfully able to identify light-saturated macroalgae and, among these, assess the degree to which they were nutrient limited. These results enable us to test hypotheses arising from numeric models predicting the impact of changes in light penetration and nutrient supply on benthic primary production.
authors.affiliation: Aquatic Ecosystem Management Research Division, Water Science and Technology Directorate, Science and Technology Branch, National Water Research Institute, Environment Canada, 867 Lakeshore Road, Burlington, Ontario, Canada, L7R 4A6University of New Brunswick, Biology Department, P.O. Box 5050, Tucker Park Road, Saint John, New Brunswick, Canada, E2L 4L5University of Waterloo, Biology Department, 200 University Avenue W, Waterloo, Ontario, Canada, N2L 3G1.
authors.forename: Véronique P
authors.initials: VP
authors.lastname: Hiriart-Baer
authors.affiliation: Aquatic Ecosystem Management Research Division, Water Science and Technology Directorate, Science and Technology Branch, National Water Research Institute, Environment Canada, 867 Lakeshore Road, Burlington, Ontario, Canada, L7R 4A6University of New Brunswick, Biology Department, P.O. Box 5050, Tucker Park Road, Saint John, New Brunswick, Canada, E2L 4L5University of Waterloo, Biology Department, 200 University Avenue W, Waterloo, Ontario, Canada, N2L 3G1.
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Arciszewski
authors.affiliation: Aquatic Ecosystem Management Research Division, Water Science and Technology Directorate, Science and Technology Branch, National Water Research Institute, Environment Canada, 867 Lakeshore Road, Burlington, Ontario, Canada, L7R 4A6University of New Brunswick, Biology Department, P.O. Box 5050, Tucker Park Road, Saint John, New Brunswick, Canada, E2L 4L5University of Waterloo, Biology Department, 200 University Avenue W, Waterloo, Ontario, Canada, N2L 3G1.
authors.forename: Sairah Y
authors.initials: SY
authors.lastname: Malkin
authors.affiliation: Aquatic Ecosystem Management Research Division, Water Science and Technology Directorate, Science and Technology Branch, National Water Research Institute, Environment Canada, 867 Lakeshore Road, Burlington, Ontario, Canada, L7R 4A6University of New Brunswick, Biology Department, P.O. Box 5050, Tucker Park Road, Saint John, New Brunswick, Canada, E2L 4L5University of Waterloo, Biology Department, 200 University Avenue W, Waterloo, Ontario, Canada, N2L 3G1.
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Guildford
authors.affiliation: Aquatic Ecosystem Management Research Division, Water Science and Technology Directorate, Science and Technology Branch, National Water Research Institute, Environment Canada, 867 Lakeshore Road, Burlington, Ontario, Canada, L7R 4A6University of New Brunswick, Biology Department, P.O. Box 5050, Tucker Park Road, Saint John, New Brunswick, Canada, E2L 4L5University of Waterloo, Biology Department, 200 University Avenue W, Waterloo, Ontario, Canada, N2L 3G1.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Hecky
keywords: Cladophora sp.; Fv/Fm; Great Lakes; nutrient limitation; pulse-amplitude-modulated fluorescence