Total phosphorus–chlorophyll a size fraction relationships in southern Québec lakes

Abstract

The study is a first attempt to generate a series of Total Phosphorus–Chlorophyll a (TP–Chl a) predictiveOC models relating the quantitative responses of four algal size fractions to phosphorus gradients. The study was carried out in 27 glacial lakes from two regions in southern Quebec, the Laurentians and the Eastern Townships, and covered a relatively modest range of trophic conditions (TP, 3–34 µg P L‐1; Chl a, 0.3–7.6 µg L−1). Algal biomass was estimated using measurements of Chl a, and the total Chl a was divided into four operational size fractions: picophytoplankton <3 mm, nanophytoplankton 3–20 mm, nanophytoplankton plus picophytoplankton <20 mm (edible fraction), and microphyto‐plankton >20 mm (inedible fraction). We tested the hypothesis that the slopes of the TP–Chl a regression models developed for algal size fractions would increase consistently from the smallest to the largest algal size fraction, as suggested by the first half of the sigmoidal TP–Chl a models. Although there was no consistent trend in the magnitudes of the slopes of TP–Chl a relationships for picophytoplankton (slope = 1.14), nanophytoplankton (0.93), and microphytoplankton (1.22), Chl a concentrations in the largest size fraction increased more rapidly with phosphorus enrichment than in either of the smaller fractions. When included as an additional variable, lake water alkalinity improved the prediction of Chl a and presented differential effects on size fractions. The effect of TP enrichment on microphytoplankton is more pronounced in well‐buffered lakes, whereas TP enrichment has a stronger effect on nanophytoplankton in low‐alkalinity lakes. The effects of alkalinity may be the result of either a pH influence on phytoplankton carbon uptake or a stronger top‐down grazing effect on small algae in well‐buffered lakes.

Distribution of picophytoplankton and nanophytoplankton along an anthropogenic eutrophication gradient in French Mediterranean coastal lagoons

“…A similar result is observed in hypertrophic freshwater lakes where PEUK numerically dominate (Hepperle & Krienitz 2001). NANO are decreasingly important as lagoon eutrophication proceeds, similarly to freshwater lakes (Masson et al 2000). The growth of large phytoplankton (> 3 µm) is strongly regulated by nutrient availability (Chisholm 1992, Bec et al 2005.…”

Regional ecosystem variability drives the relative importance of bottom-up and top-down factors for zooplankton size spectra

“…Bottom-up drivers were best represented by TP in the Eastern Townships, and although Chl a has previously been found to be related to TP in the Laurentians (Masson et al 2000); in 2005, we found that TN and lake area were better predictors of lake potential productivity. Increased precipitation increases DOC inputs into lakes (Schindler 1998), and coloured DOC can change the relationships between nutrients and primary productivity (Carpenter et al 1998).…”

Effect of phosphorus and temperature on chlorophyll a contents and cell sizes of Scenedesmus obliquus and Microcystis aeruginosa

“…Despite many models of chl a and TP, most are linear regression, in which R 2 ranged from 0.42 to 0.95 (e.g., Dillon and Rigler 1974;Mazumder 1994;Jones and Knowlton 2005). This means that other factors, such as light, alkalinity, catchment area, and mixing regime, could affect the stimulation of TP-chl a relationship (Nichols and Dillon 1978;Ahlgren et al 1988;McCauley et al 1989;Van Nieuwenhuyse and Jones 1996;Masson et al 2000;Havens and Nürnberg 2004;Huszar et al 2006). However, the effect of temperature was seldom considered in building the model between chl a and TP.…”