Phosphorus Kinetics in Lake Superior: Light Intensity and Phosphate Uptake in Algae

Abstract

nivel:~i~ qf Toronto, Toronto, Ont. MIC bA4 AND H. SHEAR Great L a k s Bialimieolr>gy Lobomtoql, Fisheries and 0ceara.r Cu~zadu, Burlir~ytora, Ont. L7R 446 NALEWAJKO, C . , K. LEE, AND H. SHEAR. 1981. Phosphorus kinetics in Lake Superior: light intensity and phosphate uptake in algae. Can. J. Fish. Aquat. Sci. 38: 224-232. Epilimnetic phytoplankton in Lake Superior in September, 1979, had low bk values (75-190 pE -mu" ss-'), low N/P ratios (8 to 13 : 1) and "~0 4 -P uptake kinetics that were not consistent with a state of extreme phosphorus limitation. Parallel laboratory experiments with Chlorells~ py~-elaoidosa indicated that phosphorus content per cell was higher and uptake rates of phosphate were lower in cells grown under low light (57 pE: . m-2 . s-') than those under high light (340 pE m-' . s-I). Maximum 3'~04 uptake occurred at about 50-60 pE -n~-~ . s-' in both cultures indicating 3 2~0 4uptake kinetics are light dependent at very low light levels, below or close to their bk values. It appears that light and not phosphorus limited phytoplankton growth in Lake Superior at the time of our experiments. Antecedent solar radiation prior to our experiments coupled with complete mixing of the top 20-25 m of the Lake possibly resulted in a low light-adapted phytoplankton population. We suggest that phosphorus control need not be the correct management strategy to maintain oligotrophy in Lake Superior.En septembre 1979, le phytoplancton Cpilimnetique dea lac Superieur avait de basses valeurs de Ik p8. E . n~-~ s-I), de fdibles rapports N/P (8 a 13 : 1) et une cinktique d'assimilation de "~0 4 -P en contradiction avec un Ctat d7extr2me limitation de phosphore. Bes expbriences paralltles en laboratoire avec CBzlorc.lla pyrenuiskPsta indiquent que le contenu en phosphore par cellule Ctait plus 6levC et les taux d'assimilation des hosphaaes moins klevCs dans les cellules cultivtes B une hible luminositk (57 pE * m-' . s-l) que dans celles cultivkes h une fane luminosit6 (340 pE --mu" ssl'). L'assimilation maximale de " '~0~ se produisit B environ 50-60 pE . m-' s-' dans les deux cultures, signe qeae la cinktique d'assimilation de 3 '~~4 dbpend de la lumitre a des trks faibles niveaux d'intensite Iumineuse, au-dessous ou se rapprochant de leur valeur de Ik. I1 semble que Ia lumikre, et non le phosphore, limitait la croissance d~a phytoplmcton dans le lac Supbrieur au anoment de nos expkriences. La radiation solaire avant nos experiences, couplke B un meIange conaplet des 20-25 m sup6rieurs du lac a probablement produit une population phytoplanctonique adaptCe i une faible intensite Iurnineuse. I1 est possible que Ie contr6le du phosphore ne soit pas nkcessairement la bonne stratkgie de gestion pour maintenir l'oligotrophie dms le lac Seapirieur .

The Deep Chlorophyll Maximum in Lake Superior

“…The C:P ratios seen in our study indicate moderate to severe P limitation (Healey and Hendzel 1980). Other physiological indicators of P status, such as alkaline phosphotase activity and P debt, have also shown Lake Superior to be highly P limited during the stratified period (Guildford et al 1994, Guildford and, although it has also been pointed out that P deficiency is not as severe as would be expected on the basis of P concentration in the lake (Nalewajko et al 1981, Guildford et al 1994.…”

“…Nalewajko et al (1981) have argued that even epilimnetic phytoplankton in Lake Superior can be light limited during the stratified period. They found that Chlorella cultures adapted to low light levels and grown at phosphate levels approximating those found in Lake Superior exhibited reduced P uptake rates and had a per cell P content 2.8 times higher than that of those grown in a high light environment.…”

Primary production and size-fractionated structure of the Black Sea phytoplankton in the winter-spring period

“…30 to 40 m g P-PO4 m-3, Dobrzhanskaja 1967; 111.9 k 25.7 mg N-NO3 m-3, n = 65, Kirikova pers, comm. -the same early spring cruise 1988) is only advantageous for those algae that, drifting downwards, are able to adapt to dim light or even total darkness over rather long periods of time, about 20 to 30 h or probably more (Nalewajko et al 1981, Smith & Barker 1985, Nalewajko & Valtolina 1986). Hence they should b e characterised by extremely low respiratory losses.…”

Influence of sunlight on the proliferation of cyanobacterial blooms and its potential applications in Lake Taihu, China

“…However, nutrients were found to be significantly correlated with phytoplankton biomass in those groups treated with high shading ratios (EG3 and EG4). This phenomenon might be caused by light limitations (Nalewajko et al, 1981;Havens et al, 2001;Powell et al, 2008;Duhamel et al, 2012), which was consist with the results by Sterner et al (1997). In this study, phosphorus was considered to be enhanced if the light was reduced (Sterner et al, 1997).…”