Extracellular phosphatases in a Mediterranean reservoir: seasonal, spatial and kinetic heterogeneity

Abstract

1. Epilimnetic alkaline phosphatase activity (APA) was measured in longitudinal profiles of the canyon-shaped, eutrophic Sau Reservoir (Catalonia, Spain) during the autumn, winter and spring periods of 1997-2000. 2. The spatial pattern of APA depended on lake circulation. During periods of stable stratification, when the ratio of mixed to euphotic depth (z mix /z eu < 1.7) was low and the Chlorophyll a (Chl a) concentration high, APA was also comparatively high (0.5-3.4 lmol L )1 h )1 ) and located mostly in the >2-lm size-fraction. APA increased towards the dam at the same time as the concentration of soluble reactive phosphorus (SRP) decreased. In periods of unstable stratification, deep mixing (z mix /z eu > 2.4) and low Chl a concentration, APA was low (<0.1 lmol L )1 h )1 ) and without longitudinal changes, consistent with a high and stable SRP concentration. 3. A high input of mostly dissolved (in the <0.2-lm size-fraction) phosphatases from the river Ter was found in 1997-98. At the river inflow, independently of season and despite a continuously high SRP concentration, APA was approximately 0.7 lmol L )1 h )1 and decreased towards the dam within the inflowing, canyon-like part of the reservoir. 4. Analysis of saturation kinetics revealed the kinetic heterogeneity of APA. Low-affinity APA was localised in the >2-lm (algal) size-fraction while, in the <2-lm (picoplankton, mainly bacteria + dissolved) size-fraction, high-affinity APA, or a mixture of both, was found. The presence of two kinetic components, whose substrate affinities (i.e. in Michaelis constants, K m ) differed, was confirmed statistically in 13 of 18 cases analysed. The range of K mH values of the high-affinity component was 0.15-2.4 lmol L )1 , K mL values of the lowaffinity component ranged from 18 to 275 lmol L )1 .

Limitations of using extracellular alkaline phosphatase activities as a general indicator for describing P deficiency of phytoplankton in Chinese shallow lakes

“…When ambient available P is scarce, phytoplankton can produce extracellular phosphatase to hydrolyze organic phosphorus for compensation of P deficiency (Gillor et al 2002;Spijkerman and Coesel 1998;Feuillade et al 1990). Therefore, algal alkaline phosphatase activity (APA), roughly represented by that associated with larger particles (Nedoma et al 2006) or total APA (Pettersson 1985;Chrost et al 1984) was inversely proportional to phosphorus concentration, such as total P (Berman 1970;Smith and Kalff 1981) or soluble reactive phosphorus (SRP) concentration (Pettersson 1985; (Healey and Hendzel 1980;Thingstad et al 1998;Jamet et al 2001;Rose and Axler 1997;Istvanovics et al 1992) or in periphyton (Burkholder et al 1990;Rejmankova and Komarkova 2000;Newman et al 2003). Furthermore, some rectified APA, such as chlorophyll-specific total APA (Istvanovics et al 1992), surface-area-specific APA (Newman et al 2003) was sensitive enough to show changes in the P status of algae.…”

The role of river inputs on the hypolimnetic chemistry of a productive reservoir: implications for management of anoxia and total phosphorus internal loading

“…In the case of Sau Reservoir, the Ter River directly introduces nitrate into the deep layers of the water column during the stratification period, thus proceeding like a natural nitrate bioremediation measure. Nevertheless, this beneficial effect should be considered in the context of a phosphorus-limited environment like Sau Reservoir (Nedoma et al 2006). Obviously, in a nitrate-limited water body the validity of the above conclusion would be dubious.…”

Influence of phosphorus availability on the community structure and physiology of cultured biofilms

“…The impacts of P availability on the development and physiology of cultured biofilms were obvious. Phosphorus limitation in the low nutrient water body was indicated by APA (Healey and Hendzel, 1979;Singh and Tiwari, 2000), which often showed an inverse relationship with P availability (Whitton et al, 2005;Nedoma et al, 2006;Boge et al, 2012). The production of APA was one possible strategy to overcome P insufficiency (Rejmankova and Komarkova, 2000;Strojsova et al, 2005).…”

“…However, many studies concerning the relationship between phosphatase activity and P fractions are contradictory. The relationship between them can be positive (Barik et al, 2001;Zhou et al, 2001;Zhang et al, 2007Zhang et al, , 2012, negative (Vrba et al, 1993;Zhou and Zhou, 1997;Singh and Tiwari, 2000;Nedoma et al, 2006;Boge et al, 2012), or even irrelative (Jamet et al, 1997;Romani and Sabater, 2001), so phosphatase activity may be used only as a supplementary indicator of P content.…”