Variations nycthémérales de l'activité phosphatase alcaline d'une Diatomée :Synedra capitataet de deux Cyanobactéries :Microcystis aeruginosaetAphanizomenon flos aquae

Abstract

The results we present here were on three quasi monospecific settlements : Synedra capitata (Diatom), Microcystis aeruginosa and Aphanizomenon flos aquae (Cyanobacteria). The alkaline phosphatase activity (APA) (EC : 3.1.3.1) exhibited a nycthemeral variation for Diatoms as well as Cyanobacteria, though every species had its own characteristic. Under similar experimental conditions, the enzymatic activity was, in the average, 32 times higher (per unit of biomass) for Microcystis aeruginosa than for Synedra capitata and 3 times higher for Microcystis aeruginosa than for Aphanizomenon flos aquae. Under LD (16 : 8), Synedra capitata and Aphanizomenon flos aquae had a maximal enzymatic activity during the day time (maximal APA around 425 umol pNPP/l/h at 5 a.m., 11 a.m. and 5 p.m. for the Diatom and around 850 umol pNPP/l/h at 11 a.m., 3 p.m. and 7 p.m. for the Cyanobacteria) while the enzymatic activity of Microcystis aeruginosa was maximal at the beginnique of the night time (maximal APA around 1500 (imol pNPP/l/h at 9 p.m.). The observed daily rythm disappeared when the samples were placed in the darkness (DD) or under permanent light (LL). In the last case (LL), the mean enzymatic activity of Microcystis aeruginosa was maximal and, on the contrary, the mean APA of both Synedra capitata and Aphanizomenon flos aquae was minimal. There was a difference between the phytoplanktonic species in the orthophosphate assimilation and in the capacity for mineralizing organic phosphorus because of the phosphatases. This difference in the enzymatic behaviour might explain ecological successions within the planktonic settlements.

Physico-chemical properties of Alkaline Phosphatases released by a Planktonic Crustacean, Daphnia Magna (Cladocera)

“…APA studies have mainly focused on algae (Healey, 1973;Giraudet et al, 1998;Spijkerman & Coesel, 1998;Nedoma et al, 2003), and have scarcely dealt with zooplankton activity, even though zooplankton is also known to release AP (Rigler, 1961;Jansson, 1976;Wynne & Gophen, 1981;Boavida & Heath, 1984;Jansson et al, 1988;Jamet & Boge, 1998;Hoppe, 2003;Jean et al, 2003). The predominant phosphatase released by zooplankton was found to be alkaline phosphatase, but it also released some acid phosphatase.…”

Size‐Fractionated Alkaline Phosphatase Activity in the Hypereutrophic Villerest Reservoir (Roanne, France)

“…According to Petterson (1980), the primary portion of APA is particulate, but Stewart and Wetzel (1982) demonstrated that at least 50% of the total APA is the result of enzymes in the dissolved fraction. Phosphatase activity has also been shown to vary with the trophic status of the lake (Olsson, 1990) and the taxonomic composition of the phytoplankton (Giraudet et al, 1998, andRivkin andSwift, 1979) or bacteria (Chrost et al, 1986) communuities. Berman (1970) found that phytoplankton were significant contributors to the total APA, whereas Stewart and Wetzel (1982) attributed all of the activity to bacteria.…”