Cell-Specific Extracellular Phosphatase Activity of Dinoflagellate Populations in Acidified Mountain Lakes1

Abstract

High bulk extracellular phosphatase activity (PA) suggested severe phosphorus (P) deficiency in plankton of three acidified mountain lakes in the Bohemian Forest. Bioavailability of P substantially differed among the lakes due to differences in their P loading, as well as in concentrations of aluminum (Al) and its species, and was accompanied by species-specific responses of phytoplankton. We combined the fluorescently labeled enzyme activity (FLEA) assay with image cytometry to measure cellspecific PA in natural populations of three dinophyte species, occurring in all the lakes throughout May-September 2007. The mean cell-specific PA varied among the lakes within one order of magnitude: 188-1,831 fmol AE cell )1 AE h )1 for Gymnodinium uberrimum (G. F. Allman) Kof. et Swezy, 21-150 fmol AE cell )1 AE h )1 for Gymnodinium sp., and 22-365 fmol AE cell )1 AE h )1 for Peridinium umbonatum F. Stein. To better compare cell-specific PA among the species of different size, the values were normalized per unit of cell biovolume (amol AE lm )3 AE h )1 ) for further statistical analysis. A step-forward selection identified concentrations of total and ionic Al together with pH as significant factors (P < 0.05, Monte Carlo permutation test), explaining cumulatively 57% of the total variability in cell-specific PA. However, this cell-specific PA showed an unexpected reverse trend compared to an overall gradient in P deficiency of the lake plankton. The autecological insight into dinophyte cell-specific PA therefore suggested other factors, such as light availability, mixotrophy, and ⁄ or zooplankton grazing, causing further PA variations among the acidified lakes.

Presence and patterns of alkaline phosphatase activity and phosphorus cycling in natural riparian zones under changing nutrient conditions

“…Despite decades of research focusing on dissolved reactive P (DRP, mainly as inorganic phosphates), growing evidence indicates that dissolved organic P (DOP) is an important driver of limnological production (Labry et al, 2002;Boyer et al, 2006). As a most-studied enzyme, capable of hydrolyzing a broad spectrum of DOP, alkaline phosphatase (APase) and its activity (APA) have also received increasing attention and are considered to be indicative of P status in both algal cultures and natural phytoplankton populations (Cembella et al, 1984;Dyhrman et al, 2002;Novotna, 2010). For example, Gao et al (2006) found that APase can hydrolyze ~58% of total P in a shallow lake in China (Lake Taihu) and thereby compensate for the growth of algae.…”

Constraints on the biological recovery of the Bohemian Forest lakes from acid stress

“…The seston C : P ratio (plankton stoichiometry) resulted from the allocation of P into phytoplankton or bacterial biomass , which was controlled by the total Al content. Thus, the overall decrease in Al concentration probably resulted in the relative alleviation of P stress in the phytoplankton (Novotn a et al, 2010) and in the decreasing trends of seston C : P in the low-Al lakes during this study. In contrast, the C : P ratio remained extremely high in the high-Al lakes.…”

“…In addition, Al controlled in-lake P availability and, consequently, both primary and bacterial production, as well as the seston C : P ratio (cf. Vrba et al, 2003aVrba et al, , 2006Nedbalov a et al, 2006;Novotn a et al, 2010). This complex of synergistic processes largely affected the recovery of plankton and littoral assemblages as the Al concentration was always the major factor governing directly the composition of assemblages and species abundance in phytoplankton, rotifers and aquatic bugs, and indirectly species abundance in crustaceans.…”

3D restoration microscopy improves quantification of enzyme‐labeled fluorescence‐based single‐cell phosphatase activity in plankton

“…Therefore, non‐linearity is a phenomenon that is restricted to the smallest values of SCHP, which constitutes a minor problem in the current state‐of‐the‐art. Although reported SCHP values ranged from 0 to 1831 fmol·cell −1 , including the nonlinear range of fluorescence intensity, in current state‐of‐the‐art, small amounts of fluorescence originating from fluorochromes in the sample other than ELFA (DAPI, degraded chlorophyll autofluorescence, etc.) may show overlap of their emission tails with the ELFA emission peak window and may account for a significant proportion when object ELFA intensity is very low.…”