Phosphatase activities of the aquatic moss Warnstorfia fluitans (Hedw.) Loeske from an acidic stream in North-East England

Abstract

A study was made of the aquatic environment, tissue nutrient composition and surface phosphatase activities of the aquatic moss Warnstorfia fluitans in Brandon Pithouse Stream, a small acidic stream in N-E England. The water, which originates from an underground spring, had been pH 2.6 for at least 30 years, but about 3.9 during the present study. The moss was by far the most abundant phototroph during all this period. Seasonal changes in aqueous nitrogen and phosphorus fractions were measured over a 2-year period near the source. Most of the filtrable N and P were at times organic, but the very high N:P ratio (even if organic N is excluded) suggests that only organic phosphate is likely to be important Handling editor: S. M. Thomaz

Response of root and sediment phosphatase activity to increased nutrients and salinity

“…The results of simple correlations and path analysis indicated that while increasing concentrations of both, plant-available and tissue P led to a signiWcant decrease in phosphatase activity, the direct eVect of plant-available P on enzyme activity was more signiWcant. Contrary to our results, Christmas and Whitton (1998) and Ellwood and Whitton (2007), who studied surface phosphatase activities in aquatic mosses, found the internal P concentration to be responsible for regulation of phosphatase activities, but no signiWcant correlation between phosphatase activity and water P. Similarly, Martinez-Crego et al (2006) reported a negative correlation between both root and leaf tissue P and extracellular phosphatase activities in seagrass, Posseidonia oceanica, but no relationship with P in water. The investigated mosses and seagrass came from environments, streams and a coastal sea meadow respectively, with water P Xuctuating more than in our mesocosm experiment.…”

“…This is in agreement with Johnson et al (1999) and Phoenix et al (2003) who found higher enzyme activities in Plantago lanceolata and several calcareous grassland species that were exposed to increased sediment nitrogen. Phoenix et al (2003) explained the stimulatory eVect of increased N availability on phosphatase activity by a phosphate starvation inducible type response-their results suggested that the expression of genes in the proposed phosphate starvation rescue system could be sensitive to shoot and soil N as well as P. An inverse relationship has been reported between tissue N and water/sediment P (Phoenix et al 2003, Ellwood andWhitton 2007). Similarly, Eleocharis and Typha in our experiment showed a signiWcant decrease in root tissue N with increasing P in the sediments (P = 0.003 and 0.016, respectively).…”

“…Enhanced enzyme activity has also been reported as a response to increased nitrogen availability and subject to stressors, namely salinity (DuV et al 1994). The majority of reports on root or sediment phosphatase activities focus on the potential role of these enzymes in improving P economy of agricultural crops (Tarafdar and Claassen 1988;Asmar and Gissel-Nielsen 1997;Tarafdar and Gharu 2006) and on exploring possibilities of use of the phosphatases as biomarkers indicating the level of water eutrophication (Hernandez et al 2002;Newman et al 2003;Martinez-Crego et al 2006;Ellwood and Whitton 2007).…”

“…We hypothesized that (1) phosphatase activities will decrease with increasing P and the decrease will depend on both plant tissue and sediment P concentrations, (2) the activity of the enzymes will be stimulated by higher sediment and plant N concentration, and (3) the enzyme activity will decrease with increasing salinity. While there is a general consensus in the literature on the enzyme responses to P and N (Sinsabaugh and Moorhead 1994;Christmas and Whitton 1998;Ellwood and Whitton 2007), the reports on phosphatase response to increasing salinity are conXicting and range from a decrease in activity (Nausch 1998;Rejmánková and Komárková 2005) to no response (Sirová et al 2006) or increased activity (DuV et al 1994;Hernandez et al 2002). We did not have a clear prediction for potential diVerences in phosphatase activities among the investigated species.…”

Importance of organic phosphate hydrolyzed in stalks of the lotic diatom Didymosphenia geminata and the possible impact of atmospheric and climatic changes

“…Such activity in aquatic phototrophs is usually induced under conditions of moderate P limitation and hence the rate of activity provides a measure of P limitation (Jansson et al, 1988;Christmas & Whitton, 1998a, b;Ellwood et al, 2002;Whitton et al 2005), though it may sometimes also reflect the fact that the only P source available is organic (Whitton et al, 1991;Ellwood & Whitton, 2007). It was therefore planned to compare changes in surface phosphatase activities of Didymosphenia in Stony Gill, North Yorkshire, during the main part of one growth season with concentrations of N and P fractions in the water.…”