Exploring the distance between nitrogen and phosphorus limitation in mesotrophic surface waters using a sensitive bioassay

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Hrustic , E , Lignell , R , Riebesell , U & Thingstad , T F 2017 , ' Exploring the distance between nitrogen and phosphorus limitation in mesotrophic surface waters using a sensitive bioassay ' , Biogeosciences , vol. 14 , no. 2 , pp. 379-387 . https://doi.org/10.5194/bg-14-379-2017

Title: Exploring the distance between nitrogen and phosphorus limitation in mesotrophic surface waters using a sensitive bioassay
Author: Hrustic, Enis; Lignell, Risto; Riebesell, Ulf; Thingstad, Tron Frede
Contributor: University of Helsinki, Tvärminne Zoological Station
Date: 2017-01-25
Language: eng
Number of pages: 9
Belongs to series: Biogeosciences
ISSN: 1726-4170
URI: http://hdl.handle.net/10138/231633
Abstract: The balance in microbial net consumption of nitrogen and phosphorus was investigated in samples collected in two mesotrophic coastal environments: the Baltic Sea (Tvarminne field station) and the North Sea (Espegrend field station). For this, we have refined a bioassay based on the response in alkaline phosphatase activity (APA) over a matrix of combinations in nitrogen and phosphorus additions. This assay not only provides information on which element (N or P) is the primary limiting nutrient, but also gives a quantitative estimate for the excess of the secondary limiting element (P+ or N+, respectively), as well as the ratio of balanced net consumption of added N and P over short timescales (days). As expected for a Baltic Sea late springearly summer situation, the Tvarminne assays (n = 5) indicated N limitation with an average P+ = 0.30 +/- 0.10 mu M-P, when incubated for 4 days. For short incubations (1-2 days), the Espegrend assays indicated P limitation, but the shape of the response surface changed with incubation time, resulting in a drift in parameter estimates toward N limitation. Extrapolating back to zero incubation time gave P limitation with N+ approximate to 0.9 mu M-N. The N : P ratio (molar) of nutrient net consumption varied considerably between investigated locations: from 2.3 +/- 0.4 in the Tvarminne samples to 13 +/- 5 and 32 +/- 3 in two samples from Espegrend. Our assays included samples from mesocosm acidification experiments, but statistically significant effects of ocean acidification were not found by this method.
Subject: ALKALINE-PHOSPHATASE ACTIVITY
NORTHERN BALTIC SEA
NUTRIENT-LIMITATION
N-P
PHYTOPLANKTON
OCEAN
MECHANISMS
RESPONSES
FIXATION
KINETICS
1181 Ecology, evolutionary biology
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