AUTHOR=Konopáčová Eliška , Nedoma Jiří , Čapková Kateřina , Čapek Petr , Znachor Petr , Pouzar Miloslav , Říha Milan , Řeháková Klára 

TITLE=Low Specific Phosphorus Uptake Affinity of Epilithon in Three Oligo- to Mesotrophic Post-mining Lakes

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.735498

DOI=10.3389/fmicb.2021.735498

ISSN=1664-302X

ABSTRACT=<p>Epilithon contributes to phosphorus (P) cycling in lakes, but its P uptake traits have been rarely studied. We measured the chemical composition of epilithon and its inorganic P uptake kinetics using isotope <sup>33</sup>P in three deep oligo- to mesotrophic post-mining lakes in April, July, and October 2019. Over the sampling period, epilithon biomass doubled, while the P content in biomass dropped to 60% of the April values, and the seasonal changes in P content expressed per epilithon area were only marginal and statistically not significant. High epilithic C:P molar ratios (677 on average) suggested strong P deficiency in all investigated lakes. Regarding the kinetic parameters of phosphorus uptake, maximum uptake velocity (<italic>V</italic><sub><italic>max</italic></sub>, seasonal range 1.9–129 mg P g OM<sup>–1</sup> h<sup>–1</sup>) decreased by an order of magnitude from April to October, while half-saturation constant (<italic>K</italic><sub><italic>S</italic></sub>, seasonal range 3.9–135 mg P L<sup>–1</sup>) did not show any consistent temporal trend. Values of epilithic specific P uptake affinity (<italic>SPUA</italic><sub><italic>E</italic></sub>, seasonal range 0.08–3.1 L g OM<sup>–1</sup> h<sup>–1</sup>) decreased from spring to autumn and were two to four orders of magnitude lower than the corresponding values for seston (<italic>SPUA</italic><sub><italic>sest</italic></sub>), which showed an opposite trend. Considering our results, we suggest a possible mechanism underlying a stable coexistence of planktonic and epilithic microorganisms, with plankton prospering mostly in summer and autumn and epilithon in winter and spring season. Additionally, a phenomenon of reversible abiotic P adsorption on epilithon was observed.</p>