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Advisor(s)
Abstract(s)
Temperature and salinity changes can affect nutrient assimilation
dynamics in primary producers. Green macroalgae use nitrate as a main source
of nitrogen for their metabolism. Nitrate needs to be reduced by nitrate reductase, before amino acids synthesis. Our aims were to study the effect of temperature and salinity changes on nitrate reductase activity (NRA) in Ulva rigida
and Enteromorpha clathrata, and to assess if this enzyme can be used as an
environmental indicator for changes in such abiotic factors. The study of NRA
was carried out using potassium nitrate as substrate and propanol as a membrane
permeabilizer, letting the produced nitrite to exit the macroalgae cells into the
assay medium, allowing its quantification through a colorimetric method. This
procedure was carried out at five temperatures (10, 20, 30, 35 and 40 °C) and
three salinities of the assay medium (0, 15 and 36 g/kg). Results show that both
Ulva and Enteromorpha have maximum NRA at salinities of 36 g/kg, although
nitrate reduction can occur in freshwater or brackish water, but at significantly
lower rates. NRA varied significantly with temperature for both macroalgae,
although Ulva showed maximum NRA at 30 °C, while NRA peaked at 35 °C in
Enteromorpha. Likely adequate models were tentatively fitted to NRAtemperature data at different salinities. NRA is a suitable proxy of the effects
of temperature and salinity changes on the ability of green macroalgae to uptake
and metabolize nitrogen nutrients and can thus be the base for macroalgae
proliferation models under climate change model scenarios.
Description
Keywords
Nitrate reductase Temperature Salinity Optimum (Growth) model
Citation
Publisher
Springer