Assessing inorganic nitrogen transport in marine phytoplankton assemblages through the 15N-tracer technique and metatranscriptomics
Journal
Marine Ecology Progress Series
Journal Volume
726
Start Page
17
End Page
30
ISSN
0171-8630
1616-1599
Date Issued
2024-01-11
Author(s)
Abstract
The availability of inorganic nitrogen is considered one of the limiting factors for primary production in the ocean. However, different phytoplankton possess unique strategies to take up and assimilate nitrate and ammonium to cope with environmental changes. To investigate the nitrogen uptake characteristics of different size-fractionated phytoplankton in natural assemblages, 3 research cruises were conducted in the southern East China Sea in 2018 and 2019. The nitrogen uptake characteristics of 2 size-fractionated natural assemblages, microphytoplankton (20–200 μm) and pico-nanophytoplankton (<20 μm), were measured using the 15N-tracer technique. At most of the stations, significantly higher potential maximum uptake rates of ammonium than of nitrate were detected in the pico-nanophytoplankton, indicating that small phytoplankton possess a relatively superior capacity to take up ammonium. By contrast, comparing the potential maximum uptake rate for nitrate between microphytoplankton and pico-nanophytoplankton showed that microphytoplankton exhibit a higher capacity for nitrate uptake as a nitrogen source compared to pico-nanophytoplankton. However, repressed uptake rates of ammonium and nitrate in microphytoplankton were sometimes found at the coastal station even when ambient nitrate concentrations remained high. Metatranscriptomic analysis of nitrogen transporter genes in microphytoplankton suggests that most diatoms utilize regenerated ammonium before nitrate to maintain their populations at the end of blooms. Metatranscriptomic approaches identify the transcriptional responses of dominant diatoms to explain how diatoms regulate their nitrogen transporter genes to cope with environmental changes in natural assemblages.
Subjects
Ammonium
Metatranscriptome
Nitrate
Nitrogen transporter genes
Nitrogen uptake
Phytoplankton
Southern East China Sea
Publisher
Inter-Research Science Center
Type
journal article