Effect of Ambient Nitrogen on the Growth of Phytoplankton in the Bohai Sea: Kinetics and Parameters

Abstract

Changes in nitrogen forms and levels affect biogeochemical processes, but little is known about the quantitative effect of ambient nitrogen on phytoplankton growth in biogeochemical kinetics. Based on a new experimental data analysis method, we investigated the phytoplankton growth and nitrogen uptake processes of typical phytoplankton subjected to different nitrogen forms in the Bohai Sea. We employed a nonlinear differential model to fit the kinetic processes of phytoplankton growth, death, and nutrient uptake considering multiple equations and parameters. The maximum nitrogen uptake rate (k up), half-saturation coefficient (k s), and maximum phytoplankton growth rate (k G) were obtained based on the multivariate nonlinear differential mothed. The k up and k s were related with k G for different ambient nitrogen forms (urea, ammonium, and nitrate) in the N sufficiency experiment group I (SGI) treatment, showing that phytoplankton grew faster in the presence of ammonium and nitrate than in the presence of urea, owing to quicker nitrogen uptake rate. The k up , k s , and k G in the N-Starvation experiment group II (SGII) treatment were lower than that in the SGI treatment, indicating higher nutrient affinity of phytoplankton at lower nitrogen concentrations. Hence, we can infer that eutrophic algae such as Nitzschia closterium may easily become the dominant species in the SGI treatment with abundant nitrogen supply and high k G , k up , and k s. In contrast, oligotrophic algae such as Leptocylindrus danicus and Asterionellopsis glacialis may easily become the dominant species in the SGI or SGII treatments with an insufficient supply of ambient nitrogen and low k G , k up , and k s. Plain Language Summary The ecosystem is vulnerable in coastal waters, suffering by human activities associated with anthropogenic nutrients, such as harmful algae bloom. The forms and levels of nutrients affect phytoplankton growth, while little is known about the biogeochemical kinetics. We investigated the phytoplankton growth and nitrogen uptake kinetics of typical phytoplankton subjected to different nitrogen forms (e.g., urea, ammonium, and nitrate) in the Bohai Sea. We proposed a multivariate nonlinear differential fitting method to analyze ecological experimental data, considering multiple kinetic equations and parameters of phytoplankton growth, death, and nutrient uptake. Based on the in situ batch culture experiment, the phytoplankton grew faster in ambient ammonium and nitrate than in ambient urea in the N sufficiency experiment group conditions, whereas, they grew and acquired nutrient significantly lower in the N starvation experiment group conditions. The phytoplankton domain community was different in different ambient nitrogen forms and levels, where eutrophic algae such as Nitzschia closterium might easily become the dominant species in the N sufficiency treatment with abundant nitrogen supply, whereas, oligotrophic algae such as Leptocylindrus danicus and Asterionellopsis glacialis might easily become the dominant spe...

Was Dissolved Nitrogen Regime Driving Diatom to Dinoflagellate Shift in the Bohai Sea? Evidences From Microcosm Experiment and Modeling Reproduction

“…The biomass of different dominant algae (Bio i ) was estimated by the equation Bio i = Bio total × DI i , where DI i is Berger–Parker dominance index of each algal species. The biomass of diatoms and dinoflagellates (Bio) was described by the modified logistic equation (Gao et al., 2020) and the limiting factors of PAR and T : $$$\frac{\text{dBio}}{\text{dt}}={\mathrm{K}}_{\mathrm{G}}\cdot \left(\frac{{\text{NO}}_{3}-{\text{NO}}_{3\,\text{min}}}{{\text{Ks}}_{{\text{NO}}_{3}}+{\text{NO}}_{3}-{\text{NO}}_{3\,\text{min}}}\cdot \frac{1}{1+\frac{{\text{NH}}_{4}}{{\text{NH}}_{4\,\text{in}}}}+\frac{{\text{NH}}_{4}-{\text{NH}}_{4\,\text{min}}}{{\text{Ks}}_{{\text{NH}}_{4}}+{\text{NH}}_{4}-{\text{NH}}_{4\,\text{min}}}+\frac{{\text{DON}}_{\text{terrestrial}}-{\text{DON}}_{\text{terrestrial}\,\text{min}}}{{\text{Ks}}_{{\text{DON}}_{\text{terrestrial}}}+{\text{DON}}_{\text{terrestrial}}-{\text{DON}}_{\text{terrestrial}\,\text{min}}}+\frac{{\text{DON}}_{\text{algal}}-{\text{DON}}_{\text{algal}\,\text{min}}}{{\text{Ks}}_{{\text{DON}}_{\text{algal}}}+{\text{DON}}_{\text{algal}}-{...$$…”

“…The biomass of different dominant algae (Bio i ) was estimated by the equation Bio i = Bio total × DI i , where DI i is Berger-Parker dominance index of each algal species. The biomass of diatoms and dinoflagellates (Bio) was described by the modified logistic equation (Gao et al, 2020) and the limiting factors of PAR and T:…”

“…where I PAR is the in situ intensity (W/m 2 ) of PAR, I opt is the optimal intensity (W/m 2 ) of PAR, Γ is the temperature coefficient (°C −1 ), and T is the temperature (°C). We used the modified Monod equation (Gao et al, 2020) to determine nutrient uptake kinetics and added the limiting factors of PAR and T; first-order differential dynamics equations were used to describe ammoxidation, nitration, DON from excretion (DON excretion ), DON from detritus (DON detritus ), DON terrestrial , and DON algal . Therefore, DIN (NO 2 -N, NO 3 -N, and NH 4 -N) and DON (DON excretion , DON detritus , DON terrestrial , and DON algal ) can be described by equations:…”

“…It is difficult to elucidate the effects of different DN migration and transformation processes on different algae, which is subject to the multiprocess analysis and parameterization of microcosm experiments. The biogeochemical or ecological dynamics equation or mechanism of a single process has been clarified previously by linear or nonlinear fitting methods based on controlled incubation experiments (Gao et al., 2020). However, for complex ecological dynamics processes, it is necessary to apply numerical models, such as Nutrients–Phytoplankton–Detritus (NPD) or Nutrients–Phytoplankton–Zooplankton–Detritus (NPZD), to optimize processes and parameters according to in situ experiments (Slawig, 2013).…”

Detection of marine microalgae (phytoplankton) quality to support seafood health: A case study on the west coast of South Sulawesi, Indonesia

“…Periodic increases in microalgae populations are natural phenomena (Visciano et al 2016). They do not always cause detrimental effects so long as algal growth remains within normal limits and does not cause a significant disturbance to the surrounding ecosystems (Gao et al 2020). However, if there is a dramatic increase in the population of unwanted or harmful organisms, the situation can require an immediate response (Zohdi and Abbaspour 2019).…”