The Contribution of Small Phytoplankton Communities to the Total Dissolved Inorganic Nitrogen Assimilation Rates in the East/Japan Sea: An Experimental Evaluation

Abstract

As a part of Korean-Russian joint expeditions in the East/Japan Sea during 2012 and 2015, a set of total and small (<2 μm) phytoplankton NO3− and NH4+ uptake rate estimations were carried out. The study aimed to assess the spatio-temporal variations in dissolved inorganic nitrogen (DIN) assimilation by the total and small phytoplankton. The results show that the total NO3− uptake rates during 2012 varied between 0.001 and 0.150 μmol NL−1h−1 (mean ± SD = 0.034 ± 0.033) and that the total NH4+ uptake rates ranged between 0.002 and 0.707 μmol NL−1h−1 (mean ± SD = 0.200 ± 0.158). The total uptake rates during 2015 were ranged from 0.003 to 0.530 (mean ± S.D. = 0.117 ± 0.120 μmol NL−1h−1) for NO3− and from 0.008 to 1.17 (mean ± S.D. = 0.199 ± 0.266 NL−1h−1) for NH4+. The small phytoplankton NO3− and NH4+ uptake rates during 2015 ranged between 0.001 and 0.164 (mean ± S.D. = 0.033 ± 0.036) μmol NL−1h−1 and 0.010–0.304 (mean ± S.D. = 0.101 ± 0.073) μmol NL−1h−1, respectively. Small phytoplankton’s contribution to the total depth-integrated NO3− and NH4+ uptake rates ranged from 10.24 to 59.36% and from 30.21 to 68.55%, respectively. The significant negative relationship observed between the depth-integrated total NO3− and NH4+ uptake rates and small phytoplankton contributions indicates a possible decline in the DIN assimilation rates under small phytoplankton dominance. The results from the present study highlight the possibility of a reduction in the total DIN assimilation process in the East/Japan Sea when small phytoplankton dominate under strong thermal stratification due to sea surface warming. The present study’s findings agree with the model projections, which suggested a decline in primary production in the global warming scenario.

Temperate urban wetland plankton community stability driven by environmental variables, biodiversity, and resource use efficiency: A case of Hulanhe Wetland

“…High concentrations of TN made the zooplankton community more stable (Figure 10C). Bhavya et al (2020)have shown that the total uptake of nitrogen by phytoplankton is in the range of 10.24-59.36% and 30.21-68.55%. Therefore, high concentration of TN promotes the reproduction of phytoplankton (Liu et al, 2022).…”

Marine Nitrogen Fixation and Phytoplankton Ecology

“…Marine phytoplankton are an important indicator of marine ecosystem changes in response to climate-induced environmental change [2,[4][5][6], since they are major primary producers that consolidate solar energy into organic matter and transfer it to marine ecosystems throughout the food web. Recently, increasing numbers of roles of small phytoplankton as a major contributor to primary production have been reported in various oceans, and it has been found that small phytoplankton could become more prominent under an ocean warming scenario [2,4,[6][7][8][9]. The ecological and biogeochemical traits of small phytoplankton are very different from those of large phytoplankton [3,4,9].…”

“…Recently, increasing numbers of roles of small phytoplankton as a major contributor to primary production have been reported in various oceans, and it has been found that small phytoplankton could become more prominent under an ocean warming scenario [2,4,[6][7][8][9]. The ecological and biogeochemical traits of small phytoplankton are very different from those of large phytoplankton [3,4,9]. Therefore, it is urgent to verify the different biological and chemical properties of small phytoplankton and understand their ecological roles under ongoing environmental changes.…”

Impact of Phytoplankton Community Structure Changes in the South Sea of Korea on Marine Ecosystems Due to Climate Change

“…Recently, primary productivity in Korean waters has exhibited a rapidly decreasing trend, with phytoplankton miniaturization purported to be the primary contributing factor [17][18][19]. Indeed, small phytoplankton play an important role in primary productivity and the marine ecosystem food web [18,[20][21][22][23]. However, past research on phytoplankton in the South Sea has primarily focused on the coastal region, with relatively limited studies reporting the phytoplankton community structure during specific periods in the nearshore areas [11,[24][25][26][27][28][29][30].…”