2024-03-28T09:55:37Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/764732022-11-17T02:08:08Zhdl_2115_20049hdl_2115_141Dynamics of particulate and dissolved organic and inorganic phosphorus during the peak and declining phase of an iron-induced phytoplankton bloom in the eastern subarctic PacificYoshimura, TakeshiNishioka, JunOgawa, HiroshiTsuda, AtsushiPhosphorusOrganic matterInorganic matterPhytoplankton bloom660Phosphorus (P) is an essential element for all organisms and thus the P cycle plays a key role in determining the dynamics of lower trophic levels in marine ecosystems. P in seawater occurs conceptually in particulate and dissolved organic and inorganic (POP, PIP, DOP, and DIP, respectively) pools and clarification of the dynamics in these P pools is the basis to assess the biogeochemical cycle of P. Despite its importance, behaviors of each P pool with phytoplankton dynamics have not been fully examined. We measured the four operationally defined P pools (POPop, PIPop, DOPop, and SRP) during an iron-induced phytoplankton bloom (as part of the subarctic ecosystem response to iron enrichment study (SERIES)) in the eastern subarctic Pacific in summer 2002. During our observations of the iron-enriched patch from day 15 to day 26 after the iron infusion, chlorophyll-alpha concentration in the surface layer decreased from 6.3 to 1.2 mu g L-1, indicating the peak through decline phase of the phytoplankton bloom. At the bloom peak, P was partitioned into POPop, PIPop, and DOPop in proportions of 60, 27, and 13%, respectively. While chlorophyll-alpha and POPop showed similar temporal variations during the declining phase, PIPop showed a different peak timing with a 2 day delay compared to POPop, resulting in a rapid change in the relative proportion of PIPop to total particulate P (TPP = POPop + PIPop) at the peak (25%) and during the declining phase of the bloom (50%). A part of POPop was replaced by PIPop just after slowing down of phytoplankton growth. This process may have a significant role in the subsequent regeneration of P. We conclude that measurement of TPP alone is insufficient to show the interaction between P and phytoplankton dynamics and fractionation of TPP into POPop and PIPop provides useful insights to clarify the biogeochemical cycle of P.ElsevierJournal Articleapplication/pdfhttp://hdl.handle.net/2115/76473https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/76473/1/Yoshimura.pdf0924-7963AA10775411Journal of marine systems177172018-01enginfo:doi/10.1016/j.jmarsys.2017.09.004© 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/author