title: Blue carbon in human-dominated estuarine and shallow coastal systems.
abstract: Estuarine and shallow coastal systems (ESCS) are recognized as not only significant organic carbon reservoirs but also emitters of CO2 to the atmosphere through air-sea CO2 gas exchange, thus posing a dilemma on ESCS's role in climate change mitigation measures. However, some studies have shown that coastal waters take up atmospheric CO2 (Catm), although the magnitude and determinants remain unclear. We argue that the phenomenon of net uptake of Catm by ESCS is not unusual under a given set of terrestrial inputs and geophysical conditions. We assessed the key properties of systems that show the net Catm uptake and found that they are often characteristic of human-dominated systems: (1) input of high terrestrial nutrients, (2) input of treated wastewater in which labile carbon is highly removed, and (3) presence of hypoxia. We propose that human-dominated ESCS are worthy of investigation as a contributor to climate change mitigation.
authors.affiliation: Coastal and Estuarine Environment Research Group, Port and Airport Research Institute, 3-1-1, Nagase, Yokosuka, 239-0826, Japan. kuwae@ipc.pari.go.jp.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Kuwae
authors.affiliation: Department of Ocean Sciences, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo, 108-8477, Japan. jkanda@kaiyodai.ac.jp.
authors.forename: Jota
authors.initials: J
authors.lastname: Kanda
authors.affiliation: Department of Ocean Sciences, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo, 108-8477, Japan. kuboatsushi0412@gmail.com.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kubo
authors.affiliation: Department of Urban Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan. nakajima@env.t.u-tokyo.ac.jp.
authors.forename: Fumiyuki
authors.initials: F
authors.lastname: Nakajima
authors.affiliation: Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba, 277-8564, Japan. hogawa@aori.u-tokyo.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ogawa
authors.affiliation: Mizuho Information and Research Institute, 2-3, Kanda-Nishikicho, Chiyoda-ku, Tokyo, 101-8443, Japan. sohmanzz@aol.com.
authors.forename: Akio
authors.initials: A
authors.lastname: Sohma
authors.affiliation: National Institute of Advanced Industrial Science and Technology, AIST Tsukuba West, 16-1 Onogawa, Tsukuba, 305-8569, Japan. m.suzumura@aist.go.jp.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Suzumura
mesh_terms: D000383:Agriculture; D002244:Carbon; D002245:Carbon Dioxide; D057231:Climate Change; D063366:Estuaries; D006802:Human Activities; D012623:Seawater; D014865:Waste Disposal, Fluid
chemical_list: D002245:Carbon Dioxide; D002244:Carbon
keywords: CO2 fluxes; Carbon cycles; Carbon sequestration; Climate change; Urban ecology