Table 1.

Marine NCD environments

	Environment	Known or theorized NCD habitat/lifestylea	Representative references
Water column	Open ocean: euphotic	Free-living; suspended and sinking particles; plankton holobionts	Proctor (1997), Zehr et al. (1998), Langlois et al. (2005, 2008, 2015), Church et al. (2005a, b), Fong et al. (2008), Moisander et al. (2008, 2014), Farnelid et al. (2010,2011) Bombar et al. (2011), Kong et al. (2011), Zhang et al. (2011, 2016), Halm et al. (2012), Shiozaki et al. (2014,2017) Sunagawa et al. (2015), Azimuddin et al. (2016), Benavides et al. (2016b), Gradoville et al. (2017a), Delmont et al. (2018), Chen et al. (2019), Wu et al. (2019), Yang et al. (2019), Cheung et al. (2020, 2021), Raes et al. (2020), Pierella Karlusich et al. (2021), Hallstrøm et al. (2022a)
	Open ocean: aphotic	Free-living; suspended and sinking particles	Hewson et al. (2007), Bonnet et al. (2013), Benavides et al. (2015, 2018c), Selden et al. (2019), Acinas et al. (2021)
	Oxygen minimum zones	Free-living; suspended and sinking particles	Fernandez et al. (2011), Hamersley et al. (2011), Löscher et al. (2014), Jayakumar et al. (2017), Chang et al. (2019), Reeder and Löscher (2022)
	Temperate coastal ecosystems	Free-living; suspended and sinking particles; plankton holobionts; resuspended sediments; terrestrial particles	Short et al. (2004), Moisander et al. (2007), Rees et al. (2009), Mulholland et al. (2012), Messer et al. (2015, 2021), Scavotto et al. (2015), Shiozaki et al. (2015), Bentzon-Tilia et al. (2015b), Gradoville et al. (2017a), Pedersen et al. (2018), Cabello et al. (2020), Turk-Kubo et al. (2021), Hallstrøm et al. (2022b)
	Inland seas	Free-living; suspended and sinking particles	Bostrom et al. (2007), Man-Aharonovich et al. (2007), Farnelid et al. (2013), Rahav et al. (2013, 2016), Benavides et al. (2016a), Kirkpatrick et al. (2018), Geisler et al. (2020), Ridame et al. (2022)
	Polar seas	Free-living; suspended and sinking particles; sediment resuspension; terrestrial input	Blais et al. (2012), Fernandez-Mendez et al. (2016), Shiozaki et al. (2018b, 2020)
Benthic	Coral reefs and sponges	Associated with released mucus, coral tissues, coral skeletons, associated macroalgae, and microbial mats, surrounding seawater	Mohamed et al. (2008), Olson et al. (2009), Lema et al. (2012, 2014), Ribes et al. (2015), Yang et al. (2016), Liang et al. (2020), Moynihan et al. (2022)
	Macroalgae	Living and decomposing tissue, surrounding seawater	Hamersley et al. (2015), Zhang et al. (2015), Raut et al. (2018), Raut and Capone (2021)
	Coastal and continental shelf sediments	Sediment-associated	Fulweiler et al. (2013), Brown and Jenkins (2014), Newell et al. (2016), Jabir et al. (2018)
	Oxygen-deficient zone sediments	Sediment-associated	Gier et al. (2016, 2017)
	Abyssal pelagic	Associated with methane seeps, hydrothermal vents, whale falls	Mehta et al. (2003), Mehta and Baross (2006), Pernthaler et al. (2008), Dang et al. (2009), Dekas et al. (2009, 2014, 2016, 2018), Miyazaki et al. (2009), Kapili et al. (2020)
	Microbial mats	Microbial mat associated, surrounding water	Zehr et al. (1995), Steppe et al. (1996), Olson et al. (1999)
	Seagrass rhizosphere	Sediments, roots	McGlathery et al. (1998), Mohr et al. (2021)

^aAllocation of NCDs between free-living and particle-association is not well-resolved.