from Assessment of Major Ecosystem Services from the Marine Environment (Other than Provisioning Services)
Published online by Cambridge University Press: 18 May 2017
Primary Production
Definition and ecological significance
Gross primary production (GPP) is the rate at which photosynthetic plants and bacteria use sunlight to convert carbon dioxide (CO2) and water to the high-energy organic carbon compounds used to fuel growth. Free oxygen (O2) is released during the process. Net primary production (NPP) is GPP less the respiratory release of CO2 by photosynthetic organisms, i.e., the net photosynthetic fixation of inorganic carbon into autotrophic biomass. NPP supports most life on Earth; it fuels global cycles of carbon, nitrogen, phosphorus and other nutrients and is an important parameter of atmospheric CO2 and O2 levels (and, therefore, of anthropogenic climate change).
Global NPP is estimated to be ∼105 Pg C yr-1, about half of which is by marine plants (Field et al., 1998; Falkowski and Raven, 1997; Westberry et al., 2008). Within the euphotic zone of the upper ocean, phytoplankton and macrophytes respectively account for ∼94 per cent (∼50 ﹜ 28 Pg C yr-1) and ∼6 per cent (∼3.0 Pg C yr-1) of NPP (Falkowski et al., 2004; Duarte et al., 2005; Carr et al., 2006; Schneider et al., 2008; Chavez et al., 2011; Ma et al., 2014; Rousseaux and Gregg, 2014). All NPP is not equal in terms of its fate. Marine macrophytes play an important role as carbon sinks in the global carbon cycle, provide habitat for a diversity of animal species, and food for marine and terrestrial consumers (Smith, 1981; Twilley et al., 1992; Duarte et al., 2005; Duarte et al., 2010; Heck et al., 2008; Nellemann et al., 2009; McLeod et al., 2011, Fourqurean et al., 2012). Phytoplankton NPP fuels the marine food webs upon which marine fisheries depend (Pauly and Christensen, 1995; Chassot et al., 2010) and the “biological pump” which transports 2-12 Pg C yr-1 of organic carbon to the deep sea (Falkowski et al., 1998; Muller-Karger et al., 2005; Emerson and Hedges, 2008; Doney, 2010; Passow and Carlson, 2012), where it is sequestered from the atmospheric pool of carbon for 200-1500 years (Craig, 1957; Schlitzer et al., 2003; Primeau and Holzer, 2006; Buesseler, et al., 2007).
Changes in the size structure of phytoplankton communities influence the fate of NPP (Malone, 1980; Legendre and Rassoulzadegan, 1996; Pomeroy et al., 2007; Maranon, 2009).
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