Abstract
Net community production (NCP) is a community level process informing on the balance between production and consumption, determining the role of plankton communities in carbon and nutrient balances fueling the marine food web. An assessment of net and gross community production (NCP, GPP) and community respiration (CR) in 86 surface plankton communities sampled between 15° and 36° South along coastal Western Australia (WA) revealed a prevalence of net autotrophic metabolism (GPP/CR > 1), comprising 81% of the communities sampled. NCP, GPP, and CR decreased with decreasing nutrient and chlorophyll-a concentrations, from estuarine, to coastal and oceanic waters. CR, standardized per unit chlorophyll-a, increased with temperature, with higher activation energies (Ea) than GPP per unit chlorophyll-a (Ea 1.07 ± 0.18 eV and 0.65 ± 0.15 eV, respectively) either across ecosystem types and for coastal and estuary communities alone, indicating plankton CR to increase much faster with warming than GPP. These results characterize surface plankton communities across Western Australia as CO2 sinks, the stronger thermal-dependence of respiration that gross primary production rates suggests that their role may weaken with future warming.
Highlights
Plankton communities play an important role in the carbon cycle affecting the air-sea water exchange of O2–CO2 and fueling marine food webs through their metabolic processes (Gazeau et al, 2005; Duarte, 2011; Calleja et al, 2013)
Chlorophyll-a concentrations followed the same pattern as nutrient concentrations, decreasing from estuarine waters to coastal areas and open ocean waters (Table 1)
All Western Australian ecosystem types showed a prevalence of autotrophic (GPP/community respiration (CR) > 1) plankton metabolic balance
Summary
Plankton communities play an important role in the carbon cycle affecting the air-sea water exchange of O2–CO2 and fueling marine food webs through their metabolic processes (i.e., gross primary production, respiration, and net production) (Gazeau et al, 2005; Duarte, 2011; Calleja et al, 2013). The AUSW province is divided into three subregions: (i) the tropical southern coasts of Sumatra and Java, (ii) the subtropical Western coast of Australia from Cape Bougainville (14◦N) to Cape Leeuwin (34◦S); and iii) from Cape Leeuwin to the Bass Strait along the temperate coast of the Great Australian Bight. These three subregions are ecologically diverse as different atmospheric and oceanic forcing characterize the northern and southern parts of the large province (Longhurst, 2007)
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