Particulate nutrient fluxes over a fringing coral reef: relevant scales of phytoplankton production and mechanisms of supply

Oceanographic forcing of nutrient uptake and release over a fringing coral reef

“…Surprisingly, such understanding is generally lacking at a community or ecosystem level, because most studies have focused on individual organisms or specific processes (reviewed in Atkinson and Falter 2003). The major difficulty with conducting a comprehensive community-level study of nutrient dynamics is that reef communities continuously take up and release nutrients from different sources, including in dissolved inorganic (Pomeroy et al 1974;Muscatine and Porter 1977;Muscatine and D'elia 1978), dissolved organic (Stephens 1960;Sorokin 1973;Tanaka et al 2011), and particulate organic forms (Ayukai 1995;Genin et al 2009;Wyatt et al 2010). Uptake of these nutrients often occurs under submicromolar concentrations and at rates that are very difficult to detect in the field.…”

“…However, these studies focused almost exclusively on the larger size-fractions of the particulate organic matter (POM), for which uptake was quantitatively small even in comparison to MTL dissolved inorganic nutrient fluxes (Sargent and Austin 1949;Johannes et al 1972). It is now known that living POM in oligotrophic systems is mostly dominated by the smallest size fractions, particularly the picoplankton , 2 mm (Ducklow 1990;Ribes et al 2003;Wyatt et al 2010), and benthic uptake of smaller particles is higher independent of their concentration (Ribes et al 2003;Houlbrèque et al 2006;Ribes and Atkinson 2007). Given an abundant supply and high flux of small particles, it is not surprising that allochthonous POM alone has recently been shown to be a significant nutrient input to some reefs (Genin et al 2009;Wyatt et al 2010;Patten et al 2011).…”

“…Uptake of these nutrients often occurs under submicromolar concentrations and at rates that are very difficult to detect in the field. Consequently, the relative contribution of different nutrient sources supporting coral reef communities has rarely been examined, but is of particular interest given the increasing recognition that nutrient supply is likely be to be closely linked to variations in regional oceanographic forcing (Genin et al 2009;Wyatt et al 2010).…”

“…It is now known that living POM in oligotrophic systems is mostly dominated by the smallest size fractions, particularly the picoplankton , 2 mm (Ducklow 1990;Ribes et al 2003;Wyatt et al 2010), and benthic uptake of smaller particles is higher independent of their concentration (Ribes et al 2003;Houlbrèque et al 2006;Ribes and Atkinson 2007). Given an abundant supply and high flux of small particles, it is not surprising that allochthonous POM alone has recently been shown to be a significant nutrient input to some reefs (Genin et al 2009;Wyatt et al 2010;Patten et al 2011). Furthermore, the potential for a significant flux of dissolved organic matter (DOM) was acknowledged early on (Odum and Odum 1955).…”

“…The Ningaloo fore-reef experiences significant variations in the supply of dissolved inorganic nutrients and POM between seasons and over relatively short time-scales (e.g., days to weeks) in response to changes in a regional current system that operates over a narrow shelf (, 30 km) separating the coastline from the deeper Indian Ocean (Feng and Wild-Allen 2010;Wyatt et al 2010;Rousseaux et al 2012). It is, thus, an ideal site to assess reef-level nutrient dynamics in the context of oceanographic forcing.…”