Nitrate uptake by the reef coral Diploria strigosa: effects of concentration, water flow, and irradiance

High phosphate uptake requirements of the scleractinian coral Stylophora pistillata

“…-2 h -1 for 0.5 and 3.5moll -1 NO 3 in seawater, respectively) and from other coral species (from 2.5 to 20nmolNcm -2 h -1 for NO 3 concentrations of 0.5 to 4moll -1 ) (reviewed in Badgley et al, 2006). Because the uptake of nitrate is clearly inhibited by the presence of ammonium in phytoplankton (Berges and Harrison, 1995;Guerrero et al, 1981;Syrett, 1981;Vergara et al, 1998) and corals (Grover et al, 2003), the discrepancies among the results might be linked to the ammonium supply of the colonies (which was relatively low in the present study, <0.5moll -1 ), as well as to the ammonium content of the cells, although this point remains to be further investigated.…”

“…In the oligotrophic surface reef waters, phosphate and inorganic forms of nitrogen (ammonium and nitrate) display a characteristic depletion, with concentrations often well below 0.5moll -1 (Atkinson, 1987;Atkinson et al, 1995;Furnas, 1991). Zooxanthellae, the dinoflagellates living in symbiosis with corals, are known to take up from their host and concentrate, through active transport, dissolved nutrients, which are then transformed into organic molecules (Badgley et al, 2006;Bythell, 1990;D'Elia and Cook, 1988;D'Elia et al, 1983;Domotor and D'Elia, 1984;Godinot et al, 2009;Muscatine and D'Elia, 1978) and transferred back to the host for its metabolism (Muscatine and Porter, 1977). Such nutrient recycling within the symbiosis is often used to explain the success of corals in nutrient-poor environments.…”

“…However, the effect of phosphate limitation on ammonium or nitrate uptake has, to the best of our knowledge, never been investigated in corals. On the contrary, it is well-known, for example, that nitrate uptake is generally inhibited in the presence of ammonium (Badgley et al, 2006;Domotor and D'Elia, 1984;Grover et al, 2003), either through a repression of the nitrate reductase (Berges and Harrison, 1995;Guerrero et al, 1981;Syrett, 1981;Vergara et al, 1998) or a competition of ammonium and nitrate uptake mechanisms for energy resources, leading to the preferential uptake of ammonium (Terry, 1982a;Terry, 1982b). Therefore, we tested two additional questions.…”

Enduring physiological and reproductive benefits of enhanced flow for a stony coral

“…Fast responses are commonly the outcome of flow-induced changes in mass flux across the water-coral interface. Examples include the augmentation of photosynthesis by enhanced efflux of oxygen (Lesser et al 1994;Finelli et al 2006;Mass et al 2010) and the increase in nutrient uptake (Atkinson and Bilger 1992;Thomas and Atkinson 1997;Badgley et al 2006). Enhanced photosynthesis in corals is expected to boost the growth and quantity of soft tissues (Anthony et al 2002), which in turn increases the reproductive output (Ward 1995;this study).…”

“…Consequently, water motion greatly affects corals' rates of growth (Jokiel 1978), calcification (Dennison and Barnes 1988), particle capture (Sebens and Johnson 1991), photosynthesis, respiration (Dennison and Barnes 1988;Patterson et al 1991;Bruno and Edmunds 1998), and susceptibility to bleaching (Loya et al 2001;Nakamura and van Woesik 2001). Flow speed also affects the tissue concentration of ultraviolet (UV)-absorbing compounds (Jokiel et al 1997), rates of nutrient uptake (Atkinson and Bilger 1992;Thomas and Atkinson 1997;Badgley et al 2006), and transport of oxygen across the concentration boundary layers adjacent to the coral surface (Lesser et al 1994;Finelli et al 2006;Mass et al 2010). Additionally, different morphologies can be induced by flow, especially in Pocilloporid corals, which display striking morphological variability in colony shape depending on the flow conditions under which they grow.…”