Measurements of primary productivity and nitrogenase activity of coral reef algae in a chamber incorporating oscillatory flow

Abstract

Diffusive limitation of C and nutrient uptake can be an important factor regulating metabolic processes in aquatic plants. Relationships between the flow regime and both primary productivity and nitrogenase activity (ethylene production) of coral reef algal components were studied via a productivity chamber that simulates oscillatory flow. Net primary productivity of algal turfs was increased significantly by flow speeds (steady flow equivalent) up to 16 cm s-l. The mode of water flow also was important; primary productivity of algal turfs increased by 2 1% under an oscillatory flow regime as compared to vortex flow created by stirring. Acunthophora spicifera exhibited increased primary productivity at flow speeds up to 10 cm s-l, while primary productivity of another rhodophyte, Coelothrix irregularis. increased up to 4 cm s-I. Rates of nitrogenase activity exhibited by algal turfs also were affected significantly by flow speed. These data indicate that diffusive limitation is important to varying degrees in reef algal turfs and macroalgae and suggest that primary productivity and rates of nitrogenase activity depend on ambient flow speeds and boundary-layer dynamics.Estimates of metabolic rates for marine organisms are essential to the understanding of trophic web structure and energy and material transfer in marine environments. Calculations of primary and secondary productivity for marine communities often rely on chamber measurements of metabolism. Estimates of respiration and photosynthesis most often are made from measurements of carbon or oxygen flux over time when the organism is confined in an enclosure. Although the techniques to estimate the rates of C fixation and respiration have become more sophisticated, the organism under --

Mass‐transfer limitation of nutrient uptake by a wave‐dominated reef flat community

“…This is even more likely considering that (1) increased water motion enhances rates of photosynthesis in reef coral and alga (Dennison and Barnes 1988;Carpenter et al 1991;Patterson et al 1991), and (2) rates of gross and net community production decrease with increasing distance from the reef crest (Barnes and Devereux 1984;and Kinsey and Davies 1979). More recently, Russ (2003) found that rates of algal productivity, grazing, and grazer biomass were greatest on the reef crest, where the dissipation of flow energy is usually highest.…”

Inorganic carbon acquisition by aquatic photolithoatrophs of the Dighty Burn, Angus, U.K.: uses and limitations of natural abundance measurements of carbon isotopes

“…Thus, the lower COĉ oncentration in seawater than in the Dighty Burn (MacKarlane & Raven, 1990;Maberiy el al., 1992) could help to explain the lower A value of the marine species than of Cladophora glomerata if all three species only used CO.^. A further consideration is the influence of water movement on diffusion boundary layers; the two intertidal, rockpool marine Cladophora species are exposed to a much more temporally variable water flow regime than the freshwater Cladophora glomerata; it is not certain whether the fiow regime over the marine species leads to smaller diffusion boundary-layers than those over Cladophora glomerata, even when the lower diffusion houndar\-layer for a given mean flow velocity (irrespective of flow direction) for oscillatory than unidirectional water flow (Jonsson, 1980;Carpenter, Hackney & Adey, 1991) is taken into account. No data seem to be available on the ability tu use HCO^" by Hildenbrandia rubra or Hildenbrandia rivularis.…”

Modeling flow in coral communities with and without waves: A synthesis of porous media and canopy flow approaches

“…This is particularly important given that frictional dissipation can play a major role in the transformation of waves propagating inshore when the bottom is naturally very rough, that is, over rocky bottoms (e.g., Adams et al 2002), aquatic vegetation (e.g., Mendez and Losada 2004), or coral reefs (e.g., Lowe et al 2005a). Flow within living canopies can also be important to benthic communities (Carpenter et al 1991;Atkinson and Bilger 1992;Lesser et al 1994). For example, under oscillatory flow, nutrient uptake by corals can be twice as fast as under unidirectional flow as a result of the greater in-canopy flow generated (Lowe et al 2005c;Reidenbach et al 2006a).…”