Contribution of benthic biomass to overall metabolism in New Caledonia lagoon sediments

Publisher Website
Google Scholar
Abstract
Granulometric parameters, benthic biomasses of living organic matter, and oxygen and nitrogen fluxes at the water-sediment interface were investigated on triplicate samples, or in dark experiments, at 12 stations in the lagoon in SW New Caledonia. Analysis of functional characteristics of 3 bottom types revealed significant differences in the benthic food-webs . Onshore muddy bottoms had the lowest respiration, related to the lowest ATP pool and meiofauna density, in spite of high organic and pigment content. Near-reef white-sand bottoms were a sink for DON (dissolved organic nitrogen), exported no significant DIN (dissolved inorganic nitrogen), and supported the highest living biomass (ATP) via meiofauna and active microphytes. Intermediate grey-sand bottoms had the highest respiration related to macrophyte cover and to a lesser extent to larger macrobenthos biomass, and were a source of nutrients for the water-column (DIN and DON). Partitioning of benthic biomass was investigated using non-linear multiple regression. Oxygen consumption was mainly related to ATP content, considered as representative of micro-and meiofauna biomass, then to macrophyte biomass and to a lesser extent to macrofauna biomass. Pigment content did not improve the relationship. Depletion of inorganic nitrogen efflux, when compared to high respiration rates, increased from muddy bottoms to white-sand bottoms. Organic nitrogen (DON) exchanges were an order of magnitude greater than DIN exchanges indicating a considerable nitrogen demand in the sediment.