Experimental studies of the effect of organic deposition on the metabolism of a coastal marine bottom community

Publisher Website
Google Scholar
Abstract
Experimental laboratory microcosm studies using intact sediment cores of a benthic community from mid-Narragansett Bay, Rhode Island (USA) were conducted to determine the influence of the rate of supply of organic matter on benthic metabolism and nutrient remineralization. Enrichment experiments of 3-4 mo. duration were carried out at 15.degree. C using seston filtered from bay water. Replicate benthic microcosms were either starved, given regular (every 3 d [day]) organic inputs, or exposed to large pulses of organic matter equivalent to 3-5 mo. of metabolic loss. With particulate starvation, sediment O2 uptake and inoragnic N release rates decreased only slowly, approximately halving in 80-120 d. O2 uptake, CO2 release, and NH4+ release all increased immediately in response to a pulse input, subsequently declining exponentially towards the original levels within 1-2 mo. Rates increased gradually under regular organic additions and declined quickly when the inputs were discontinued. The magnitude of the increase in dissolved fluxes was a function of both the quantity deposited per unit time and the initial remineralization rate of the added organic matter. The results offer direct evidence that organic input from the water column can exert a major influence on the magnitude (and variability) of sediment-water exchange rates. Within 2 mo., about 24-30% of the organic N and 11-20% of the organic C experimentally deposited to the sediment surface had returned to the overlying water as dissolved inorganic decomposition products. For the in situ mid-Narragansett Bay sediment community, over 80% of the annual C and N deposition are calculated to be remineralized and returned to the overlying water. Although having demonstrated a pronounced effect of organic inputs on benthic metabolism, the effect may still be underestimated since the initial remineralization position may be even more rapid than in the experiments.

This publication has 1 reference indexed in Scilit: