Nutrient regeneration in shallow-water sediments of the estuarine plume region of the nearshore Georgia Bight, USA

• Published in: Marine biology 1987-01, Vol.94 (1), p.127-142
• Main Author: HOPKINSON, C. S. JR
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Marine; Sea water ecosystems; Synecology
• ISSN: 0025-3162; 1432-1793
• DOI: 10.1007/bf00392905

In situ flux measurements, sediment cores, sediment diagenesis and core analyses were carried out on samples obtained from the nearshore region of the continental shelf in the Georgia Bight. Core samples were analysed for wet and dry mass, porosity, bulk density, organic matter, organic carbon and total nitrogen. Pore waters were obtained by centrifuging cores after exchange with potassium chloride solutions and were analysed for ammonium, nitrate, nitrite and soluble reactive phosphate. Sediments were not in steady state with respect to nitrogen and phosphorus and showed the characteristics of enhanced interstitial water movement by benthic animals. Total nitrogen flux averaged 1812 uM per m2.day from the sediments. Ammonium flux accounted for the majority of the nitrogen flux (77 per cent). Phosphorus flux averaged 537 uM per m2.day. Ammonium fluxes measured in situ did not agree well with the rate of ammonium produced in incubated whole cores. Relative rates of carbon, nitrogen and phosphorus release varied throughout the year. Nutrient fluxes were not simply correlated with respiration or temperature. Respiration-regeneration may be decoupled from exchange across the sediment-water interface. The annual carbon/nitrogen/phosphorus flux stoichiometry was 130:3.1:1, whereas the stoichiometry in incubated cores was 120:21:1. This was attributed to a combination of denitrification and wave- and current induced sediment nutrient flushing. Benthic nutrient flux contributed 40 per cent to the annual phosphorus but only 11 per cent to the annual nitrogen requirements of the pelagic primary producers. A bibliography of 68 references is appended.