Nutrient regeneration processes in bottom sediments in a Po delta lagoon (Italy) and the role of bioturbation in determining the fluxes at the sediment-water interface

• Published in: Hydrobiologia 1992-01, Vol.228 (1), p.1-21
• Main Authors: Barbanti, A, Ceccherelli, VU, Frascari, F, Reggiani, G, Rosso, G
• Format: Article
• Language: English
• Subjects: Brackish; Freshwater; Hydrobia ventrosa; Marine; Polydora ciliata
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1007/BF00006471

Nutrient regeneration processes and nutrient fluxes at the sediment-water interface were studied at 2 stations in a shallow lagoon. Parameters measured included grain size, porosity, carbon and nitrogen for solids; orthophosphate, ammonia, nitrate, sulphate, total carbonate, silica for the liquid. Organic matter decreased in nitrogen and phosphorus relative to carbon as depth increased. The precipitation of authigenic calcite, apatite and rhodochrosite in sediments was considered possible. Fluxes were quantified in situ by experiments with benthic chambers and by applying a modified version of Fick's first law to models of pore waters. The model permitted an estimate of bioturbation-irrigation influence near the interface by means of a cumulative differential coefficient. Directly measured fluxes always exceeded the theoretical values. Apart from inherent differences, the disparities were ascribed to surface processes not affecting pore water concentration. A comparison between macrobenthic populations and flux values showed a clear relationship between organism numbers and benthic fluxes within each station: flux variations between stations were attributed to different arrangements of the tubes of polychaetes in the sediment. There are 74 references.