Direct contribution of clams (Ruditapes philippinarum) to benthic fluxes, nitrification, denitrification and nitrous oxide emission in a farmed sediment. (5th March 2015)

• Record Type: Journal Article
• Authors: Welsh, David T.; Nizzoli, Daniele; Fano, Elisa A.; Viaroli, Pierluigi
• Is Part Of: Estuarine, coastal and shelf science. Volume 154(2015)
• Page Start: 84
• Page End: 93
• Publication Date: 2015-03-05
• Subjects: nitrous oxide -- denitrification -- nitrification -- aquaculture -- Ruditapes philippinarum -- manila clam; Estuarine oceanography -- Periodicals; Coasts -- Periodicals; Estuarine biology -- Periodicals; Seashore biology -- Periodicals; Coasts; Estuarine biology; Estuarine oceanography; Seashore biology; Periodicals; 551.461805
• DOI: 10.1016/j.ecss.2014.12.021
• Languages: English
• ISSNs: 0272-7714

Abstract

Abstract: The influence of the manila clam ( Ruditapes philippinarum ) on N-cycle processes, and oxygen and nutrient fluxes in a farmed sediment was investigated using a multiple core incubation approach and parallel incubations of individual clams. Clam population/biomass density varied ∼8-fold between cores and all sediment-water column solute (O2 . N2, N2 O, NH 4 +, NOX and DIN) fluxes and benthic process (N-regeneration, nitrification and denitrification) rates were strongly and significantly correlated with clam density/biomass. Isolated clams exhibited high rates of respiration, N-excretion, nitrification and denitrification of 2050 ± 70, 395 ± 49, 201 ± 42 and 235 ± 40 nmol individual −1 h −1, respectively. The direct contribution of the clams and their associated microbiota to benthic processes was estimated by multiplying the per individual rates by the number of clams in each incubated core. The clams on average directly accounted for 64–133% of total rates of sediment oxygen demand, N-regeneration, nitrification and denitrification, indicating that they regulated processes primarily through their own metabolic activity and that of bacteria that colonise them. Clams and the farmed sediments were significant sources of the greenhouse gas N2 O, but this was primarily due to their high nitrification and denitrification rates, rather than high specific N2 O yields, as N2 O emissions represented <1% of total N2 O + N2 production. The clam-farmed sediments had a high denitrification efficiency of 67 ± 10%, but this ecosystem service came at the environmental cost of increased N-regeneration and N2 O emission rates. The measured N2 O emissions indicate that bivalve aquaculture may be a significant source of N2 O. It is therefore recommended that N2 O emissions should be included in the impact assessments of current and future bivalve-farming projects. Highlights: All benthic fluxes and N-cycle processes were strongly correlated with clam biomass. High nitrification, denitrification and N2 O emission rates were associated with clams. Clams and associated bacteria accounted for majority of benthic fluxes and processes. Clams promoted denitrification, but had no effect on denitrification efficiency. Bivalve aquaculture may be a significant source of the greenhouse gas N2 O.