Irrigation, the effect of the pumping activity by benthic infauna on pore water solute distribution and fluxes, may be represented by a nonlocal irrigation function, α (units: 1/time) in the general diagenetic equation. We derived α from the distribution of a solute tracer, bromide, during laboratory incubations of sediment cores containing their natural faunal community. Sediments were sampled on 4 occasions over a period of one year from a site at 30 m depth in the southern North Sea. Fitting an irrigation function exponentially decaying with depth, we arrived at α-values ranging from 25 to >200 yr-1 at the sediment water interface and α < 10 at 16 cm depth. The importance of meaningful horizontal averaging was shown by contrasting our values with unreasonable high α based on inappropriate sampling. Variability of α between adjacent samples (n = 3-6) was as large as seasonal differences, and this fact underlines the necessity for cautious interpretation of data from single cores. No temperature effect on α was observed in the temperature range of 5-16°C since abundance of fauna and their behavior completely dominated the magnitude of α. Nutrient fluxes associated with this nonlocal irrigation are highly variable on a spatial scale reflecting macrofauna heterogeneity. The irrigation flux reduces the relative importance of temperature as a factor on benthic-pelagic solute fluxes.