Nitrogen fixation in polluted intertidal sediments of Waimea Inlet, Nelson

Nitrogen fixing potential was measured in summer 1975 by acetylene reduction in situ at 5 stations on the intertidal flats of the Waimea Inlet, Nelson, New Zealand, which receive nutrients from several sources. Highest values (644 μ mol•m −2 .d −1 ) were obtained on sediments near an apple cannery effluent discharge and were linear through at least two tidal cycles. The cannery waste had the highest carbon to nitrogen ratio (10.3 : 1.0) of all the effluents examined and exhibited the highest rate of acetylene reduction (14.0 μ mol• ‐ l −1 .d −1 ). Sizeable populations of the nitrogen fixing bacteria Klebsiella pneumoniae were isolated from the cannery effluent (2 × 10 4 per millilitre) and also from the mud adjacent to the discharge pipe (5 × 10 5 per millilitrc). The stimulatory effect of the cannery effluent on nitrogen fixation in the sediment was shown to be restricted to close to the discharge point. Sediments in areas affected by slaughterhouse and sewage effluents exhibited the second and third highest rates of acetylene reduction, (130 & 28 μ mol•m −2 .d −1 respectively). In both places, the activities were not restricted to the immediate vicinity of the effluent channels. Nitrogen fixation was lowest in sediments fronting a catchment of grazed pasture. Fixation was low also in sediments affected by effluents from the hydraulic debarker of a woodchip mill.