Stimulation of Regeneration of Inorganic Nitrogen and Phosphorus in Surface and Bottom Waters of a Eutrophic Inlet by Adding Effective Bacteria.

Abstract

Two promising bacterial strains, one isolated from the sediment surface of the study site (9410-O, mesophilic) and the other isolated from the Antarctic (AN-1, psychrotolerant) were used to enhance inorganic nitrogen (DIN) and phosphorus (DIP) regeneration in surface and bottom waters from a eutrophic coastal inlet in different seasons. Unfiltered waters with or without added bacteria were incubated in the dark at in situ water temperatures and at 10°C for 10-15 days, and the accumulation of DIN and DIP was monitored. Bacteria were always added as resuspensions prepared in filtered (0.2 μm) in situ waters. Strain 9410-O stimulated DIN and DIP net regeneration by ca. 2-6-fold in surface water, and 3-25-fold in bottom water at relatively high in situ/incubation temperatures viz. 23 and 26°C. However, it caused little enhancement of nutrient regeneration at 10°C. On the other hand, strain AN-1 stimulated net DIN and DIP regeneration in waters at both relatively high (23.5°C; 2-4-fold) and low temperatures (10-12°C; ca. 2-10-fold). Live cells of either strain yielded remarkably higher DIN releases than the same volume of killed counterparts indicating that the activities of the added bacteria rather than their utilization as organic matter were primarily responsible for additional nutrient regeneration.