Effect of Boron on Primary Production of Nanoplankton

Abstract

Addition of boron (30 mg L−1) to 20-μm fractions (nanoplankton) of phytoplankton collected from Bedford Basin had a significant effect on primary production. During November through May when a high level of nitrates, phosphates, and silicates and low temperature were prevailing, consistent stimulation (up to a maximum of 168%) of primary production (mg C m3 h−1) and carbon assimilation rates (mg C mg Chl a−1 h−1) were observed in the presence of boron, while during June–October when the nutrients were low and temperature was high, photosynthesis was inhibited (to a maximum of 62%). Similar treatment with boron inhibited photosynthesis in 5-d-old unialgal cultures but enhanced photosynthesis in 14-d-old cultures of certain species, showing that the effects of boron could be species specific. It appears that boron, under conditions of boron excess, could alleviate nutrient deficiency in some phytoplankters and might cause temporal variations of phytoplankton composition in coastal waters.Key words: boron pollution, primary production, nanoplankton, algal cultures