Culture Studies on the Effects from Borate Pollution on the Growth of Marine Phytoplankters

Abstract

The autotrophic growth of 19 species of marine phytoplankters, from 10 classes of algae, was tested on axenic cultures with boric acid additions of 0–100 mg/liter B to a nutrient-enriched, pH-controlled seawater medium. All the growth rates were virtually unaffected by the incorporation of 5–10 mg/liter B, while 26% of the species were strongly inhibited by 50 mg/liter B and this proportion was increased to 63% species inhibited at 100 mg/liter B. Several species required prolonged periods of adaptation before exponential growth with 50–100 mg/liter B. Both the adaptation period and the degree of inhibition were gradually mitigated on sequential transfer of certain species from lower to higher boron concentration. Such sequential transfer tests showed that the majority of initially inhibited species could recover good growth at 50 mg/liter B but not at 100 mg/liter B, which concentration appeared to be lethal to 37% of the species tested. These results predict that, in the absence of stress from nutrient deficiency and pH adversity, inorganic borate pollution would be facilely tolerated by phytoplankton up to 10 mg/liter B; higher borate concentrations up to 100 mg/liter B are expected to cause species redistribution tending to favor growth of some forms by suppressing that of others.